Lean issue

[killerkali]

I've recently developed an issue where I am running slightly lean between 3-4k. I am running EV14 72lbs, Walbro 450 relayed on e85. Was fine all winter, but oddly after a dyno (put down 400whp), I now run about .5 lean up to around 4k, past that it enriches ok. It floats around 12.7 during that period to 4k, and the car obviously is breaking up . Since all this started, my fuel pump has been making more noise. I checked inside the tank, and it seems I am getting a buzzing type sound from the fuel EXITING the return line, and if I remove my direct relay and plug the factory harness in , it quiets down. I was thinking some restriction in the return side? Last thing I did to check this was my fuel pressure. At idle, it sits at 58 psi. At WOT I was getting about 78 psi with boost at ~22. Is the fact that I am missing a few psi in my fuel pressure an issue? I thought it is supposed to be FPR pressure (4bar/58psi) + boost (22) = 80? All filters were replaced within 15k. Fuel trims are still spot on as usual, and Inj duty cycle isn't getting ramped up like a failed pump would usually indicate.... Any pointers are appreciated.

[Dalers08]

I would check the fuel filter. I had the same symptoms and it ended up being the filter killing the pump.

[killerkali]

I would check the fuel filter. I had the same symptoms and it ended up being the filter killing the pump.

It was replaced less than 7 months ago, although it could still be an issue since Ive swapped from 91/e85 3 times.....

Any insight on the fuel pressure issue? If my car is running 22, my FP should be spot on at 80 then correct? As i tested, it was maybe 3psi below that, is that enough to cause a lean issue? I don't fully understand the FPR system.... Who else is running a walbro 450, any issues with return line size?

[julex]

You're pegging your FPR at idle, a normal thing with such high flow pump on stock FPR. That's why you're seeing 58psi at idle.

At idle, with 4bar FPR (4bar * 14.5psi = 58PSI), you should normally see 4bar + manifold absolute pressure (at idle it is about 18-20inhg whihc is about -10psi) for a net of 58psi + (-10psi) = 48psi

At boost you should see 58psi + boost which is actually accurate in your case since FPR is not pegged.

Why stock FPR pegs? Simply because return orifice is a little pin hole and thus it creates backpressure. The pressure goes up until the flow out of orifice matches incoming pressure, which in this case equals to 58psi.

Now, what this means is that at idle and low loads your fueling is rich which prompts ECU to pull fuel (check your vagcom block 032 to see how much). Somewhere in the mid-high load point there is a breakpoint where the FPR starts responding properly BUT your ECU is still pulling fuel as if the FPR was overfueling and you get the lean condition. ECU gets confused further if the tune runs underscaled load (very common thing...) and it cannot properly use fuel adaptation ranges to correct for fueling quirks.

Tuner no doubt left the fueling alone to work itself out for normal driving, then adjusted WOT fueling and called it a day leaving mid point lean.

You only hope is to do something with FPR. I modified stock fpr successfully before to have a slightly larger orifice with a small drill bit since stock FPR outlet is funnel sized narrowing towards the tip, so drilling it to uniform maximum allowable diameter (be careful to not hit diaphragm inside) alleviated some of that pegging, but in the end I ended up with proper adjustable FPR with interchangeable orifices.

I hope this helps.

HEre is stock like adjustable FPR with small orifice so no improvement over stock situation:


Here is adjustable FPR with big orifice (so no pegging at FPR but stock fuel return lines might still be pegged by high flow pump):

[julex]

Also, 2psi less than expected at 80psi is only sqrt(80/78) = 1.0124 or 1.24% difference (at 11.5 afr that's barely 0.14AFR points or so, no big deal).

[killerkali]

You're pegging your FPR at idle, a normal thing with such high flow pump on stock FPR. That's why you're seeing 58psi at idle.

At idle, with 4bar FPR (4bar * 14.5psi = 58PSI), you should normally see 4bar + manifold absolute pressure (at idle it is about 18-20inhg whihc is about -10psi) for a net of 58psi + (-10psi) = 48psi

At boost you should see 58psi + boost which is actually accurate in your case since FPR is not pegged.

Why stock FPR pegs? Simply because return orifice is a little pin hole and thus it creates backpressure. The pressure goes up until the flow out of orifice matches incoming pressure, which in this case equals to 58psi.

Now, what this means is that at idle and low loads your fueling is rich which prompts ECU to pull fuel (check your vagcom block 032 to see how much). Somewhere in the mid-high load point there is a breakpoint where the FPR starts responding properly BUT your ECU is still pulling fuel as if the FPR was overfueling and you get the lean condition. ECU gets confused further if the tune runs underscaled load (very common thing...) and it cannot properly use fuel adaptation ranges to correct for fueling quirks.

Tuner no doubt left the fueling alone to work itself out for normal driving, then adjusted WOT fueling and called it a day leaving mid point lean.

You only hope is to do something with FPR. I modified stock fpr successfully before to have a slightly larger orifice with a small drill bit since stock FPR outlet is funnel sized narrowing towards the tip, so drilling it to uniform maximum allowable diameter (be careful to not hit diaphragm inside) alleviated some of that pegging, but in the end I ended up with proper adjustable FPR with interchangeable orifices.

I hope this helps.

HEre is stock like adjustable FPR with small orifice so no improvement over stock situation:


Here is adjustable FPR with big orifice (so no pegging at FPR but stock fuel return lines might still be pegged by high flow pump):

Very good info thank you Julex. I have an entire spare stock rail so Im going to see what drilling it does. So correcting the tune wouldn't help you think? Next step I can only see is aftermarket FPR+rails..

[julex]

Very good info thank you Julex. I have an entire spare stock rail so Im going to see what drilling it does. So correcting the tune wouldn't help you think? Next step I can only see is aftermarket FPR+rails..

Pegging pressure will change with fuel temperature and system voltage (that varies quite a bit between summer and winter for battery charging pusposes) as pump outputs more or less fuel volume/pressure so it is not possible to nail with a tune. It is a hardware issue, period. Get that adjustable FPR from USRALLY at http://www.usrallyteam.com/index.php...roducts_id=673 and call it a day, it has big return, certainly bigger than what you can hope to drill stock FPR out to.

[killerkali]

Pegging pressure will change with fuel temperature and system voltage (that varies quite a bit between summer and winter for battery charging pusposes) as pump outputs more or less fuel volume/pressure so it is not possible to nail with a tune. It is a hardware issue, period. Get that adjustable FPR from USRALLY at http://www.usrallyteam.com/index.php...roducts_id=673 and call it a day, it has big return, certainly bigger than what you can hope to drill stock FPR out to.

That looks promising, didn't know I could keep the stock rails . Thanks again Julex I appreciate the info