This is a conceptual question more than anything, and based upon what I've been reading about the new BMW M3 and M5.

So, how do you get a V-8 to rev up to 8,000+ RPM? Is this a stroke-length limitation, is this a valvespring/retainer limitation issue, both, or more? Would it be possible to do it with our motors?

I have to say, the prospect of getting a V-8 to 8,000 RPM both scares and excites me at the same time.

 

go try it and get back to us


yikes

 

8k little high, with the right cam and intake 7k is doable pretty easy.

 

Stress on the components is exponential, not linear, with velocity.

There is a reason F1 V8s only have a stroke of 28mm, as opposed to the ~4 inches (102mm) of our V8s.

 

Hence my question.

So I guess smaller mass (smaller components and lighter weight) coupled with lower velocity (shorter stroke) are the main variables contributing to rev-ability?

Taking this info into account, since the 4.8L has the shortest stroke (3.268) out of all the LS1-based engines, would this be the crank to use if you wanted to rev it up?

I just realized that at the end of the day, the engine still has to mate up with a transmission, and the 4L60E/4L80E/6L80E are likely not up to the task of accepting 7500 RPM+ input....or are they?

 

4.8's are known to love higher rpm; Hell Quik revs his turbo stock bottom end 4.8 to 7000+ on a regular basis. I'd like to see a block with LS1 pistons and a 4.8 crank or even a 6.0 block with one to see what it'd do; low end would be non-existent but it'd scream up top.

I'm also under the impression that its rpm that kills a lot of 4L60's; might not always be the case but I think it has a lot to do with it.

 

Yeah, that's what crushed my joy - realizing that even if I could get an LS1-based motor to rev to 7500-8000, I'd still be left with how to apply the power to the ground.

Anyone know what the practical (vs. theoretical or spec'd) limits are on the 4L60/4L80 trannies?

 

The m5 has a 305ci V10 and the M3 has a 4l V8. The smaller engine with a smaller stroke is what is allowing them to achieve 8000rpm limits.
The larger your stroke the more mass your moving and the less stable things will be at high rpms.

For instance the Ariel Atom3 comes with a 2.4L V8 pushing 500bhp and revs to 10,000rpm.

 

thats just like a little skinny guy being able to run faster than a big heavy tall guy

 

There's also a trade-off in the TQ department when you build a motor to rev high. I think the M5 is ~500HP/400TQ while the M3 is ~400HP/300TQ.