Stock turbo rating

[daveismissing]

Given that all the vendors apply horsepower rating to their turbos:
What is the "horsepower rating" of the stock turbo?
Te-44?

[PacecarTA]

http://www.gnttype.org/techarea/turbo/turboupdate.html

[trashmechlv]

Heres another link with turbo specs and hp rating.  http://www.nolimitmotorsport.com/precision-turbo/buick-turbos.html

Im not trying to promote this site in any way, they just have a badass turbo chart.

[Scoobum]

Not sure of the HP rating...but Norbs squeezed one to 30 PSI...and it ate itself.

[Steve Wood]

I have never seen a compressor map or flow rating for a stock turbo.  Based upon performance, I would say the hp rating would be about 400-425.

Boost is a pretty meaningless number when trying to discuss turbo performance or hp.  It is more meaningful when discussing a particular turbo in a particular combination.  We know that a stock turbo on a stock drivetrain quits making more power around 21-22 psi of boost because it has started to move into a lower efficiency zone on the compressor map.  In other words, charge temperature is rising faster than air density as the boost increases past 21-22 psi in a stock combination on straight fuel.

We used to rate turbos by flow volume in cfm.  To convert to hp for theoretical reasons, we multiplied flow cfm by .69.   Some assume that that 1.45-1.50 cfm is required to make one hp which is in the same ball park as multiplying by .69 (which I got from Joe Lubrant many years ago).

The weakness in the above calculations is that they are using volume and not density so it is not too bad and normal air temps but tends to go astray due to excessive charge heating.  A better rule of thumb might be to use lbs of air which reflects density.   Some suggest that one lb of air will make about ten hp.

Given that most turbo manufacturers tend to sell the squeal of the pig rather than the pig, we often don't know anything specifically about a turbo other than what is advertised or what we see with our own eyes which is usually colored by the particular combination it is used on and we often discard combination  conditions to buy the latest magic in a turbo.

A guy in Vegas buys a turbo because he read that Joe Blow ran 10.31 at 133 mph on the east coast on a cold day when the density altitude was 100 ft below sea level with a T66 and he figures that is the turbo he needs and never thinks about ambient conditions, drivetrain combo, tuning ability etc.  Then he runs a 12.01 and wonders why and tries to solve it with another turbo.

It's not the hardcore racers that keep vendors in business.  It's the guys that believe in magic.  Hardcore racers are looking for hundredths of a second while Joe Blow is looking for seconds from a simple swap.

[Forzfed]

Here's a Map.

[Steve Wood]

That would suggest about 370 hp...thanks, I had never seen that before...glad I am still around to learn something

[Top Speed]

One for the archives.

[motorhead]

That would suggest about 370 hp...thanks, I had never seen that before...glad I am still around to learn something

When I was building the twin turbo system for the Monte that fact and the stock GN turbo map fit the N/A engine nicely.

[Forzfed]

That would suggest about 370 hp...thanks, I had never seen that before...glad I am still around to learn something

I think your post before hit the nail on the head!  My low milage car on a warm day went 12.3@108 with a 1.67 60ft, 19 psi letting it shift into OD.  My other car which could only muster mid to high 1.7x's pulled a 1.61 60ft on a crazy cold day!  My low milage car put down 370rwhp according to the Moroso slide ruler calculator.  So, I'm thinking my low milage car would have produced over 400rwhp on that same cold day and 60ft in the 1.5x range.

[Steve Wood]

Yeah, I remembered a few low 12 second cars with the stock unit and that was where I guessed the 400-425.  Maybe the cold air gave enough density to get there

[Scoobum]

He lives in Winterpeg...lo ts of cold air there.

[Steve Wood]

Back around 1990, I went to the strip there a couple of times...not in the winter, tho...

[motorhead]

You can (apparently) extend the compressor map of most any turbo by injecting a small amount of fluid on the inlet side, this effectively closes up the tolerances between the housing and compressor wheel. 

I wonder if the active PCV system which filled the turbo with oil was added for just this reason? LOL... nah.

[Forzfed]

Yeah, I remembered a few low 12 second cars with the stock unit and that was where I guessed the 400-425.  Maybe the cold air gave enough density to get there

Spool on a cold day is insane, almost instant!  My buddy ran his 7.9@179 on a 3' day still not as cold as the one day I ran where it was actually snowing.  His 7.9 was done with 24psi using Conley's modified T-88 that was on Tweak.