Need Advice with Fuel Issues

[Steedaq]

Hi all,

I've done a few searches here and at other forums and haven't quite found a definitive answer to how I'm going to solve my problem. Here are the details:

• 2001 Mustang GT
• Have the stock GT tank with dual Cobra injectors (red tops)
• Making good pressure all the way up to redline (42 psi)
• Pumps are at max duty cycle around 4900-5000 at WOT which is causing me to lean out a bit up top - Max power is coming in at 5800
• Bumped up the voltage a bit and tried to dump more fuel but that didn't help

I realize that I need to upgrade, but I'm not sure to what yet.... What do you guys think?

Any help is much appreciated...

 

[wmburns]

Upgrade what???? Fuel pressure a constant 42 PSI all the way through the pull. Fuel pump sounds OK to me. Would expect to see a drop in fuel pressure if the pump were not keeping up.

What is the injector duty cycle?

What is the MAF voltage at max power?

What about the long term and short term fuel trim?

 

[Steedaq]

Upgrade what???? Fuel pressure a constant 42 PSI all the way through the pull. Fuel pump sounds OK to me. Would expect to see a drop in fuel pressure if the pump were not keeping up.

What is the injector duty cycle?

What is the MAF voltage at max power?

What about the long term and short term fuel trim?

Yea, that's what's not making sense to me either, as I'd expect a drop in pressure too... The pattern we saw is that as the duty cycles were pegged, my A/F started to lean out.

I'm not sure about the MAF at max power.. That's a good question.. How would that affect this?
Another good question about the long term and short term fuel trim - Can you explain?

Thanks.

 

[wmburns]

The MAF's max voltage is just under 5 volts. At 5 volts, the MAF is metering all of the air it can. Therefore, any additional increase in air flow will not raise the voltage above 5 volts. The PCM will see this as constant air flow. However, the actual air flow is greater. Hence the lean condition.

If the injectors are at max flow, the duty cycle will be > 85 percent.

To diagnose will need to know the MAF voltage and injector duty cycle.

 

[Steedaq]

The MAF's max voltage is just under 5 volts. At 5 volts, the MAF is metering all of the air it can. Therefore, any additional increase in air flow will not raise the voltage above 5 volts. The PCM will see this as constant air flow. However, the actual air flow is greater. Hence the lean condition.

If the injectors are at max flow, the duty cycle will be > 85 percent.

To diagnose will need to know the MAF voltage and injector duty cycle.

Makes sense - Let me look into this...

 

[Steedaq]

The MAF's max voltage is just under 5 volts. At 5 volts, the MAF is metering all of the air it can. Therefore, any additional increase in air flow will not raise the voltage above 5 volts. The PCM will see this as constant air flow. However, the actual air flow is greater. Hence the lean condition.

If the injectors are at max flow, the duty cycle will be > 85 percent.

To diagnose will need to know the MAF voltage and injector duty cycle.

Ok... I got the latest...

The MAF was not pegged and the injectors weren't the problem either. The tuner said that he thought we didn't see a pressure drop as it leaned out so close to redline. He thinks that the twin Cobra pumps are draining the bucket at high RPM and that I should go with the Cobra tank - What do you guys think?

 

[SaleenGT2001]

there shouldnt be a bucket anymore if you are running twin pumps. that part should have been taken out to fit the twin pumps.

how much power is the car making?

 

[wmburns]

Could someone help me understand how it is possible to starve (cavatate) a fuel pump and it NOT show up in the fuel pressure? Esp at high flow?

My BS detector is on alert.

 

[Steedaq]

there shouldnt be a bucket anymore if you are running twin pumps. that part should have been taken out to fit the twin pumps.

how much power is the car making?

No, the bucket is still in there as this was the bucket that Steeda sold. I don't think they make this any more.

 

[Steedaq]

Could someone help me understand how it is possible to starve a fuel pump and it NOT show up in the fuel pressure? Esp at high flow?

My BS detector is on alert.

I don't understand this either....