[s-cars] Clutch comparo

[CaptMagu at aol.com]

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s-heads

I just got back from a UAL trip with a layover in SFO. Hooked up with Brian
Billotti and that gave me a chance to do some back to back comparisons of our
2 cars. These cars are both heavily modified. Their major differences are;
head, intake, turbo, clutch. I have a ported and polished head and Brian's
does not. I have the Pederhousen Big MAF while Brian uses the RS2 MAF. I use
a conventional Garrett sleeve bearing 54 trim turbo and Brian has a 50 trim
Innovative dual ball bearing unit. I use a Centerforce clutch with ASW
aluminum flywheel and Brian has a Spec clutch with the same flywheel. We both
have big FMICs but mine is a bit more Happersized;-) Beyond these differences
we are more similar than different.

I started the trip with a spirited drive from Evergreen to the airport at
4:00am Monday morning. Not much traffic out so I was able to do some playing
with my car along the way. The specific goal here was to get a good seat of
the pants feel for 3rd thru 5th gear pulls. I arrived in SFO that afternnon
and Brian and I met shortly after. He insisted that I drive his car so I
happily obliged. My first impression was that the Spec clutch was much more
grabby than the Centerforce. You really have to use some rpm to pull away
from a stop. Big difference here. As we got onto the highways we were able to
do some serious pulls in all gears. The Innovative turbo does spool very
quickly. It is very loud with a high pitched whine. I had experienced this
with Mike Pederson's car but he has moved on to a different and bigger turbo.


Brian's boost threshold is around 3000rpm. It was a little different every
pull. I saw it at 2900rpm once and 3100rpm other times. My car's threshold is
about 3200rpm. What was the most striking difference was the rate at whgich
the boost guages came up. Brian's was much quicker. There are the altitude
differences, 5200ft vs sea level, that do affect this comparison. To keep
things as equal as possible these comparisons were done in 6th gear up an
incline. The biggest differences was the power feel above 4000 rpm. My car
definately has the edge here even with the altitude difference. I'd really
like to feel my car at sea level.

Brian would like to do the Big MAF upgrade and he just might be convinced
that porting his head might be in order.

Hap, back in Everboost, Maguire