My cousin's car is currently at a shop being tuned and things aren't going so well. The car had previously been tuned on a Dyno Dynamics and made roughly 290 hp at 17 psi using 850cc injectors with a Supra 260lph pump. He was having some fuel pressure issues so it stopped there. Injector duty cycle on the AEM was approximately 70%. The car was brought back to the shop a month or so later and after testing, they found that the fuel pressure would climb up from 43.5 psi base about 5 psi, then drop approximately 15 psi while full throttle. They diagnosed the problem to be the fuel pump, and swapped it out with a new Aeromotive 340lph pump. After testing the car again on the dyno, the fuel pressure still dropped. They then replaced the Aeromotive fuel pressure regulator and the problem was solved. This time while tuning the car on the dyno, the injector duty cycle is at 80% at only 240hp with 10 psi of boost. The shop is saying that the injectors are out of room and need to be upgraded. I find it hard to believe that an 850cc injector is at 80% idc using a 340lph pump, when it was significantly lower with more power/boost before. How can I determine if the problem lies with the fuel pump rather than the injectors? They are stating that the fuel pressure is great so it's not the pump. Any information would be appreciated.

 

I made 460 hp @ 80% ~IDC with 1kcc injectosr on a single walbro 255hp. This was at 26psi on a 6262

I can't imagine running out of injector on 850 injectors at 20psi on any turbo short of a 42r, and at that he'd be making more than 240hp.

What turbo is he running anyways? can you post any logs?

 

He's on the road right now with his laptop so I don't have any logs at the moment. The car is actually a MR2 with a 50 trim turbo running AEM. I made more safe power than this 10 years ago on 550s, but the shop is saying that his injectors are either dirty or not actually 850cc. I'm guessing that this pump is probably the problem, but I'm gonna have to prove it to them when I get to the shop on Saturday.

 

Lol, well being that this is an Evo board, The car being a different make is kind of a large factor ;-)

 

Not especially. Air and fuel consumption from one 4 cyl. car to another can be somewhat relative. What type of fuel are we talking about? 850cc injectors should easily support more power than that no matter what size turbo you are running.
Dan

 

This is on a 93 octane map. These cars are very similar to tune. I just trying to figure out how to tell if a fuel pump not performing vs fuel injectors being maxed.

 

Is fuel pressure gonna be my only indicator? I had my injector duty cycle jump over 100% in my 2g Talon when I had a fuel leak. Unfortunately, my fp gauge was under the hood so I was unable to see how the pressure responded. The shop is arguing that the pump is good because the fuel pressure is good. It doesn't make sense though that the idc was good when the car pulled into the shop.

 

Just because you have pressure doesn't mean you have volume. Check the O-ring and make sure it didn't push out when installing the new pump. If you had the shop that "diagnosed" (poorly I might add) your problem install it, I would say that there is a good chance of error on the install as well.
Dan

 

^^ x2

 

if you do have decent fp in the fuel rail @ 80% inj duty w/afr's where they need to be, you maynot be running 850cc injectors or the injector scaling within the cal is way off.

what injectors are you running?

 

I believe they are Siemens 850cc.

 

Here is a log from friday night. Steven(my cousin) was riding with me when the pull was made.