On Wed, 29 Jun 2005 Lizirbydavis@cs.com wrote:
> The supercharger sounds like the way to go. My engine is lightly modified.
> The compression is about 9.5:1. I'd hate to pull the head and put a thicker
> gasket on to lower compression.
If you are going to supercharge anything, you need to start with low
compression... lower than 8:1 is best. If you start off at 9.5:1 and then
boost the inlet pressure, the cylinder pressures will be way too high and
if you are lucky you'll just blow head gaskets... if you are not lucky,
you'll put holes in the pistons or break rings or worse because of
detonation. Detonation in a boosted engine is MUCH WORSE than it is in a
normally aspirated engine.
If you have a modified head, you can make up the difference by utilizing a
thicker head gasket. The folks at www.gasketworks.com can make you a nice
copper gasket to get things dialed in.
> Will my engine tolerate the stress? What
> sources are available for kits? Is the eaton (62?) the unit of choice?
The engine will take the stress is you stay in the lowish boost range
(like 8 lbs. or less), but if you're thinking about more boost, then at
some point you'll have to consider forged pistons at least and possibly
stronger rods. But with 8 lbs., the theoretical HP increase is probably 40
HP which is a really nice HP increase.
A side note on supercharging needs mentioning. The supercharger only
boosts inlet pressure - you're pushing more air/fuel volume in. That's it.
It does not increase the volumetric efficiency of the motor. So there are
two items worth noting. First is fuel quality (e.g. octane). With a
boosted motor, you MUST use the highest grade fuel that you can obtain.
Without engine management, if you use 87 (R+M/2) octane fuel and you tromp
on it, you will get detonation. The other side effect is that because the
volumetric efficiency has not changed, you will use a LOT more fuel when
you tromp on it. You also get crappy fuel economy when the car idles in
traffic.
So, keep the initial compression ratio low-ish, don't over boost and look
into engine management (with a knock sensor!!) and you can have a blast
with your supercharged car.
> Joe Davis
regards,
rml
'74 TR6 - driver, original owner
'73 TR6 - race car - 11:1 compression
'04 Saturn Ion Redline Quad Coupe - Daily driver - SUPERCHARGED -
0-60=6.1 seconds. Yee ha!
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