R13_Braz

Evening, gents.

Got my car dyno-tuned yesterday. Have a fueling problem in the higher RPM range, and my tuner is pretty sure it's related to the pump.

I have Racetronix's Walbro 255lph kit, with harness that goes directly to the alternator. I bought the booster kit as well, but I didn't wire it up and honestly wasn't sure how to even build it. Using the vette filter/reg, and 3/8's SSB line's with AN-6 fittings. All lines that aren't straight have gradual curves; I was meticulous when I ran them.

He said that the injector duty cycle wasn't even close to being maxed out, with it sitting at about 75%, but past 5.8k rpm the flow wasn't keeping up with the commanded levels. His recommendation was to change the pump out, but he didn't have a suggestion on which one.

I was planning on going with a dual 255 setup later to accommodate the turbo build, but now I'm not so sure. I called Aeromotive, and the guy I spoke with wasn't any help... essentially saying they didn't have anything that could work with my "old car setup", but immediately went on to recommend the Dual Phantom EFI system... of course. And to get rid of the filter/reg and use their products... again, of course. The shop that did the tune uses the filter/reg on almost all of their LS builds, so I don't think it could be that.

Is the pump the issue? The fuel line size? Is there a better pump setup that can go in tank without major modifications? I don't mind modding the sending unit to work, as long as it clears this issue up and I can get the tune to be where I want it.

R13_Braz

Would this be a suitable replacement? Will it fit in the stock sender?

redmaroz

iTrader: (4)

Thats odd that you would have a fueling issue, anything is possible i guess. I have the same setup as you, only I made my fuel line out the braided russel stuff. I havnt had any issues with mine. Do you think that maybe you might have a bad pump? I only ask becuase i thought i read a couple threads a while back where some guys were having issues with the whalbro pump. Hopefully you get it worked out, best of luck.

Lonnie P

The single 255 should be good to 550rwhp.
The 3/8" lines with rear mounted filter/regulator close to 700rwhp before pressure becomes unstable.


If you want to diagnose a problem... first get a pressure gauge on the car to see if the fuel pressure is really the problem. Steady pressure at high rpm (wide open throttle) means the pump & lines are sufficient.


Give me some feedback & I'll try to help you out.

R13_Braz

Yeah, after sleeping on it last night, I'm picking up a pressure gauge tomorrow after work.

Rear mounted filter in stock location, Russell SSB, etc.

However, had a thought... might have a vapor lock problem. When I ran the lines with the first engine, I had 3-3.5" between the line and header. With the latest engine, the positions of the headers have moved... enough to where the passenger side header contacts the frame rail and I only have about 1" on the driver side.

I'll update with what I'm seeing tomorrow after some some redline pulls, but I have a feeling the heat off the headers might be a problem.

92BLKL98

Sub'd

R13_Braz

So, yeah... Sears pressure tester was junk.. not a long enough hose to position the gauge where I can see it. Just ordered one off of Amazon that has a 6ft hose with the proper adapters for the rail.. will be here tomorrow.

Car drives amazing as is, plenty of oomph and get-up and go... obviously this will tell me what the fuel system is doing, but one thing I didn't notice in the video they took of the dyno was any fans in front of the car, which seems stupid... Yeah, the car runs cool, but you're running it up to high RPM in a stationary position with no airflow pulling the heat away from the underside of the car! That makes me REALLY suspicious of the numbers now.

R13_Braz

Now I'm really scratching my head...

Hooked the tester up, switched the pump on... 60 psi.
Started the car, got it idling good and warming up, 62 psi.
Rev it up to about 5.5 and held it... 62 psi.
Let it get to op. temp and repeated the 5.5k test... 60-62 psi.

So, I take it out on the road.

Normal driving, 62 psi.

Get it on the highway and punch it.. briefly (MAYBE a second) drops to 58, then goes right back to 62psi.
Row through the gears with it being WOT... hovers at 60-61.
Stick it in 3rd and keep it floored to about 5.7-5.8k for a sold minute and still 62 psi.

I can only conclude that I have *** 0 *** fuel pump/regulator/line problems from the above tests. 0 leaks, pump keeps up and is receiving voltage directly from the alternator, pressure is slightly higher than the 58 psi I thought it was supposed to be, but I don't think that's an issue. Only thing that could possibly correlate with what the tuner said would be injector issues... but not if the duty cycle wasn't maxed I don't think. Unless, of course, he was full of it and being lazy... but I don't want to assume that. Only thing I can think of is to try to get data logs from them so that I can see where it happened, as well as play 20 questions in regard to the process they used... since they did it without me being there, even though I requested a heads up.

One thing of note: After shutting the pump off, pressure drops down to about 45 psi, then starts bleeding down after about 20-30 seconds and hovers at 20. I didn't let it sit overly long because I can't monitor it through the night, and I have read that the Walbro pumps are notorious for bleeding pressure off so I'm not sure it's really an issue, especially since it starts immediately.

