[s-cars] Turbo Compressor Maps

[Michael Gough]

The stock 130hp motor flows....lets say 13lb/min of air. So if I add a some
sort of compressor (roots blower, turbocharger, etc) it will have to flow at
least 13lb/min of air just to keep up with the demands of the naturally
aspirated motor. So you have to consider the airflow requirements of the
total system when doing these calculations. 380hp equates to a certain mass
of air per unit of time, whether it's on a turbocharged engine, naturally
aspirated engine, or whatever. That mass of air (we assumed 38lb/min) is the
amount of air flowing through the airfilter, turbo, intercooler, engine etc,
so that is the figure to use when looking at the maps.
A "Stage V" is just a term used to describe an oversized Garrett T3 series
turbine wheel.
"Stage I" would be the stock Garrett T3 wheel, packaged with Saab, Ford,
Volvo etc cars.
Stage I has a 1.898" exducer and a 2.319" major diameter
Stage II has a 2.122" exducer and a 2.559" major diameter
Stage III has a 2.229" exducer and a 2.559" major diameter.
I can't find the specs for the Stage V wheel anymore, they're around here
somewhere, but you get the idea. The bigger stages have bigger wheels, and
housings to match. The form factor of the exhaust housings however are the
same, with the exception of the larger exducer bore.
I would not do ceramic ball bearings with one of the antiquated "T3/T4"
series turbos. I know Turbonetics pushes them, but if you're going to spend
the large amount of money for a ball bearing'ed T3/T4 hybrid, you're MUCH
better off spending about the same money for one of the GT series turbos.
They're the newest technology, designed and built by Garrett rather than
Turbonetics or some other turbo shop, and the turbine efficiency of the new
GT series turbos is FAR superior to the old technology.
HTH
Mike+

> Ok...so you dont count the HP that the car would have if it was Normally
> Aspirated?  As I was taking my incorrect NA number of 130 and adding to the
> 25 lb/min = 380.  But if you say I dont count that initial number and say I
> want 380HP then I need to flow 38 lb/min...
>
> If that is the case the Compressor maps make more sense now...in terms of
> efficiency ranges and plots for the 50 and 54 trim.
>
> One thing I still am fuzzy on, among others, what does it mean to have a
> Stage V turbine?  What is the difference?  Also any one think it is worth
> doing Ceramic Ball Bearings?
>
> cp
>
> -----Original Message-----
> From: Michael Gough [mailto:mdg3369 at newtsplace.com]
> Sent: Wednesday, August 06, 2003 3:46 PM
> To: Cody Payne; s-car-list at audifans.com
> Subject: Re: [s-cars] Turbo Compressor Maps
>
>
>> Now if the 2.2L engine normally aspirated could say put out 130 HP then to
>> get up to around 380 HP I would need around 25 lb/min right?
>
> No...
> A very rough estimate is 10hp = 1 lb/min. This leads to 38lb/min for 380hp,
> and at a pressure ratio of 2.63:1, both the 54 and 57 trim compressors are
> about 70% efficient, based on my quick look at the maps right now. Now of
> course this assumes that you are actually flowing 38lb/min of air through
> the motor at 2.63:1 pressure ratio, if you're flowing more or less, you have
> to re-plot these points on the maps.
> And of course if you're flowing 38lb/min of air at 6000 RPM, you'll flow
> roughly (Not exactly because of changes in VE) half that much air at 3000
> RPM, which would put you very far to the left of the surge line. Make sure
> you size the exhaust housing large enough so that you don't make 25psi of
> boost at 3000 RPM, or program your boost control so that it doesn't allow
> you to make too much pressure at too low of an airflow so that you stay out
> of the surge area.
> HTH
> Mike