What did the factory set the boost at?
07-12-2006, 09:14 AM
#16
Racer
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Thanks all for the replies. Very interesting to say the least. My '90 951 is still stock so it would be interesting to tap in an accurate boost guage to see what boost it makes. I don't expect it is still making what it did when new which appears to be around 10 to 10.9 PSI but it would be interesting to find out before I start the modding process.
07-13-2006, 02:09 AM
#17
Rennlist Member
From Clark's Garage:
5.2 What is the maximum boost I should see on my boost gauge?
This has long been a point of contention among 944 Turbo owners. For early 944 Turbos, I've heard ranges from 1.7 - 1.75 bar while the numbers for the Turbo S cars range from 1.75 - 185 bar. However, the factory shop manual clearly states that the maximum boost for both models is 1.75 bar. "Maximum boost pressure of 1.75 bar (absolute pressure) is reached at approximately 3,000 rpm. At higher engine speeds (engine type M 44.51) the boost pressure drops off again and reaches a boost pressure of 1.52 ±0.03 bar (absolute pressure) at 5,800 rpm. With engine type M 44.52, the boost pressure remains constant at 5,800 rpm (1.75 bar absolute pressure) and drops only after this value has been passed."
M 44.51 1986-1988 Model 944 Turbos
M 44.52 1988.5-1989 Model 944 Turbos
There does seem to be some variance between models, but I don't know that anyone's ever actually proven if the later model cars produce a higher maximum boost. The factory does indicate that there is a 10% tolerance at maximum indicated boost. So, that means that the indicated maximum boost could range anywhere from 1.58 bar to 1.93 bar. Start looking for problems if your maximum boost is consistently less than 1.6 bar.
5.2 What is the maximum boost I should see on my boost gauge?
This has long been a point of contention among 944 Turbo owners. For early 944 Turbos, I've heard ranges from 1.7 - 1.75 bar while the numbers for the Turbo S cars range from 1.75 - 185 bar. However, the factory shop manual clearly states that the maximum boost for both models is 1.75 bar. "Maximum boost pressure of 1.75 bar (absolute pressure) is reached at approximately 3,000 rpm. At higher engine speeds (engine type M 44.51) the boost pressure drops off again and reaches a boost pressure of 1.52 ±0.03 bar (absolute pressure) at 5,800 rpm. With engine type M 44.52, the boost pressure remains constant at 5,800 rpm (1.75 bar absolute pressure) and drops only after this value has been passed."
M 44.51 1986-1988 Model 944 Turbos
M 44.52 1988.5-1989 Model 944 Turbos
There does seem to be some variance between models, but I don't know that anyone's ever actually proven if the later model cars produce a higher maximum boost. The factory does indicate that there is a 10% tolerance at maximum indicated boost. So, that means that the indicated maximum boost could range anywhere from 1.58 bar to 1.93 bar. Start looking for problems if your maximum boost is consistently less than 1.6 bar.
07-13-2006, 02:15 AM
#18
Rennlist Member
Originally Posted by tommye
Not at all - you're probably talking about atm (athmosphere).
If you substitute Bar with atm in your statement above - then it is not too far off.
1 atm = 1.013 Bar
I think the Porsche workshop manual (as posted by Hosrom) is to be taken as reference. They state the level at 0.75 and the unit as Bar:s.
0.75 Bar = 10.878 PSI
If you substitute Bar with atm in your statement above - then it is not too far off.
1 atm = 1.013 Bar
I think the Porsche workshop manual (as posted by Hosrom) is to be taken as reference. They state the level at 0.75 and the unit as Bar:s.
0.75 Bar = 10.878 PSI
1 atm = 1.01325 bar = 14.7 PSI
1 bar = 14.5 PSI
.75 bar = 10.9 PSI
