Re: T3/T4 is a good choice - Saab Performance Bulletin Board - Saabnet.com
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Re: T3/T4 is a good choice
Posted by Alex [Email] (more from Alex) on Fri, 25 Jan 2002 19:11:41
In Reply to: T3/T4 is a good choice, Keith S, Fri, 25 Jan 2002 17:42:17
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Efficiency from turbo to turbo doesn't vary much though. I have trouble believing that his T3/T4 is boosting just as hard at 12 PSI as the T3 was at 20. That would require about 200°F drop in outlet temperatures with the T3/T4.
The following assumes a 70°F ambient temperature and 14 PSI at the turbo inlets. Now, let's give him the benefit of the doubt and assume the T3/T4 operates at 72% efficiency where the OEM T3 would operate at 55%.
The formula for calculating outlet temperatures is:
To = Ti + ({Ti[(Po/Pi)^0.288 - 1]}/e)
With all temperatures in deg R, and all pressures in PSIa.
Therefore, for the T3/T4:
To = 530 + ({530[(26/14)^0.288 - 1]}/0.72)
To = 673.66°R
And, for the T3:
To = 530 + ({530[(26/14)^0.288 - 1]}/0.55)
To = 718.07°R
As you can see, this huge difference in efficiency only causes a 44° difference in temperature. In order to get a 200° difference, the efficiency of the T3 would need to be around 30%, which is simply unheard of.
Granted, some power gains could be seen from less backpressure in the system with the T4 compressor attached, but how much power will that give? 5 hp? 10 maybe?
posted by 152.113.19...
Posts in this Thread:
- Which turbo to use? (Long), Alex, Fri, 25 Jan 2002 14:08:12
- Ditch the redline....hehehehe ;)~, Mr.SPG, Sat, 26 Jan 2002 12:02:16
- Alex: referral to a turbo "doctor", Keith S, Sat, 26 Jan 2002 08:45:28
- garret Gt series?, dave n, Fri, 25 Jan 2002 21:40:25
- T3/T4 is a good choice, Keith S, Fri, 25 Jan 2002 17:42:17
- Re: Which turbo to use? (Long), sully, Fri, 25 Jan 2002 15:29:59
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, Fri, 25 Jan 2002 20:03:35