VATN, blowers, etc.

[Jason]

With this talk about superchargers and turbos running rampant, I'll
throw in my two cents regarding street cars, turbos, and blowers...

The VATN unit is a good idea, but unfortunately they don't make larger
trim levels. The concept of having a variable exhaust turbine is great,
and the Aerodyne VATN does it very well. Also, the VATN unit is the only
turbo I know of that has a self contained lubrication system. In other
words, the VATN turbo has a fluid reservoir designed to hold a specified
amount of special lubricant...no more oil lines to the pan! Simply
change the fluid in it like you would the oil in the engine. No need to
"tap" the oil or anything like that. Like I said though, the largest
VATN unit will only push about 350hp-400hp though. A little Garrett T03
can do that. 

Garrett (Allied Signal) also has a special variable geometry exhaust
turbine unit too, although it's not popular in the aftermarket scene.
Probably does more duty in large turbo diesel engines...

Apples and Oranges alert: I think that a properly selected and
configured turbo will easily outperfom any supercharger, on a street
car. For instance, I've played with the Eaton M60 and Vortech V1
blowers...and they pale in comparison to a turbo. The Eaton, simply by
its positive displacement design...is decent for low end torque on V6s.
The Vortech V1 unit really doesn't impress me. Doesn't matter if you
stick it on a LT1, or a 302...give me a turbo instead. The linear boost
thing just doesn't cut it, in my book. Parasitic drag that robs hp is
another bummer. Then there's that damn gear driven noise...some love
it...I think maybe I'm too old for that crap now days. It gets old.
Pulling up to every light and just hearing that "whine" can scare some
away. I prefer stealth. Give me my T3/T04E ceramic bearing unit...and
you'll hear a little whistling "whooosh" as I easily run away and hide.
Very nice. 

Upgrade to more power? Well, with a SCer...you're looking at swapping a
pulley. Smaller pulley equals more boost. Boost is limited by rpm, and
it's usually a linear scale. Full boost occurs at max rpm, and it sucks
to be you at 1500 rpm! Ha ha. Turbo? Easy, just dial up the boost. The
age of mechanical boost control is gone. It's all about fuzzy logic
controllers and stepper motors to regulate boost. Extremely repeatable
and reliable. 

The drawbacks? Lots. Turbos produce heat, more than SCers. The air
charge is pretty damn hot, and so is the engine compartment. Turbos
require a few more controllers and gadgets to make things work (blow off
valve, boost controller, wastegate, usually an intercooler). Fuel
ecomomy? BUHAHA!! Regulate your mileage with your right foot. Some seem
to think that the increase in cylinder pressure reduces engine life. I
say it depends on what level of boost you run (and yout static CR), the
quality of the engine internals,type of fuel, the type of forced
induction, the specific model of the blower or turbo, the type of
driving you do, the fuel/ignition mapping, ambient temps, and a slew of
other factors. Knowing a few things about turbos can help you ensure
reliability (don't hammer the car at full boost for twenty seconds, and
then shut the car off without letting things cool down first). With a
Vortech blower, always change the oil every 3k miles or so (turbo too),
using synthetic oil. Always inspect the serpentine drive belt for dry
rot, cracks, and tightness. There are some "break-in" techniques as
well, when the blower or turbo is brand new. Lots of little tips and
tricks that will keep the car on the road, and off the jack stands. 

Anyway, looks like I drifted a little off topic. Bottom line: forced
induction is far superior to displacement for performance and
convenience, let alone economics. Oh yeah, a variable geometry intake
manifold LOVES boost! Some of you guys should try one, or make one.
Enjoy. 

Jason
'93 SLC