Questions about fuel system regulation
10-29-2005, 11:07 PM
#18
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If you have an A/F meter, you could disconnect the vacuum lines to each part of the fuel system (and plug the open line so the other parts keep vacuum) and see if the mixture changes.
10-29-2005, 11:21 PM
#21
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The dyno showed two GTSs running at 11.5 and my GT running at 10.5. Roger, Jim and I are suspecting the dyno, but the readings were at different times and with different sniffers on the same dyno.
Where does an air/fuel meter measure the mixture and how does it measure it?
Where does an air/fuel meter measure the mixture and how does it measure it?
10-30-2005, 12:03 AM
#22
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10.5 doesn't sound overly rich to me for WOT, infact 11.5 seems not rich enough. You want it to run richer as that is how you make the most power. Usually the problem is the other way where it goes lean because you can't get enough fuel to keep up with the large amount of air. There aren't many ways for something to fail and give you more fuel at WOT or else people would do that on purpose.
But perhaps someone has modified something to give it more fuel? Has it always done this, or is this a recent problem? Is the power down on the dyno?
But perhaps someone has modified something to give it more fuel? Has it always done this, or is this a recent problem? Is the power down on the dyno?
10-30-2005, 12:26 AM
#23
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10.5 is too rich and leaves a lot of power on the table. The ideal mixture ar WOT is around 13 to 1. I've got an X-pipe with no cats into a stock cat back system with an RMB and I should be running a little lean to just right with the stock FPR.
10-30-2005, 12:49 PM
#24
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Originally Posted by Jim_H
I think Mark K said he ran without his damper? Could be an easy fix 
10-30-2005, 05:27 PM
#25
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Ernest,
My GT ran 11.8 close to redline (I think it was from 6200 up) when stock on the dyno with the tailpipe sniffer to check the mixture (dynojet). I would check fuel pressure with and without vacuum. If it is in spec, then possibly look to the MAF for being a few percent out of spec if original. John Speake looked at mine and it was a few percent out. Pull the vacuum lines off the dampers and check for raw fuel leaking into the lines. Possibly injectors with a bad spray pattern(wild *** guess).
I have my original regulator stored, if you want to give a different one a try.
Have you looked at the plugs after a WOT run? May be worth a check to see if they all look the same.
Jim
My GT ran 11.8 close to redline (I think it was from 6200 up) when stock on the dyno with the tailpipe sniffer to check the mixture (dynojet). I would check fuel pressure with and without vacuum. If it is in spec, then possibly look to the MAF for being a few percent out of spec if original. John Speake looked at mine and it was a few percent out. Pull the vacuum lines off the dampers and check for raw fuel leaking into the lines. Possibly injectors with a bad spray pattern(wild *** guess).
I have my original regulator stored, if you want to give a different one a try.
Have you looked at the plugs after a WOT run? May be worth a check to see if they all look the same.
Jim
10-30-2005, 05:41 PM
#26
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Hey Jim,
Thanks for the thoughtful response.
I'll check the damper vacuum lines.
John Speake said that a failing MAF will tend to make the car run lean.
The injectors were cleaned and balanced about two years/10K ago.
I'm going to install a fuel pressure meter and an RRFP, but thanks anyway.
Thanks for the thoughtful response.
I'll check the damper vacuum lines.
John Speake said that a failing MAF will tend to make the car run lean.
The injectors were cleaned and balanced about two years/10K ago.
I'm going to install a fuel pressure meter and an RRFP, but thanks anyway.
10-30-2005, 06:20 PM
#27
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Both dampers hold vacuum and the stock fuel pressure regulator holds vacuum and the vacuum line going to it works.
It would appear that if there is a fault in the fuel pressure line it must be the regulator itself.
It would appear that if there is a fault in the fuel pressure line it must be the regulator itself.
10-30-2005, 06:28 PM
#28
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MAFs don't always go lean when failing, that's just their usual mode of failure. Adding the fuel pressure meter and ARRFPR are probably the best thing to do.