- 21 hours ago
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"Dang, them long-stroke engines are just torquier." While this is often true, it's not for the reasons many of us think. Technical Editor Kevin Cameron and Editor-in-Chief Mark Hoyer talk about Bore and Stroke Ratio and how it influences engine horsepower and torque.
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"Dang, them long-stroke engines are just torquier." While this is often true, it's not for the reasons many of us think. Technical Editor Kevin Cameron and Editor-in-Chief Mark Hoyer talk about Bore and Stroke Ratio and how it influences engine horsepower and torque.
Find us on Patreon! https://www.patreon.com/cw/CycleWorldPodcast
Become a Channel Partner: https://octanemedia.co/home/become-an-advertiser/
Subscribe to Cycle World Youtube: http://www.youtube.com/c/cycleworld?sub_confirmation=1
Listen on Spotify: https://open.spotify.com/show/6CLI74xvMBFLDOC1tQaCOQ
Read more from Cycle World: https://www.cycleworld.com/
Buy Cycle World Merch: https://teespring.com/stores/cycleworld
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SportsTranscript
00:00:00Welcome to the Psycho World Podcast. I'm Mark Hoyer. I'm the editor-in-chief. I'm with Kevin Cameron, our technical
00:00:06editor. Thanks for joining us. If you've never been with us, we've been doing this a while. We're close to
00:00:15about 130 episodes. We have a very big back catalog. You can find us on YouTube, which is probably where
00:00:20you got us, but on Spotify. And we also have a Patreon, Psycho World Podcast Patreon. There's a link in
00:00:27the description.
00:00:27If you join us over there, you get everything commercial-free plus bonus content. That means more podcasts. We do
00:00:34some short-form stuff. And as I like to say, we've hit topics such as the excellence of butter. And
00:00:41there was a lot to talk about. And it was motorsports related.
00:00:44Anyway, thanks for being with us. Today, we're going to talk about primarily the effects of an engine's bore-to
00:00:52-stroke ratio. We'll probably talk about connecting rods because I have props. Here's a connecting rod. And maybe a little
00:01:00bit of connecting rod surface treatment and rod ratio.
00:01:05Carefully note the darkening of the small end of the small end of that rod.
00:01:09Yes. Yes, indeed.
00:01:11That's where the heat is.
00:01:13Yeah, we'll get... Well, let's get underway. I guess, you know, if you've never joined us, and even if you
00:01:19have, what are we working against?
00:01:23We're trying to work against the mythologies of mechanics and things that people say and believe that maybe aren't necessarily
00:01:31rooted in fact, such as one that we're going to talk about here is, do long strokes make more torque?
00:01:39And while there are reasons that long strokes and small bores might be torquey, they're not for some of the
00:01:47mythological reasons, sorry, that we sometimes talk about. So go ahead, Kevin. Tell us what's up, man.
00:01:54Well, I've been hearing this thing about Harley's having, being so torquey, which they are, because they have to be
00:02:06to start a heavy cruiser or tour bike from rest without a lot of revving up and embarrassing clutch flipping.
00:02:16You want to just glide powerfully away. And the engines that Harley has built, their two valve engines, have produced
00:02:25strong bottom torque for this purpose.
00:02:29And I want to emphasize for this purpose, because there are no statements like, do long strokes make big torque?
00:02:42All there are is engineering a device for a specific purpose. And in the case of the Harley with its
00:02:52tendency towards long strokes, it's, it's slowly going away up there on Juneau Avenue, but they keep it around.
00:03:03And there's a good reason for wanting good bottom torque. Now, for that, for their type of motorcycle, one of
00:03:16the things that is not often discussed is, oh, some people are going to call it intake mock index, but
00:03:25I want to call it limits of intake flow.
00:03:28So, if you have, let's say we have four valves. Most engines do now, including the big tour at last.
00:03:40And we're going to try to operate this engine at various RPM.
00:03:45And we notice that as the engine revs up, the torque has been pretty level. Recent designs generate really strong,
00:03:59wide torque. So it's more like a torque plateau than a torque curve.
00:04:06But we notice that as the engine revs up more, that the torque begins to fall. And the rising horsepower
00:04:14carries on for a while, but then it too softens and hooks over. And it begins to make less power
00:04:22as you rev it up.
00:04:23And the reason for this principle reason for this is that as the speed of airflow through the intake ports
00:04:32rises towards half of the speed of sound, it encounters losses that fix it.
00:04:42So that applying more suction on the engine side will not pull more air through the port.
00:04:50And that's why the torque falls off. And good old Harry Ricardo, one of the fathers of the internal combustion
00:04:58engine, called this wire drawing.
00:05:01And what that meant was that, what he meant by it was that the harder you pull on the intake
00:05:10port, the less dense the air becomes because there's a resistance to flow.
00:05:16So when the English were developing their wonderful racing singles, AJS, Velocet, Norton, et cetera.
00:05:30If they get to take a drink, if you say Velocet is what I want to know.
00:05:34Oh, we hadn't thought of that.
00:05:37And if I say TZ750, does that count?
00:05:40I'm sorry, go ahead.
00:05:42All right.
00:05:46When engine developers reached this point, they knew that their engine was not going to be able to operate at
00:05:54another 500 RPM higher.
00:05:56But they're thinking to themselves, well, the guys at the competing manufacturers are sure going to show up at the
00:06:04Isle of Man TT with more power than they had last year.
00:06:07And we have to do even better.
00:06:11So what did they do?
00:06:13They couldn't get more airflow through the valve and intake pipe because they had streamlined them as best they could.
00:06:25Good old Harry Westlake got into the airflow business 1926 or so.
00:06:32So he was, his services were for sale.
00:06:37He was in business to improve airflow and a lot of people took him up on it.
00:06:42And so what you had to do at this point is you had to increase the size of the intake
00:06:48valve and the intake port in order to move engine operation up by a few hundred RPM.
00:06:56Oh, well, we put a bigger intake in last year and we were playing around with it.
00:07:04And we saw that the edge of the intake valve is pretty close to the cylinder wall.
00:07:09And this valve isn't going to flow anymore here because it's in the way and the cylinder wall is in
00:07:19the way.
00:07:20What we need is a larger bore, not a lot larger, but enough larger to accommodate a bigger intake port.
00:07:28And that's why if you look at these various designs, they slowly got larger bores and shorter strokes.
00:07:40Now, it's common today to say, oh, well, you've got to have a large bore and a short stroke because
00:07:46a short stroke lets your engine rev up more.
00:07:50And you put those big valves in to make sure you get the good stuff in and the burnt stuff
00:07:58out in the shorter time available as you raise the rev.
00:08:01So, that's approximately true.
00:08:04But the English weren't going to try to go to the ultimate in one jump.
00:08:11What was the ultimate?
00:08:13Well, during the period when they were running Formula One engines to 20,000 RPM,
00:08:23the largest number, bore divided by stroke, that I saw was 2.25.
00:08:34Which means that the stroke is just going away.
00:08:39It was down in the 30s millimeters.
00:08:42And the bore was tremendous.
00:08:50So, the English didn't run into these problems that we're going to discuss here because they were making the progress
00:08:59that was possible for them.
00:09:01Because at the same time, they were starting out with engines with iron heads and cylinders, which didn't cool very
00:09:07well.
00:09:08Hmm, maybe we'll make a bronze head.
00:09:10Many of you will have heard of bronze head versions of various engines, such as Vincent's Racing 500 Single with
00:09:19the bronze head.
00:09:20Cool, better than iron.
00:09:22Yeah.
00:09:23Yeah.
00:09:23The 40 Triumphs, there was a bronze head that they used on the 500 Twins.
00:09:28Yeah.
00:09:30And so, they're changing that.
00:09:33Oils are improving.
00:09:34Fuels are improving.
00:09:36So, you can't really put your finger on any one thing.
00:09:40But there is this trend throughout.
00:09:42Somewhat larger bores to allow larger valves whose airflow will serve the engine at a somewhat higher RPM.
00:09:53And racers are conservative.
00:09:56They have to be.
00:09:57Their experience guides them to conservatism.
00:10:00Because when you decide, I'm going to try out all my crazy ideas at once, usually you have a long
00:10:11period of fixing problems.
00:10:14So, it's best, like the old-timer said, don't bring a new bike to Daytona.
00:10:20Bring a bike that is worked out, that you understand perfectly.
00:10:25Anyway, the big thought here is that the intake port has limits, has flow limits.
00:10:34If you try to rush the air through it too fast by revving up an engine without making the valves
00:10:41bigger,
00:10:42then you're going to run into that point where the torque curve starts to, oh, I'm tired.
00:10:48And the horsepower curve also softens and starts back down.
00:10:53That's why Harleys are all done.
00:10:57I'm talking about the two-valve designs now.
00:11:00They're all done at 4,800 to 5,000 RPM.
00:11:04Why?
00:11:07They don't need any more than that.
00:11:09They want them to pull strongly at 3,500 RPM to accelerate up on ramps and for passing.
00:11:16Why?
00:11:19And, to be fair, they're using a large displacement to give you that.
00:11:23Sure.
00:11:23A tremendous displacement.
00:11:25I mean.
00:11:26But their valves are quite limited and they basically choke the engine out.
00:11:33It wheezes out at 4,800 or 5,000.
00:11:37That was accepted for years.
00:11:39That was the thing.
00:11:41It was okay.
