Jack Clark wrote:
>
> After reading the article, it "appears" to be a fairly straightforward
> process, and the beauty is that the rest of the car remains stock. I am sure
> you would need an engine in better than average condition to handle the
> extra umph! I would be tempted to try it myself, if first there is no
> possibility of a kit coming on the market.
>
> What is the opinion of the list?
I wonder about "the rest of the car remains stock." I haven't read the
article, admittedly, so I don't know what amount of boost is being
generated. However, if the supercharger is raising a stock 110 hp or so
to 190 hp, that's bound to be boost on the order of 10-12 psi--no small
amount.
I've just looked at the Eaton web site, and apparently, from the little
information there, a Model 45 is probably being used, which apparently
has a peak pressure of 10 psi. I would guess that the boost is being
controlled by the bypass valve, which is vacuum-operated.
There are considerations regarding the rest of the engine, if one wants
it to last with some hard driving. Producing more power means more heat,
which has to be dissipated, to keep the engine alive. Given the relative
number of complaints here about overheating in the summer months, the
cooling system will have to be in top shape. If the engine is capable,
under boost, of as much as 75% greater power, simple physics says the
mean effective pressures are 75% higher, and that means better
block-to-head sealing is required. It also means the pressure on the
piston crowns can be 75% higher--forged pistons are almost a necessity.
My limited experience with GT6/TR6 connecting rods is that they have
tendency to stretch, which leads me to believe they won't be strong
enough for hard use under high boost, so better rods are probably
required, as well.
Another consideration would be the effect of 190 hp on the rest of the
drivetrain. How much that is over design limits is hard to say. But,
it's probably a sure way to find out which components are getting weak.
<smile> Because torque is much higher across the range, the opportunity
for wheel spin at higher speeds is a distinct possibility, so better,
and larger, tires would be in order. (!)
Another item worth mentioning comes from the Eaton web site. Quoting
them, "The Eaton supercharger system incorporates a specially designed
bypass valve, which is actuated by a vacuum motor near the throttle
body, and recirculates the supercharger air flow when boost is not
required. During typical driving conditions, the engine is under boost
around 5% of the time, which means the remaining 95% of the time the
engine is under vacuum, allowing for better fuel economy and a quieter
ride."
Which is to say that the compressor is unloaded about 95% of the time,
with _normal_ driving. If you have your foot in it a lot of the time,
the engine is being fed boost a lot of the time, because the system is
controlled by vacuum.
Eaton also says numerous 500-hour durability tests have been done on the
unit, but there is no mention if this was loaded all the time, or
unloaded 95% of the time (the abovementioned duty cycle). Perhaps those
answers are available directly from Eaton.
Don't get me wrong--190 bolt-on horsepower is a very attractive notion.
I just think that it's a good way to break a stock engine into many
large and small pieces. The real cost of adding a supercharger, with
machining for better head gasket sealing, better pistons, better rods,
slightly stiffer valve springs to resist boost, etc., would probably
bring the actual total well above the $1700-2000 mentioned above... more
like $4K, or higher, depending upon machine shop costs in your location.
Anyway, here's the URL for the Eaton supercharger site:
http://www.eaton.com/supercharger/index.html
Cheers.
|