I have "proof" NA ECU doesnt like boost. Too a po

[douglas vincent]

The way the NA ecu doesnt like the boost, is when you boost enough to get the MAF to read 4.4-4.5 and higher.

I often would get a higher reading on the MAF, but all that air wasnt getting into the engine due to the AWIC causing the boost to get reduced down to 7 psi. And so the engine "seemed" to run fine. But at the same time, from time to time, the engine would seem to have problems at high rpm. I put this down to a fuel issue.

but no.

Now that I am running so well, with no intercooler, I have been playing really paying attention to the way the wagon runs. So with my various on ramps runs, I would occasionally notice that the engine would "cut out" at 5000 rpm or so.

And then I remember this mythical number of 4.4.

I decided to do a few runs with my $7.50 AFC turned all the way up. This means the ECU gets the full MAF reading. As soon as the reading hit 4.4-4.5, it cut out.

So I turned down the MAF reading and did it again. I was able to go a little higher in rpm before the MAF hit 4.4-4.5 and cut out.

So I turn it down just a bit more. Full boost in 3rd gear all the way to 6000 rpm, max 4.35 on the MAF, no cut out.

So there you go, don't push your NA ecu and MAF over 4.4-4.5.

And by cutout, I mean I was WHAAAAAAAAAAAAAAAAAAAAA,(hit cutout), UGGGGGGGGGGGGGHHHHHHHH. It wassnt jerky or anything. It just REALLY cut fuel and timing hard.

[azn2nr]

time to stick in fattie injectors and turn the maf down some more.

[vrg3]

Doug - Interesting. A MAF-based fuel cut.

The restriction in the intercooler didn't mean that air the MAF was reading wasn't making it into the engine. As long as there are no leaks, all the air going through the sensor still gets through the intake ports.

Jason - Or swap two wires and try dropping in an EJ22T ECU.

[All_talk]

Doug - Interesting. A MAF-based fuel cut.

The '87+ Ea82T ECUs have this as well, they have no way to sense pressure so they use the MAF output to detect wastegate falure/overboost. And its a real bugger to work around if you wanna mod.

Gary

[vrg3]

Yeah, and DSMs do it that way too.

[rallysam]

Do our turbo ECU's have a MAF-based fuel cut?

[vrg3]

Maybe.

Not the same type as Doug's seeing, though. It takes more than just a signal higher than a particular voltage; I regularly rail my MAF sensor and hold it there without experiencing fuel cut.

[douglas vincent]

I topped out 2nd twice today off boost to see what the MAF reads.

3.85 at 6000 rpm, give or take.

[scuzzy]

I topped out 2nd twice today off boost to see what the MAF reads.

3.85 at 6000 rpm, give or take.

Surprising, coulda swore I read mine in the low 4's today.

could be the drag from your supercharger reducing the off-boost flow.

[douglas vincent]

Scuzzy, was that with or without boost? At 6000 NA I was 3.85.

[scuzzy]

Scuzzy, was that with or without boost? At 6000 NA I was 3.85.

that was without.

On my EJ22T, without boost, I tagged 4.43 volts today (scantool said so) at 5700rpm. Mind you I'm using my NA intake manifold and headers.

[douglas vincent]

Are you using the aluminium or the plastic MAF?

I have the aluminium one.

[scuzzy]

Are you using the aluminium or the plastic MAF?

I have the aluminium one.

Definitely the aluminium one.

Here's an older picture with the old engine in the car (same MAF)

[sammydafish]

I'm seeing the same thing too. Now that it's colder out, I have to turn to boost down. When I push it close to 10psi it just dies. I assumed this was due to the MAF not beeing able to read the extra air. I go way lean, no knock or missfire though. Wasn't sure if the ECU was cutting fuel or just no longer adding fuel because it can't recognize the extra air. Basicaly the engine falls flas on it's face. It's not dramatic or anything and there is no MIL, just suddenly no power. I don't have an AFC and my R-500 can't measure pulsewidth, so I really don't know fo sure what the injectors are doing.

I think it's time for a fuel computer and maybe just raise the fuel pressure. What slightly larger injectors can I put in an EJ22 NA rails? I see a lot of threads on injectors, but it's pretty turbo specific, are the rails the same and therefore the options the same?

douglas, what's this $7.50 AFC?

BTW, I have a 90, so I have the aluminum MAF, is the plastic one better? Can I run it plug n' play?

[douglas vincent]

My Ghetto $7.50 AFC

http://forums.nasioc.com/forums/showthread.php?t=688943


You can run the srdet20 injectors available in 370 440 550 and larger in the 91-94 NA fuel rails (I may be off a year on those).

[Legacy777]

Only the 92-94 n/a rails work.

[sammydafish]

ahh... that's pretty cool as I have a set of 92 NA rails. What size are the stock injectors? I remember a thread about different injectors and what fits, mostly noting nissan injectors. for some reason I can't seem to find it now

[douglas vincent]

stock na are 270, turbo are 370

[douglas vincent]

Crazy update.

I have installed a Perfect Power SMT6. It wouldnt run AT ALL. Then I turned my ghetto AFC knob back up to 100%. Runs fine.

So as a refresher, remember that I would have cutout problems at high rpms UNLESS I turned the MAF signal down.

Well, now I havent suffered this symptom at all. Never a problem at any rpm.

But........at the same time I installed the PP, I also upgraded my fuel pressure significantly. I am definately running a tad rich now.

So I don't know which item has eliminated the power cut, but I did eliminate it.