Nistune Forums

having a issue of going lean being held back then going rich super quick and off the car goes

I've changed the cas sensor as i was getting random drop outs in my logs which seems to have been solved
changed and cleaned the stock maf twice
Now i've fitted a z32 afm

put a very safe timing map on the car
with all the o2 flagged part of the map zero'd off
i adjusted k from 38398 as it was idleing at 10 afr and the car was coughing and spluttering with even a hint of boost.
K now set to 27000 and got low load driving in 4th to around 14.7 -15.0
tried adjusting the fuel map figures to stop it going lean but it didnt have any of it,


spec
s14a sr20det
stock t28 18-17psi
555's
z32 afm - with added airflow correcting screen

seems like the injection ms is being held back for some strange reason even tho ttpmin/ttpmax are zero'd/maxed out
or possibly the k constant set too lean?

its easy to see the issue in the 3rd gear pull log from 4:35 to 4:54

raised the k up to 28800 and latency to back to 580 and it seems to have cured it
thank god for that i was starting to think my z32 i brought was duff

Altho i still think that i should be hitting higher load scales at 17-18psi boost
Might
double check the vvt is actually working correctly
go back to a manual boost controller incase my elecy one is duff
block off my stock recirc incase its leaking boost off

ok getting little tired of this issue now

the k is spot on after fine adjusting

Still cannot stop the injection ms from getting held back causing my running lean issue

Have tried,
ttp max 255
closed loop cut off in feeback switchs and o2 sensor disconnected
putting the closed loop cut to 0 kmh
adjusting the map fully rich
reprogramming with base board programmer
even the fpr
maf is clean
swapped cas sensor for new unit base timing set at 15 correctly
tps is at 0.46 on idle at 80c
tps on off switch working ok
p/n switch working ok

think i'm going to go mad determined to find this problem, i'm starting to think a table in nistune isnt doing what it should be

Can someone have a look at this log and see if they have any ideas
3rd gear pull from 1700rpm to 6kish

the timing seems very conservative... have you tried upping it a bit?
is the VTC working properly ?

timing map is safe untill i sort out this coming on boost fueling issue

vtc is working

its as if ttpmax isnt working looking over some other logs everytime it hits 2800rpm the injection time goes up and the fueling goes down, altho its set 255 way before 2800rpm in the table


going to fill it up and do some extensive logging while playing around with the throttle offset etc

have you tried tweekining MAF translation tables? afrs really lean at 3.2v but good at 3.3v

Yup tried that aswell, still holds back the injection time ms, It does go slightly richer for the same injection time between 1500rpm-2800rpm on a 3rd gear wot pull, but then this makes accelerating in say 5th from 70mph super rich as it goes slower through the same increased value maf translation cells etc

i've decided to ignore this for the moment otherwise i'll go mad

Would be interesting if someone else could do a log run to see if there's does this aswell
3rd gear
1500rpm - redline wot pull
just need rpm, injection time, and afr to be logged

This might help. Previously I've had reported that the ECU is holding back injection time .... or if holding at a particular load point the injection changes

So did some further investigation and found that the Nissan ECUs will hold back the injection time for 3 seconds and then let it go.

The trigger for this was that it went from a low injection point to a high injection point in a short period of time and then got held there until 3 seconds had elapsed

What I found was when starting with a factory S14A fuel map the problem did not occur. Adjusting TTPmin, TTPmax, K constant, VQ maps etc made no difference. You would have also noticed this

What did make a difference was the fuel map itself. Adjusting the fuel map so it transitioned from a low point to a high point in a short space repeated the issue, where it would hold onto the lower injection time before finally going to higher injection time

Definitely a problem where you are not getting the fuel when and where you need it. What you need to do here is smooth out the fuel maps so it ramps up smoothly and then this condition doesn't seem to repeat itself

I dont know where in the code it is doing this (given its grabbing previous fuel values and comparing against present fuel values and using a counter for three seconds its been impossible to find so far) and I have no ideas why yet (wondering if Nissan patents have this covered) but smoothing your fuel maps is the best answer I can provide given what I know about these

Not everyone sees this either, so it depends on mapping smoothness and areas where the ECU seems to perform this hesitation

Another thing to add was during this investigation I was doing logging also to check this.

I would accelerate (on bench) from point A to point B (usually load only) and jump up say from 40 to 90 values in the fuel map and watch the injector time. Injector time would go up to say 7ms and hold then change to 11ms on the log graph after 3 seconds period

Use your logger to monitor this and see if you get a jump where the problem is occurring when you hold the rpms

I've tried the holding S14's for 3 seconds plus on the dyno and I gotta say I couldn't repeat the problem. But I DO tend to smooth my fuel maps and avoid any sudden changes. I've never needed to add sudden changes to get a tune right.

Fordy, is your fuel pressure OK? Is it holding OK up top?

It's not unusual to see inj time drop off a little up top as load decreases. Particularly in 3rd gear.

I'll run up your bin on the bench tonight and see if I can see anything weird going on. The logs don't look too unusual to me. I'll dig some of mine out and post them too.

PL

I'd get some timing into it too. 8 degrees will be retarded enough to really mess it up. Fine around peak torque, but up top you could feed it in up to around 16 degrees or so. This would wake it up a lot and possibly increase your TP values up top = more fuel.

PL

Here's my mate's tune I did a few weeks back. S14 SR20DET on Datto 1600 running E10/100. 52T 2871 running 16psi, Z32/550 with Bosch 044 pump.

I've converted to .xls format, so view in Excel. Note how both TP and inj time taper off from about 4700 to redline.

PL

But wait there's more. Here's one I did awhile back. Drift car so a bit conservative. S14, T28, Z32/550 + Poncams. 14psi.

Hope these graphs are not as big as last one. Sorry about that...

PL

as said that map is purely for diagnosing the problem at hand hence the fuel going richer up top

i've got it much better since i've moved away from trying to find that problem

heres the current revised bin and the last log i took today at 15-16psi

if you look at time 13.50 to 14.05 (3rd gear pull from 2k) the fueling is much much better and not going lean

then again if you look at time 11.30 to 11.50 in 5th with the boost set to 8 psi the fueling is held back again

then if you look at 11.11 to 11.17 i think a short burst of 8 psi in 5th the fueling comes in perfectly again

kinda guessing the fuel map needs smoothing like matt has said to fix this issue

Pete

I'd hope the fuel pressure is holding but i've not checked it on the road. Its got a brand new stock nissan fuel reg and hardwired walbro fuel pump and quite new fuel filter, but the pump has been in there for 2 years so i wonder if its starting to die

PL wrote: Fordy, is your fuel pressure OK? Is it holding OK up top?

Did a bit of investigating into this, seeing as my pump is hardwired to the battery in the boot to get full voltage didnt think there would be a problem with the live side and the fuel pressure reg and fuel filter are brand new nissan ones.

Check resistance between the top fuel tank connector and the battery earth and found 20+ohms of resistance, dont know why as the rest of the car from the front to the boot battery is 0 ohms. the service manual doesnt state where this earth goes to, so i just spliced in another cable and ran it to another earth point.

Now the fuelling goes much richer up top

Also found out that by completely zeroing off the tps enrichment trigger which i patched in from another thread. The fueling does as it should with a smoothed off map now albeit it slightly rich where there is too much fuel in part throttle