Originally Posted by Doc_Z
Thanks Nathan. What you're saying makes some sense at least.
Is the clatter mainly on 6 cylinder motors?
I'm still unsure why my SR20 with 13:1 CR and a solid 8lb fly has no clatter, but the VQ with what 10.x:1 has the issue.
You make no mention of what vehicle your SR20 motor is fitted too, but the with such a HC & an 8lb flywheel with no clatter I'd almost be certain that it is in a FWD car.
With the compact size of the motor transmission & final drive (2ltr) sharing the same rubber mountings & with large solid driveshafts & CV joints plus all the weight being right over the top of the drive wheels there is a lot less chance of compression to cause clatter & the car itself sort of acts like a flywheel.
I'll give an example of compression.
My son won the Australian production car championship in 2001 in a 2ltr Mitsubishi FTO (FWD). Late in the year he was invited to test a 5ltr V8 Ford Falcon ute (US= pick-up) for a race series that we run hear in Australia.
Well the 1st time he downshifted at high speed he never heel & toe'd correctly to rev match & locked the back wheels & spun out at about 190 kph.
He had only ever raced FWD cars & while he always rev matched on downshifts, the larger capacity RWD vehicle with not much weight over the rear wheels had compession locked the back wheels because he had not rev matched properly.
He was so suprised as he had never had that happen to him in his FWD Honda's & Mitsubishi.
Now if your car is a RWD Iv'e got egg on my face so disregard everything I've said as it's all BS.