increase engine power

[Hawk]

330BHP does sound like an absolute untamed beast for any road racing bike never mind a 2 stroke. I doubt even with modern electronics and tyres it would allow for the full practical use of that power without major technical problems never mind a riders ability to be able to handle that power sensibly and safely? What's possible on paper doesn't always transfer onto the track. 

Even Rossi had the BHP of his last Honda NSR 2 stroke 500 dumbed down from 210 down to 198BHP if I remember rightly.... It was just too much power for the bikes of the time. I've no doubt with modern tyres and electronics it would be feasible to handle the same BHP that the 4 stroke MotoGP bikes have nowadays, but to be honest I think they have found there sensible limits today for todays technology, otherwise I'm sure the factories could easily increase the BHP on todays MotoGP bikes, yet they have not done so.... So what does that tell you? 

Hawk.

[Vini]

330hp would be the "theoretical"/impossible value.
300hp is only 25-30hp more than current MotoGP bikes. I don't think that difference will make the bike untamable.

True but back then they had to find a compromise between power and ridability, which is not necessary when you have AW and TC.


...I'm pretty sure the factories would increase the power if they could. Honda and Yamaha most probably do not like seeing the Duc pull away on every straight. ~68hp for one 250cc 4T cylinder is already pretty crazy. F1 only managed to get ~10hp more in the V10 days which of course is unattainable for an extremely compact 4 cylinder motorcycle.

[Hawk]

330hp would be the "theoretical"/impossible value.
300hp is only 25-30hp more than current MotoGP bikes. I don't think that difference will make the bike untamable.

That just depends on how close they are to current technology  limits. 25 - 30hp is a pretty big jump. You'd certainly notice the extra power in a big way put it that way. 

True but back then they had to find a compromise between power and ridability, which is not necessary when you have AW and TC.

Very true too.... and thank you for pointing out that modern MotoGP bikes are a lot easier to ride now than the old school 500GP bikes.... Totally agree with you on that. 

...I'm pretty sure the factories would increase the power if they could. Honda and Yamaha most probably do not like seeing the Duc pull away on every straight. ~68hp for one 250cc 4T cylinder is already pretty crazy. F1 only managed to get ~10hp more in the V10 days which of course is unattainable for an extremely compact 4 cylinder motorcycle.

Yes.... the other factories were caught with their pants down on that one for sure. Lol
Will be interesting to see Honda, Yamaha, and Suzuki's response for next year. 

But overall I'll be interested to see what you can come-up with this bike your creating. 

Hawk.

[HornetMaX]

...I'm pretty sure the factories would increase the power if they could. Honda and Yamaha most probably do not like seeing the Duc pull away on every straight.

As far as they (duc) finish behind in all the races (which is the case at the moment), I don't think Honda and Yam will bother too much: champagne and pretty girl are for the one that finishes 1st, not the one that is fastest on the straight

[Vini]

true but that's just because the bike turns like shit (lacks apex speed) due to the inferior chassis (that does not give enough flex and feedback) not because the Duc has "too much power".
if that were the case they would have trouble getting the power down out of corners (inferior acceleration) which is definitely not the case, compared to the other bikes.
plus, don't forget that the electronics also manage to tame the bikes enough to make them ridable in the wet!

[HornetMaX]

Never said they have too much power. Just that raw power is not everything that matters, there's plenty more that matters, including, as pointed out by Hawk, rideability.

[Vini]

of course.
it would take a lot of testing and tweaking of the chassis to get the bike to compete with MotoGP bikes in terms of handling, specifically the swingarm.

those are just details, though, the potential is there. less (rotating and overall) mass and better weight distribution than a 4T inline-4 should mean better handling in theory. given enough time and money, it should be possible to modify the chassis so that it can utilize that potential.

edit: in real life, a gp800 chassis might be the best choice.

[h106frp]

Amazing what you find looking st used bike ads. 


http://www.ebay.co.uk/itm/Yamaha-TZ1500-V8-TZ750-Dragster-racing-motorcycle-SUPER-sprint-Bike-race-Vintage-/112081316143?hash=item1a1891292f:g:RGYAAOSwZ1BXfNES

TZ1500 V8 - for a tuned 2T drag build it surprisingly only generates 280BHP and needs nitrous to get 520BHP

As Max noted - the exhaust requirement even for 4 cylinders is huge

£28,500 and only just down the road - do you think they are up for test rides? 

I suspect that scaling a 2T piston ported cylinder may be a case of diminishing returns due to port heights/stroke and available cylinder wall area - has anybody plotted cylinder capacity vs HP ?You may end up going down the Honda route of numerous tiny cylinders to build a large capacity 300bhp engine

[Vini]

lol nice find!

TZ1500 V8 - for a tuned 2T drag build it surprisingly only generates 280BHP and needs nitrous to get 520BHP

As Max noted - the exhaust requirement even for 4 cylinders is huge

£28,500 and only just down the road - do you think they are up for test rides? 

I suspect that scaling a 2T piston ported cylinder may be a case of diminishing returns due to port heights/stroke and available cylinder wall area - has anybody plotted cylinder capacity vs HP ?You may end up going down the Honda route of numerous tiny cylinders to build a large capacity 300bhp engine

Yes, I have done plenty of research on this kind of stuff (got most of this information from the Aprilia RSA 125 builder himself) and scaling a two-stroke cylinder from 125 to 150cc still works quite well (again, I already took into account the losses, 55*150/125 would be 66hp per cylinder).
I'm not ignoring that two-stroke exhausts require much more space (note: not much more weight) but five would definitely fit if that one guy fit six on a GP500 V4 chassis (and Suter had no problems fitting the regular four on a Moto2 chassis).
The engine in that drag bike consists of two 40 years old Yamaha TZ750 engines welded together. It makes no sense to compare this to modern two-strokes. Even if you were to put 55hp kart cylinders on the engine, you would not get more power out of it because the crankcase is simply not capable of getting enough air to the combustion chamber. It's the same problem RGV500 replica builders have with the RG500 engine (even worse is the Yamaha RD500 crankcase with it's tiny transfer and intake ports).

[HornetMaX]

I'm not ignoring that two-stroke exhausts require much more space (note: not much more weight) but five would definitely fit if that one guy fit six on a GP500 V4 chassis (and Suter had no problems fitting the regular four on a Moto2 chassis).

The problem is not really the number of cylinders but the total displacement: your 750cc is 50% more of a 500cc.

[Vini]

yeah, which means one more pipe, so three under the bottom of the bike instead of the traditional two. it's possible to fit four under a regular 500 V4 chassis with some clever intertwining as the "RG750 Delta" proves. as i wrote earlier, the size difference between 125cc and 150cc exhaust pipes is negligible (a comparison between the Suter MMX in the 500cc and 580cc version would show this nicely) and if this was actually the deciding factor, you could increase the bore slightly and end up with no increase in exhaust pipe size at all.

[HornetMaX]

Well yes, if you say you can fit one more pipe piece of cake and 125->150 makes no difference then ok, everything is possible. Why not make it a 900cc v6 then ? Just increase the bore, fit an extra pipe, job done

[Vini]

come on max, you obviously can fit one more pipe, otherwise that guy would not have been able to fit SIX into a V4 chassis.
and if you tune the engine/exhaust to a different rpm you can keep the exact same 125cc exhaust pipes.

[HornetMaX]

You can fit 4 more if you can make them smaller.

[Vini]

then you would need extreme overbore ratio which would kill the efficiency (power per capacity) of a 2T.