legacycentral bbs

Do what I did and simply "tune" down the MAF signal? I am assuming that those of you hitting 5 amps due to whacko sized turbos also have upgraded injectors. And if your ECU is doing what mine is doing, then you can "tune" down the MAF signal just a smidge and still get 15-20 mpg and less than 5 amps at full boost.

Would this help?

I think it's 5 Volts, not amps.

But I see what you are saying.

The problem with that, is that messing with the MAF signal alters load calculations, which effect on-boost-timing.

I am running lean, with stock 370cc injectors, so the mod your talking about still wouldn't do anything for me. That, and I don't feel like building a fuel setup right now, until I know what I want to do for engine management and stuff.

Ok volts, amp, cobras, it all kills us in the end.

Anywho... since you havent upgraded your injectors yet, you are kinda in the boat I was in with my 270 injectors with to much maf signal and not enough injector to back it up

. If you could get slightly larger (20-40% larger) then you could do exactly what I am doing and NOT have to immediately upgrade to a standalone. Maybe.

Just food for thought when you get some 440 injectors.

I am extremely happy with my setup now, other than not enough boost of course. And this is because of my modified MAF setting with my larger injectors. And remember, I have the same MAF you do, the aluminium sexy beefcake.

I am curious if the ECU would see the amount of fuel going in, and scale itself?

How long did you run without the mod?

The ECU can read rich and lean condition through the O2 sensor, so I'm curious if it would work...

I ran maybe a week without the mod and it ran PIG RICH. Smelly rich. Don't drive behind me rich.

I think the ECU does read the o2 sensor somewhat and has learned to scale back the fuel a little, but by simply turning down the MAF signal that little bit, I am able to keep somewhat better milage, and most importantly, actually keep from getting TOO much fuel when on boost.

As it was, I was getting a MAF signal reading of about 4.6-4.7 at 7psi or so. But this was triggering too much fuel so I trimmed the signal down to 4.4 or so and now no problems.

I don't know if you have done this, but simply hook up a multimeter to the MAF signal line and watch your signal as you drive around. I also hooked up a multimeter to my o2 sensor and can analyze it at the same time.

wait. our stock injectors are 370cc???

azn2nr wrote:wait. our stock injectors are 370cc???

Yep.

NA 270 cc
turbo 370 cc

I installed 370 cc Nismo injectors though in 92-94 NA rails

if the maf signal increased in a linear fassion along with the injector duty cycle then putting a (excuse me for i dont know my electronics lingo) clamp or resistor to turn down the signal so you would run at optimum afr's it would problay work. but only if the signal along with the duty cycle was linear. you would also need a wideband and a way to adjust the "clamp" so as to not lower it down too far.

a 50k pot can turn down the signal about a max of 10%. You can literally feel the minimum right spot if you are cruising along at a steady rpm and turn the pot up and down.

The nissan injectors are rated at 43.5 PSI. At your fuel pressure of 36.3 PSI those injectors are only flowing 338 cc/min. You installed 338cc injectors.

add 7 psi to 36 and what do you get?

rrfpr 1-1

Yes, it's 5 volts. But the units don't matter. The point is that it's hitting the limit of the sensor's range.

The sensor's output is proportional to the square root of measured airflow.

Uh... Isn't a 1-to-1 RRFPR the same thing as a non-rising-rate FPR? 43 psig at 7 psig manifold pressure is still 36 psi differential pressure.

Right. But to continue that. If you were using 43.5 psi of fuel pressure plus the 7psi of boost it'd be 50.5psi and it'd be flowing 399cc instead of the 369cc you get with 43.3psi including boost.

You know, I dont have a clue.


But I do know that these injectors put out way to much fuel for 7psi to use. Ok, not WAY too much fuel, but enough to bog the engine at high rpm. So in reality they are good, in theory they dont work.