mx5cartalk.com

I was just wondering what sort of revs you can get out of a built bp motor? With say 10:1 comp ratio (forgies) and a fully done head (springs, valves, seals, cams etc) do you think you could get 8000rpm safely? is the stock crank up to it?

Mine's stock inside and revs cleanly to 8000rpm, although i generally only use 7500.

Been doing it for about 20000klms with no side effects(yet).

Peter

cool so its probably a case of specing to the builder i need bits that are effective to 8000rpm. thanks!

16bit wrote:cool so its probably a case of specing to the builder i need bits that are effective to 8000rpm. thanks!

Some of the race guys have engines reving well into 8500 - 9000 however they generally flat line in the power stakes from 7500.

If you want a set of forged 1800 pistons I have a good second hand set from my old race motor. 11:1 wisco pistons 20thou over, just need rings.

Neil

car is supercharged so 11 might be a bit high (unless I run 110ron race fuel on the road - could be good ) but thanks for the offer. Because boost is progressive I should hopefully make power all the way through to 8000.

I only run about 10psi boost so I don't want to drop the comp ratio.

thanks for the info - 9000 would be awesome. Imagine the sound in a tunnel

My old NA motor used to rev beyond 8700rpm. You will need a lot more than forged pistons to rev above 8000rpm. You have to reduce every single piece of rotating mass otherwise it will not rev. You also have to have cams and heads designed to make power in that area - not as simple as you might think.

like ct said if the cam isnt meant to run above 7500 rpm theres not much point. however it will let you avoid changing gears in some cases. for example you might pretty much be bouncing of the rev limiter going into some corners but if u went up to the next gear youd be changing down litterally straight away back to the original gear and maybe through further gears. but if you had a slightly higher rev limiter you could ride that gear out a little bit longer till the brakeing point avoiding an extra gear change and giving you more time to set your self up for the corner.

You should ask Danny what his NC revs to!

saboteur wrote:You should ask Danny what his NC revs to!

they go to 32,000 rpm those things!! I've seen a Mazda video where they tested them in development at those revs

I've seen a few B series cams snapped, the owners of both engines suggested it was due to over revving. That said I cannot qualify that as being fact, I'm not sure either did any sort of testing...

Reminds me of the video on the net of the guy in the honda street racing, he grabs second instead of fourth! The tacho needle goes a hell of a long way round the dial...