Top Fuel bike engine
Top Fuel bike engine
(OP)
Designing a V4 2500cc, OHC 4 valve engine based on the yamaha VMAX engine. Target is 1000HP @ 9500rpm!supercharged, nos, running ELF race fuel. Help me out with the right bore/stroke ratio, rod/stroke ratio, valve sizing, etc. Very interested to hear your results





RE: Top Fuel bike engine
The best bore is the largest that retains sufficient strength to minimise blow by and retain structural integrity under maximum cylinder pressure.
The correct stroke is the longest that retains enough structural integrity and piston speed to endure the rpm you will use.
The correct rod to stroke ratio is very likely the longest you can fit in without compromising the ring lands.
The correct valve size is that which gives the highest airflow when the effects of shrouding from cylinder wall and valve to valve spacing are considered.
The flow ratio of inlet to exhaust should be less biased against the exhaust than for NA petrol engines due to the extra volume of exhaust to air. As far as I know, exhaust flowing about 80% of inlet is considered normal for top fuel.
Regards
Pat
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RE: Top Fuel bike engine
RE: Top Fuel bike engine
Valve size should be in the order of 39 to 40mm inlets and 35 to 36mm exhausts
Regards
Pat
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RE: Top Fuel bike engine
RE: Top Fuel bike engine
You did notice this is an engineering tips website?
RE: Top Fuel bike engine
RE: Top Fuel bike engine
RE: Top Fuel bike engine
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Ya gotta give us racers enough credit to distinguish most of the really impossible goals.
Rod
RE: Top Fuel bike engine
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Rod
RE: Top Fuel bike engine
RE: Top Fuel bike engine
I know this kind of power is very achievable.
So if it's a clean piece of paper on the drawing board, why are you staying with a vee configuration? Why not go rotary (3 cylinder w/master rod ala aero engine) or 4 opposed?
RE: Top Fuel bike engine
RE: Top Fuel bike engine
RE: Top Fuel bike engine
RE: Top Fuel bike engine
Rod
RE: Top Fuel bike engine
Finding somebody loony enough to aim it would probably be more difficult! I hesitate to use the verb "ride" for a machine like that.
RE: Top Fuel bike engine
Take away the forced induction, and make the engine run on pump gasoline, and make it have to produce that power output for an extended period of time, and the maximum BMEP goes down a lot.
RE: Top Fuel bike engine
I must admit I am still not quite clear with regards to just how clean the sheet is and what restrictions "based on" imposes.
Regards
Pat
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RE: Top Fuel bike engine
Regards
Pat
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RE: Top Fuel bike engine
In fact it is pretty much the opposite - which is why it was used for anti-detonation purposes in F1. As far as being toxic - it is reasonably safe to handle - far less dangerous than its cousin benzene for instance.
The 1300HP from 1.5l is a temarkable figure (- I have even seen 1500HP mentioned) from non-oxygen bearing, hydrocarbon-only fuel. The power per litre is similar to that claimed by nitro-fuelled drag cars.
RE: Top Fuel bike engine
RE: Top Fuel bike engine
The term pilot seems more fitting than rider and being a little nuts does help. The harley motors are the most common, due to the large bores needed to get the capacity it is very hard to ignite the quantity of fuel needed. Keeping in mind that nitromethane carries its own oxygen. Magneto's and twin plugs per cylinder still cant keep up.
Yes the BMW F1 engine was around the 1500HP mark, was a wild fuel that would burn you eyes while still in the drum! That was using the cast iron road car block, they found them to be best after 200,000km of use, with enough heat and compression cycles to settle the casting.
Impossible? That is what NASA said about propelling a rubber tyred vechile under the 6 second mark. Now they are in the mid 4's
Top Fuel engines are producing 1000 HP per litre, with restricted nitro content and limits on blower overdrive.
RE: Top Fuel bike engine
RE: Top Fuel bike engine
RE: Top Fuel bike engine
The valve size is about the same as a Honda S2000 scaled up to 4" bore with a slightly larger exhaust valve.
For cam I would copy the S2000 vtec engaged cam, add ten degrees of duration and increase lift in proportion to valve size and add another 0.75 mm of lift.
Rod length of 6" with the 3" stroke.
Regards
Pat
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RE: Top Fuel bike engine
RE: Top Fuel bike engine
Actually toluene releases only about 3/4 the energy on combustion (3730 kJ/mol) of basic hydrocarbon fuels like heptane (4850 kJ/mol), and much less than isooctane (5450 kJ/mol). Hydrazine is much higher still (6,300 kJ/mol), making it especially attractive when bang/pound is at a premium.
BTW, nitromethane releases a measley 709 kJ/mol, so obviously engine tuning has more to do with the final power results (as well as spectacle in a blowup) than fuel chemistry alone.
RE: Top Fuel bike engine
The Nitro deal is to cram as much fuel in the engine as possible because it brings so much oxygen that you can burn more nitro than gasoline per cycle. They inject so much nitro that is why the fuel engines "drop cylinders" during a run because they flood the cylinder and twin 45 amp mags still can't always ignite the liquid/air mixture. They use something like 8 gals. of nitro in a 1/4 mile run. It's insanity.
