I'm trying to learn how to select a turbo by plotting the engine characteristics/requirements on the compressor chart. The engine in this case is a 360ci small block with a max rpm of 6000 and a max VE of 95 - 100%. Did I do it right?

 

Well, based on that chart, it looks like at 15 psi, you will be at best efficiency supporting around 200 hp. Tell me this is for a twin-turbo application!

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Old: 1989 Formula, 383", DFI, built 700R4, TFS heads, Mini-Ram, Vortech S-trim 15 psi, 3.70 gears
Best ET: 10.796 @ 125.8 mph

New: 1989 T/A, 406" Bow-Tie NASCAR Tall-Deck, Accel Pro-Ram, DFI, AFR heads, HRC T76 Turbo, NOS 150-hp dry kit, TH400 w/GV overdrive, 12-bolt w/3.70 gears, 8-pt. S&W rollbar, Spohn suspension, 18" wheels, Baer brakes
Best ET: Spring 2001

Employed at:
Hahn Racecraft
Accel EMIC/DFI Tuning
Turbosystems & Custom EFI

Member of Midwest F-Body Association www.mfba.org

 

LOL, yes in theory it would be for a twin setup... in reality, I'm just trying to learn how to read the charts.

How do you figure out the HP it (they) will support?

Are you saying they support 200 hp at 75%? How about at 70%?

I guess I'm looking for more of a tutorial on how to read the charts and select a turbo for an application.

 

Very, very quick figures:

Pressure ratio = 14.7 + boost / 14.7
Airflow = usually 10 lbs. per 100 hp for V8

With this map, your highest power level should be in the highest efficiency island.

In your case, a pressure ratio of about 2.0 and an airflow of 20 puts you on the edge of the "sweet spot" on the graph. An airflow of 20 is about 200 hp...

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Old: 1989 Formula, 383", DFI, built 700R4, TFS heads, Mini-Ram, Vortech S-trim 15 psi, 3.70 gears
Best ET: 10.796 @ 125.8 mph

New: 1989 T/A, 406" Bow-Tie NASCAR Tall-Deck, Accel Pro-Ram, DFI, AFR heads, HRC T76 Turbo, NOS 150-hp dry kit, TH400 w/GV overdrive, 12-bolt w/3.70 gears, 8-pt. S&W rollbar, Spohn suspension, 18" wheels, Baer brakes
Best ET: Spring 2001

Employed at:
Hahn Racecraft
Accel EMIC/DFI Tuning
Turbosystems & Custom EFI

Member of Midwest F-Body Association www.mfba.org

 

So if I'm reading this correctly..
(compressor map for a Turbonetics T-76 turbo)

..that means that at 15lbs of boost, the pressure ratio is 2.02, roughly.. so 15lbs from a T-76 turbo would support roughly 550hp? Interesting... (I might be totally wrong though.)

 

Most of the compressor charts I have are in CFM, whats the conversion from LB/Min to CFM?

In one of the Turbo books I have, Maximum Boost, The author charts a line across the chart where the turbo will operate... this line always extends past the peak efficancy island. Are you saying that you should not run a turbo past the peak efficancy island and if you do, what is the effect on power?

 

Actually, that is the turbo I am using. If you follow 2.02 (15 psi) over from the left, it will be on the edge of 78% efficiency at near 600 hp. It is a very versatile turbo. Nothing wrong with 70%, but that 78% island is the sweet spot! I will still be at 73% efficiency when pushing my 800 hp.

[This message has been edited by GMI FAST (edited January 26, 2001).]