Nistune Forums

Hi, have this 300ZX for 10 years now, engine has been totally rebuilt in 2009.
I'm hunting for a safety mode due to knock since the engine has been rebuild.
Tested all things that I could test, fixed some leaks, but the safety mode always come back.
The car is pretty stock except 14PSI, downpipes, AGR & AIV Delete.

After several years past, running the car with det sensor shunt, I decided to put again some efforts to fix this.
I started with a Dyno and a knock detector.
It turns out that the knock really exist, I think it's what we can listen on this video :

https://www.youtube.com/watch?v=kqu55ZuvaWc
Dyno results are also not very nice, 318HP with 14PSI I think it should be closer than 350 ?
The car was using JWT Rom chip. (like stock on low/mid TP)

So I decided to take the plunge, and mount 2 Wideband sensors, and Nistune board.

In summary :

Car problem :
- Knock around 0PSI
- Idle vibrations @ 700RPM
- Rich AFR at idle, and always richer on one side (L 12 / R 13)

First Nistune & wideband feedback :
(I'm using stock base MAP for all mesures below)

- Can't get idle @ 14.7 without reducing K from 288 to 275 and latency from 750 to 500
On closed loop I get trims @0 with K @280 and latency 560
So I finally lowered the idle fuel cell from 188 to 175.

- On closed loop @ 2000rpm , both sides are balanced @ 14.7, so O2 seem to work correctly.
And trims under 5%

- During full load, both AFR are close (L 10.4 / R 10.9 with Long trim @0)
When decelerating down to 1000RPM, AFR is almost balanced, 13.9 vs 14.6, then under 1000rpm, back to 1 point difference.

- Despite the car use stock MAF & injectors size, it hits the MAX TP pretty soon : (K is 280)
88TP @WOT @ 3350 RPM @ 3.615V MAF (Injection time : 14.6ms / duty : 40%)
98TP @ WOT @ 3650RPM @ 3.85V MAF (Injection time : 16.5ms / duty : 49%)
105TP @ WOT @ 5187RPM @ 4.405V MAF (Injection time : 19.5ms / duty : 84%)

Questions that I ask myself :

- Why one side richer ? Except a bad injector I don't see ...

- Why the idle is creating vibrations ? Even when set @ 14.7

- Why the car, that is stock except 14PSI, exceed the max TP ?


I still didn't tried to fix the knock, because it seem the base is not clean ..
I would love to have your opinion about this ?

I put attached below a quick Nistune log with 2nd and 3rd WOT pull.
Then a longer one with various drive behavior :

We could speak in french.

I have JWT90.bin in my archive for reference.

I had a look to your logs. You have too much advance in midrange compared to stock european 300zx, and too much advance for unleaded fuel (SP95 or SP98).
This is the reason of knock.
Btw, it looks like the OEM knock detection of the ECU has been disabled as the timing does not get retarded in the knock detection area.

Max. TP evolves across the RPM range. JWT tuned them.
Your max TP values look ok for 14psi boost.

You are far too rich at full boost, 10.4'-10.9 is too low, 11.5 would be good.
Modding K is not the way for getting idle right.

Salut RomChip

Hum, from what you are telling me, I have a doubt about the Rom file I was really using.
I got this ROM from a friend, who told me he had JWT chip...

One the Dyno I was using the "JWT" Rom chip, but Nistune log has been made with the stock base map with K set @280, that is same that the original one of my car.

When I compare "JWT" with my stock ROM, timings are pretty similar, only reduced above 72 TP.
Fuel tables are is pretty different.

Ok, I just seen my stock ROM "MAX Load TP" table is 106 while my "JWT" is 135.
I had understood, that the car should not reach the MAX TP of fuel or Timing table, but both ROM have a max TP of 80/96.

Ok about full boost, I will tune that when back on dyno with the tuner.

About idle I tried +/- 10° timing, and to reach the 14.7 AFR, but nothing really make it smooth.
And reducing latency is not enough, even @500us i'm still too rich, and I don't think that I have super quick injectors that run @300us

I don't remember how my car was at the start, but I don't think a V6 should shake you at idle ?
The worst is at 700 RPM, above 1000 there are no more vibration, but we can still feel them touching the engine.

This, plus the AFR imbalance, make me think I could have a defective or leaking injector.

