I currently have the Vortech w/ 3.12 pulley, AAM fuel system w/ 440 injectors. It is currently set at 51lbs. It runs good, but I think my injectors are up in the 80-90% duty after 6400rpm. (rev limiter is 7100) I asked my tuner about raising the pressure and he said it shouldn't be raised and called that a band-aid. Any opinions would be appreciated.

 

Is this 51psi with the vaccum line connected...or disconnected?

 

Are you asking about when it was set? I am not sure. I am just going by the Defi gauge. Even so, I thought there was only a couple lbs difference.

 

it is usually going to be about 8-10psi difference and greater depending on boost level. i have mine set at 50psi static (vacuum line disconnected) then drops to about 42-3 at idle.

 

Does the vacuum line matter only when setting the pressure or do you leave it disconnected... I'm confused? My psi is usually between 49-52, but increases slightly under boost... maybe 55.

 

typically you want to just set the static fuel pres. with the vacuum line disconnected then just hook the vacuum line back up when finished.

 

Correct. With the vaccum line disconnected, you are setting what is called differential fuel pressure. This is the actual pressure coming out of the injector, when taking manifold pressure into effect.

 

How can one tell If the injectors are at 80 to 90 % duty cycle ? with the 3.12 and 440 injectors...you shouldnt be close to maxing them out

 

with the e-manage and the e-manage ultimate, you can get monitor duty cycle... (can graph it on a datalogger with the ultimate)..if the injectors reach 90-100% and the mixtures get leaner, then they are approaching their limit...

 

This is my Fuel Pressure set up APS TT kit + AAM Fuel Return system
Is this O.K for Fuel Pressure set up ????
With Out Vaccum Line 350kpa = 51 psi
With Vaccum Line Fuel Pressure drops to about 300kpa at idle. = 42.6 psi

So My Fuel Pressure set up is O.K ??????

 

yup, good place to start.

the eu will only tell a correct duty cycle if you have the injector signal cut from the injector size parameters. i am cutting it from both the injector parameters and airflow maps so the eu won't give me correct duty cycles on the injectors.

 

OK guys, I have another issue. I have done NOTHING to adjust pressure, but now my pressure reads 58-60psi during steady driving. As soon as I get on the throttle/boost, it drops immediately to 50psi and stays or raises slightly to 52psi. What is going on? It used to stay at 51psi and raise with boost. It never dropped before.


(btw, my injectors are at 80-85% so I am ok based on everyones input.)

 

I have been fighting with my fuel pressure, too. It seems to be affected by temperature. When it is really hot outside and my car has been driving for awhile, my pressure drops to 40-42, when it is cool outside it is around 62. When it is up high and I hit the gas it drops to the mid 50's. I am going to drill out the siphon jet a little more and see if that helps. I cannot get steady fuel pressure, it is always wrong. I have seen it hit 80 psi. I really think heat has something to do with it. When I drilled out the siphon jet, the first time, I put my hand in the fuel tank to move the line from the pump assembly and noticed that the fuel was extremely warm, like hot bath water.

Does anyone know if the fuel pump always works at a constant voltage? I notice my voltage drops as the car and weather warm up, too. This might be a coincidence, but when my voltage drops to 13.4V my corresponding fuel pressure is 42-45 psi. If my voltage is 14.4V, I get the 62-65 psi readings.

 

Actually, the EU will report correct duty cycles, regardless of the method in which the injectors are scaled. If you reduce the MAF signal, it will reduce IPW, but the reported injector duty cycle will always be correct.

 

I was curious about the temps outside as well. It wasn't until overnight temps fell to the 30s and daytime highs were in the 50-60 range that it started doing this. Let me know if you figure anything out.

Thanks.

 

Could this be a problem with your specific custom fuel system rather than having a return kit by AAM or CJM?

 

I have the AAM.

 

I was more refering to badmonkey's car

 

I really don't know. The system is pretty straight forward. I ran all of my fuel lines under the car in the stock positions. I have thermo wrap around my feed lines. The only difference is that I am usuing an Aeromotive FPR. I talked with their tech guys and they said that temp under the hood would not affect their FPR. I do know that the FPR does get real hot, though. I thought about moving my return lines and FPR further from the engine. I currently have the FPR mounted on the front of the timing cover. Here is a pic:



You can see the FPR on the front leftside of the engine. I held a heat gun to it when the engine was cold, to see if it would affect my pressure, but it didn't seem to change. I did the same to my sender from my fuel pressure gauge and it dropped almost immediately, which made me think it was only a sending issue. My car has bogged down under WOT around 6300-6500 RPM's, when the pressure was low, so, that tells me I am maxing out my injectors at the low pressure. Now that the temps have been in the 60's I haven't had the problem. It is when it is 80-90 degrees outside is when I really notice it. You can see the sender on the front of the FPR, I now have it moved with some -4 AN line all the way into the battery compartment, to get it out of the heat.