Erratic idle after Doolz install

[RobH]

Hi guys, finally got around to installing a Doolz intake today. I have an FMIC so I had to use the Doolz extensions to relocate the filters in the stock SMIC locations (300ZX Z32, what a PITA!). Problem is the idle is really erratic, if I set K to give me a reasonable AFR when on boost the car will stall when I come off the accelerator and slow down. If I set K for a smoother idle (AFR about 12.5:1) it runs very rich when on boost. i.e. with single intake it was running at approx 11.5:1 and is now around 10:1. Adjusting injector latency doesn't seem to help much either :-\.

I'd previously set it up with a single intake system and it was running well. I'm wondering if the MAF sensor isn't so good at reading very low air flow (i.e. half normal idle air flow)?? The voltage is reading approx 900 at idle, not really fluctuating significantly.

I also noticed the TPS voltage was fluctuating between 0.42 and 0.44V whilst the TPS idle switch remained on (?)

I'm starting to think I should have stuck with the single intake and 550BHP limit . It's a bit of a setback as I'm starting to get the hang of Nistune and had made some really good power gains.

One more question, does the 300ZX 'learning mode' still apply when using a Nistune daughterbaord?? Perhaps a reset might help?

Festive regards.

RobH

[Matt]

You can reset the learning through active test reet.

Display - Consult Active Test

Select 'Clear Self Learn' from drop list and turn test on then 'start'

I dont think K sohuld be changed for idle if it was fine throughout the rev range before. If latency doesnt make enough difference, what about adjusting mixtures in the fuel map instead around idle?

[RobH]

Hi Matt, and merry Xmas.

I've been looking at a couple of logs I made yesterday as I suspected some reversion, it doesn't look like reversion is an issue (I'm using BOVs anyway). It's weird, it'll run perfectly well with load but off load it's often all over the place :-\. The MAF sensor readings are good and stable. I would suspect a bad connection somewhere but it was all working perfectly well before the Doolz install.

I think changing the mapping around idle will make things worse, it seems to idle perfectly well some of the time, then the AFR goes screwy for no good reason and it starts hunting/almost stalling. My O2 sensors aren't currently connected but that's never caused any issues like this before so I've ruled that out.

I'll try a reset and do some more logging. I'll probably resort to putting the old intake back on for the time being.

Cheers
RobH

[RobH]

Hmm...I just performed the reset and noticed the 'fuel pump relay' switch was red whilst I was looking at the consult vehicle display. I've never seen this switch on before, is that normal or does it indicate a problem? Car is still running so I assume the relay is working..

Cheers
H

[Matt]

Relay light should be on whilst its running (ie pumping fuel). It will only be enabled with the consult digital control registers enabled (when initially connecting to consult and these ticked)

[RobH]

I now have a nice idle and have been able to change K and latency to reasonable figures (i.e. they're no longer compensating for deficiencies elsewhere). I've not driven the car yet but I'm keeping fingers crossed that it'll be all good.

All I've done is increase the value of TTPMin in the idle rev range to 8, instant transformation, it increased the injector duty but changing the latency back to a lower value has resolved this. A bit of a bodge but I suppose it was a bit dumb of me to expect the Doolz setup to be perfect without adjusting more than just K.

Slightly worryingly the MAF voltage is getting to 4V at high load even with the Doolz setup (only measuring half of the airflow), looks like 5V is the absolute ceiling for the Z32 MAF. I'm wondering if I need to make some adjustments in the VQ table?

Cheers
H

[Matt]

You will find since the table is a curve you will require upto double the load to reach 4.5 volts in that table. It requires a lot more air flow to hit the higher levels. Changing the VQ map wont be required

[RobH]

Thanks Matt. That's how I understood it but I was surprised to see how high the voltage was getting with the dual intake. I'm reverting to the single intake as my mods improved idle but made the car feel a bit odd on the overrun, at low speed and when lightly opening the throttle. The issue now is that I'm going to max out the MAF with a single intake :-\

The filters and MAF adapter flanges I was using with the Doolz have seen better days so I'm ordering some shiny new ones and will perhaps try again when I can be confident in the entire kit.

Cheers
H

[RobH]

Ok I've had to go back to the single intake for the time being. I think I'm close to the single intake limiting my power output now, the MAF sensor is getting to around 5V on full load.

As mentioned previously, I'm getting some new filters etc to rule them out of the equation but concensus seems to be that the ECU code needs more than a simple K mod to make it run correctly at idle.

Has anyone ever dumped/compared the Ash/JWT code for the Doolz chip? I'm wondering if there are other parameters I've missed that need changing. Ideally I'd like to have a look at it in Nistune.

My other thought was that the reduced airflow may highlight any imperfect operation of the MAF sensor, perhaps it's on its way out??

Hoping for some good news :-\

Cheers
H

[Matt]

The code wouldnt be changed, at best the K const and VQ Map

If someone has a copy of it I can compare the two here

[Eric]

>> I'm wondering if there are other parameters I've missed that need changing. Ideally I'd like to have a look at it in Nistune.

dual intake systems on the Z32 are always a bit problematic (tuningwise) if you are just using 1 AFM.

This because the system is not perfectly balanced once the IACV is operating, as it pulls the extra air from the left intake only.
You will need a large (~2,5"-3") balance pipe to overcome most of this problem and you will basically need to connect/join the left and right intake together (as on the stock T-pipe)
The only system where I got it to work near perfect with 1 AFM was where I basically made a variant of the stock T-pipe, but with 2 ports for 2 airfilters ...sort of like a 'double T' pipe

the balance situation/pipe as used on the doolz or JWT dual intake systems is not big enough or at the wrong position to really work with just 1 AFM.
JWT also messes with the VQ table, which is just a bad effort to patch up the imbalance (imo) and it does not work

Other/better solution is to use 2 AFM's and a selin translator or Apexi V-AFC that will merge the 2 AFM signals into one

[RobH]

Thanks for the replies.

Matt you've got me thinking about the VQ map now, with the single intake idle is at about 1.45% (value 947) whereas with the dual intake it's 0.49% (319) - less than 1/3 of the 'normal' value, surely this would be too low for the ECU to accommodate correctly (i.e. appears as though it's about to stall)?! Do you think it would be worth trying setting the value at idle to 947 for the dual intake and smoothing the curve either side, adjusting K, latency and the fuel map to accommodate the changes in AFR?

Eric, I have seen the low speed driveability mod supplied for use with the JWT intake but as far as I'm aware this shouldn't be necessary for the Doolz. The left and right air intakes are merged after the AFM where the 'X' pipe is joined to give an average flow to both banks. Effectively this does a similar job to your modified 'T' intake.

Cheers (again!)

RobH

[Matt]

You could try tweaking the VQ map for the lower areas (increasing the values similar to where you were with single intake) to compensate for these idle issues. Probably what JWT is doing