Mdenz3

iTrader: (7)

Can you post a picture of a run with the A/F ratio?

or a datalog file of the run?

R13_Braz

That's the thing.. they didn't give me anything! I had to fight them for a picture of the power pull! And it took them so long, I was in a rush to get home as they were over an hour away from my house and I had to fight rush hour the whole way back.

This "ghost problem" is really starting to stink...

Edit: I'm going to try to run a data log using the app I've got that monitors the ECM... see if it can monitor the A/F when at WOT. Unfortunately, I can't afford HPtuner's right now.

Mdenz3

iTrader: (7)

Torque app?

That will give you the commanded A/F and the O2 feedback, but without a wideband it won't do much good.

That said, under WOT your O2s should be ~0.9V

R13_Braz

Yup.

It's worth a shot anyway. As it stands, she drives great... but I just want to make sure it's not a problem in the future when I start my TT build, ya know?

I'll check it out tomorrow when I get home from work and post my findings.

Lonnie P

With stable pressure, I think you ruled out the fuel pump/lines as being the problem.


Now you need a wideband to prove the car is actually leaning out.


What is the car doing that you originally suspected a problem?

R13_Braz

Car wasn't doing anything for me.

I got it tuned last Friday and the tuner said he couldn't get the injectors to flow more fuel at the higher RPM, even though the duty cycle wasn't maxed out. *HE* said that it's probably the fuel pump.

It's speculation at this point until I can try to convince them to give me any logs they took.

Edit: However, now that I think about it, I'm running the 28.8 lb injectors... which is definitely a weak spot... and I'm sure they have an RPM limit. I planned on jumping to 76-80 lb'ers later but I may need to do it sooner if I want to maximize what I've got now.

Mdenz3

iTrader: (7)

For the power you're making the injectors are sized correctly

https://www.rceng.com/technical.aspx

Is the tuner doing a MAF or speed density tune?

R13_Braz

For the power I'm making, yes.. but I don't agree with it. There's always going to be differences between engines, and I know that... but an almost 60 HP difference compared to similar builds? There's a weak link somewhere. It may even be the tuner who is the weak link.. especially if he did a conservative tune instead of what I wanted, even if being forced to by not enough flow in the upper range.

MAF. I've got the 85mm truck MAF.

At this point, I'm going to say the injectors are my issue. They work fine, but aren't enough for the future. 80 lb'ers are too big for it as is, and I won't need them until I TT, so I'm looking into 42's. I want to maximize what I have, and to do that I need to make sure that they flow properly at all RPM's... being stuck to peak power falling off at 61-6200 rpm because it can't flow is not kosher with me.. especially since I wanted it to go up to at least 7k.

Mdenz3

iTrader: (7)

They can flow, the computer just isn't telling them too.

I'd have another tuner look at it, also check that your MAF is clean.

R13_Braz

I thought so, but after reading 4-5 threads on them last night, the general consensus is they can't flow properly past 6200 rpm. I wish I had my duty cycle log so I could see what they were at.

MAF is clean, brand new, and functioning properly, thankfully.

Edit: I might, but they are expensive around here and for the cost to do it again, I could just buy HPtuner and learn to do it myself... which really is what I want to do.

R13_Braz

Torque app is great for a lot of things... this isn't one of them. It won't even give me the commanded A/F.

Only thing yesterday's log showed was that the o2's peg a .9v at WOT and stay there until I let off. Otherwise, they oscillate properly. I have a friend who has a wideband you just stick in the tail pipe, so I might see if I can get him to let me borrow it, but as it stands I'm stuck until I can get a better tuning program.

Anyone have suggestions on a PC program that lets you monitor what the computer see's? I have a USB-to-OBD2 adapter and a laptop lol.

Mdenz3

iTrader: (7)

Sounds like it is getting plenty of fuel.

Do you have any exhaust leaks?

R13_Braz

It is going to 6200. He claimed it couldn't go any further though.

Good question, but I don't really think so. I do need to check the header bolts to make sure they are tight, as with the last engine I found a leak at cyl 4 due to loose bolt.

The more we dig into this, the more this whole thing just stinks. I'm looking to get an appointment with a local place that has a dyno to make a couple of runs to see what comes up.

Mdenz3

iTrader: (7)

Going to another shop is the best idea for sure.

Exhaust leaks will cause bad O2 and wideband readings.

Did he just forget to turn off the rev limiter?

R13_Braz

Not going to pay someone else to tune it though... I can't justify another $500+ on this when I can just get the tuning software myself and learn it for that much.

The o2 readings are not bad though. They are consistently adjusting themselves. I'll know for certain if I can get a wide band on it.

No, I asked him to get it up to 7k at minimum, but he claimed it leaned out after 6300 when he tried to get the injectors to command 5% more fuel. That's what started this whole mess.