Fuel return after already tuned

[zdawg801]

Am I going to have to retune my car if I decide to put a fuel return line in.. I've heard a lot of different answers and looked everywhere so I have come here for my last hooah... plus I got my car tuned when it was like 40 degrees out and colder.. since Im in a lot warmer weather what problems may I encounter?

[SRT-What?]

Installed my fuel return setup (w/ bottle neck fix) last weekend. Setup the fpr to 58 psi static. Didn't hook up the boost reference at this time. Kept the 'fuel return table' as stock S2.

Car ran #1.

we were messing with the fuel pressure with the car idling. car kept 14.7 afr (would have like to see the fuel trim try to manage that !)

Once set to 58 psi went back home and saw the difference between return less and full return setup.

Before : The car was leaning badly @ 20 psi (50T). Starting at 11.7@3500 rpm to 13.5 @ 6500.

After : The car is running 11.5 all the way to redline were it climbs rapidly to 12.5. I think 60lbs injectors are not enought at 58 psi. I was planning on putting in the boost reference this weekend and retune the 'fuel return table'.


I think all I have to do is put '1.0' in all the cells since I'll be running it from a boost/vacuum source (I was thinking using the stock boost line that goes to the boost gauge inside the car since I'm relocating my aeroforce there).

Someone could confirm ?

[julius717]

Quote: Originally Posted by SRT-What?

Installed my fuel return setup (w/ bottle neck fix) last weekend. Setup the fpr to 58 psi static. Didn't hook up the boost reference at this time. Kept the 'fuel return table' as stock S2.

Car ran #1.

we were messing with the fuel pressure with the car idling. car kept 14.7 afr (would have like to see the fuel trim try to manage that !)

Once set to 58 psi went back home and saw the difference between return less and full return setup.

Before : The car was leaning badly @ 20 psi (50T). Starting at 11.7@3500 rpm to 13.5 @ 6500.

After : The car is running 11.5 all the way to redline were it climbs rapidly to 12.5. I think 60lbs injectors are not enought at 58 psi. I was planning on putting in the boost reference this weekend and retune the 'fuel return table'.


I think all I have to do is put '1.0' in all the cells since I'll be running it from a boost/vacuum source (I was thinking using the stock boost line that goes to the boost gauge inside the car since I'm relocating my aeroforce there).

Someone could confirm ?

u wanna T off the throttle body for your boost reference for the return line. just cap the boost gauge line under the dash. im doing the same with my aeroforce also.

[Nick Fury]

@SRT-What?

Hmm, I'm having the same issue.

A few weeks ago my fuel line inside the canister went ( i have the BNF ). I replaced the line and took the car out for a ride. All the little stumbles I was having went away and the car was driving around town better than ever, until WOT. At around 3500 it leaned out to the 13s, so I added more fuel up top, still the same. I'm running 750's, BNF @ 58psi and I'm also running a stage 2 based tune. I havent had time to mess with it, but since my boost goals were all under 22psi I didnt think about putting on a boost source since I though I had plenty of fuel.

Basically you saying that you just put on the boost source and it cured your problem? Any addtl things you have tried?

Also, for anyone that sees this, make sure when you do the bottle neck fix not to use the standard 'fuel line' you get at most auto parts store in there. Its fine for fuel on the side, but when its submerged in the tank it will decay. Go with an sae30r10 rated hose (usually about $20 a foot) which is rated to be submerged in the tank and not have this issue.

[SRT-What?]

Quote: Originally Posted by Nick Fury

@SRT-What?

Hmm, I'm having the same issue.

A few weeks ago my fuel line inside the canister went ( i have the BNF ). I replaced the line and took the car out for a ride. All the little stumbles I was having went away and the car was driving around town better than ever, until WOT. At around 3500 it leaned out to the 13s, so I added more fuel up top, still the same. I'm running 750's, BNF @ 58psi and I'm also running a stage 2 based tune. I havent had time to mess with it, but since my boost goals were all under 22psi I didnt think about putting on a boost source since I though I had plenty of fuel.

Basically you saying that you just put on the boost source and it cured your problem? Any addtl things you have tried?

Also, for anyone that sees this, make sure when you do the bottle neck fix not to use the standard 'fuel line' you get at most auto parts store in there. Its fine for fuel on the side, but when its submerged in the tank it will decay. Go with an sae30r10 rated hose (usually about $20 a foot) which is rated to be submerged in the tank and not have this issue.

Actually I'm having way more issues now than when I started last week.

When I'm running static 58 psi, my injectors are at 96-97% duty cycle @ 20 lb boost. The bottle neck and retunr line only help much (about .5 AFR).

And when I hook up the reference to the FPR, everything get fucked up. Let me explain....

I hook everything correctly. Go for a test drive, knowing that the ECU would not like it since I would be putting not enought fuel under vacuum and putting way more fuel under boost. Effectivly, the car is having difficulty to idle but is driveable. Go back home to modify the fuel return table. Put '1.0' everywhere since I'm having a vacuum/boost reference. Go for a test drive. Car runs super fine. Fuel trims are about the same as before.

But when I go WOT, that's where the problems start... car runs 12.X AFR (was running 11.5 before hooking up the FPR, only changed the fuel return table). I'm like WTF !!!

Go back home. Modify the fuel return table again, but this time, I keep the stock values for the over 0 kPa values thinking that I would run alot richer if I don't tell the computer that I have a rising rate. Go for a test drive. Go WOT. Result : 13.x AFR after 0.5 sec. SHIT !!!

So I'm back to static fuel pressure, trying to figure out what is wrong.

I do have some questions :
- How can the SCT values go all the way down to -175 kPa the MAP and TIP are only good for (about) -16 psig ?

- Why the hell do we have to put '1,0' ? I mean, this value is a modifier right ? Is it to compensate for the pressure in the manifold helping/restraining the fuel from going from the fuel line to the manifold ?

- And most importantly : HOW COME I'M RUNNING LEANER WITH THE FPR HOOKED UP !!!! Next step is to extend my gauge under the hood to the windshield to see if the pressure is really going up or not. Hope the FPR is not the problem... Or that something went wrnog in the canister which is preventing me from having a higher fuel pressure....liek the pump !!! ARGH !!!

Next thing I'm going to try is raise the static pressure higher (68psi let's say) and see what's going to happen....

[NoLSDSrt]

boost source for fpr needs to be a boost only source not the line that runs to the guage. Also make sure your static on the fpr is set with the vac line off. Theres no reason why you would need 68 psi base.