Re: Turbo engine questions (SC28)
Is the engine stock with a turbo or has it been built from scratch for turbo work specifically? 300hp (measured at the crank or tyre?) is well over double the original designed power of around 125 at the crank. If you're measuring it at the tyre you're almost triple what the engine was designed for and it's probably running close to self-destruction anyway.
I've never built a 300hp bike motor myself but rod bearings usually fail because something else is wrong which throws out the bearing clearance disrupting its ability to soak heat away into the rod and then the bearing overheats and comes apart.
Assuming you are ensuring all clearances are spot on when you're building it (bearing crush is going to be critical in this engine) I can only suggest trying heavier rods. If you can't buy some you can certainly get some made to your own spec. The 893 is an old engine to begin with so I'd be _at least_ running brand new OEM rods with that sort of horespower. Boosting a motor by these sorts of percentages could cause any number of hard to sort problems. Even the cases themselves could be flexing when the plugs fire :-)
I'd be hesitant to increase pump speed by much due to possible cavitation but a higher-volume pump might be an option.
You could possibly drill an oil jet into a gallery and spray oil directly at the bigends to try to keep them cooler. Maybe also try a much deeper sump for more capacity and a bigger and/or additional cooler to cool the oil down as much as possible before putting it back into the engine. I'd also run an oil temperature sensor.
Are the rods or crank pins ovaling at all?
Are the insides of the engine blueing from excessive heat?
Under what circumstances are the bearings failing?
"I won't forget that ride for a while. Maybe you're right. Living fast might be worth the final crash. Maybe that's the secret you fliers know." - Flight of the Intruder
Last edited by bladeracer; 08-27-2007 at 11:38 PM.