Relationship between temperature and fuel pressure.
Thread Starter
Melting Slicks
Joined: May 2005
Posts: 3,461
Likes: 161
From: Las Vegas Nevada
St. Jude Donor '08
Relationship between temperature and fuel pressure.
On a cool day (45-55*), my fuel pressure gauge reads about 62lbs. at idle and goes down to about 59lbs at full throttle. On a warmer day (70-85), the pressure is about 60lbs. at idle and goes down as much as 56lbs at full throttle. Is this normal? And just how does temperature relate to fuel pressure. Also, should I get a boost-a-pump or something similar to be on the safe side? 
Thanks,
Clayton from Las Vegas
Thanks,
Clayton from Las Vegas
Safety Car
Joined: Jun 2004
Posts: 4,353
Likes: 22
From: Bella Vista Ca
My car was similar to what you are describing as the temp increased. If your tune takes into acount the fuel pressure falling of you should be OK. Getting a boost a pump would be a good idea. I ended up going with the ECS fuel system. The boost a pump didn't help my pressure out enough to give me a warm fuzzy about the pressure. Now I am at 60lbs at all RPMs and temps. 
Supporting Vendor
Joined: Jul 2003
Posts: 6,486
Likes: 2
From: http://www.mphparts.com 800-364-1975
As fuel temp increases, your pressure will decrease a bit. Going down to 56psi at WOT is probably nothing to be alarmed at if your tune was done with the car warm and your air/fuel is still good at 56psi (which it likely is).
Ask your tuner how your car was setup. It was likely tuned with enough fuel to account for small changes in pressure.
Ask your tuner how your car was setup. It was likely tuned with enough fuel to account for small changes in pressure.
Le Mans Master
Joined: Apr 2001
Posts: 5,941
Likes: 281
From: Was New Orleans but swam to Baton Rouge LA
Cruise-In IX Veteran
where is the pressure gauge located? The C5 fuel system on 01's and later have a pressure regulator in the rear of the car. This means that when the gauge is in the front of the car by the rails you will see more drastic pressure drop as the fuel is being pumped from front to rear. as for the tempurature changes in pressure it has to do with the rising vapor pressure of the fuel. The rise in vapor pressure changes the density of the gasoline making it a lighter component. It is normal to see movement of the pressure to about 5-10 PSI in the system.
Former Vendor
Joined: May 2005
Posts: 3,749
Likes: 4
From: Valencia Ca
On a cool day (45-55*), my fuel pressure gauge reads about 62lbs. at idle and goes down to about 59lbs at full throttle. On a warmer day (70-85), the pressure is about 60lbs. at idle and goes down as much as 56lbs at full throttle. Is this normal? And just how does temperature relate to fuel pressure. Also, should I get a boost-a-pump or something similar to be on the safe side?
Thanks,
Clayton from Las Vegas
Thanks,
Clayton from Las Vegas
If you are running without a boost a pump, add one.
Charlie
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