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What are the largest fuel injectors the factory EJ22t ECU can control, without outside help(afc's...)?

Stock.

I ran 440's (greytops) off an EJ20G for a while, and it did fine with those up to 17 psi on a VF8 before the MAF ran out of range...

The off boost AFRs were quite rich though, so an AFC would be a good idear

I kinda suspected that the factory ECU could control up to 440cc injectors, as I read somewhere that the ecu can trim fuel +/- 20% ,& 370 x 1.20 (120%) = 444.
So 444cc would be the biggest injectors the OEM ECU could control @ factory fuel pressures in theory.
But - Sometimes what works in theory, does not work in real life.

555BCTURBO, did you by any chance run the 440's with a walbro fuel pump & stock fuel pressure regulator (as this combo on my Impreza increased base fuel pressure from about 37psi with vac. to about 57 psi with vac.)?

Thanks for the real life experiance response!

BXSS wrote:
555BCTURBO, did you by any chance run the 440's with a walbro fuel pump & stock fuel pressure regulator (as this combo on my Impreza increased base fuel pressure from about 37psi with vac. to about 57 psi with vac.)?

Thanks for the real life experiance response!

That is the exact combo I ran...and it worked surprisingly well. It would probably have enough fuel to run well into the 20's of psi, but the MAF is the limiting factor, because instead of going 100% when it rails, it goes into panic mode and I was seeing AFRs of around 15

Thank god for knock sensors!!!!


With the 440's and the Walbro, you should be able to safely do 17 psi on your TD05

I think if you were to check fuel pressures you will probably find that they are above stock figures (43 psi no vac. connected to FP- regulator).
If that is the case I think a aftermarket fp-regulator should solve your low load afr issues (I use an Aeromotive FPR & it works very well, just make sure to get one with a 1:1 rise with boost) without having to resort to outside electronics.
You may have to lower base fuel pressure a few pounds (I use a 40 psi base on my Impreza with +20% larger injectors with no issues, but it is OBDII -my'99) to get everything perfect.
Thanks for the findings re. the MAF.
Has anyone tried the NICO-WRX MAF trick yet?
Let us know what you find re. Fuel pressure.

Doug Vincent did the Nico MAF thing, and he datalogged and found that it made no difference...


As far as the fpr thing, I ran a rising rate for a while and wasn't happy with it, and I have a piggyback in my car, so I shall just use that for my corrections...

I do want to know how the fpr works out for you, as I am always interested in different ways to do stuff!!

Maybe someone who has this problem now, may be able to solve it before they intstall a piggy-back using the info in this post.
Since you have the 440ccinjector / walbro fuel pump / OEM fuel pressure regulator set-up on your Legacy SS I'm going to sort of refer to your set-up 555BCTURBO, if Devan is runnig 440's/walbro... & is having the same problem you had this may be a solution for him.

First off a rising rate regulator will not change your BASE fuel pressure, it will just increase fuel pressure x-psi per pound of boost, which is not nec. with your fuel-pump/injector set-up.

I think the low load issue can be solved without using a piggyback by doing the following if the stock FPR is not able to control the walbro. Here is what has to be done

1. Get a brass "T" & place a pressure gauge (you can use a small automotive(at least 100psi max) one or one for use on an air-compressor(150-200psi max, (this is what I use)) between the output of your fuel filter & the fuel rail. Check that the fuel pressure @ idle is not more that 43 psi with the vac. removed from the OEM regulator.
If it is more than 43psi, than the cause of your low load AFR issue is probably the walbro fuel pump over-running your stock FPR & should move on tho step 2.

2. This problem can be solved be buying a subaru FPR adapter from e-bay ($21.49 shipped) so that you can eliminate the stock FPR & install an aftermarket one (summit racing sells an adjustable MSD 1:1 Rise with boost FPR fo about $50, (I use an aeromotive on my Impreza - $100-120+cost of fittings)).

Once the aftermarket one is installed set the base fuel pressure @ 43psi with no vac. Then install the vac., reset ecu, & test the car.
It should be running better @ low loads, but if it is still a little rich lower the base fuel pressure to 40psi(without vac.), reset again & you should be GOLDEN !