00:11:42Everyone agreed.
00:11:45But now we get to this thing, do long strokes equal high torque?
00:11:52People have explained it to me as if I were stupid time and again.
00:11:56They said, well, come on, man.
00:11:58It just stands to reason.
00:12:00I mean, it's like, you know, you're trying to bust loose some big bolt.
00:12:04You put an extension bar, you increase the stroke, gives you more leverage.
00:12:10So, what you're doing is you're letting the force on the piston act on the crankshaft at a larger radius
00:12:19and thus it has to make more torque.
00:12:23But I'm the same size piston.
00:12:26Yes.
00:12:27On the torque wrench.
00:12:28That's the problem.
00:12:30If we're building a 1,000cc engine or a 74-inch engine or whatever it happens to be, and we
00:12:37decide to increase the displacement, we could increase the stroke.
00:12:46And just leave it at that.
00:12:48All we've increased is the stroke.
00:12:50Then we have to agree.
00:12:52There's more leverage.
00:12:54The piston is the same size as before, so there's the same force acting on a longer lever.
00:12:59So, the torque goes up.
00:13:01But in fact, if you're building a 74 and you increase the stroke, it won't be a 74 unless you
00:13:09also make the piston smaller.
00:13:11So, if you're building into a class, if you do the arithmetic on this, you'll find that the area of
00:13:21the piston decreases exactly as much as the stroke increases.
00:13:28That is, the force acting on the piston is reduced by the same amount that the stroke is increased.
00:13:37So, there is no increase in torque.
00:13:39Now, at this point, another idea needs to be introduced, and that is that the word torque means different things
00:13:50to different people.
00:13:51In the laboratory, in the old dyno shack, with the terrible noises coming out, torque means how much twisting force
00:14:05in pounds-feet is the engine generating at xrpm.
00:14:11It is a physical quantity which you can measure.
00:14:14Hey, guys, gather around.
00:14:16Look at this.
00:14:17What's it say?
00:14:18And they all say the same.
00:14:20Yeah, 62 pounds-feet.
00:14:24You write it down.
00:14:27But when people are saying, I bought a bin years.
00:14:32I swore I was never going to do it, but I bought a Harley.
00:14:35Laughed her all around.
00:14:36Well, you know, I've had it with breaking my back on some stretched-out sport bike, and I'm just going
00:14:43to kick back and enjoy myself.
00:14:45Yeah, okay, yeah, sure.
00:14:50But, man, it sure is torquey.
00:14:56Now, that's a different meaning of the word torque.
00:14:59What he means is that almost without regard to how fast the engine is turning, if he turns the throttle,
00:15:08the bike will accelerate in a forceful way.
00:15:12That is torquey.
00:15:14A torquey engine has a broad torque curve that is strong enough to accelerate the motorcycle.
00:15:27And long stroke engines tend to be torquey for a solid physical reason.
00:15:35If the stroke is long, the bore is small, and so are the valves, which means that their best, their
00:15:45region in which their velocity does the best job of filling the cylinder,
00:15:53with none of that fade at the end of the curve, those small valves are going to give this engine
00:16:01a broad and strong torque.
00:16:06And if you look at valve timings for Harley-Davidson's and other motors of the type that pull big, heavy
00:16:16bikes,
00:16:16you'll find that they are like Volkswagen valve timings.
00:16:22The intakes open pretty close to top dead center, and they close pretty close to bottom center.
00:16:32And that short timing does not carry on towards higher RPM very well.
00:16:41But there's no reason why these bikes should pretend to be road warriors when, in fact, they are touring machines.
00:16:52Signing off at 5,000 is just fine.
00:16:58And so it's always well, if people start talking about torque, to get it clear, are we talking about something
00:17:06that can be measured on a dynamometer,
00:17:08or are we talking about a feeling we get when we ride the bicycle?
00:17:15And when people say, that's a torquey bike, I really like it, it's easy to ride, et cetera.
00:17:23And that, in a two-valve engine, used to mean that the intake valve is delivering its best flow sort
00:17:36of right in the middle of the engine's operating range
00:17:40so that it pulls strongly off the bottom, and it goes up the on-ramp, and it passes traffic competently.
00:17:49The valves could be made bigger by changing the bore-stroke ratio so that the bore is bigger with more
00:17:58room for valves.
00:17:59But then, the best operating point for those bigger ports would be up at higher RPM.
00:18:19Because you don't like the vibration, because you don't like the racket, and the feeling, this thing is wearing out
00:18:28so fast, I may not make Denver tonight.
00:18:35So, a long stroke creates, making the stroke longer, increases piston-shaking force,
00:18:43because piston-shaking force is directly proportional to stroke.
00:18:48But piston-shaking force is also proportional to the square of RPM.
00:18:57So, what people want in these big, torquey bikes is smoothness, and that's why they give them an overdrive ratio,
00:19:05so that when you get up to cruising speed and shift into sixth, the engine's down there just purring away,
00:19:13or the rubber mounts are doing their good job, or the balancers, and it's a pleasant ride.
00:19:21You know, I just rode my wife's Sportster today, XR1200X, so the enhanced brakes and adjustable suspension.
00:19:30And, you know, it's the old air-cooled parallel push rods.
00:19:35Three-and-a-half-inch bore, or 88.9, and the stroke is 96.8 millimeters, or 3.812, so
00:19:43getting close to a four-inch stroke.
00:19:45What's neat about the XR is it has that Sportster torque, so that at 2,500 rubber mount Sportster, 2
00:19:51,500, it feels great.
00:19:53Like, you, right off the bottom, it's feeling well.
00:19:58But they did a lot of hot rod work to it.
00:20:00Now, when I went on the press launch for that bike, I asked the engine guy, I said,
00:20:03oh, you probably talk, this is 2008 when I went on the press launch.
00:20:08And I asked the engine guy, I'm like, well, you know, you guys probably talk to Buell,
00:20:12you know, get a little pointers.
00:20:15It was very distinct.
00:20:18Buell has nothing to do with this motorcycle.
00:20:21I mean, very, very definitive.
00:20:23So they hotted up their Sportster engine for the sporty.
00:20:27You know, the XR was the naked kind of a street tracker-inspired sporty bike.
00:20:34Pulled nice.
00:20:35It tapers off, you know, as it gets up to seven, but it is really broad,
00:20:40and it has very great bottom-end torque and keeps pulling.
00:20:46It's a really nice combination, but it is two-valve,
00:20:48and it's exactly what you're talking about, Kevin,
00:20:50even in the sportiest version of the Sportster.
00:20:54Well, this is why the big tour rigs are shifting to four valves, as follows.
00:21:08If your riders are saying, you know, I think my bike could use a little more punch
00:21:15for passing and on-ramp because I got it loaded pretty good,
00:21:22and my life partner is no featherweight either,
00:21:27and we just think it would go better with a little more punch.
00:21:32Well, it's easy to get more horsepower from a two-valve engine.
00:21:38Just leave the intake valve open longer after bottom center,
00:21:43and then at higher speeds, when the intake air is going fast enough
00:21:49that when the piston is rising and the intake valve is still a bit open,
00:21:54the rushing air overcomes the tendency of the piston to push the air back up
00:22:00the intake pipe, and the valve closes, and it traps a good solid charge.
00:22:07But by keeping the intake open longer at low speed,
00:22:12the piston is going to push it back out because the intake velocity isn't high enough.
00:22:21So this is how Jerry Branch was able to get 100 horsepower from a 74 40 years ago
00:22:29by revving it up to 7,600.
00:22:33Try touring with that.
00:22:37So how are they going to get more power?
00:22:41Well, one thing is if you switch to four valves,
00:22:45you can put in quite a lot of more valve area with two intakes
00:22:49than with one great big one,
00:22:51and the two intakes can open and close more quickly because they're lighter.
00:22:57The two valves weigh less than the one previous valve
00:23:04because of the old square cube rule.
00:23:10The weight is in the volume in the valve,
00:23:12which is usually the cube of dimension,
00:23:16and the area of the valve,
00:23:18which is what's delivering airflow, is the square.
00:23:22So what they did was they said,
00:23:26we know that with four valves, we can run short timing,
00:23:30the timing that our customers love.
00:23:34And yet, because the intake valves have greater area,
00:23:37we can deliver a lot of power up high that wasn't there before
00:23:43because the single valve was squeezing out.
00:23:50And, oh, but if you make those big ports,
00:23:53then they're going to have a low flow velocity.
00:23:58Because we're opening close to top center
00:24:01and closing close to bottom center,
00:24:03which means we have to get the air in there quickly,
00:24:07which means velocity.
00:24:09So you've created intake area,
00:24:12but now you're going to use it
00:24:16at a high speed for a short duration.
00:24:20So you end up with the kind of punch
00:24:24that people want at 3,500,
00:24:25and which keeps on pulling.
00:24:29I'm not going to let that Goldwing guy embarrass me.
00:24:35So they all end up with a similar solution
00:24:38because that's physics.
00:24:41You know, people look out to the limits of the universe
00:24:44and the molecules, the electrons, the protons,
00:24:49all seem to be obeying the same physical laws.
00:24:55I don't like the word, as we have here.
00:24:58And they're 14 billion years in the past.
00:25:01So pretty reassuring.
00:25:05I like the idea that the electrons will behave
00:25:07when I get to my hotel room,
00:25:09just as I expect them to.
