Rb20 Lean Out Problem, Just Installed 440cc's

[r3240sx]

I recently got my car running again with the new motor. I lost my last motor due do a faulty brain (leaned out and chewed away at most of my pistons, I'm retarded).

Anyway, my car's back on the road with a fresh bottom end and a fuel system that can support my power (about 280whp).

Walbro 255lph

Supra 7mgte injectors with resistor (440cc's)

Nismo fuel pressure regulator (48 psi)

It seems to be around 2700-3700 if I lay into the throttle slowly but completely, the wideband takes a dive for the lean end of the gauge, I usually catch it before it gets past 15.5:1 and let off. Keep in mind the turbo has probably only spooled 3-5 psi by then. If I were to stay in the throttle and not let off, the gauge would peg lean 17+:1 and I'd feel the car surge a little because of the terribly lean mixture.

I do not have a reflashed ECU and the only thing I'm tuning with is an SAFC. I know this is not ideal, and I'm not expecting perfection, but I would at least like to know what is causing the leanout. If I have huge injectors (nearly twice the size of stock), shouldnt the car run rich in any given situation?

Does anyone else have this problem?

Thanks!

-Max

BTW: This is in an s13, and once I downshift a gear to above 4000 rpm or so, she richens up to around 11:1-10:1 and RIPS!!! This motor makes me happy. Kbye

[tacker]

bite the bullet and get a better tuning option with a programable ecu. Not sure how it could be anything else if you have good AFR's higher up the rpm range where more fuel is consumed.

[r3240sx]

bite the bullet and get a better tuning option with a programable ecu. Not sure how it could be anything else if you have good AFR's higher up the rpm range where more fuel is consumed.

I know I would benefit from an ecu, but I'm not looking for what my car would benefit from at the moment. I am however looking for something that my motor needs fixed to not melt itself or detonate. This is a very light load area of the rev range, how does this happen? I want to know why, or what to check, what to look for, not all the stuff my car could use.

It makes no sense having large injectors, that are only slightly corrected by a signal modifier, leaning out in excess of 17+:1 because I have a stock computer. That sounds so opposite of itself. And if it is true, I would like to know why... Not "might as well not be cheap and get an ecu..", because I know that, but I'm not going to spend thousands on a guess, and hope it fixes the problem.

Thanks for the reply..

-Max

[paulr33]

diff injectors + piggybacks + stock ecu = timebomb

im sorry - you are asking for trouble

you should really get a stand alone ecu or remap your current one

running stock maps etc and larger injectors is a bad idea

[Guilt-Toy]

yeah what paul said. get a power fc or nistune.

Try checking your AFM, is it dirty? clean it and try again.

[Tangles]

dodgy no-name "walbro-branded" fuel pump????

perhaps?

edit: maybe direct battery feed this fuel pump of yours, and see how it goes? cheapest option, and apparently the walbros should be hooked up to 13.8V anyways

[R31Nismoid]

diff injectors + piggybacks + stock ecu = timebomb

im sorry - you are asking for trouble

Thats it

Crazy to run non factory injectors on a stock ECU.

I can fully understand why you've already killed one motor

[Simon-S14]

remap FTW

[r3240sx]

My questions have still not even been touched. Seems the bandwagon answer is its bad, followed by mockery, with no evidence, or constructive criticism. BTW thanks for the bash about blowing a motor, we all make mistakes, wtf does that give you the right to mock me like that?

Okay, forget it, too much to ask for someone to read a whole post before responding..

2 posts were just claims without a supporting arguement.. and to those who gave me suggestions, thanks for helping.

AFM is clean, yeah I checked that.

Walbro was purchased from a reputable shop here in the states, I'll look into wiring the pump directly..

I'm starting to think there may be a problem with my TPS where at a certain throttle position the ECU may not see the TPS and cut fuel.. I have yet to test this, but I dont think it will be very hard to diagnose... Any thoughts?

If the problem was running the factory computer with the larger injectors, then this would be the opposite problem.. That doesnt make any sense at all guys, and if I'm wrong, tell me WHY! I know I need a reflash, and it will come with time and money... But a reflash will not fix this if my theory is correct, so please, be my guest, and prove me wrong.

