mjb

wot bhp can a 2.5 crankshaft take?

EngineMapper @ Group B Motorsport

How long is a piece of string? lol no in all seriousness, I've had this discussion many times before with other engine builders. You are likely never to induce your crankshaft to fail from pure power alone, i.e a crack, split, bend etc. It is more likely that the crankshaft would fail at higher hp due to lack of oil flow, debris in the lubrication system, a rod failing and so on. That is, unless it has a manufacturing defect!

However, that said, it isn't really strength that you're probably really asking about. More than likely it will be the cyclic loading that the crankshaft is subjected to that would likely make it fail, (providing the above doesn't happen before). The more miles the crank has done in it's life, the less cycles you are able to do with it before it ultimately shows signs of fatigue and fails.

My personal opinion on the matter is all about service interval. You could most likely subject a 2.5 crankshaft to 500bhp+ as standard, (again providing the engine is built to take it also), with regular inspection and replacement of oil and filter you can spot the real killer, bearing failure before it destroys the rest of the engine.

There is however a good reason RCM and the like suggest billet crankshafts in high bhp builds. They would never take the risk on a customers engine, plus a £1500 crank on the price of a 20k engine build is relatively cost effective for piece of mind.

I would be interested to know of anyone that can pin a failure of an engine on purely the crankshaft being the problem? I've not as yet seen one.

mjb

ok mate thanks 4 ur help