RE: Top Fuel bike engine
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Once upon a time...<smile>...I watched (from a distance) a couple of "top fuel" cars simultaneously "blow" while trying for that magical "nitro/hydrazine" mix. Pretty spectacular it was for sure. I think one of the blowers went into low orbit! NHRA outlawed ALL fuel cars for several years after that one.
Oh yeah, I'm still a "rabid naysayer" about that 600hp stock block nasp. Mopar on pump gas. I'm not holding my breath. Last weekend we were pitted next to a nice little 68 Camaro with a 383 Edelbrock. Owner claimed "500hp" on pump gas. Car was nice, I'm not convinced about the 500, though. He was a second and a half slower than our 197hp@8100 Lotus...In his behalf, we are about 800 lbs. lighter...Still, weight/power just doesn't match up.
Rod
RE: Top Fuel bike engine
RE: Top Fuel bike engine
Nitromethane typically runs at about 1.6: air to fuel ratio.
709 X 9 = 6381 which is substantially higher than isooctane per unit of air consumed.
Regards
Pat
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RE: Top Fuel bike engine
Hydrazine is not just a monopropellant, but it will decompose energetically if it gets hot enough, or encounters a catalyst. Releases heat, and combustible hydrogen/ammonia species as it does so.
From recollection, nitromethane is a "monopropellant" also, in that it well decompose energetically if given enough reason to do so.
I'd always thought maybe that was one of the reasons for using it, as a sort-of "backup" ignition system.
RE: Top Fuel bike engine
460hp is the highest power 383cu-in that Edelbrock makes and that's supposed to be a production run of 250 signature series engines with black valve covers with Vic's signature and a serial number engraved in them. The next 383cu-in is 408hp which is fuel injected with a LT1 looking intake. Edelbrock has some power packages but none of the SB ones give over 500hp either. So, he's either full of it or had an engine with some Edelbrock parts that actually was dyno'd to 500hp. That is doubtful too though since it seems that there are other manufacturer's to use if you actually want 500hp from a 383cu-in.
On another note, here's 1001hp out of a 433cu-in LSX engine.
http://
I doubt the technology you'd find in a stock block 360 the same as what that LSX engine is holding. I think the naysaying part of not believing the 600hp 360cu-in was the other post that also claimed a stock HEMI was something like 800rwhp.
RE: Top Fuel bike engine
And for power density lets not forget what Fueling did with the Qaud 4, though it was turboed I think.
RE: Top Fuel bike engine
I think the concerns for the OP is reliability and minimal operational issues? 1000 HP from 2500 cc on nitro is not really difficult at all. Building a mechanically strong engine that will last at that power level is a bit more of a challenge.
RE: Top Fuel bike engine
Get the e and u in the right place...
RE: Top Fuel bike engine
RE: Top Fuel bike engine
One of the vehicles I deal with maybe makes an honest 350hp. Small blower (144ci) on a mild 355, more of a street drivable noise generator than an actual all-out performance engine. The owner is advertising the vehicle for sale as making 900hp! I felt like taking our company-logo machined valve covers off of it out of embarassment.
RE: Top Fuel bike engine
I just doubt, based on the actual on track performance, that it was anywhere near that number.
I am truly one of the "rabid naysayers" when it comes to published hp numbers. At least by the mfgrs of the engines in question. Even the 197 of our latest 1600 is only a good talking point. I'm pretty sure I could make just about any number I needed on another dyno. I trust the 197 number only because of all the other engines that have come from this unit are pretty accurate, vis a vis, on track performance.
Still, using a dyno as a tuning tool is invaluable. Just don't get all wrapped up in big numbers.
Rod
RE: Top Fuel bike engine
We have SAE dyno Horseys which are few but strong. We have race engine builders with lots of tiny Horseys to make big numbers. We have magazine Horseys which you obtain by taking a un-SWAG and then multiplying that number by 1.5 to obtain California HP. Then we have chassis dyno "corrected" Horseys where you use as high a driveline loss correction factor as a really ignorant fanboy will believe. Then we have race track B.S. Horseys where you tell everyone that your stock block 350 CI engine with one 4-barrel makes 600 HP @ 8000 rpm even though the valves float at 6500 RPM.
Ya definitely need a scorecard if you're gonna talk horsepower, so you can tell the players, the liars and the damn liars.
RE: Top Fuel bike engine
Regards
Pat
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RE: Top Fuel bike engine
Don't forget to enter the driver variable into any on-track performance numbers. As Rod is well aware, the applicator of pedal to metal does make a difference. Even if the '68 Camaro did make 500 HP, just switching drivers could produce faster times.
Having played with a '69 Z/28 back when, horsepower numbers were for egos. Chassis set-up on early pony cars was where you could quietly make a real difference.
Yosh
RE: Top Fuel bike engine
I think that the 1989 SAE paper on the Honda F1 engine gives good, reliable numbers.
http
The summary (above link) doesn't give the power numbers that correspond to the 4 bar absolute manifold pressure setting, but I think I remember those numbers as 1100 bhp from a 1.5 liter engine.
I think Toluene (methyl benzene) was used for two purposes: 1. It has good knock resistance, and 2. It has a high volume specific energy, which fit well with the then current F1 fuel quantity rules.
Dick