00:25:15So there was a grand old Southern boy motorcycle tuner
00:25:23called Mississippi Round Man Larry Worrell.
00:25:28He's no longer with us,
00:25:30but he had a great deal of experience,
00:25:34two-stroke and four-stroke.
00:25:36And he enjoyed his work.
00:25:39And on some bus ride somewhere,
00:25:43he described to me three engines
00:25:45that they had built at American Honda
00:25:48during their entry to AMA Superbike beginning in 1980.
00:25:55And he said,
00:25:57what we found was the fastest combustion
00:26:00occurred in the engine with the smallest bore.
00:26:06Now, one way to look at this would be to say,
00:26:09well, the distance from the spark plug
00:26:10in the center of the cylinder
00:26:12out to the cylinder wall is shorter.
00:26:14So yeah, you'd expect it.
00:26:17But there's another effect going on.
00:26:20And that is
00:26:22that as the piston comes up
00:26:23and compresses the charge
00:26:26and stops at top dead center,
00:26:28the smaller the bore,
00:26:29the taller the space above the piston.
00:26:35And if there's plenty of room above the piston,
00:26:38whatever motion you've given the air,
00:26:41whether it's circular swirl
00:26:42or if it's tumble motion,
00:26:45is going to be able to persist longer
00:26:47in a more open chamber
00:26:49than it will if the bore is larger
00:26:52and the stroke is shorter,
00:26:54which means that there's hardly any gap
00:26:58between the piston and the cylinder head.
00:27:02And this is the main reason
00:27:03why the larger you make the bore in general,
00:27:09the earlier you have to ignite the charge.
00:27:13And in some of these really racy engines
00:27:17with extreme bore stroke ratios like two to one,
00:27:21they were timing the spark
00:27:24at 60 degrees before top center or more.
00:27:31And once I happened to be
00:27:34in the office of Ducati's,
00:27:38he's the CEO now,
00:27:39but back then he was a jack of all trades.
00:27:42He did whatever they,
00:27:43whatever needed doing.
00:27:45And I asked him,
00:27:49how does,
00:27:55why do they keep pursuing larger bore
00:27:58and shorter stroke
00:27:59as they were doing in Formula One
00:28:02when this early ignition timing
00:28:05means a longer period of heat loss
00:28:10from the burning charge
00:28:12to the metal inside the engine?
00:28:16And he said,
00:28:17oh, it's very simple.
00:28:18He said, yes, the losses are serious,
00:28:20but so are the gains.
00:28:22And the gains are greater than the losses.
00:28:25So that's why they go that way.
00:28:29But when the,
00:28:32when Dorna created MotoGP,
00:28:36their four-stroke class,
00:28:39their first one,
00:28:40they put a limit on bore
00:28:42at 81 millimeters
00:28:43for,
00:28:45well, now it's a thousand cc's.
00:28:49It was 81 by 48.5.
00:28:52So not two to one,
00:28:55more like 1.75 or so.
00:28:59Because they didn't want
00:29:02an RPM race
00:29:04with everyone
00:29:06with everyone
00:29:06furiously building
00:29:07one prototype
00:29:08after another.
00:29:09When BMW got into
00:29:11Formula One
00:29:12years ago,
00:29:14they built
00:29:15more than 100
00:29:17test engines
00:29:18with different characteristics,
00:29:20different bores
00:29:21and strokes,
00:29:22and evaluated them
00:29:25in detail.
00:29:26Do you think that costs money?
00:29:29I do think so.
00:29:31So,
00:29:33they were trying
00:29:34to avoid that.
00:29:35And,
00:29:38that was the reason.
00:29:39Because you're,
00:29:40you're trying
00:29:42to push RPM up
00:29:43by having
00:29:44an enormous bore
00:29:45with gigantic valves
00:29:47in it
00:29:47and a little
00:29:49tiny stroke.
00:29:51And you've created
00:29:52an engine that is
00:29:54not entirely practical.
00:29:56And,
00:29:58now,
00:29:59racing class,
00:30:01of course,
00:30:01doesn't have to be
00:30:02entirely practical.
00:30:04But,
00:30:05it shouldn't be laughable.
00:30:07Should it?
00:30:09So,
00:30:10anyway,
00:30:10this was,
00:30:12this has been a problem.
00:30:14Now,
00:30:14another thing
00:30:15that comes up
00:30:16quite frequently
00:30:17in engines
00:30:18with larger bores
00:30:19and shorter strokes
00:30:21is
00:30:23a terrible compromise,
00:30:25which we all hate.
00:30:26We want,
00:30:27we want a,
00:30:28a set of principles
00:30:30that will guide us
00:30:31unerringly to the goal
00:30:32of winning races
00:30:34or having an excellent
00:30:35street bike
00:30:36or whatever the goal is.
00:30:38But,
00:30:39what they found was
00:30:42Steve Johnson
00:30:44was building these
00:30:46FCR 750
00:30:49superbike engines.
00:30:51And,
00:30:52he found that
00:30:53if he pushed
00:30:54the compression rate
00:30:55ratio up,
00:30:57it would be
00:30:58the combustion
00:30:59chamber
00:30:59became
00:31:01wafer thin
00:31:03and the
00:31:04motion of the
00:31:05intake flow
00:31:07coming into the
00:31:08cylinder
00:31:08at hundreds of
00:31:09feet per second
00:31:10to create
00:31:11a tumble motion
00:31:14to store
00:31:15that energy
00:31:16to turn it
00:31:16into
00:31:17flame accelerating
00:31:18turbulence
00:31:19at top center.
00:31:21By the time
00:31:22the piston
00:31:23got to top center,
00:31:24all that material
00:31:26was crowded
00:31:27into such
00:31:27tight
00:31:29combustion chamber
00:31:30that it had
00:31:31lost most
00:31:31of its energy.
00:31:33So,
00:31:33they had to
00:31:34advance the timing
00:31:34and advance it.
00:31:36Oh,
00:31:36here's the maximum.
00:31:37Yeah,
00:31:38we got 58 degrees.
00:31:43And,
00:31:43of course,
00:31:44lots of heat
00:31:45going into
00:31:46engine oil
00:31:46and coolant.
00:31:48Disappearing.
00:31:49We paid for it,
00:31:51but we're getting
00:31:51nothing from it.
00:31:54so they began
00:31:56to build
00:31:56different engines
00:31:57for different
00:31:58racetracks.
00:31:59For a short
00:32:00racetrack with a lot
00:32:01of accelerations
00:32:02off of the
00:32:03several corners,
00:32:04they would build
00:32:05a high compression
00:32:06engine that had
00:32:07lousy top end
00:32:09because of this
00:32:10loss of
00:32:11turbulence.
00:32:13And then for
00:32:15the high speed
00:32:16track,
00:32:17they would lower
00:32:18the compression
00:32:18to open up
00:32:19the chamber
00:32:20so that they
00:32:21could store
00:32:22intake charge
00:32:24motion and
00:32:24turn it into
00:32:25turbulence.
00:32:27But they'd
00:32:28lost some
00:32:28acceleration
00:32:29because of the
00:32:30lower compression
00:32:31ratio.
00:32:32And this
00:32:34has been
00:32:35a problem
00:32:37in Formula
00:32:37One and
00:32:38MotoGP
00:32:38and in
00:32:39any form
00:32:40of
00:32:42engine
00:32:43development
00:32:43that moves
00:32:44in the direction
00:32:45of larger
00:32:46bore and
00:32:46shorter stroke.
00:32:48and
00:32:49those people
00:32:51at that time
00:32:51were really
00:32:54annoyed
00:32:55at what
00:32:56was happening
00:32:57because they
00:32:58couldn't
00:32:59make an
00:33:00engine that
00:33:01would
00:33:03perform well
00:33:04on all types
00:33:05of circuits.
00:33:07So,
00:33:08the curse
00:33:10of compromise.
00:33:11Well,
00:33:12the long
00:33:12timings too,
00:33:13we have
00:33:15seen many
00:33:15applications of
00:33:16more than
00:33:16one spark
00:33:17plug.
00:33:18you light
00:33:18the flame
00:33:18in two
00:33:19areas
00:33:20and half
00:33:21the distance
00:33:22it needs
00:33:22to cover.
00:33:23There's
00:33:23an aftermarket
00:33:26Jaguar
00:33:27XK
00:33:28cylinder head
00:33:28that has
00:33:30completely
00:33:30redone
00:33:31flow.
00:33:31It looks
00:33:32like a
00:33:32Jaguar head
00:33:33but it
00:33:33has twin
00:33:34plugs
00:33:35and it's
00:33:35a fresh
00:33:36piece and
00:33:37the torque
00:33:38numbers are
00:33:39astronomically
00:33:40higher.
00:33:41like many
00:33:42of the
00:33:42engines
00:33:43that Kevin
00:33:43is talking
00:33:43about in
00:33:44the old
00:33:44days,
00:33:45the two
00:33:45bowels,
00:33:45they were
00:33:46getting
00:33:46hemispherical
00:33:48heads,
00:33:49you know,
00:33:49the Hemi.
00:33:50Oh,
00:33:50well,
00:33:50actually,
00:33:51what you
00:33:51want is
00:33:51the wedge.
00:33:52But the
00:33:53Hemi,
00:33:54you're
00:33:55doming the
00:33:55piston.