I send you my ROM in PM if you want to check it.

Any comments welcome

OEM K is 288

OEM latency is 750us.
Your injection pulse @idle is in the range of 2ms. Injector latency is not the problem.

Idle should be very smooth.

To check the injectors are leak-free, check fuel pressure with engine off, the fuel rail should stay > 2bars more than 10 minutes.
AAC valve is the air regulator at idle, check it.
You have <700rpm @idle, prefer 750-800.
Make a pressure test of the intake to highlight any air leak (inject 1 bar where the AFM is and listen for air leak)

With turbo engine, you may have (dummy example):
_max column TP index (i.e. 16th column) = 75
_max TP at full boost = 85
_max TP from ECU @3600 = 88
85>75 is not a problem as you want accuracy at low/mid TP range, on boost the amount of fuel injected “follows” the boost (more air more fuel)

Not balanced AFRs:
_they usually occur at idle or cruising (light load, very small amount of air and fuel, unequal combustion b/w the 2 banks), this is the purpose of the short term and long term trims as they are corrected at idle too).
_they should not occur on boost except if you long term trims are not balanced at all. Be aware these jeopardize the fueling on boost (you have -1% and 3%, a delta of 4%).

Record speed too in your Nistune logs.

OEM K is 288
OEM latency is 750us.
Your injection pulse @idle is in the range of 2ms. Injector latency is not the problem.
Idle should be very smooth.

I have reconditionned (tested and balanced) ebay injectors, that are very similar to the stock ones, but with light pink insulation.
I agree that their latency should be same than stock.
But with stock latency and K, WB are reading 12 Left/13 Right AFR

Last time I tested fuel pressure it was ok @ 2.6Bar, and AFR are even richer if I disconnect Pressure Regulator vacuum.

To check the injectors are leak-free, check fuel pressure with engine off, the fuel rail should stay > 2bars more than 10 minutes.
Make a pressure test of the intake to highlight any air leak (inject 1 bar where the AFM is and listen for air leak)

I will try to do again these tests, but for the fuel it could be FPR that is not 100% watertight.
About the air test, are you sure that the pressure should stay ? I remember that the air was entering into the engine...

AAC valve is the air regulator at idle, check it.
You have <700rpm @idle, prefer 750-800.

IACV is correctly working, I think the hiss noise that come from it at idle is normal.
Ok, with Nistune I will now be able to set a higher idle.

85>75 is not a problem as you want accuracy at low/mid TP range, on boost the amount of fuel injected “follows” the boost (more air more fuel)

Thanks for the info, It's more clear now.

Not balanced AFRs:
_they usually occur at idle or cruising (light load, very small amount of air and fuel, unequal combustion b/w the 2 banks), this is the purpose of the short term and long term trims as they are corrected at idle too).
_they should not occur on boost except if you long term trims are not balanced at all. Be aware these jeopardize the fueling on boost (you have -1% and 3%, a delta of 4%).

You are right, even if short trim are both @9% steady, it seem that long trim are affecting idle, as I have one side with more injection time.
At the end, on low load both side are pretty balanced except idle, so the ECU and O2 are correctly working.




At full load, I only have one log, but it seem that there is still the left side richer, around 0.4AFR.
I think that if there was a air leak the lean offset of right channel should change for a rich offset.

This line concerns me:

reconditionned (tested and balanced) ebay injectors

Did you get them tested and balanced, or were they sold like that .... most on ebay are drilled out. More info
http://injectordynamics.com/articles/dr ... -dipshits/

I've seen some horrible injector mismatched results over the years. You may find one is not flowing as much on one side (unless you have a leak)

Thanks for the info Matt.

They come from here, but bought 9 years ago and old style ('90 connector) :
https://www.ebay.com/itm/Fits-Nissan-RB ... 3161986712

I had some doubts about them, but now more over with wideband feedback
I still have my stock injectors, maybe I should put them back.

Today I decided to unmount these injectors.
Looking at them closely it look like their are not Nissan refurbished ones

So I installed my old OEM ones, and tested them for leak with 3bar of air.
Not yet finished reassembly.

These are phase 1 injectors, they cannot be redrilled as they are pin-type injectors. Maybe Subaru used the same type in the past.

I have 370cc phase 2 redrilled = 740cc, so far so good, since 8 years with E85.

