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RE: saab turbo'd engine in tr7 ?

To: <triumphs@autox.team.net>
Subject: RE: saab turbo'd engine in tr7 ?
From: "Randall Young" <ryoung@navcomtech.com>
Date: Fri, 7 Nov 2003 18:08:05 -0800
> I don't need to run down the list of vehicles available with a roots
> supercharger that you can buy at any of your local dealers.

Yes, but the question was what works best at altitude.  Every one of those
supercharged engines will suffer the same performance loss at altitude as a
naturally aspirated engine, because the boost level is fixed as a multiplier
of the barometric pressure. (Unless of course they've started using variable
drives, in which case you're right about my being behind the times <g>)

However, my simple Dodge Caravan will not suffer _any_ loss of power,
because it's boost level is set to an absolute pressure.  I have verified
this, it will still squall the front tires at 11,000 feet ... (or would
before it got as decrepit as it is today).

All of the things I stated are true, even with the new whiz-bang
supercharger technology.  The only real problem is, for a high performance
car, turbo lag sucks big time and there's no way to fully get rid of it.

> In my opinion, the greatest fault of a turbocharger is the exhaust back
> pressure it creates.

The turbo has to get it's power somewhere, that's where it comes from.  BUT,
a supercharger sucks more power, and directly from the crankshaft.  A turbo
at least gets some of it's power from waste heat.

> As for consuming power, Mercedes employs electro-magnetic
> clutches on their
> Eaton superchargers, which means when they're not creating boost they are
> consuming absolutely no power.

Yes, but I was talking about while under boost.  A decent blower can consume
20 bhp or more, just when you'd rather have it to turn the wheels.

>  the rotors will also not absorb any
> heat so they won't pass on heat to the air passing through the blower.

Sorry, the rotors absorbing heat has nothing to do with heating the air.

Cheers
Randall




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