Boost gauge question
Thread Starter
Melting Slicks
Joined: Apr 2007
Posts: 3,290
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From: Willow Springs IL
Boost gauge question
I installed cyberdyne fuel pressure and boost gauges tonight. The wires from the boost sending unit were not that long to allow the sending unit to be installed under the hood, so I moved it into the car so the wires would reach up into the a pillar. The gauge is not reading accurately. It says I have 17psi at idle and actually goes down as I rev the motor. Is it possible to have locate the sensor too far away from the vacuum line at the brake booster? Would this cause my problem?
Le Mans Master
Joined: Oct 2007
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From: Greater Detroit Metro MI, when I'm not travelling.
I installed cyberdyne fuel pressure and boost gauges tonight. The wires from the boost sending unit were not that long to allow the sending unit to be installed under the hood, so I moved it into the car so the wires would reach up into the a pillar. The gauge is not reading accurately. It says I have 17psi at idle and actually goes down as I rev the motor. Is it possible to have locate the sensor too far away from the vacuum line at the brake booster? Would this cause my problem?
Also if you have 17PSI at idle before your throttle body your BOV is sticking...
Remember analog gauges run the vac/boost line into the car and right up to the gauge itself. Having a long run like that introduces a slight delay on the readings, but it does not account for massive errors like that.
Last edited by PowerLabs; Mar 7, 2010 at 01:00 PM.
Thread Starter
Melting Slicks
Joined: Apr 2007
Posts: 3,290
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From: Willow Springs IL
No. You hooked it up incorrectly. I bet you're looking at pre-throttle body pressure.
Also if you have 17PSI at idle before your throttle body your BOV is sticking...
Remember analog gauges run the vac/boost line into the car and right up to the gauge itself. Having a long run like that introduces a slight delay on the readings, but it does not account for massive errors like that.
Also if you have 17PSI at idle before your throttle body your BOV is sticking...
Remember analog gauges run the vac/boost line into the car and right up to the gauge itself. Having a long run like that introduces a slight delay on the readings, but it does not account for massive errors like that.
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From: Raleigh, NC
St. Jude Donor '15
what does it say with the car off?
and if it were saying -17 it would make sense that it go closer to 0 when you give it some gas.. that's what it should do, obviously
and if it were saying -17 it would make sense that it go closer to 0 when you give it some gas.. that's what it should do, obviously
Le Mans Master
Joined: Feb 2007
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From: Mt Pleasant, TN
If I remember right (could be way off here) but with those when it changes from vaccum to boost the number get brighter and there isnt a negative symbol, but like I said I could be thinking of a different gauge.
Thread Starter
Melting Slicks
Joined: Apr 2007
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From: Willow Springs IL
Is there a limit to the length of tubing you can run from the boost source (brake booster, intercooler etc...) and the pressure transducer? I ran it all the way to the passenger side of the car so I wouldn't have to drill a hole in the firewall. I wouldn't think there would be a problem with the length though. pressure is pressure right?
Race Director
Joined: May 2004
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From: Raleigh, NC
St. Jude Donor '15
perhaps you should answer my question. if it's not reading correctly when the engine isn't even running then clearly there is a problem that isn't related to how this thing is connected.
Speedy
Joined: Mar 2007
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From: Tn
2024 C8 of the Year Finalist - Modified
Is there a limit to the length of tubing you can run from the boost source (brake booster, intercooler etc...) and the pressure transducer? I ran it all the way to the passenger side of the car so I wouldn't have to drill a hole in the firewall. I wouldn't think there would be a problem with the length though. pressure is pressure right?
maybe your sending unit wires are backwards?
Thread Starter
Melting Slicks
Joined: Apr 2007
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From: Willow Springs IL
Thread Starter
Melting Slicks
Joined: Apr 2007
Posts: 3,290
Likes: 0
From: Willow Springs IL
Sending unit wires are ok. I checked that. I thought it may be a ground problem but I tried running a ground from the motor right to the gauge with the same problem. I am stumped.
Melting Slicks
Joined: Sep 2004
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From: Union City CA
Just want to get the fact straight. Your Boost/Vacuum gauge reads 17 at idle, does it go down if you give it some gas? If it does then you are reading vacuum and not boost. cyberdyne vacuum does not have a - sign, it just display the number.
Last edited by csun213; Mar 7, 2010 at 11:47 PM.
Speedy
Joined: Mar 2007
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From: Tn
2024 C8 of the Year Finalist - Modified
what happens if you go wot to redline?
Thread Starter
Melting Slicks
Joined: Apr 2007
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From: Willow Springs IL
Didn't try that. It does read 17 at idle and go down when I give it gas. Is it really possible to have 17 inches of vacuum at idle though? That just seemed a little off to me. I assume I probably wont see mush boost without a load on the engine. Maybe I'll button it up and take it for a little road test and see what it reads.