Thread: SR20VE/Nismotronic AFM Voltage Issue

Hi guys, looking for a little advice on a problem I'm having with my VE. At 1200-2000rpm, given a decent jab of throttle, the AFM voltage will peak extremely high - as high as it normally gets at double that RPM and full throttle. This immediately throws it off the end of the fuel maps, and the car runs massively rich causing it to misfire and buck. I've attached a log that shows what I mean, as well as my tune file. This seems to have only started happening recently after replacing the intake pipe, but swapping different intake pipes and even a different MAF has made no change.

Relevant specs on the car:
SR20VE, stock AFM, N1 intake/TB, stock cams, 3" exhaust w 20V headers, NEMU board on an N15 Pulsar SSS ECU.

I've tried playing with the dTPS settings, as John from JKTuning has suggested via email, but it doesn't appear to have helped at all, and the issue occurs at steady 100% throttle as well.

At the end of my knowledge and experience here and I'd really appreciate any advice. I'm not even sure whether this is a tune issue, a mechanical issue, or some kind of electrical fault.

Thanks in advance!

I'm at work, so I cannot look at the logs...

but If you don't feel like spending time troubleshooting this issue, you could just convert to MAP? 1Bar/3Bar sensors are as cheap as they get now...

Try resetting the "ACCEL MAX MAF LOAD" values from the "B13 SR20DE MAF" base TCD. Your values are way too high.

Thanks! I assume you mean the "B13 SR20DE stock" TCD? The "ACCEL MAX MAF LOAD" values in all the VE bases are all similar or higher than mine, but under normal acceleration my car isn't anywhere near the max values from the B13 base.



Just for the sake of drivability I'd rather stay MAF, and the New Zealand dollar is complete rubbish at the moment, so everything from the States is stupid expensive!

Yes.

Ive had exactly the same issue with a Nemu before on a VE, tried getting John to look at it and changed a lot of stuff and never got it sorted, ended up fitting a daughter board in the end.

Where in the country are you? Im in Auckland

Do these values work for load or just for the initial load on accel?

Ive been chatting to OP, and to someone else with exactly the same issue, and ive had this exact issue myself. Lowering the values in that table dont stop the problem as shown in the log he has attached.

It looks like the maf voltage is spiking unusually high for the rpm and how much power the engine would be making.

These values apply only while dTPS accel enrichment is active.

The erratic MAF voltage could be caused by where the MAF is located in the intake tract, or the orientation (clocking) of the MAF sensor relative to the air flow within the intake. Since it started after replacing the intake pipe, that's probably where the problem lies. In ant case, the values in the "ACCEL MAX MAF LOAD" table should be less than the maximum MAF load values in the fuel and timing maps.

He has tried different mafs, and different intake pipes, including one that is super long to move away from the throttle as far as possible.

The car i had do this on i fitted a daughter board to the same ecu, with no changes whatsoever mechanically, and the car ran perfect and never had this issue. Im getting one of the guys to do some testing monitoring maf voltage direct at the wire to see if the numbers match what the software is showing.

I know it makes no sense, it looks like the maf voltage is cranking up and causing the high load situation, but there is no logical reason for the maf to generate this voltage.

This is a screen shot of part of the log, the maf voltage seem high, maybe its just me, but why is the load so high if its not the maf voltage?

I understand there isnt a way to limit the load value, there shouldnt need to be.

If we take maf reversion out of the picture, since stock intake pipes and after market intake pipes, which have never proven to be a problem outside of these 3 cars, then is there any chance there is a firmware issue that is causing a false reading of the voltage from the maf?