00:33:56I don't
00:33:57have my
00:33:57domed piston
00:33:58but you're
00:33:58doming the
00:33:59piston and
00:34:00imagine,
00:34:01you know,
00:34:01why do you
00:34:02make a tunnel
00:34:02to go through
00:34:03the mountain?
00:34:03Well,
00:34:03it's less
00:34:04steep and
00:34:05it's a
00:34:05shorter trip.
00:34:06So the
00:34:07straight line
00:34:07under the
00:34:08Hemi is a
00:34:08shorter line.
00:34:09So that's
00:34:09why we do
00:34:10flat,
00:34:10you know,
00:34:11flat pistons
00:34:11because the
00:34:12flame travel
00:34:12just goes
00:34:13this way
00:34:13instead of
00:34:14over the
00:34:15mountain to
00:34:15the other
00:34:15side.
00:34:16So if you
00:34:16light it
00:34:16over here,
00:34:17it's got to
00:34:17go all the
00:34:18way over
00:34:18here and
00:34:19that's why
00:34:19we get
00:34:19detonation
00:34:20and,
00:34:21you know,
00:34:22the problems
00:34:22and with
00:34:22the Hemi,
00:34:24if you have
00:34:25the Hemi
00:34:25and that's
00:34:25what you're
00:34:26sticking with
00:34:26and you put
00:34:27two plugs
00:34:27in,
00:34:28you're just
00:34:28having the
00:34:29distance that
00:34:29the flame
00:34:30has to
00:34:30travel to
00:34:30meet itself.
00:34:31You're
00:34:31shortening
00:34:32the time
00:34:32of heating
00:34:33that Kevin's
00:34:34talking and
00:34:34what he
00:34:35means in
00:34:35the most
00:34:36base sense
00:34:37about heat
00:34:38going into
00:34:38the oil
00:34:39and heat
00:34:39going into
00:34:40the coolant
00:34:40is you're
00:34:41making the
00:34:41heat and
00:34:42all that
00:34:43energy should
00:34:44be pushing
00:34:45the piston
00:34:45down,
00:34:46not heating
00:34:46the other
00:34:47parts promptly
00:34:48right away,
00:34:50right?
00:34:50Not dwelling
00:34:52in there and
00:34:52growing and
00:34:53getting hot
00:34:54and,
00:34:55you know.
00:34:55So good
00:34:58old Keith
00:34:58Duckworth,
00:35:00after spending
00:35:01two years
00:35:02trying to
00:35:02get one
00:35:03of his
00:35:03little
00:35:04fours to
00:35:06burn in
00:35:08a short
00:35:08time using
00:35:09squish to
00:35:10generate
00:35:10turbulence and
00:35:12failing,
00:35:14he decided
00:35:15to take
00:35:16another
00:35:16direction and
00:35:18it was four
00:35:19valves and
00:35:20then with
00:35:21four valves
00:35:21you think to
00:35:22yourself,
00:35:22well,
00:35:23we can't
00:35:24really offset
00:35:25the ports
00:35:26and have
00:35:27rotary swirls
00:35:29so what
00:35:30what can
00:35:31we do?
00:35:32And he
00:35:33came up
00:35:33with the
00:35:34idea of
00:35:35tumble and
00:35:39he
00:35:43made the
00:35:45valve angle,
00:35:47included angle
00:35:48between the
00:35:49exhausts on
00:35:50one side of
00:35:50the head and
00:35:51the intakes
00:35:52on the other,
00:35:5232 degrees
00:35:54so that the
00:35:55combustion chamber
00:35:56was nearly
00:35:57flat.
00:35:58Now here's
00:35:59something that
00:35:59doesn't get
00:36:00much
00:36:03conversation and
00:36:04that is that
00:36:05a true
00:36:05hemi with
00:36:07the valve
00:36:08stems at 90
00:36:09degrees to
00:36:09each other
00:36:12has twice the
00:36:13surface area
00:36:14of a flat
00:36:15disc of the
00:36:17same diameter
00:36:18as the
00:36:18bore,
00:36:19twice,
00:36:20which means
00:36:21twice the
00:36:22exposure to
00:36:23heat from
00:36:24the hot
00:36:24combustion
00:36:25chamber,
00:36:26twice.
00:36:27And this
00:36:28is why
00:36:29all those
00:36:30West Coast
00:36:31tuners,
00:36:33I'm most
00:36:34familiar with
00:36:35the late
00:36:36Kenny
00:36:36Augustine,
00:36:38wanted,
00:36:39yearned
00:36:40inexpressibly
00:36:41to put
00:36:42the equivalent
00:36:43of Norton's
00:36:45export twin
00:36:46cylinder head
00:36:47with its
00:36:48valves at
00:36:4858 degrees
00:36:50onto the
00:36:51650 Triumph
00:36:52which had
00:36:5390 degrees
00:36:55and a
00:36:55deep
00:36:57Boku
00:36:58surface area
00:36:59hemi
00:37:00combustion
00:37:01chamber.
00:37:02Now,
00:37:03are all
00:37:04those people
00:37:05who praise
00:37:05the hemi
00:37:06chamber
00:37:06full of
00:37:08undesirable
00:37:10matter?
00:37:12No.
00:37:14Because it
00:37:16turns out
00:37:16that in
00:37:19terms of
00:37:20airflow in
00:37:20cubic feet
00:37:21per minute,
00:37:25versus the
00:37:27area of
00:37:29the valve
00:37:29head in
00:37:31square inches
00:37:31was better
00:37:33in a
00:37:34two-valve
00:37:35hemi head
00:37:35than in
00:37:36any four-valve
00:37:38pent-roof
00:37:39head.
00:37:39Better.
00:37:42And for a
00:37:43long time,
00:37:44from 1923
00:37:45right on
00:37:46through the
00:37:4750s,
00:37:47it was
00:37:49the fervent
00:37:51belief
00:37:51of the
00:37:52faithful
00:37:53that the
00:37:54hemi head
00:37:54rules.
00:37:57And
00:37:58people who
00:37:59had worked
00:37:59at Triumph
00:38:02knew about
00:38:04the overheating
00:38:05problems with
00:38:06their engines.
00:38:07Because if
00:38:08you have
00:38:0990-degree
00:38:10valve angle
00:38:11in a deep
00:38:11hemi chamber,
00:38:12how are you
00:38:13going to get
00:38:14to 10-to-1
00:38:15compression
00:38:16ratio?
00:38:16I'll tell
00:38:17you.
00:38:18By filling
00:38:18the chamber
00:38:19with a
00:38:19giant lump
00:38:20of aluminum.
00:38:21Mondial
00:38:22pistons.
00:38:22I bought
00:38:23my 58
00:38:23Triumph
00:38:24Trophy
00:38:24years ago
00:38:25and it
00:38:26had some
00:38:27problems
00:38:27and I
00:38:28decided to
00:38:29do the
00:38:29top end
00:38:30and I
00:38:31pulled the
00:38:32barrel off
00:38:33and I
00:38:34pulled the
00:38:34head off
00:38:35and what
00:38:35did I
00:38:35find?
00:38:36Mondial
00:38:36high
00:38:37compression
00:38:37pistons.
00:38:38They were
00:38:3810 or
00:38:3811-to-1
00:38:39piston and
00:38:40they had
00:38:40a huge
00:38:41wedge on
00:38:42the top
00:38:42to go up
00:38:43and fill
00:38:43the chamber
00:38:44and what
00:38:44else does
00:38:45that do?
00:38:46Blocks the
00:38:47flow.
00:38:50It also had
00:38:51a tremendous
00:38:52amount of
00:38:52clearance.
00:38:53The running
00:38:54clearance for
00:38:54that was
00:38:5610-thow,
00:38:5711-thow.
00:38:58I measured
00:38:58it and I'm
00:38:59like,
00:38:59well,
00:38:59this must
00:38:59be wrong
00:39:00and then
00:39:00later on,
00:39:01no,
00:39:01in fact,
00:39:02because it
00:39:02was getting
00:39:03so hot.
00:39:03Getting
00:39:04so hot
00:39:05because the
00:39:06dome of
00:39:07the piston
00:39:07increases its
00:39:09surface area
00:39:10and that
00:39:11hot combustion
00:39:12gas just
00:39:14beats and
00:39:15pounds those
00:39:16molecules are
00:39:17so many
00:39:17little Joe
00:39:18Lewis's and
00:39:19all that
00:39:20beating and
00:39:20pounding by
00:39:21molecules is
00:39:23temperature.
00:39:26And in a
00:39:27gas,
00:39:27it's the
00:39:28speeding,
00:39:29zipping,
00:39:30zooming velocity
00:39:31of the
00:39:32molecules and
00:39:33in solid
00:39:34materials,
00:39:35it's the
00:39:35furious
00:39:36vibration of
00:39:37atoms around
00:39:39their places
00:39:40in the
00:39:41crystal lattice.
00:39:42It's sort
00:39:43of like the
00:39:43individual in
00:39:44society,
00:39:45yearning to
00:39:46be free.
00:39:47I can just
00:39:48vibrate,
00:39:48but I can't
00:39:49get loose.
00:39:51But in the
00:39:52case of these
00:39:53hot running
00:39:53pistons,
00:39:54they could get
00:39:55loose because
00:39:55the pistons
00:39:56could melt.
