I will need to have the unit dynoed to truthfully get the right answer. I will "let the cat out of the bag"
a bit and say that the RBox unit uses K7 > GSXR1000 output shafts rated at ~90lbsft of torque and +/- 160-170 Hp. Many GSXR bikers who turbo their engines, running beyond 300 HP end up tearing the splines where the spocket or prop adapter fits (not the gear splines though). You can run 200-250hp all day long on the stock oem output shafts. BUT Robinson Industries makes a 30 mm HD output shaft for turbo heads instead of the stock 25mm and they have been pretty much bullet proof. Unfortunately, the HD output shaft for the GSXR 1000 or BUSA is $300.00 bucks alone , and you need two for the RBox -ouch!!. The good news is I can integrate the HD shafts into the RBox effortlessly, of course at the added shaft cost.
I have a 02' busa engine setting in a 1000lb frame, but I haven't pushed the protoype box (I built in 2010) to those limits you suggested (300hp / ~120lbs torque)
Here in Charlotte, NC we have one of the foremost expert engine-tuners/dragracers with gxxers/busas (Lee Shierts - http://www.leesperformance.com
) in the US. I'll speak with him and get some additional feedback.
What kinda engine are you running producing 300 HP?
here's a quote from a gxxr site link. Makes a lot of sense though:http://www.gixxer.com/forums/showthread.php?t=245459
Originally Posted by Kraig Murley
sorry guys should have given you some details.......
The problem i have is associated with a combination of power and weight....... I use 2 gsxr1000 engines in a race car.... off road dirt circuits, just the boxes are the weak link....
And it has no chain, it uses a rather special drive box that sits over the sprockets.
at £1000 per engine every year running costs aren;t cheap.... as well a s the 4 sets of clutches that I get through every year also...
the main problem is the the output shaft stretches. but i also have bearing failures on the inner bearing also.
There's your obvious problem right there. You put a motor designed for a 500lb total bike into a car that weighs more than double, you're bound to have more strain. Oh, you have two motors? Well how heavy is the car/always being pushed at 12,000rpm, tremendous strain at any RPM... The motor simply wasn't designed for that constant strain like vehicular motors are. Ever wonder why a 2.0L car motor only puts out 150hp and a 1.0L motorcycle motor puts out 170+? Torque values are determinant on engine design, not just "SUZUKI MOTORS SUCK AND DONT WORK"
The only option I can give you is to experiment with different year's motors or try another Brand's motor. Newer Suzuki motors optimize newer technology in terms of material, dynamics, balancing, etc. If you're running used 2001 GSX-R 1000 motors, the first year faults are the obvious problem. They're cheap, but they're cheap for a reason.