Thanks

-Max

[Tangles]

a lot of people have been "done over" by branded walbro fuel pumps that arnt in fact walbro

also, the 255lph claim of the walbro is only true if, IF, you have it with a direct feed from the battery.

ie, 12v = 200? (guess), 13.8v = 255

1st thing to try is a direct battery feed for the fuel pump

2nd thing is aftermarket ecu management

ie safc 1 or 2 + sitc, emanage ultimate, remap ecu, power fc, etc

[tacker]

Easy enough to check the TPS for a R32 GTR

.5volts at an idle to 4volt wide open not sure of the values for a 240sx TPS.

Although i would have thought the ECU would have gone to rich and retard rather than fuel cut. And although i have not experienced fuel cut, surely it would cut fuel down to a point where the wont run rather than lean it out to the point where it could damage itself.

Also as you are just starting to make boost as you mention are you confident that your rising rate fuel pressure reg is functioning correctly.

Again it might not have been the rpm window you refer to that killed you engine, the ingition timing higher up the rev range could be causing knock and chipping away at your pistons. Would pay to get the car on a dyno with some det cans to check both AFR and knock that way you can discount the knock /det problem and concentrate on the fuel issue.

And by the way i would not discount anything Paulr and nismoid say they have been at this for years and have a great understanding of what works and what wont.

[esky_mad]

some people prefer mockery mate, dont take it to heart.

as said above a dyno run would clearly outline the problems your running into.

the factory computer simply cant keep up with injectors much larger than factory, larger injecters doesnt mean you will recieve more fuel if the ecu isnt tuned for it.

1. get the car on a dyno.

2. once your satisifed, upgrade to a better piggyback if not a replacement ecu.

oh yeah and one of the first posts read "diff injectors + piggybacks + stock ecu = timebomb"

not all piggybacks are bad mate. the greddy emange, even the blue is awesome for the price. 1/3 the price of the powerfc which is way out of alot of peoples reach.

[TurboX]

This is a strange issue as I agree that the mixtures should be too rich right through the range.

The FPR seems high as well which should contribute even richer mixtures.

Have you run it without the SAFC fooling the ECU inputs and see if it runs rich as expected throughout the range?

ALSO have you replaced the Fuel Filter!? This may be contributing to the issue as well.

[R34GTFOUR]

if it was me i would take out the resistor pack and put the stock injectors back in if you still have them.

At least that way you can cross out the injector side of things

i would much prefer to run stock injectors on low boost on a stock ecu, than to run larger supra injectors on higher boost on a stock ecu

[335]

Thats it

Crazy to run non factory injectors on a stock ECU.

I can fully understand why you've already killed one motor

So you cant run larger injectors with a stock ecu and a piggyback? Thats how I have been suggested to go. The tuner I will use and people from this forum suggested a piggy back computer if I go with larger injectors and a after market fuel pump.

What's right?

[r3240sx]

Okay guys, I've fixed the problem.

I must have checked for boost leaks a hundred times, and ruled them out because my intercooler couplers were tight, and no holes to be found, and it held boost (no bleeding) in the high rpms. However, I'm running a blow through maf and a maf adapter is bolted to the maf housing to allow you to run a coupler to another pipe. What had happened was a bolt on the bottom had loosened up, and allowed air to leak in under partial throttle.. I dont know why it made the car run lean, as it was still before the sensor, but tighening this adapter fixed the problem.

Holds boost fine now, partial throttle is still a little sputtery and rich, and WOT brings the A/F ratio around 10.5:1. A buddy of mine here in the states made me a conservative rom tune to compensate for the larger injectors, and remapped timing (again, very conservatively) for the extra boost, based on his tune when he ran these injectors. He also raised the rev limit to 8200rpm.

Out of curiosity, what would you all suggest as a safe shifting point with a stock valvetrain? I'd imagine everything being stock, the motor could rev to 8000 provided it keeps making power. What concerns do I have at that rpm? Do any components have tendency to fail with only a 500rpm increase? Everything in this motor seems to be built pretty stout, except perhaps the oil pump drive..

I may not even make more power past 7500, only a dyno run will tell..

Major mods include

Garrett T3 turbo (probably equiv to a large Hi flow)

tomei 256 cams 8.5mm lift.

ported exhaust side of the head.

Thanks for the help guys.

-Max