00:39:59So Keith
00:40:00Duckworth did
00:40:01us all a
00:40:01favor by
00:40:03squashing the
00:40:04combustion
00:40:04chamber down
00:40:07to a
00:40:08disc.
00:40:09And the
00:40:10valve-included
00:40:12angle kept
00:40:13getting narrower
00:40:14and narrower.
00:40:14Kawasaki got it
00:40:15down to 25
00:40:16degrees.
00:40:17And I'm
00:40:17speaking to
00:40:18one of their
00:40:18engineers,
00:40:19and he said,
00:40:20you know what?
00:40:21He said,
00:40:21we'd like the
00:40:22valve-included
00:40:23angle to be
00:40:24zero.
00:40:24We'd like all
00:40:26the valve
00:40:26stems standing
00:40:27up straight like
00:40:28they do in a
00:40:29General Motors
00:40:30diesel,
00:40:31and we
00:40:32but we
00:40:33can't because
00:40:34the drive
00:40:34sprockets on
00:40:35the end of
00:40:35the camshaft,
00:40:36they won't go
00:40:38any closer
00:40:38together.
00:40:40Sounds like an
00:40:41excuse, but
00:40:42it makes a good
00:40:43story.
00:40:45So that's where
00:40:46we've ended up
00:40:47is with
00:40:49larger bores
00:40:50than strokes
00:40:51because in
00:40:52engines that
00:40:53are supposed to
00:40:54make a lot of
00:40:54power, you
00:40:55need valves
00:40:56big enough to
00:40:57flow the air
00:40:58at an intake
00:41:00velocity that
00:41:01is in the
00:41:02comfort zone
00:41:03of air.
00:41:05One of the
00:41:06things that
00:41:07happens in
00:41:07intake ports
00:41:08is that
00:41:08shocks form.
00:41:10Remember the
00:41:11P-47 Thunderbolt,
00:41:13the aircraft
00:41:14that GIs
00:41:15called the
00:41:16jug?
00:41:18Oh,
00:41:18do we?
00:41:19It was just
00:41:20a big old
00:41:21milk bottle
00:41:22that was
00:41:23crammed through
00:41:23the air by
00:41:24an R-2800
00:41:2518-cylinder
00:41:27radial.
00:41:28and it
00:41:29began to
00:41:30get sonic
00:41:31flow on
00:41:31various parts
00:41:32of its
00:41:33robust body
00:41:35because the
00:41:36air was
00:41:36having to
00:41:37do what
00:41:38Mark was
00:41:38just talking
00:41:39about,
00:41:40climb over
00:41:41the hill
00:41:41going the
00:41:42long way.
00:41:43The air,
00:41:44in order
00:41:46to keep
00:41:47up, was
00:41:48reaching the
00:41:48speed of
00:41:49sound in
00:41:49various places
00:41:50and shock
00:41:51waves formed
00:41:51and carried
00:41:53away energy.
00:41:53Oh,
00:41:54let's eat
00:41:55this.
00:41:56And,
00:41:56well,
00:41:57we have
00:41:57a bird
00:41:58feeder out
00:41:58here.
00:41:59There's
00:41:59squirrels
00:41:59and jays
00:42:01and all
00:42:01the living
00:42:02creatures
00:42:03come as
00:42:03if there
00:42:04was no
00:42:04food
00:42:05anywhere.
00:42:08So,
00:42:11then some
00:42:12bad things
00:42:12happened.
00:42:15Everyone
00:42:16was making
00:42:16the change
00:42:17to four
00:42:17valves.
00:42:19Everyone
00:42:19was making
00:42:20the change
00:42:20to liquid
00:42:21cooling.
00:42:25at one
00:42:25point,
00:42:26I think
00:42:261990,
00:42:27Kawasaki
00:42:28decided
00:42:28that with
00:42:29their
00:42:29750,
00:42:30which was
00:42:31the basis
00:42:31for the
00:42:32superbike,
00:42:33that they
00:42:34were going
00:42:34to shorten
00:42:34the stroke
00:42:35from 51.5
00:42:36to 47.3
00:42:38or something.
00:42:41Rob
00:42:42Muzzy
00:42:42told me,
00:42:43it took
00:42:44us,
00:42:44it took
00:42:45me,
00:42:45he said,
00:42:46took me
00:42:46two years
00:42:47to equal
00:42:48the power
00:42:49of the
00:42:49longer
00:42:49stroke
00:42:50engine.
00:42:52And in
00:42:531988,
00:42:54Suzuki
00:42:54shortened
00:42:55their
00:42:55stroke
00:42:56from
00:42:57high
00:42:5740s
00:42:58to
00:42:59mid
00:42:5940s.
00:43:01And
00:43:03they
00:43:03couldn't
00:43:03get it
00:43:04to work
00:43:04right.
00:43:05Could
00:43:05not.
00:43:07And so
00:43:08what did
00:43:08they do?
00:43:10After a
00:43:10year of
00:43:11suffering,
00:43:11they went
00:43:12back to
00:43:12the old
00:43:13longer
00:43:14stroke.
00:43:17So
00:43:18something
00:43:18was happening.
00:43:19You know,
00:43:19this is
00:43:20supposed to
00:43:20be a
00:43:20smooth
00:43:21process
00:43:22of
00:43:22progressive
00:43:23engineering.
00:43:24We're
00:43:24going to
00:43:24shorten
00:43:25the
00:43:25stroke,
00:43:26make the
00:43:26bore
00:43:27bigger,
00:43:27put in
00:43:28bigger
00:43:28valves.
00:43:29We're
00:43:30going to
00:43:30accelerate.
00:43:30closer to
00:43:30perfection.
00:43:31Yeah.
00:43:31Yeah.
00:43:32We're
00:43:32just,
00:43:34you know,
00:43:35we're like
00:43:35the faithful
00:43:36praying in a
00:43:37church of
00:43:37our own
00:43:38making,
00:43:38and then
00:43:39being swept
00:43:41away by
00:43:41an avalanche.
00:43:42Wait a
00:43:43minute,
00:43:43this isn't
00:43:44supposed to
00:43:44happen.
00:43:45good.
00:43:48So I
00:43:49was at
00:43:51Ducati
00:43:52one time
00:43:52and talking
00:43:53with
00:43:54Claudio
00:43:55Domenicali,
00:43:56and I
00:43:56said,
00:43:57I see
00:43:58that at
00:43:59least two
00:43:59of the
00:44:00Japanese
00:44:00companies
00:44:01tried to
00:44:02build a
00:44:03Duckworth
00:44:03engine and
00:44:05couldn't.
00:44:05They couldn't
00:44:06make it
00:44:07work.
00:44:07When they
00:44:08shortened the
00:44:08stroke one
00:44:10more time,
00:44:11everything ran
00:44:12out of gas
00:44:13and it
00:44:14was not an
00:44:15improvement.
00:44:15Well,
00:44:16he said,
00:44:18I can't
00:44:19comment on
00:44:20what they
00:44:21do because
00:44:22I'm not
00:44:23part of
00:44:23their
00:44:24organization,
00:44:24but I
00:44:25can tell
00:44:26you what
00:44:26we do.
00:44:28And he
00:44:29said,
00:44:30we vary
00:44:32the intake
00:44:33port
00:44:33downdraft
00:44:34angle.
00:44:37The old
00:44:38Triumphs
00:44:39twins had
00:44:40horizontal
00:44:40intake
00:44:41ports,
00:44:41pretty
00:44:42close to
00:44:42it.
00:44:43So that's
00:44:44zero
00:44:45downdraft.
00:44:47Norton
00:44:47singles had
00:44:4812 degrees
00:44:49for a while
00:44:50and I
00:44:50think they
00:44:51went up
00:44:51to 20,
00:44:52somewhere
00:44:53like that.
00:44:53And you
00:44:53can see,
00:44:54looking at
00:44:55them,
00:44:55you can
00:44:55see that
00:44:55the
00:44:56carburetor
00:44:56is sloping
00:44:57down.
00:44:58So that
00:44:59was one
00:44:59of Domenicali's
00:45:00variables.
00:45:02And the
00:45:03other one
00:45:04was intake
00:45:05port
00:45:05diameter,
00:45:06which
00:45:07controls
00:45:08intake
00:45:09velocity.
00:45:10velocity.
00:45:12Now,
00:45:13the
00:45:14downdraft
00:45:15angle
00:45:17determines
00:45:18whether the
00:45:19energy of
00:45:20the intake
00:45:20flow,
00:45:21which,
00:45:21as I've
00:45:21said,
00:45:22can be
00:45:22several
00:45:23hundred
00:45:24feet per
00:45:24second,
00:45:28can be
00:45:29used to
00:45:30generate
00:45:31this
00:45:34barrel
00:45:35motion,
00:45:35which we
00:45:36now call
00:45:37tumble,
00:45:37by reducing
00:45:40the
00:45:41downdraft
00:45:41angle so
00:45:42the flow
00:45:42goes straight
00:45:43to the
00:45:43other
00:45:43cylinder
00:45:44wall,
00:45:44turns
00:45:44down,
00:45:45hits the
00:45:45piston,
00:45:46and creates
00:45:47this
00:45:47tumble
00:45:48motion.
00:45:49Or,
00:45:50we can
00:45:51stand the
00:45:52port up
00:45:52more
00:45:53steeply
00:45:55and fill
00:45:56the
00:45:56cylinder
00:45:58more
00:45:59completely
00:46:00and to
00:46:01hell
00:46:02with
00:46:03tumble.
