Clipse3GT

iTrader: (10)

Here is my little story... to go in junction with the failing blue relay theory.

I started to have a lean out issue near the top end 6500 rpm+

I have FIC 1100cc injectors (more than enough for a FP Green on 93 octane).

I also have a in-tank Walbro F20000169 255HP...

I am running right now 90-100% IDC... It is strange because doing the math I should be around 75-85% IDC MAX.

This started to throw red flags a few weeks ago.

First remedy attempt to lower base pressure from 50 psi base, uptop the AFRs were 11.8-12.

Lowered to 45 psi base pressure, the AFR's richened a bit more uptop. 11.5-11.7




Lowered to 38 psi base pressure, the AFR richened more to 11.1-11.5.

Interesting, during this time I scaled the MAF each time and it lowered my MAF voltage each time.

So now it looks like the fuel pump flows a bit more at a lower base pressure. Either way, this fuel pump should be flowing more than this to supply a set of 1100cc injectors on 93 octane.

Now for the pictures... of the comparison. Same day pulls only change FPR.

I borrowed the Aeromotive FPR from my race car.

Aermotive FPR (38 psi base pressure) WOT PULL 3rd gear...

Now if I am out of fuel in 3rd gear, I will be out of fuel in 4th and 5th when load increases.








Now... the Fuelab Mini FPR (38 psi base pressure) WOT PULL 3rd gear...







P.S. Also note it is pointless to warranty a Walbro pump since you need to send them a check for $40 dollar to cut the pump in half and they never issues you a new pump.

So it is not the injectors, it is not the FPR, it is not the fuel filters both the inline and the sock are clean.

UT_EvoX

All I can tell you is get an in-cabin fuel pressure gauge to monitor pressure up top to see if it's the pump, lines, or filters.

fostytou

iTrader: (15)

Why don't you just try a new fuel pump rather than ripping into your car with lean AFRs like that? The stock fuel pump should actually probably provide plenty of flow for you if you are on 93.

Higher base pressures will reduce the flow of any pump, but remember we have a rising 1:1 fpr (which is why it needs a boost reference). It looks like you could be running 30psi, so at 1:1 you are at a minimum of 80psi fuel pressure (since you said you lowered to 50psi)... If I remember correctly a single walboro will flow enough for 4x1000cc at 43.5 psi of fuel pressure, so its much less than that at higher pressure.. Are you setting your base fuel pressure with the boost reference disconnected?

Can we see what is in your fuel map and your fuel calibration map?

Clipse3GT

iTrader: (10)

Thanks for your response but you do not have to reply to this post like I am a total noob.

First of all the car is not running lean, 11.2 is not lean. There is no knock.

Secondly, I tired two 1:1 FPRs on the car. The FPR is not the issue. The problem occurs with two different FPRs.

The filter sock and inline filter are both clean as whistles.

The base pressure was set with no reference to 45 psi, with reference it is around 37-38psi.

Thirdly, I was testing different fuel pressures to remedy the problem. I know pumps flow more at lower psi due to less heat and resistance.

Fourth, I prefer not to share my fuel maps nor calibration maps, I don't feel like some body plugging them into their setup and blowing up their car. The calibration map is driven more at the top end to deliver more fuel. We will see when I install the new fuel pump what the out come will be.

Basically at the midrange I am hitting 11 AFR WB with the AFR map set to about 11.1, but near redline I need to drive the map to 8.5 to hit 11's, forcing myself to drive the injectors more to deliver the required fuel.

I have a new GSS342 pump on order. I will post results when I install it next week.

The next item is that not all fuel pumps flow the same, even though they are rated for a certain gph/lph. Some flow less some flow more, I might have a pump that just flows less or is on the way out. Either way we will see with the new fuel pump.

As of recent I seen more Walbro pumps fail, and their warranty sucks. No point when you can buy a new pump for $70 bucks.

Hiboost

iTrader: (9)

Probably pushing the base fuel pressure to 50 psi resulted in 78 psi when @ 28 psi boost so while that helped the injectors flow more at lower RPM's, the pump was not happy and flowed less at the top end which resulted in the wacky tuning to ramp up the duty cycles of the injectors. Likely your pump is weak or starting to fail which of course shows up on the top end first.

Hopefully a replacement will do better but I would stick with the fuel pressure at a normal base pressure unless you are running out of injector and need a bandaid to increase their effective cc flow rate. Maybe I shouldn't say bandaid, but raising the base fuel pressure is only a good idea if you know the fuel pump has extra headroom for flow when running at higher pressures.

Definitely report back once you swap that pump to let us know what the issue likely was!

mlomker

iTrader: (1)

The GSS342 doesn't flow well above 70psi unless you mod the relief valve.

criptballer

iTrader: (3)

i'm working on write up on the effects of a kenne bell boost a pump on a walbro 255 lph in tank pump. and also some of the faults that our stock wiring has in regards to providing power to the oem pump. i'm sure you'll find it very interesting. I'll get around to posting it one of these days when i get a break from school and work

murlo26

iTrader: (9)

i think it is 75psi...but lomker is right. If you don't mod the relief spring, the walboro will start to bleed off pressure like mad at 75ish+ psi...but if you do mod it, it works awesome at those higher pressures.

fostytou

iTrader: (15)

Sorry, I'm so used to noob questions around here I must have injected a "Wut happen!?" at the end of your post.

... I was lead a little off-path when you mentioned the 11.8-12AFR though. As far as the fuel maps, I was hoping it would be a guide to see how far off things are. If some newb dumps a bunch of 8's into their fuel map thinking its a tune that is their own problem! I didn't have a reference since people regularly ask "How come when I put in 11afr I don't get 11afr out of the car?!"

I'm all with it now. Let us know if the new pump helps fix things!

Also, you could attempt to mod the relief on your current pump and see if that helps at all... maybe it came loose. If nothing else, it would be good practice for the new pump (if you intend to stay at a higher base fuel pressure).

Clipse3GT

iTrader: (10)

I tried the Bypass Mod on the Walbro pump.

Here are the results.

No change @ 38 psi base pressure + 27 psi @ Redline.

It seems that the pump is slowly failing.




The new GSS342 is going in tomorrow once I get it from USPS will post results.

Clipse3GT

iTrader: (10)

Update: Installed a Walbro GSS342 intank w/ Bypass Mod.

Started the car up.. The fuel pressure can go up. It stays now right around 49 psi base pressure it cannot be lowered.

The fix is I will enlarge the return orifice a bit more.

I am 99% that the issue was the fuel pump went bad. I will get the system to the proper operating pressure at idle and will report back.

The new fuel pump is flowing much more than the old pump and I can't even lower the pressure. Due to the Bypass mod, the pump can't vent the extra base pressure. So I will have to enlarge the return hole size.

Clipse3GT

iTrader: (10)

Results: I enlarge the return orifice to 7/64ths.

Got a base pressure of 43 psi w/ FPR.

Now here are the results. This is with the original Fuelab Mini FPR.

Yes, the IDC are still a ~100% since I am driving them the same since I am using the same map as before. I need to adjust them more.




Here is the dyno results... well yeah... I lost power. Running 10's (lowest for AEM UEGO), I am sure I was in the 9's.




Hope this thread helps someone diagnose their fuel pump problem.

2.4evo

iTrader: (19)

I had issues with my 255 a few months back and thank god my tuner called it.

Clipse3GT

iTrader: (10)

Yeah, the quality of Walbro has went downhill over the years. Hopefully this one lasts longer than 8 months.

derekste

iTrader: (9)

I like Bosch 044s as an alternative