Setup: h22 motor with 13:1 comp.
ID730cc Injectors
Walbro 255LPH fuel pump
hondata s300 ecu
fuel: e85

I am running the stock fuel lines from the oem gas tank to the engine bay. The hardline has a -5 to -6 union in the engine bay. From the gas tank, I have a stock line converted to -6 braided line. This line goes to an Aeromotive fuel filter. Then a -6 line comes out and connects back to my oem -5 hard line under the chassis and runs into the engine bay.

The line goes to my FPR, goes thru the FPR, and runs to my fuel rail. The FPR also has a return line that goes back to the gas tank.

My issue is that I am running lean in 4th gear after 7k rpm. This only happens on the track, never on the dyno. I have tried to recreate the situation on the dyno with no luck.

My tuner added fuel where it was leaning out but nothing changes. 1st through 3rd gear run super rich and then 4th gear comes around and it runs lean (17:1+ A/F ratio)...

Basically, What I am asking is if anyone has had this issue and what they have done to overcome it.

Depending on feedback, I will elaborate more on the issue... I appreciate any help folks might be able to provide.

 

this can be quite risky to run, i had kinda a similair issue, motor ran lean only in 4th gear, We try to richen it up but nothing changed. it damage my pistons, and combustion chamber a week later.

 

Car must feel pretty weak then?

Sounds like it could be related to the acceleration of the car....tried something really obvious like a totally full fuel tank?

 

If it is acceleration dependent, it is a problem in the tank.

Have you had the problem when the tank is full or near full?

If the problem is narrowed down to your pump pickup, a surge tank is a good cost-effective solution, or a dual pump setup.

If your fuel supply size was an issue (injectors/hard lines/rail), the problem would be reproducible on a dyno.

 

Did you ever figure out what the issue was?

It feels weak as soon as the car starts to run lean. It happens sometimes in 3rd and 4th gear and other times just in 4th gear.


If the problem was acceleration dependent, I would imagine the car would run lean off the line.

I have never run the car with a full tank but I have added gas in between passes, I have added even 2-3 gallons after a pass and have still had the same problem on the next run. =\

 

Yeah, those are my thoughts also.

 

Anyone think it could be the way my FPR is setup? I can take pics if my explanation of the setup isn't descriptive enough...

 

you may need to sump the fuel tank. i have a feeling your pushing the gas to the back of the tank and starving the pump.

 

Are you able to monitor your fuel pressure during your runs at the track? What gear do you dyno on?

 

whats your FPR @ right now.. before we go any futher..

 

re-read "My issue is that I am running lean in 4th gear after 7k rpm. This only happens on the track, never on the dyno." FPR wouldnt effect this....his fuel is obviously shifting to the back of the tank and causing the fuel pump to suck air and drop pressure....

how much fuel is he is running in the gas tank when he is at the track is the first question i would ask. if its 1/4 tank or less then ive seen this exact problem before....either sump the tank or run more fuel in the tank.

 

Don't do that. Fuel must flow through the fuel rail, then to the regulator. This may not be your problem but I have tuned cars with this type of setup and it has caused problems.

 

depends on who's fpr he is running....some are designed to work like this. if it didnt do it on the dyno it leads me to believe its from the fuel shifting to the back of gas tank under acceleration.

 

What type of fpr are you running?

 

It is possible that you are starving the pump at launch, but the volume of existing fuel in the system is enough to maintain pressure until you reach 3rd and 4th gear.

Just a thought.

 

easy way to tell would be to datalog the fuel pressure during a run and see if it in fact is dropping pressure.

 

we have about the same setup in our coupe as far as what you have, but also I was wondering if you still had the stock oem fuel filter?

Have you been able to monitor fuel psi while driving? I mean can you see the gauge>

We had a car at the shop yesterday that had a collapsed filter element, it would run all day long just eventually the demand for fuel would be greater than the restriction.

You have plenty of injector and 1 pump should do it. I would move the regulator as even though you "can" do the bypass like that its not optimum for our cars. It doesnt provide an even fuel psi distribution across the rail.

We have our H22 on e85 as well and it runs outstanding so I would say try a couple of the suggestion in here and get back to us.


I have seen a few bad walbros over thepast year so if you had another one or one available, i would say swap it out. It really sounds like your fuel volume delivery is the culprit across the rail

 

oo

 

I thought the same thing but like I said, it only happens in high RPM in 4th gear and sometimes in 3rd gear as well, after 7500rpm...


It sucks because all I have is the fpr gauge in the engine bay. I'm working on getting some AEM pressure sensors, one for fuel and one for oil pressure. The oil pressure has nothing to do with this but I just threw that in. ahha.

My tuner actually suggested getting a pressure sensor for fuel as well, or at least run some kind of gauge for fuel pressure inside the car...


I've heard this before but I know of several people running their setups this way. I asked my tuner about my fuel setup the way it is and he aggrees that it should be the problem since the FPR only returns fuel with the whole system is pressurized. I do understand what you are saying though, I am going to make some new lines anyway and see if that makes a difference, just for arguments sake. haha. I'll try to do a back to back comparison if possible...


Not sure what you mean? what is my fuel pressure? 70psi...

It is an "SX FPR" I believe...

 

I don't think so because I would imagine it is a great deal of fuel demand off the line, in between gears during the shift, and during 2nd gear, that is a lot of fuel to be moved and consumed. I could be wrong but I doubt it.

I agree, that is why I am willing to try out all the alternative, or oem style method for my fuel lines. I am going to make a looped system and see how that does. I will still have the FPR off the rail though because it just won't work the way my manifold setup is. It will hit the TB or the shock tower in my case because I have a K series IM and fuel rail...

btw, are you guys still on stock fuel lines?

ONE THING I WANT TO ADD TO THIS THREAD IS THAT I DON'T HAVE THIS PROBLEM AT LOWER FUEL PRESSURE'S SUCH AS 40PSI. IT STARTED HAPPENING WHEN I BUMPED MY PRESSURE TO 70PSI. Let me know if you have any thoughts on that. Thanks in advance, and sorry for yelling. haha

 

This is a problem with stock diaphrams.

 

what fuel pump do you have? some fuel pumps become inefficient at that high of a Fuel pressure. if its a walbro should switch to a bosch.

 

i think 92 type r is probably right, the fuel system is losing pressure at some point there is no other explanation. If there is some delay then it is probably related to the fuel in your regulator, -6 lines and fuel rail, being used up at a certain point, and the pump can't push the fuel at such a high pressure through the stock lines, or there is some restriction somewhere at a bend or something, and thus by the time 3rd or 4th rolls along the pressure has dropped enough to change AFR.
past 7k the injectors are open so much of the time that maybe your regulator setup is the culprit, and by design it is trying to return more fuel than it should be thus slightly starving the injectors.

any reason you need to be at 70psi with such large injectors?

 

the higher you can run those injectors, the better they atomize fuel

 

I was mainly going for efficiency on the injectors but I guess I am going to have to run them at a lower pressure until I get the entire fuel system upgraded.

I appreciate the help folks. Everyone has put in some valuable info and I will take everything into consideration.