00:46:04So,
00:46:05it's a
00:46:05compromise.
00:46:06How much
00:46:06of this
00:46:07do we
00:46:07need to
00:46:08go with
00:46:09how much
00:46:09of that?
00:46:11And by
00:46:12controlling
00:46:12the intake
00:46:13velocity,
00:46:15they were
00:46:16deciding how
00:46:17much energy
00:46:17to invest
00:46:19in all
00:46:20of this
00:46:21energy
00:46:22storage
00:46:22bank,
00:46:23because
00:46:24that's
00:46:24what
00:46:24swirl,
00:46:25which the
00:46:26British
00:46:26invented
00:46:27in 1922
00:46:28with the
00:46:29offset
00:46:29intake
00:46:29port,
00:46:30or tumble,
00:46:31which
00:46:32Duckworth
00:46:33invented
00:46:34in 1967,
00:46:36two ways
00:46:37to store
00:46:37intake
00:46:38energy
00:46:38to be
00:46:39transformed
00:46:40as the
00:46:41piston
00:46:42approaches
00:46:42top dead
00:46:43center
00:46:43into
00:46:44random
00:46:44turbulence.
00:46:45And there
00:46:46are some
00:46:46wonderful
00:46:47visualizations
00:46:48of what
00:46:48this
00:46:49turbulence
00:46:49looks like.
00:46:51it looks
00:46:52like cotton
00:46:52candy that
00:46:53is being
00:46:54pressed flat,
00:46:55you know,
00:46:55that kind
00:46:56that's
00:46:56wiggly,
00:46:57wiggly.
00:46:59Very
00:47:00deeply
00:47:00wrinkled
00:47:01flame
00:47:02fronts.
00:47:02Now,
00:47:03the flame
00:47:03doesn't go
00:47:04crackle,
00:47:05crackle,
00:47:05from the
00:47:06spark plug
00:47:07out to
00:47:07the cylinder
00:47:08wall.
00:47:08Instead,
00:47:09what's
00:47:09happening
00:47:10is that
00:47:11violent
00:47:11motion
00:47:12shreds
00:47:13the original
00:47:13flame
00:47:14kernel
00:47:14into
00:47:15pieces
00:47:16that are
00:47:17burning
00:47:17and carries
00:47:18them in
00:47:18random
00:47:19directions
00:47:21to all
00:47:22parts of
00:47:22the chamber
00:47:23so that
00:47:24the resulting
00:47:26area of
00:47:27flame is
00:47:27so great
00:47:28that the
00:47:30chamber
00:47:30burns in
00:47:31a reasonable
00:47:32length of
00:47:32time.
00:47:33If you
00:47:34turn that
00:47:34into a
00:47:35flame
00:47:36velocity,
00:47:37which you
00:47:37can do
00:47:38with simple
00:47:38arithmetic,
00:47:39how far
00:47:39is it
00:47:40from the
00:47:40spark plug
00:47:40to the
00:47:41cylinder
00:47:41wall,
00:47:42how fast
00:47:43is the
00:47:43engine
00:47:43turning,
00:47:44et cetera,
00:47:45you find
00:47:46that the
00:47:47velocity is
00:47:48from 50
00:47:49to 200
00:47:50feet per
00:47:51second
00:47:53flame
00:47:53velocity.
00:47:54People refer
00:47:55to this
00:47:56as an
00:47:57explosion.
00:47:59If you
00:47:59were trying
00:48:00to do
00:48:02surface
00:48:02mining
00:48:04using that
00:48:05kind of
00:48:05an explosive,
00:48:06you would
00:48:07wait a long
00:48:07time for
00:48:08your paycheck
00:48:08because that
00:48:10is not
00:48:11an explosion.
00:48:12But if
00:48:13you get
00:48:14serious
00:48:15and get
00:48:16to high
00:48:16explosives
00:48:17like RDX
00:48:18or PETN,
00:48:20hmm,
00:48:21what is the
00:48:22flame velocity?
00:48:24Rather, I
00:48:24should say
00:48:25reaction
00:48:26velocity because
00:48:27what's happening
00:48:27is the
00:48:28molecules contain
00:48:29both the
00:48:30fuel and the
00:48:31oxidizer and
00:48:31if you
00:48:32jostle it
00:48:33hard enough,
00:48:34they fly
00:48:35into each
00:48:36other's arms
00:48:37and are
00:48:38burned up
00:48:39in an
00:48:39instant.
00:48:4030,000
00:48:41feet per
00:48:42second.
00:48:47Speed of
00:48:48sound is
00:48:481,125
00:48:49feet per
00:48:50second.
00:48:51That's the
00:48:51speed.
00:48:52So, like
00:48:54nothing.
00:48:55So,
00:48:58just one
00:48:59of those
00:48:59things.
00:49:00Anyway,
00:49:01how did
00:49:02they know
00:49:02they had
00:49:02got the
00:49:03amount,
00:49:03how did
00:49:04Ducati
00:49:04know that
00:49:04they had
00:49:05the amount
00:49:05of turbulence
00:49:06that they
00:49:06desired?
00:49:07because they
00:49:10put an
00:49:10anemometer
00:49:11like device,
00:49:12you can see
00:49:13them on the
00:49:13tops of all
00:49:14the tractor
00:49:16trailer rigs
00:49:17at the
00:49:18drag race
00:49:19nationals.
00:49:20They're up
00:49:20there whirling
00:49:21around telling
00:49:22them the
00:49:22wind speed.
00:49:24They all
00:49:25need to know
00:49:25it.
00:49:27Anyway, this
00:49:28thing is inside
00:49:28the cylinder
00:49:29and if they
00:49:31have through
00:49:32experience,
00:49:33and they
00:49:34got plenty
00:49:35of experience
00:49:36because during
00:49:36the time
00:49:37they ran
00:49:38V-Twins
00:49:39in World
00:49:39Superbike,
00:49:40they changed
00:49:40the boring
00:49:41stroke like
00:49:41every 10
00:49:42minutes.
00:49:43It just
00:49:44seemed like
00:49:44they were
00:49:45up, down,
00:49:45and around.
00:49:47So, and
00:49:48every time
00:49:49they made
00:49:49those engines
00:49:50different,
00:49:51they remained
00:49:53notably powerful.
00:49:56They didn't
00:49:56always win the
00:49:57championship,
00:49:58but they
00:49:59always came
00:49:59close.
00:50:00So,
00:50:02the anemometer
00:50:04in the
00:50:04cylinder,
00:50:05nowadays it
00:50:06would be
00:50:06done with
00:50:07digital
00:50:08simulation.
00:50:09That told
00:50:10them how
00:50:10far away
00:50:11they were
00:50:12from the
00:50:14condition that
00:50:15they had
00:50:15found by
00:50:16previous
00:50:16experience to
00:50:17be successful.
00:50:19And this
00:50:20leaves us
00:50:21with the
00:50:22question,
00:50:23did the
00:50:25Japanese
00:50:25manufacturers
00:50:26just look
00:50:27at Duckworth's
00:50:29DFE and
00:50:29say,
00:50:30oh,
00:50:3132 degrees
00:50:32of downdraft
00:50:33angle, we can
00:50:33do better than
00:50:34that, here's
00:50:3550, and
00:50:39end up
00:50:40off the
00:50:41map, or
00:50:43at least
00:50:44near the
00:50:44edge, so
00:50:45that one
00:50:47manufacturer had
00:50:48to go back
00:50:49to the
00:50:49previous
00:50:49longer
00:50:50stroke, and
00:50:52the other
00:50:52took them
00:50:53two years
00:50:54to equal the
00:50:55performance of
00:50:56the previous
00:50:56longer
00:50:57stroke.
00:50:58And, here's
00:51:00another
00:51:00example.
00:51:03I'm giving
00:51:04these examples
00:51:05so that to
00:51:06disabuse us
00:51:08all of the
00:51:10pretend
00:51:11principle that
00:51:13shorter
00:51:13strokes, bigger
00:51:15bores, bigger
00:51:15valves, higher
00:51:16RPM, always
00:51:17win.
00:51:18How did
00:51:20Kawasaki, with
00:51:21the longest
00:51:23stroke in
00:51:24world super
00:51:24bike, 55
00:51:25millimeters, win
00:51:28six championships
00:51:30in a row?
00:51:34It could
00:51:35be, on
00:51:37the one
00:51:37hand, you
00:51:37could say,
00:51:38well, they
00:51:38got to know
00:51:39their engine
00:51:40really well, and
00:51:41the other
00:51:41companies were
00:51:42constantly changing
00:51:43things, and
00:51:44well, Ducati
00:51:44got away with
00:51:45changing
00:51:45things.
00:51:50So, to
00:51:51me, it
00:51:52looks as
00:51:52though that
00:51:55was Kawasaki's
00:51:56compromise, where
00:51:57old Steve
00:51:58Johnson was
00:51:59having to
00:52:00build his
00:52:00FZR 750
00:52:02one way for
00:52:04a track that
00:52:05emphasized
00:52:06acceleration and
00:52:07changed the
00:52:09combustion
00:52:09chamber shape
00:52:10for a high
00:52:12speed track
00:52:12that Ducati
00:52:16employed the
00:52:16scientific method
00:52:17to devise
00:52:19combustion
00:52:21systems that
00:52:22worked.