I have also bought 270cc new phase 2 injectors (chinese knock-off). Once shaved, they flow about 550cc. They are quite consistent and are my backup if the 740cc fail.

For E85, go for phase 2 + fuel rail adapters.

Oh ok
I found a small leak on injector #2, on the seal between fuel rail and lower plenum

Maybe it could be the cause of idle vibrations. I hope it will be.
If I still have vibration with other injector and no leak, I will be worried.

By the way, I tested the IACV under pressure, and it let the air pass through, even with the idle screw closed.
But I was able to test successfully by clogging the outputs with my fingers. (one is the small hole of balance tube)

Just to give an update, I replaced the injectors by the stock one.
With the same K and latency setup I was idling @19-20AFR, so the ebay one was definively richers (at least at idle)
Back to stock value give a 13/14 AFR idle.
And now both banks have the same AFR. Idle is still not smooth. "Fixed" by setting it to 900rpm.

I reconnected my new knock sensor, but the car is still going quickly into safety boost.

From Romchip advices, I made a soft map, reducing timings into the TP 48/64 and 1600-4000rpm region.
At the same time I increased "Knock retard limit" from 6 to 8°
I also increased "Max Load TP" to 128 because I was reaching 105 previous setting, now I am more in 110-120 range.

After some logs, it seem there is a big problem, the ECU is even reducing timings when running knock map.
From 22° @TP56/2000RPM I've seen a -2°

So I'm now trying to desactivate specific cylinder detection with "Knock Limit Cyl" tables.
Setting all cylinders to 255 desactivate knock sensing, and no safety boost.
But for now I didn't succeded to find the wrong bank or cylinder, new runs to do...

Except that the car is healty, and I can keep 11AFR @ 14-15 psi / ~6000 rpm / 100-107% duty cycle

-Have you ever checked the actual mechanical timing ? ..with a timing lamp: this should be identical to what realtime ignition shows in nistune.
If you are using an early type (2) ECU and your mechanical timing is all over the place, you probably have an issue with either the CAS (crank angle sensor) or the CAS drive-key in the exh. camshaft is damaged or has snapped.

-Have you checked the timing belt has been fitted correctly ?
Eg. if excessive adjustment of the CAS is needed to match electronic timing (as shown by Nistune) the belt may have slipped a tooth (or more)

-What exactly has been done to the engine during this rebuild ?
eg. have the cylinder heads been skimmed ? and if so, how much has been skimmed ?

Thanks for your reply Eric.

Yes I had set it few years ago ... from the Cyl1 wire and not PTU loop, if the timing lamp was ok it should be ok.
Considering the timing belt is correctly mounted.
During the past 10 years I changed it and checked it 2 times, from what I seen it was ok ...

About the CAS it's set about in the middle, so nothing supicious here.
A long time ago I also tried to run with -10° on the whole map, and the car was still going into safety boost.

I just made a new test today :
Desactivating knock sensing on a whole bank, and the another one with "Knock Limit Cyl" set to 255 -> Each time going into safety boost
Increasing "Knock Limit Cyl" value for all cylinders to 90 instead of 30-80 -> No more safety boost.

It's a good news, as I can keep a kind of protection for severe knock, but I have no idea what 90 value really represent.
I should now try to reduce the value for each run, until safety boost come back.

Nistune has been very usefull for that, without access to this setting I had to run without knock sensor.

AFAiR, depending on the orientation of the clamp on the wire, the timing lamp may not flash at the right time making you thinking your timing is off.
Always try both directions (upside down).
In all cases, CAS bolts should be more or less in the middle of the holes.

I have no idea what 90 value really represent

Looking on the bench, there is a 'noise' counter which increases depending on the amount of noise (near knock frequency) is received during a period of time

I've noted baseline 'noise' knock coming from the knock sensor which is calculated per each cylinder. On top of that baseline the count will increase during the event when knock actually occours.

The difference between the baseline 'noise' count and event triggered 'noise' is effectively your per cylinder knock count.

When that difference is higher than the values in the knock limit tables per cylinder, it appears when when the overall knock counter increases (and we start retarding timing). I'm writing up some firmware to report this (Z32 and R34 are my primary test ECUs for this) in a fast stream format, and then the software to log and report it. Prototype is done, but I've had to put that on hold whilst fixing up some other issues in the beta releases