A Question for other Boosted Mustangs

What does your fuel pressure do?
1. At idle?
2. When you first touch the throttle aggressively?
3. Wot 3-6k rpms?

I am in the middle having a company tune my mustang and the tuner thinks I have an issue with my fuel psi. I just want to see if my car has a problem (new build) or if he should be able to tune it.

I have the Roush TVS w/GT500 pumps, 43 at idle and part throttle, 65 WFO.

If you're using the crap relay from the GT500 kit, trash it and use a high voltage relay like these ...

good tip on the relay! Thanks

I'm gonna go get in my car in a few minutes. I will video my start up. It'll show the manifold pressure gauge right along side the fuel pressure gauge. I'll try and get a little driving up towards the hwy but there are always cops hanging out so full boost prolly not gonna happen. But you should see a direct correlation between the manifold vacuum or pressure with the corresponding fuel pressure. Now my boost gauge is off by I think about 1.5 psi but the relationship should remain constant.

I let lito worry about that stuff!

Hey, serious question: Does the pump run differently at idle then when moving?

I'm wondering if the computer slows the pump down as you slow to a stop.

1950StangJump$ said:

Hey, serious question: Does the pump run differently at idle then when moving?

I'm wondering if the computer slows the pump down as you slow to a stop.

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If you still have the returnless system then yes, as the engine slows so does the pump. Less pressure/volume is needed compared to part throttle and WOT.

Has anyone looked at their fuel pressure to see if their fuel pressure drops to around 32 when you first get on it?
I wish Lito would email me back so I could get him to tune me, i emailed him 5 times in 2 months.

My 2010 auto with Roush M90 + oem single pump shows 40 psi @ idle...or WOT @6 krpm. Only the FPDC changes. 40% at idle. 80% at krpm / wot.

Thanks for the input, I called Edelbrock about the Eforce installation to make sure my vacuum lines are correct and he said my lines were correct. The tech guy at edelbrock seemed to think that the fuel pressure drop was normal. I don't know. I hope my tuner can get me tuned right.

Justin302 said:

Has anyone looked at their fuel pressure to see if their fuel pressure drops to around 32 when you first get on it?
I wish Lito would email me back so I could get him to tune me, i emailed him 5 times in 2 months.

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You must not be using the correct email for Lito. I emailed him 2 weeks ago, and he got the car tuned within those 2 weeks. On both 93 and e85. Here is the email I used: [email protected]

I have the Edelbrock and an Interceptor gauge. But I have a Boost a Pump. I’ll be going out later and tell you what mine does.

Laga said:

I have the Edelbrock and an Interceptor gauge. But I have a Boost a Pump. I’ll be going out later and tell you what mine does.

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Set the interceptor gauge so it reads... both fuel rail pressure...and also fuel pump duty cycle.
(fpdc). The fpdc will indicate 1/2 of the actual FPDC.

I noticed on my own interceptor gauges, that with...'key on, eng off' the fuel rail pressure is 50 psi....allowing time for the gauges to boot up. Once started , pressure drops to 40 psi..and
stays put... regardless of rpm..... or boost.

Justin302 said:

Thanks for the input, I called Edelbrock about the Eforce installation to make sure my vacuum lines are correct and he said my lines were correct. The tech guy at edelbrock seemed to think that the fuel pressure drop was normal. I don't know. I hope my tuner can get me tuned right.

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1 or 2 PSI might be ok. But if it's dropping a lot that's not normal. That generally means your pumps can't keep up.

Pentalab said:

Set the interceptor gauge so it reads... both fuel rail pressure...and also fuel pump duty cycle.
(fpdc). The fpdc will indicate 1/2 of the actual FPDC.

I noticed on my own interceptor gauges, that with...'key on, eng off' the fuel rail pressure is 50 psi....allowing time for the gauges to boot up. Once started , pressure drops to 40 psi..and
stays put... regardless of rpm..... or boost.

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That's not good at all brother. If fuel pressure does not rise with manifold pressure the fuel delivery can not be calibrated effectively. If you go from -15 psi of pressure to 10 psi of boost thats a pressure difference of 25 lbs. If fuel pressure is at 40 psi when at idle or -15 psi manifold pressure, and it stays at 40 psi when manifold pressure reaches +10 psi you are not getting the same amount of fuel in there per a given injector pulse.

Justin302 said:

What does your fuel pressure do?
1. At idle?
2. When you first touch the throttle aggressively?
3. Wot 3-6k rpms?

I am in the middle having a company tune my mustang and the tuner thinks I have an issue with my fuel psi. I just want to see if my car has a problem (new build) or if he should be able to tune it.

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A couple of vids for you so you can see how pressure goes up and down in relation to manifold pressure or vacuum. From the looks of it my ECU commands the lowest ever fuel pressure to be at a minimum of about 30 psi regardless of how low the manifold pressure drops. But every time the gauge gets to -10 in manifold pressure you will see the fuel pressure rise in direct relation. Meaning that whatever the manifold pressure reads, the fuel pressure stays about 39-40 psi above that. At full boost (11.3 psi) my fuel pressure gauge reads just over 50 psi. I wasn't able to reach that boost pressure on the vids but I have my gauge set to give a warning below 50 psi at WOT.

07 Boss said:

That's not good at all brother. If fuel pressure does not rise with manifold pressure the fuel delivery can not be calibrated effectively. If you go from -15 psi of pressure to 10 psi of boost thats a pressure difference of 25 lbs. If fuel pressure is at 40 psi when at idle or -15 psi manifold pressure, and it stays at 40 psi when manifold pressure reaches +10 psi you are not getting the same amount of fuel in there per a given injector pulse.

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Depends on the PID he's watching. If he's watching Pressure Drop Across Injectors then seeing 40psi is normal. As long as it stays around 40psi in that instance he's good. If he has an aftermarket pressure gauge then yes, he has issues.

I am looking on drop across injectors. What can I do to troubleshoot?

What pump are you running now? I have this, and it will easily handle what ever the stock short block can handle: https://www.s197forum.com/threads/diy-walbro-405-pump-and-wire-kit.85899/

Install was easy, and it just works.

MrAwesome987 said:

What pump are you running now? I have this, and it will easily handle what ever the stock short block can handle: https://www.s197forum.com/threads/diy-walbro-405-pump-and-wire-kit.85899/
Install was easy, and it just works.

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I have the Gt500 pumps, my last dyno before I started getting into the new tuning through Lasota was 580whp.