Fuel pressure?

[camok5]

Any one have any ideas what I should be running for fuel pressure? Its a 383 with a bored out small block tbi unit and it has big block injectors. Also it has a high pressure fuel pump. It is set at about 13 psi right now because someone told me you dont need as much pressure with the big block injetors.

 

[4X4HIGH]

9-13 is factory settings. If you have winaldl you can play with the fuel pressure and see what your combo likes. Every engine is different and especially with mods done to it.

 

[camok5]

I have winaldl but I cant seem to figure it out yet.

 

[southernspeed]

Without reprogramming the impedance, higher fuel pressure will over power the injectors causing bad running.

 

[camok5]

It has been reprogrammed already.

 

[southernspeed]

To what pressure? It usually is a trial and error setting depending on the condition of your injectors.

 

[camok5]

To what pressure? It usually is a trial and error setting depending on the condition of your injectors.

My bad, i miss understood what you were saying. I have no idea how to reprogram the impedance. I'm just trying to figure out if my fuel pressure being set to low might be causing my surging idle problem.

 

[Jason4x4]

My bad, i miss understood what you were saying. I have no idea how to reprogram the impedance. I'm just trying to figure out if my fuel pressure being set to low might be causing my surging idle problem.

it could very well be your cam doing that.

 

[camok5]

Its not the cam. The cam is tbi friendly and this has only started more recently.

 

[dyeager535]

I've been out for a bit, so I forget if you mentioned prior, you had the PROM burned for your combo, including the larger injectors?

GM injectors are rated at the same flow rate, so when you burn a chip, it's a simple matter to change the injector size in the PROM, which if done should compensate for the additional fuel, simply modifying the amount of time they stay open...bigger injectors, same size motor, less time open. If you don't modify the injector constant when programming, obviously the larger injectors are going to throw things off...an injector flowing 25% more fuel (for example) during the same time period will obviously dump more fuel than the ECM expects.

You should run the pressure at what the injectors are rated at (13 I assume for TBI) and tune around that. Adjusting fuel pressure on EFI is a bandaid, as that is a global change, thus affecting the amount of fuel at idle up to WOT, which can be very problematic. If you were shooting for one fuel ratio during all engine operation, fuel pressure modification would work, but obviously one ratio is not best for all around driving.

 

[camok5]

Yes the prom was changed to compensate the larger injectors I played around with it a bit but ended up setting it back around 12.5-13 psi. I have still been to busy to figure out what is causing my surging idle but I'm now convinced that its not FP or my timing. I'm also still waiting for Brian(tbichips.com) to get back SEMA so he can help me out by reading my winaldl datalogs he is also the one who has burned my chips for me.

 

[dyeager535]

Yeah, I'd have to believe with his experience that the injector constant is right, and fuel pressure would be best at "normal". I'm going to go look at your logs, see if I can see anything. I really started to get into the datalogs before, but if you don't keep up on it you lose it.

I really do need to get back into it, start tuning my motor the way it should be.