Nistune Forums

Hey everyone. I've been having a couple problems, one just creeped up, and the other i've had for close to two years.

Engine specs:
r32 rb20det
Z32 AFM
HKS 2530
deatschwerks 440cc injectors

3" straight pipe exhaust
2.5" FMIC

First: Won't run when cold --- I recently did a couple mods to it, being the HKS 2530, and the Z32 AFM. I recently had the car tuned via nistune, on stock AFM and r33 turbo. It ran great. Cold start was perfect, etc. I then changed installed a hks 2530, and it still ran good (didn't beat on it knowing i would tune it soon). Before i went to the dyno, i installed a Z32 AFM, as i didn't want to hit the limit of the stock MAF on the dyno. I used the "Change Mass Air Flow Sensor" and it seemed to work. I didn't notice any problems till i went to cold start it the day of the dyno. The car would hardly run. Died multiple times. Giving it gas would cause it to bog out. Thinking that maybe the cold start enrichment was a bit heavy, we backed it off 10-15% across the board. Without being able to check the cold start on the dyno, we hoped for the best and continued with the tune. Now i went to try a cold start again today, and exactly the same thing is happening.
Could it be a faulty MAF? As soon as my temp hit ~70-80 and went into normal maps the bogging went away, and drove fine. I never had a problem before installing the new maf.

Second: Knock sensor error code. I've had this problem plaguing me since i bought the motor. I've tried everything besides wiring in a resistor and binning the sensor. I've tried different known working sensors, rewiring it straight to the ecu using shielded wiring, MULTIPLE times.
Voltage and resistance readings are in spec.
Bought a new ecu, which now holds my type 2 board, and still the error code keeps popping up. When i last had it tuned a couple months ago, we copied the main maps to the knock maps, so that even if it switched to knock maps, it should keep the same tune.
Yet when i came home i noticed a flat spot during boost transition. When it randomly jumped to knock maps, around 3-4000rpm, the timing would get retarded from 15ish degrees, to 0 or -5 degrees. The main and knock maps were identical.
Knock sensor is unchecked in the flags menu.
What else could be causing this?
Should i just wire in a 560K OHM resistor and see if that fixes it?

I assume you're probably gonna ask to see my tune. What is the proper way to download it so i can put it on the forums? I tried a couple days ago to sync from ecu, then click the download file or whatever it's called in the operations menu. It gave an error. Is there something else i need to do? I have the proper address file loaded (HCR R32 RB20DET)

Thanks for any help you can give.

Ian

"Cold Start

When using larger injectors and Z32 AFM it's often necessary to add fuel for cold running after start up. There are 2 tables for this. Cold Enrich and Warm Enrich. Which map is accessed depends on what the coolant temp was at startup. Once the engine is started it will continue to use whatever map was accessed from startup therefore it's important to copy the tuned map to both maps once tuning is finished."

Could this possibly be my problem? Does anyone have a rb20 w/ z32 afm and 440 injectors? Can i see your .bin file to compare?

yes, your fueling issue is most likely cold/warm enrich tables after MAF change.

if the car is a manual/brass button, sometimes a gear change throws the ecu in to knock maps.
doesn't explain the main/knock maps being matched and still having issues though.
check coolant sensors and look for MAF spikes.

Regarding the knock sensor - it's not unusual to have knock sensor problems now that these engines are aging. The combination of extra mechanical noise from a worn engine plus extra boost will often be enough to trigger knock. If this happens they'll just jump to the knock maps.

But yours has gone one step further. When a knock DTC is raised most ECU's will pull extra timing again - further to what's in the knock maps. Why it's raising a knock DTC I don't know. The ECU simply monitors a DC level on the knock sensor line. If it goes outside this level then it raises a code. This really only covers drastic errors like sensor open or short circuit.

Voltage supplied by the ECU to the knock sensor is around the 7V mark. When knock sensor is connected this gets pulled down to around 3.6 to 3.8V. You could check this level with a multimeter.

Pete L

Thanks for the replies!

The funny thing is i do get the proper voltage and resistance through the 4 knock sensors i have. I think it's time to get rid of them and just put a resistor in, seeing as i don't even use the functionality of them(both maps are the same).

Regarding the warm/cold enrich. Do you have any sort of help you can offer as to what values work well with a z32? Something to get me going at least? Like i said i didn't have problems with the stock rb20 maf, only after switching to z32. The VQ map is listed as Z32 300zx (500HP).

Also the proper way to download the tune, to upload onto the forum?

Also when using "change mass air flow sensor" should i have checked the box "adjust tp (load) scales"? i don't believe that i did. Should i go back and check the box? will this affect my main map AFR's?

Yes, it's usually best to get it to adjust the load scales although you'll finish up adjusting these yourself once you work out what your max boost is.

Load scales determine what part of the fuel/IGN map is accessed at what load point.

PL

okay. since i never changed that k constant after using the change afm function, i'll convert back again to stock afm, and then back to z32, making sure to check the adjust load scales.

still could use some insight into the warm/cold enrich tables.

don't keep flicking injector sizes and maf back and forward as it will eventually mess 'k' up and your load scales up.
especially if you've made changes to other parameters.

best to start with a base map, import (copy) the things you want and make 1 injector change or 1 maf change or both. but not multiple times over.

I don't quite understand why your cold starting would be an issue when changing AFM. I've never seen this. Kinda makes me question the AFM. Is it a new one?

PL

It is a used one my friend got from the wrecker he works at. It came from a 300zx. I cleaned it with electrical contact cleaner, wired it in and checked for error codes. All good then I used changed mass air flow sensor.

Should I try a diff sensor then? Seems odd my warmup would be so far out. But it runs fine like flipping a switch when it hits operating temp.

Shall I download my tune to send to you. How do I do so?

Also if the engine was warm, then cools down a fair bit to say 50c, it will start up and run fine.

Lower temperatures will use the enrichment tables which will make the tune run richer and mask the problem once properly warmed up

Sync the tune to your PC and then File-Save As and put it in a folder you remember. Attach a file to this forum from the same folder to post here

I think i may have found the AFM problem. When i wired up the rb20, i ran the maf wire across the valve covers (dumb i know), and over the past couple years i think the heat has turned the wiring crispy. When moving the wire around to install the maf i must have cracked the shielding, and exposed the wires, causing it to short. I'm going to solder in some fresh wire and re route it.

I also noticed when warming up, my timing changes from 15, to 25 degrees at idle. Is this normal?

In the mean time here is my tune.

Is there a setting in nistune that tells how much timing to pull when a knock sensor dtc occurs? or is it hard coded and can not be changed.

Yeah, while warming up it'll access various timing maps. Even once warmed they'll add/take timing to try and maintain target idle.

Timing pulled due to DTC will be hard coded.

PL