Which bike engine? (250bhp+)

[robcollingridge]

Love the 2003 R1 engine in my Fisher Fury. If I was to ever replace my car, I'd want another full-bodied BEC that's lighter (so less than 450Kg, ideally less than 400Kg) but, with more power. To make it worthwhile I'd be after at least 250bhp and a decent torque curve to match.

What are the engine options? More revs (R1 is 11,750) is good, more weight isn't. It also needs to be road legal and pass IVA/MOT tests. Not sure if it's relevant but I think I'd build something mid-engined next time. Just how much power can you reliably put through a chain drive?

[Red16]

Those R1 revs you quote seem low, my ZX10R revs out at 13,500RPM.

Are you interested in turbo engines or staying with N/A?

Although they command a bit of a premium, the best bike engine imo for tuning is the Hayabusa.

Here's a 242bhp N/A engine for sale

http://www.pistonheads.com/sales/2942845.htm

If you want to turbo it, have a look at BigCC Racing's website, your budget is the limit, they habe an 800bhp kit available!

To give you an idea of turbo power/torque curves, here is my ZX10R turbo BEC graph, showing power and torque at the wheels, blue line 12psi, red line 8psi.

[Furyblade_Lee]

Rob, sub 400kgs?? Full bodied?? Road Legal?? You have got to go some mate, that really is pushing the envolope . I can understand road legal to qualify for a championship but to actually use it as a road car, you will have no creature comforts whatsoever! What is your plan for the car?

[jason61c]

250bhp is going some, it'll have to be blown or a highly strung big bore motor of some type.

[robcollingridge]

Furyblade_Lee said:

Rob, sub 400kgs?? Full bodied?? Road Legal?? You have got to go some mate, that really is pushing the envolope . I can understand road legal to qualify for a championship but to actually use it as a road car, you will have no creature comforts whatsoever! What is your plan for the car?

My Fisher Fury R1 is mainly used on the road, despite no reverse, windscreen, doors, etc. For my next car, I'm looking for something even more extreme to be used for fun only. I'd even go to a single seat if need be. It's a third car, used purely for driver involvement, so light weight is my main criteria. I'd rather have less weight than more power. Having built my Fury (450Kg with 1/2 tank of fuel), I know I can lose 50Kg (I weighed every single part that went into it) but, it is going to cost more to do it. The bodywork will be simpler and lighter than the Fury's (it is pretty heavy and there is a lot of it) and the main panels will have to be carbon fibre. Moving from a front-engined to a mid-engined layout will save weight.

Rob

[Furyblade_Lee]

A problem too with bike engines making huge power is the clutches, I know the 1500cc Powertec Radicals have about 250bhp and think they use a regular Hayabusa gearbox??

[F40LOUD]

You get about 180 atw from a standard remapped gen 2 busa engine, perhaps 210ish at the fly. I have one and it will go like stink in a 400kg car, especially due to the 100+ lb/ft you get from 4000rpm. Value wise this is what I'd go for, concentrating on the best diff ratio for your needs to get the best acceleration. You can put a turbo on the engine down the line for about 5 grand.

[rhinochopig]

If you want 250bhp I'd go car engine if I were you. You really are getting into big money and marginal reliability IMO. You're well past the limit of the clutch and box at 250bhp. That said, when I had by 'box rebuilt at Holeshot, Jack was in-build for with his 750bhp 'busa motor, and had just fitted the same engine to a westy the same as mine. But with a turbo motor, you're taking away a lot of what makes a seven based car special.

Here's Jeffc's 250bhp 'busa (A PH'er) letting go.

http://www.youtube.com/watch?v=EeTosKBY5_E

In Jeff's words:

I reckon I was lucky as I was hitting the limiter in 6th on a couple of places on circuit and I shudder to think what would have happened if it had let go there when it did go I would be doing around 90mph and remember seeing the armco coming, I clipped it with rear arch but reckon i had a very lucky escape!!

The motor was built by Extreme engines 1550cc full race spec circa 250bhp same motor as fitted to the powertec radicals, its bored 50cc and stroked 200cc, It had done around 18 hours running when it let go , it was advised rebuild time of 17hours

when I stripped the motor it had indeed put a leg out of bed, the cause was a faulty set of pistons which when i researched was not uncommon the remaining 3 had hair line cracks around the conrod pins. was quite lively whilst it was going though!