Karl @ ART wrote:



Well what has happened to Spec Miata is always on the front of our minds for this class. We have tried hard to not make the same mistakes hope do continute that.

Right now the issue of bores and pistons is pretty simple. Stock stock stock. Now if someone want to spend 5k on a motor they certainly can. What we a rules makers need to do is try to ensure that a junkyard motor still has a chance. If you can still do well with an old junkyard motor with fresh bearings where is incetive to spend big bucks on a motor?

I do want to thank you for providing your SM experience. You do bring a different perspetive to the class and that is an asset.

As for 9.5 and 10.5 making the same power.... Well these stupid 944 motors are strangly uneffected by typical power adders. BTW... if a customer brings you a low comp motor and WANT 10.5:1 you can shave the head to get there. It may get him 2 hp, but it can be done with low comp pistons or high comp pistons.

I guess I'll just have to build two motors and do my best not to lead the experiment the way I believe it will go.

I'll keep you posted.

Karl @ ART wrote:


to echo what Joe said Thanks Karl for bringing all of that SM knowledge to 944-SPEC .

Now as for your experiment . remember those two Nationals engines ... the LC pistons made 1 more HP than the HC pistons made ... I would guess thats within the error of the dyno...

Karl @ ART wrote:


Karl - that will be very interesting. Since VFC never did build it's "über" motor, I'm curious to see what yours can do. I appreciate your open attitude with regards to this. Joe's giving away all his R-888 secrets as he discovers them,and in keeping with Spec's ideal as a driver's series, we like to be as open as possible. If there's solid data that there are loopholes that need closing, we'd love to know.

Karl @ ART wrote:


Karl,

What I'm very curious about is how the change in valve timing affects the horsepower and torque of the engine after removing that much material from the cylinder head. Yes, increasing the compression ratio is great, but since you'll effectively move the camshaft closer to the crankshaft without changing the belt length, the valve timing will be retarded.

The 944-Spec rules do not allow offset woodruff keys to restore valve timing.

It would be a great experiment to run this engine on the dyno a few times to establish solid baseline numbers, then degree the camshaft in and repeat the process. My guess is that net increase would be greater than 2hp...

dmdirks,

If I did the math correctly, 0.040 off the head is 0.96 degrees of retard. Note that while retarding the cams may reduce the peak numbers it should shift the power higher in the rev band which can be a good thing. That said, there is probably 1 degree of slop in all the attachment points.

I really am much more concerned with the piston to valve clearance. I've turned a couple non-inteference Miata motors into interference motors by cutting the head nearly 0.040.