00:52:24I recommend
00:52:26it.
00:52:26Experiment.
00:52:29Thoughtful
00:52:30consideration of
00:52:31results.
00:52:33It reminds me
00:52:34of looking for
00:52:35the sweet spot
00:52:36all the time,
00:52:37and we had a
00:52:39podcast about
00:52:40sweet running
00:52:41engines and
00:52:41what makes an
00:52:42engine work
00:52:43and not
00:52:44work.
00:52:44I don't
00:52:45know, you
00:52:46were talking
00:52:46about longer
00:52:48stroke, the
00:52:49GSXR 1000, the
00:52:50K5, the
00:52:522005, that
00:52:54era had a
00:52:54longer stroke,
00:52:55and there is
00:52:57something really
00:52:57great about that
00:52:59era engine, and
00:53:00I don't know
00:53:00is it going to
00:53:02make the peak
00:53:02power that the
00:53:03current 1000 is
00:53:04making in a
00:53:05full race
00:53:05application?
00:53:06Maybe, maybe
00:53:07not.
00:53:08I'm a street
00:53:08guy mostly.
00:53:10I like my
00:53:10Norton
00:53:11commando.
00:53:11Why?
00:53:13Because it
00:53:13lights at 28
00:53:14degrees, meaning
00:53:15it has a short
00:53:16ignition timing, so
00:53:17it's mixing well,
00:53:18the chamber's a
00:53:19good shape, and
00:53:21reduced heat
00:53:21loss, and it
00:53:22just feels good.
00:53:23It's 45, I
00:53:24think I downed
00:53:25it at 45
00:53:26foot-pounds at
00:53:27the rear wheel,
00:53:29and it's
00:53:30wonderful indeed.
00:53:31You know, it
00:53:32isn't as much
00:53:33torque as a
00:53:35Sportster 1200,
00:53:36but it's
00:53:37wonderful and
00:53:39sweet, and
00:53:39when you talk
00:53:40about optimizing
00:53:41the intake
00:53:42angle and
00:53:43getting great
00:53:44filling and
00:53:46rapid combustion
00:53:47and quick
00:53:47mixing, it
00:53:51reminds me of
00:53:53looking for
00:53:54those sweet
00:53:54spots and how
00:53:55hard, you
00:53:56know, companies
00:53:56are, I
00:53:58don't know, you
00:53:59talked about
00:53:59downdraft, I
00:54:00think back to
00:54:01the FZ series,
00:54:02the Yamahas,
00:54:03where they just
00:54:03kept going more
00:54:04and more, and
00:54:04they were
00:54:05represented, the
00:54:06FZ, um,
00:54:09the phaser, the
00:54:11phaser had this
00:54:11representation of,
00:54:14of, of intake
00:54:16angle on it, and
00:54:16this, like, sort
00:54:17of scoop-like
00:54:18thing, and it's
00:54:18just coming,
00:54:19ramming it down
00:54:20into the, into
00:54:21the engine, you
00:54:22know, and, um,
00:54:25it's interesting
00:54:26everything we try,
00:54:27where, where, where
00:54:28was the data, you
00:54:29know, what, I, I
00:54:31want to see into
00:54:32this process, I
00:54:33want to see into
00:54:34Ducati's process, and
00:54:35I want to go back
00:54:36and, and find the
00:54:38exact moment at
00:54:39Yamaha where
00:54:40somebody absolutely
00:54:42insisted we do a
00:54:43five valve and
00:54:44absolutely insisted
00:54:45that we make the
00:54:46intake incredibly
00:54:47steep because it's
00:54:48just going to go
00:54:49blam, it's not,
00:54:50doesn't have to go
00:54:51around the corner and
00:54:52get into the intake,
00:54:52it's just going to
00:54:53go like this and
00:54:56shoot straight in,
00:54:57you know?
00:54:58Well, this was
00:54:59another of, uh,
00:55:01Duckworth's comments.
00:55:02Duckworth thought he
00:55:03was, uh, pretty
00:55:05cool guy.
00:55:06Uh, he said, um,
00:55:09in this world, people
00:55:10divide in roughly
00:55:12into two camps, the
00:55:14dull, intelligent,
00:55:17and the clever, but
00:55:19lazy.
00:55:20I happen to be
00:55:22clever and
00:55:24diligent, and he
00:55:27made direct
00:55:28statements such
00:55:29as, I can get
00:55:31more air into a
00:55:32cylinder with my
00:55:34finger than those
00:55:36people across the
00:55:38English channel, he
00:55:39was probably speaking
00:55:40of Matra and
00:55:42their V12s, then
00:55:43they can get into
00:55:44their cylinders with
00:55:45all their flow
00:55:46measuring equipment.
00:55:48Basically, he was
00:55:49saying, I have the
00:55:51experience to know
00:55:52what works, and
00:55:53these fellows over
00:55:54there are masters
00:55:57of what ought to
00:55:58work.
00:56:01So, uh, I want to
00:56:03just append something
00:56:05about the, the
00:56:07hemi, uh, combustion
00:56:09chamber and the
00:56:10great flow that it
00:56:11can produce, which
00:56:13is that, uh, going
00:56:16back to the old
00:56:17business of putting, um,
00:56:20a cylinder head and
00:56:21on the flow bench
00:56:22and blowing air
00:56:23through open
00:56:24exhaust valves and
00:56:25out the port.
00:56:26And you set it up
00:56:28so you have 12
00:56:28inches of pressure,
00:56:30water pressure
00:56:30difference across
00:56:31the port, and it's
00:56:33blowing a certain
00:56:33number of CFM.
00:56:35and you take a
00:56:37piece of paper and
00:56:39roll it up into a
00:56:41cone shape, cut it
00:56:43off so that it just
00:56:45barely fits in the
00:56:46hole and the flow
00:56:46goes up 30%.
00:56:49How can that
00:56:50be?
00:56:52Well, Bernoulli
00:56:54observed, he did not
00:56:57enact a law called
00:56:58Bernoulli's law.
00:56:59He observed that
00:57:01moving air has a
00:57:02lower pressure than
00:57:04stationary air, and
00:57:06there's a good reason
00:57:07for that.
00:57:08In stationary air, the
00:57:09molecules are going in
00:57:10all different directions.
00:57:11They're not all going
00:57:12in one direction.
00:57:13When you, when you
00:57:15put the air into
00:57:16motion, a lot of
00:57:17that random motion
00:57:19now becomes organized
00:57:20motion, so there's
00:57:22less pressure.
00:57:25Anyway, uh, how
00:57:28could the flow go up
00:57:2930% just by sticking
00:57:30some paper cone in
00:57:32the hole?
00:57:33Goes up because the
00:57:36low pressure in the
00:57:37jet coming out of, the
00:57:39jet of air coming out
00:57:40of the exhaust port is
00:57:41being pinched from all
00:57:42sides by the
00:57:44atmosphere.
00:57:45It's throttling it
00:57:47down.
00:57:48And when you put the
00:57:50cone on there, it
00:57:51causes, it allows the
00:57:53air to slow down and
00:57:55recover its pressure
00:57:56without being pinched
00:57:59by the surrounding
00:58:00stationary air.
00:58:02Well, the, the
00:58:05hemi shape of the
00:58:06combustion chamber with
00:58:07the intake valve in it,
00:58:09when the flow comes out
00:58:10of the valve, it can
00:58:11immediately attach to
00:58:13that curved shape and
00:58:15travel a distance and
00:58:17make a gradual
00:58:18transition from high
00:58:19velocity to pressure.
00:58:22diffuser, it is
00:58:23diffused.
00:58:25The head surface is
00:58:27acting as a diffuser,
00:58:28which the rolled up
00:58:29paper cone is also a
00:58:31diffuser.
00:58:33So this is, this is, um,
00:58:37a wonderful thing about
00:58:38that particular deal is
00:58:40the high specific flow
00:58:42that you can get if your
00:58:43valve is surrounded by
00:58:44this nice curvature so the
00:58:47flow attaches to it.
00:58:49So, um, there's
00:58:55always more to say, but
00:58:56there isn't always more
00:58:57time.
00:58:58What are we going to do?
00:59:00Well, I just wanted to
00:59:01point out Kevin's, um,
00:59:03fun with buckets and, uh,
00:59:05get your hose and get
00:59:07your car wash bucket or
00:59:08your garden bucket.
00:59:09Don't use the garden
00:59:10bucket to wash your car,
00:59:12but, uh, take your bucket
00:59:13and get your hose and
00:59:15pretend that that's the
00:59:16intake port and, um,
00:59:18shoot it at the wall and
00:59:21watch it swirl around.
00:59:23And that's why the intake
00:59:24port is offset.
00:59:25You know, the hose is
00:59:26coming in at an angle and
00:59:27it goes, and you get your
00:59:29swirl and then you can
00:59:30aim it in to the water and
00:59:32you can watch the thing
00:59:33just roll and roll, you
00:59:35know?
00:59:36So just do that.
00:59:37Make these observations.
00:59:38Kevin's always, um, he's
00:59:40always been fond of putting
00:59:42cream into your tea or
00:59:44your coffee and pouring
00:59:45it in and watching it
00:59:46tumble and visualizing
00:59:48that as, uh, as the
00:59:51mixture getting itself
00:59:52I think about every time
00:59:53I pour the white liquid
00:59:55into the dark liquid.
