Running lean (12.5:1) above 5500rpms

[dok33]

Sorry in advance for the novel....Troubleshooting a lean condition about 5500rpms on my 2jz NA-T and was hoping I could get some suggestions. I'm running 7MGTE electronics with the Lex AFM/SAFC combo.

My fuel system is fairly overbuilt as I'm running E85-I have a walbro in-tank feeding a 2 Liter surge tank and a Bosch 044 external pump pulling from that into dual feeds on the stock 2jzge fuel rail. All fuel lines between the surge tank and rail are -6.

I'm running 880cc PTE injectors, which are roughly equivalent to running 680cc with gas on this setup. Base fuel pressure is 55psi to get around fuel cut at 20psi boost on a MP T70 turbo and I have the bypass screw all the way out on the Lex AFM.

At 18psi AFRs are solid 12:1 all the way to the rev limiter with ~20% fuel pulled on the AFC. At 20psi they spike to 12.5:1 in 2nd-4th gear above 5500rpms. Adding fuel on the AFC doesn't help anything, only lowering boost so I'm thinking I'm at capacity with something in the fuel system.

According to my calculations I should have enough fuel for ~600bhp with the 880cc injectors and I don't think I'm there but I haven't dynoed. The only other thing I can think of is that the stock fuel rail isn't flowing enough, but Scott put down close to 700whp on the stock rail in his car. Even factoring in the 30% more fuel needed for E85 I don't think I'm there. Thoughts?

 

[tissimo]

Sounds like youre out of fuel pump.

 

[tsupra]

what fpr are you running and have you hooked a fuel pressure gauge up that you can watch when you make a pull?

 

[10secdream]

I agree the Bosch really shines at high FP. I would bump up your base fuel pressure to about 50-60 psi. That way under boost the Bosch will be running at 80 or so Psi. You should be able to push 700rwhp on this setup with high enough fuel pressure.

 

[86_sports_1jz]

your walbro could be bad, you should check to make sure it isn't

 

[10secdream]

I can't see it being the Walbro as he is running a surge tank so that would not be the issue at all. I think he is just running out of fuel.

 

[pbasil1]

I may be wrong, but it seems that 880cc injecors seems a bit small for 600hp on E85. I would think around 1000cc injectors would be more suited for that much power on E85.

 

[86_sports_1jz]

I can't see it being the Walbro as he is running a surge tank so that would not be the issue at all. I think he is just running out of fuel.

really i never knew that, how does the surge tank help prevent the walbro from dying?

 

[10secdream]

I guess the Walbro could be dying but pumps usually just fail completely not partially. That is why I ruled out the pump because the car starts to lean out in the higher rpm's under full boost. Either way the Bosch pump is the one actually doing the work and the walbro can essentially flow as much fuel as possible.

 

[dok33]

Thanks for all the replies. The walbro is brand new and as 10secdream mentioned all it's doing is filling the surge tank at low pressure, which is one thing a wally is actually good for :biglaugh: I'll try bumping the FP up some and see where that gets me as well.

My estimate was made using RC's calculator on their website and some fuzzy math to estimate my larger fuel requirement for E85, so I could be out of injector as well. Anyone want to trade some 880s for 1000s :naughty:

 

[Zazzn]

Do you think the surge tank could be emptying too fast and the walbro can't keep up?

 

[hottscennessey]

It's possible, but I'd doubt that. Considering the amount that the walbro will flow with no pressure on it is far more than the 044 will flow under pressure, and whatever fuel is bypassed at the rail via regulator goes back into the surge tank.

 

[Nalleywhacker]

Why is 12.5:1 too lean? i thought that was about perfect for WOT:dunno:

 

[dok33]

It's a little on the lean side under boost, less than 12:1 is about where you want to be

 

[sk6471]

I'm running 880cc PTE injectors, which are roughly equivalent to running 680cc with gas on this setup. Base fuel pressure is 55psi to get around fuel cut at 20psi boost on a MP T70 turbo and I have the bypass screw all the way out on the Lex AFM.

According to Modular Turbo an MP T70 can flow 74 lb/min. Your fuel injectors aren't big enough to feed your motor just on pump gas let alone E-85. To feed a turbo that size with petrol you need 1100cc injectors and with E-85 you need 1450cc injectors.

According to my calculations I should have enough fuel for ~600bhp with the 880cc injectors and I don't think I'm there but I haven't dynoed. The only other thing I can think of is that the stock fuel rail isn't flowing enough, but Scott put down close to 700whp on the stock rail in his car. Even factoring in the 30% more fuel needed for E85 I don't think I'm there. Thoughts?

You calculations are wrong. :nono: On pump fuel you have enough fuel for 600 at the crank. On E-85 you'll need at least 1000cc injectors to make that. Turbo engines aren't very fuel efficient at 20 PSI. Scott got away with using 880s because he supplemented his pump fuel with a heavy dose of methanol injection pumped into the intake tract. You either need to lower your boost limit or install larger injectors. I hope that you have plenty of room in your surge tank, because if you install proper sized injectors to feed a T70 with E-85 your going to need a second Bosch 044 to feed them.

 

[dok33]

Thanks for all the replies and good information! For now I've decided to lower the boost a couple psi (been seeing perfect 12:1 AFRs in 4th) and will be putting some 1000cc injectors in as a safety measure once I find a deal on a set.

The car is fast as crap, to me at least, but still streetable (assuming spinning the tires in 3rd is considered so) so it seems like a good stopping point Plus, I think I'm pushing the limits of the Lex/AFC setup anyways and don't want to dump any more money into the car for now...

 

[tissimo]

Thanks for all the replies and good information! For now I've decided to lower the boost a couple psi (been seeing perfect 12:1 AFRs in 4th) and will be putting some 1000cc injectors in as a safety measure once I find a deal on a set.

The car is fast as crap, to me at least, but still streetable (assuming spinning the tires in 3rd is considered so) so it seems like a good stopping point Plus, I think I'm pushing the limits of the Lex/AFC setup anyways and don't want to dump any more money into the car for now...

If you can add fuel in with the SAFC and not hit fuel cut, you're not out of injector, you're out of fuel pump as I said in the 2nd post.

 

[dok33]

It'll hit fuel cut, just doesn't get any richer afr wise. Not sure if that changes things...

Bumped the fuel pressure today and the AFRs on top look good now, even at higher boost. Got a couple other projects to jump on but hopefully I'll get back to messing with it in the next couple of weeks.

 

[10secdream]

It'll hit fuel cut, just doesn't get any richer afr wise. Not sure if that changes things...

Bumped the fuel pressure today and the AFRs on top look good now, even at higher boost. Got a couple other projects to jump on but hopefully I'll get back to messing with it in the next couple of weeks.

Glad to see that bumping the fuel pressure helped. I don't think I would resort to it as a solution though as you are more than likely running out of injector.

 

[dok33]

Yea, turning the boost down for now, just figured I'd give it a shot I'm actually surprised at how well the car runs with the 7M electronics, I have to pull the EFI fuse at reset the ECU at every fillup because of the variability in E85 mixtures, but it adjusts quickly and runs well after a few miles..