Running Lean - stumped as to why

[rms]

Rona,
I guess we are not young enough to know it all !!!

[CrUZida]

Do I need to spell it out for every one again?

The fuel pressure is 12psi higher than factory. If I reduce it to where it should be (which is what I want to do) it will become even leaner.

If I reset the ecu and go for a drive it sits on 17:1 on cruise for about 10km's, then slowly comes down to 16:1

THIS IS NOT NORMAL (note, the fact that it is richening IS normal, the fact that at 54psi fuel pressure its still lean is not)

[oldcorollas]

is your fuel pressure gauge borked?
which fuel reg? not a malpassi? (edit, read back and found pressures during driving )

umm, any chance there was swarf still in the customised rail and it has made its7 way into one of th einjectors, or, the filters in the top of the injectors are blocke dup.. maybe just one or two of them?

as i (think i might have) mentioned, missing will also cause lean readings... and one very lean cylinder will make the average lean even if others are ok...
dunno how you can check each cyl tho within going EGT or whatever...

unless those inj realyl are a bit smaller than the ECU is expecting... even 5 or 10% would be enough to change the AFR that much?

[thechuckster]

you said earlier that this happened with the other ECU? are you sure the injectors are flowing what they claimed? or they are what they claim to be?

And resistors are low impedance plus no resister pack in the voltage supply to them and the ECU settings are correct for this setup?

Assuming the FPR is good and the gauge accurate and you'd not getting enough fuel at higher-than-normal pressure ... then I'd point finger at the injectors.

[CrUZida]

is your fuel pressure gauge borked?
which fuel reg? not a malpassi? (edit, read back and found pressures during driving )

Have checked with 2nd gauge (ages ago), and I can't recall any major differences.

umm, any chance there was swarf still in the customised rail and it has made its7 way into one of th einjectors, or, the filters in the top of the injectors are blocke dup.. maybe just one or two of them?

Have tried with 2nd set of injectors, same issue. But rails were clean, and I vaguely recall checked all injectors mesh before installing them the last time.

as i (think i might have) mentioned, missing will also cause lean readings... and one very lean cylinder will make the average lean even if others are ok...

Yeah, but it doesn't miss.

unless those inj realyl are a bit smaller than the ECU is expecting... even 5 or 10% would be enough to change the AFR that much?

The Soarer ecu runs 251cc injectors, the Celsior/Crown runs 215c injectors. At least thats what people say. I'll have to get an EPC and cross reference my ECU part number with the injector part numbers to make sure they are the same. I'm 99% sure they are, but it rules out something else.

you said earlier that this happened with the other ECU? are you sure the injectors are flowing what they claimed? or they are what they claim to be?

Injectors currently in the car were cleaned 5 years ago when I had them in my Cressida. They did about 2-3 years service, then sat in the cupboard. They gave roughly the same results at the set they replaced though.

And resistors are low impedance plus no resister pack in the voltage supply to them and the ECU settings are correct for this setup?

Injectors are hi impedance. AFAIK they are the correct injectors for the ECU.

Assuming the FPR is good and the gauge accurate and you'd not getting enough fuel at higher-than-normal pressure ... then I'd point finger at the injectors.

Yep, its the most obvious, but why does it do it on both sets ?

[oldcorollas]

is not something really dumb like a bad earth on the ECU? or low voltage to the injectors?

[CrUZida]

Def not bad earth. I've checked the injector voltage before, can't remember it being anything but good. I know the B+ pin in the diagnostics box was >13.8V.
But like everything, its worth checking again.


Question though, is it possible to get 54psi @ WOT (when running) and a flow rate of >300L/min @ 54psi (with engine off) with a blocked filter ?

[oldcorollas]

if the filter is before the rail? not really..
cos you got the most consumption vs the most bypassing situations, and if both have same pressure then it means both that pump can keep up, and the return system is keeping up....

well, it means that the fuel after the filter is enough to keep up with the engine and a bit more... doesn't mean filter isn't blocked, but means enough is getting thru to feed engine

if there is too much pressure differential across filter, then is blocked.. and once that differential hurts flwo it might reduce WOT pressures.... as you know...

[NME308]

This guy had a good point a few posts back...

Not mine



Only goes under 12:1 in the last 500-1000rpm. 100% factory 1uzfe & ecu

[amichie]

If you can get 12:1 AFR at WOT then the injectors will be providing ample fuel at cruise.

[abently]

Which exact Fuel pump are you using ?

Since they all drop off in Flow at higher pressures, so it may actually be below in Flow compared to the Factory one.

[CrUZida]

• Fuel pressure has been tested at 60psi!! (in both the rails and pre-rail)
• Pump flowed well over 300L/hr at 10.5V

Pump is unknown.
I'll be removing it when its solved.

[oldcorollas]

Which exact Fuel pump are you using ?

Since they all drop off in Flow at higher pressures, so it may actually be below in Flow compared to the Factory one.

but if he is making the same pressure at WOT, max fuel usage.. as he is when engine is off and max fuel is returned (both being referenced to ATM pressure), then it stands to reason that flow is not dropping off... as it has enough fuel pressure.....

if the WOT pressure dropped then maybe pump couldn7t keep up, but that is not the case?

[abently]

Pump is unknown.
I'll be removing it when its solved.

300L/Hr @ 60psi ?

Sorry, but if it were me, I would honestly just swap a good stock Fuel pump back in and watch what the wb02 sensor says. Its half a days work to swap it in and then swap it back out (assuming the worse) but at least you can cross it off the list as a possible issue.

OC is right, pressure would drop as Flow is not enough, but it wouldn't have to drop very much to show an impact on the AFR's which like you mentioned are only partially off stock numbers anyway. Having a liquid-filled or vibration free guage isn't the most accurate way of detecting such Flow issues. You would really need an electronic pressure sensor with a datalogger that had a greater frequency then the Injectors.

[CrUZida]

300L/Hr @ 60psi ?

300L/hr @ 60psi @ 10.5V

And no, at this stage I'm not swapping the pumps just to test it.
I've got other tests to perform which will give more valuable results.

Things for the weekend.

• Try spare Celsior ecu (suspected UCF10 ECU (no TRAC), had much less wires)
• Try working Celsior AFM
• Install wbo2 into Celsior and see what a good setup should do.