00:59:56And I think, um, I, I
00:59:58think a manner of
00:59:59thinking is what this is.
01:00:00Kevin is a manner of
01:00:02thinking is constantly
01:00:05analogizing your obsession,
01:00:06which is internal
01:00:07combustion, analogizing it
01:00:10to everything else in
01:00:11life.
01:00:11I need treatment.
01:00:12Well, of course, don't
01:00:15we all, we all need
01:00:15treatment.
01:00:16The treatment is more
01:00:17horsepower.
01:00:18Yes.
01:00:19I got a fever and the
01:00:20only cure is more
01:00:21horsepower.
01:00:22That's right.
01:00:23It doesn't come in a
01:00:24pill.
01:00:26Anyway, um, the boar
01:00:31stroke thing can get you
01:00:32into trouble.
01:00:33You can go so far
01:00:34towards big boar, short
01:00:36stroke, that you can't
01:00:38burn the chamber.
01:00:39And this was another
01:00:40thing that Duckworth
01:00:41said.
01:00:41He said, those
01:00:43people, there are
01:00:45people in this
01:00:45business, i.e.
01:00:47Formula One, who can
01:00:49do a wonderful job of
01:00:51filling the cylinder, but
01:00:52they can't burn it once
01:00:54they've captured it.
01:00:55They don't know what it
01:00:57takes to burn it.
01:00:58And what it takes is
01:01:00vigorous, random
01:01:01turbulence that can
01:01:04distribute the flame
01:01:05throughout the chamber in
01:01:07such a way that it
01:01:08quickly eats up all the
01:01:10unburned charge.
01:01:11The pressure goes up, the
01:01:13piston goes down.
01:01:15If all goes well, a
01:01:19good result.
01:01:22So that's how it
01:01:25goes.
01:01:28Actually understand the
01:01:30things that you're doing.
01:01:31Don't just say, this
01:01:32looks a lot like that, so
01:01:34it ought to work like
01:01:35that.
01:01:35Instead, you have to
01:01:37understand why the
01:01:39example works.
01:01:41And that's where Ducati's
01:01:43scientific method, what
01:01:44intake velocity, what
01:01:51tumble RPM, measure the
01:01:55things, find out what
01:01:57works.
01:01:58And then in your new
01:01:59design, you'll be able
01:02:01to start out with
01:02:02something that is close
01:02:04at least, rather than
01:02:06just, I like that intake
01:02:08downdraft angle.
01:02:09That looks cool.
01:02:11Yeah.
01:02:12I guess when you're
01:02:14Ducati and you're a big
01:02:16company, you can invest in
01:02:17all of your instruments and
01:02:18do all of those things.
01:02:20They showed me the rig.
01:02:21They showed me the rig.
01:02:23It was just a lot of
01:02:24junk, but it was a rig
01:02:27that worked.
01:02:27It got numbers for them
01:02:29so that they could say,
01:02:31ah, now we know what it
01:02:32takes.
01:02:34So when you're a backyard
01:02:35guy like me, everything is
01:02:37by analogy.
01:02:38Everything is by saying,
01:02:41well, that works over
01:02:41there, so I'm going to try
01:02:43this here.
01:02:43If I see that exhaust
01:02:44system and somebody
01:02:46messed with that, and I
01:02:47might look at the cam
01:02:48timings and say, what's
01:02:49the port like?
01:02:50And how big should those
01:02:52primary tubes be anyways?
01:02:54Is bigger always better?
01:02:56Not always.
01:02:57In fact, you know, if you
01:02:59watch enough videos on
01:03:00YouTube, you may learn
01:03:02something or you may learn
01:03:03the wrong thing.
01:03:04Who knows?
01:03:05One of the strong tuning
01:03:10guys got a Buell and they
01:03:14looked at the head.
01:03:15He looked at the headers
01:03:16on it.
01:03:16Those things are way too
01:03:17big.
01:03:18That can't work at all.
01:03:19So they made a complete
01:03:22other set of headers and
01:03:24lost 16 horsepower.
01:03:28Because they didn't like
01:03:29the look of it.
01:03:31Well, it's nice to, if
01:03:34wetting your finger and
01:03:36holding it up to see which
01:03:37way and how fast the wind
01:03:38blows is enough, but it
01:03:40isn't always enough.
01:03:43And so often Ducati have
01:03:46improvised.
01:03:47For example, they have
01:03:48their chassis beater, which
01:03:50is a dreadful machine.
01:03:52It has an electric motor
01:03:53driving a rotating lump and
01:03:57it beats the living daylights
01:03:59out of a motorcycle's
01:04:00suspension.
01:04:01They clamp the motorcycle in
01:04:03place, turn on the machine
01:04:05and go to lunch and come back
01:04:06and everything is broken.
01:04:09You need to know if that's
01:04:11going to happen on the
01:04:12street.
01:04:13Yeah, no, I saw it at
01:04:14Aprilia.
01:04:15I saw a similar rig.
01:04:16They were doing a chassis
01:04:17test.
01:04:18It was essentially, it was
01:04:21like a treadmill that
01:04:23somebody screwed a four by
01:04:24four onto the belt.
01:04:26Oh, that would go.
01:04:27Yeah.
01:04:29And it just kept coming
01:04:30around and that thing had
01:04:32wires all over it and it was
01:04:33just getting the daylights
01:04:34beat out of it.
01:04:35It was awesome.
01:04:36It's a fun tour.
01:04:37That was, uh, what was
01:04:38that around 2003 to that was
01:04:42part of the trip to Mugello
01:04:43with the, um, the, uh,
01:04:44Miele, uh, V twin, the, uh,
01:04:48factory version we, we
01:04:49rode around Mugello and as
01:04:51Italians often do, they
01:04:52secretly put transponders on
01:04:54the, uh, bikes.
01:04:56No one knew, but they were,
01:04:58um, they were giving awards
01:04:59that night to, uh, the people
01:05:01who set the fastest laps and
01:05:02so forth.
01:05:03And luckily I, luckily I beat
01:05:05one of my colleagues by, you
01:05:07zero one seven or zero zero
01:05:09one seven.
01:05:11So I never let them live it
01:05:13down.
01:05:16Well, I think what you said,
01:05:18um, um, the key to all this is
01:05:20not some magic formula like long
01:05:21strokes make big torque or
01:05:23ultra revs make killer power.
01:05:25Or it is careful designed aimed
01:05:27achieving specific results aimed
01:05:30at a specific result tailored to
01:05:34what you're trying to achieve.
01:05:36And that's different from just
01:05:38saying, we're going to make
01:05:39beaucoup power here.
01:05:40Watch this.
01:05:41Hold my beer.
01:05:44Um, well, that's, that's a, a, a,
01:05:49a formula too.
01:05:51So we're breaking our own rule
01:05:52here, but, uh, you get, you get
01:05:56the, the gist of it.
01:05:58I'm sure.
01:05:59I hope.
01:06:00Oh, I'm, I'm into the gist
01:06:02Kevin, of course.
01:06:03So I'm here.
01:06:04Well, thanks for listening folks.
01:06:05Join us on Patreon.
01:06:06That's where we do it all
01:06:07commercial free.
01:06:08And we do some, uh, extra,
01:06:10extra short form stuff.
01:06:11We will, we, you know, I
01:06:12promised we would talk about
01:06:13rods.
01:06:14We'll make that into a short
01:06:16form and we'll throw that up on
01:06:17Patreon and I'll get my
01:06:19collection of connecting rods
01:06:20together.
01:06:21I don't have an H beam
01:06:22Carrillo rod, you know,
01:06:24something beautiful CP
01:06:26Carrillo.
01:06:27Now I don't have one of those
01:06:28because I installed all of
01:06:30those, but okay.
01:06:31Kevin's Kevin's going to bring
01:06:32one.
01:06:33I will, I will find my, um,
01:06:36Vance and Heinz drag bike
01:06:37gigantic connecting rod that
01:06:39they gave to us to photograph
01:06:41in the studio.
01:06:42I'll bring in those valves too.
01:06:43And we'll have a regular tiny
01:06:45valves and big valves and
01:06:47connecting rods.
01:06:48And we'll do a show and tell
01:06:49on, uh, on that one, Kevin.
01:06:51How's that sound?
01:06:52Live it up.
01:06:53It'll be fun.
01:06:56The rod show.
01:06:58The rod show.
01:06:59The rod show.
01:07:01Join us.
01:07:02We'll even, maybe I'll get a
01:07:03scale.
01:07:04I don't have a, do you have a
01:07:05titanium rod?
01:07:06No, I don't.
01:07:08I don't, I don't have a
01:07:09titanium rod.
01:07:10We used to have one in the
01:07:11collection and it disappeared,
01:07:14but, uh,
01:07:16well, we can just do the
01:07:17math.
01:07:18We can measure what we'll do.
01:07:19Kevin is we'll weigh a steel
01:07:20rod and then we'll just
01:07:22calculate the percentage mass
01:07:23of titanium off of it.
01:07:25And then we'll know, but the
01:07:27dimensions might be different
01:07:28because the dimensions have to
01:07:30be different because the
01:07:31material is different.
01:07:32See, we're already doing the
01:07:32podcast.
01:07:34Yeah.
01:07:34Let's just go have lunch.
01:07:36Thanks everyone.
01:07:37We'll see you next time.
01:07:38Yep.
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