Too much boost???
06-09-2003, 09:56 PM
#1
Cruisin'
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Join Date: May 2003
Location: Ramstein AB, Germany
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Too much boost???
I have a euro spec 89 944 Turbo with the trophy cup options. The car only has about 30,000 miles on it and runs beautifully. I am a bit concerned about what my stock boost guage is telling me though. After 3500rpms when I really drop the hammer the guage will read all the way up to 1.8 bar!!! Could this be the actual boost and if so what would be allowing such high pressures?
06-09-2003, 10:13 PM
#2
Don't confuse boost with bar. 1 bar is normal atmospheric pressure at sea level =14.8 psi. Anything less than 1 bar equates to vacuum.
Anything over 1 bar is what you are 'boosting'. So on the stock gauge you are reading .8 bar (12 psi) of boost which is normal.
This as read on your stock gauge. If you install aan aftermarket boost gauge, most read vacuum (in hg, or inches of mercury) until atmospheric pressure is reached, then it measures boost.
Example below.
<img src="http://boards.rennlist.com/upload/3401.jpg" alt=" - " />
Anything over 1 bar is what you are 'boosting'. So on the stock gauge you are reading .8 bar (12 psi) of boost which is normal.
This as read on your stock gauge. If you install aan aftermarket boost gauge, most read vacuum (in hg, or inches of mercury) until atmospheric pressure is reached, then it measures boost.
Example below.
<img src="http://boards.rennlist.com/upload/3401.jpg" alt=" - " />
06-09-2003, 10:34 PM
#3
Burning Brakes
at what point should the stock boost reed above 1? just cruising @ 55mph 4th gear with about 2900 rpm should it be @ one? my stock guage read below it. is this bad? where should it read?
tia
tia
06-09-2003, 10:35 PM
#4
Cruisin'
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Outstanding that makes absolute sense! I am new to boosted cars as my usual fortay lies in American V-8 Muscle but, when in Germany...
Thanks for the info!
Thanks for the info!
06-09-2003, 10:44 PM
#5
Rennlist Member
The real issue here is gauge versus absolute pressure. Your guage reads absolute. So at one bar you are at 14.5 psi absolute. You are just on the verge of positive pressure at sea level. At 1.8 bar you are at 26.1 psi absolute which equals 11.6 psi gauge, your actual boost pressue.
1 bar = 14.5 psi
1 atmosphere = 14.7 psi
1 kilopascal = 0.1450 psi
Hope this helps,
Alan C.
1 bar = 14.5 psi
1 atmosphere = 14.7 psi
1 kilopascal = 0.1450 psi
Hope this helps,
Alan C.
06-09-2003, 10:48 PM
#6
Rennlist Member
Carl,
Just cruising you are not on the boost at 2900 rpm. So below one is ok.
Alan C.
Just cruising you are not on the boost at 2900 rpm. So below one is ok.
Alan C.
06-09-2003, 10:51 PM
#7
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by carl michael co:
<strong>at what point should the stock boost reed above 1? just cruising @ 55mph 4th gear with about 2900 rpm should it be @ one? my stock guage read below it. is this bad? where should it read?
tia</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">When cruising at a steady rpm on the highway, you won't read any boost. Normally, these cars idle at about 12 in hg and on the highway maintaing the same speed, i see 8-10 in hg. If you press the accelerator at this point the boost will rise.
Boost pressure is dependant on a few factors in these cars; throttle position, gear, and engine speed.
In 5th gear at 2600 rpms and constant throttle, not much is going on. But if you down shift to 3rd and floor the throttle, things get very exciting indeed. <img border="0" alt="[burnout]" title="" src="graemlins/burnout.gif" />
<strong>at what point should the stock boost reed above 1? just cruising @ 55mph 4th gear with about 2900 rpm should it be @ one? my stock guage read below it. is this bad? where should it read?
tia</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">When cruising at a steady rpm on the highway, you won't read any boost. Normally, these cars idle at about 12 in hg and on the highway maintaing the same speed, i see 8-10 in hg. If you press the accelerator at this point the boost will rise.
Boost pressure is dependant on a few factors in these cars; throttle position, gear, and engine speed.
In 5th gear at 2600 rpms and constant throttle, not much is going on. But if you down shift to 3rd and floor the throttle, things get very exciting indeed. <img border="0" alt="[burnout]" title="" src="graemlins/burnout.gif" />