Nistune Forums

Hey guys, I'm learning how to tweak with tuning to get correct AFR's but I am not sure if I'm headed in the right direction. I'm going to post up my latest datalog and the corresponding .bin file to view it with. If anyone has a moment to look at it and tell me what they think it would be greatly appreciated.

thanks for any input guys!

what boost pressure is this at. z1 recomends you pull some timing out with boost over 12 psi.

I'm running gt2860rs turbos at 16psi

you still are useing the stock latency with 740 injectors. It should be more in the high 800 to 1000 I think. I know not every car is the same but there is no way that 740s take the same time to open as 370s unless you have changed the fuel pressure or somthing. when you disable the o2s and clear the fuel map does it run lean when you free rev?

latency? as in the K constant? The K has been adjusted for the injectors being twice as large.

As for disabling the 02's and clearing the lower end of the fuel map, I have not done this as the car runs well low end and I was not sure exactly how to complete that procedure.

I have not played with the timing at all either, should I pull the timing back during tuning? by how much? (say drop 5 degrees in the high strain area?)

Yes I think it would be a good Idea to pull timing up top. Z1 suggests 3-5 deg's. pulling the timing will help hold off knock as long as you have good a/f mix. I would look in to how to set your injectors up right because it can cause you to run lean at full throttle. The reson your car seams to be running good is because the o2 are correcting/ compensating for your bad injector setting at everything exept full throttle. I am new to nistune and tuneing a Z but I have tuned my eclipse for five years so I under stand a little. Hope this helps.

Ok so I'll pull back the timing on the last 4 rows or so.

As for the bad injector settings, what do you mean? I changed the K constant to half the original for the injectors being twice the flow. I have not completed the task of clearing the O2 controlled area and disabling the o2's as I really don't understand that.

try unpluging your o2 sensors and tell me what a/f dose at idle ,2000,4000 with the car out of gear.

This is what concerns me, because I have done what you just suggested, and its nearly 20 AFR with the O2's unplugged at low RPMs. My stock injectors are 370cc, my new ones are 740cc (double). The original K is 288, so I cut it to 144.

If i want to get the afr's correct at low RPM's I need to adjust the filtered values to nearly 30 to achieve 14.7...

I will play with injector latency and see if that helps. I believe the 144 is the correct K to use as at higher RPM's the AFRs seem to be roughly acceptable.


edit:
Ok, tried the latency (damn that things sensitive!) and got the idle to 14.7, however anything above that (2000 rpm for example) I needed to add nearly 20 to the filtered values again to achieve 14.7. If I adjusted the latency up a bit it was easier to get 14.7 elsewhere, but the idle was too rich.

I'd assume I can reduce the numbers to negatives at idle, increase the latency to make it easier for the 2000rpm+ etc. and make the mid range rpm's positives (maybe around 6 to 10, seemingly more acceptable than 20+)

any input is appreciated.

your car is still accessing the fuel table which is throwing off your settings. So you need to turn them all to 0. you will find that latency effects the hole power band. The k value is not an exact science and will be different from car to car as will latency. It is ok if it is not half the number from stock. I found that when the latency was off that the cars idle would bounce around when droping from high revs. when latency is on it would drop and hold.

I turned all the blue boxes to zero (which are the only ones which the o2's effect I believe). I dont understand why I would make them all zero's as right now the top end is around 70 and thats about 11.5 AFR. Why would making the whole table zero's make sense? what am I missing here?

By the way, I physically unplugged my o2's during all this so I know for sure they were not effecting the AFR's (when they are plugged in it chases and stays around 14.7)

you are shooting for 14.7 at all rpms when setting your injectors so you have to take the fuel map out of the equation by setting them to zero. This is only while testing. then you have to put the map back to normal or you will blow up your car.It sound like you are understanding the process. by the way I would not test your tune at 16psi. have you done a full boost run after changing the timing? Did it knock?

No knock at 16psi at any point, even without timing pulled. 16psi is minimum for me (zero on EBC, aka wastegate settings).

so what your saying is I make the map all 0's, then tweak the K value and latency until I have 14.7 afr for all conditions up to when boost transition starts I assume? Then I tweak with the raw values until its more consistent. Then slowly start moving above into boost with seemingly rich settings and retarded timing?

you got it. post up a bin file and a full boost log when you are done. post your mod list.

Alright, tuned it up best I could and it seems to be pretty good for a rough test. I unplugged the 02's and made all effected cells 0's, then played with the K value until it was easier to tune the low end. 155 seemed to be a better fit than my previous 144.

I then began adding and subtracting from the zeros until I got a nice idle and decent loaded start up from idle to around 3000 rpm.

I then pulled around 4-5 degrees in all the areas on the ignition timing which are prone to knock. (around 4500 and up)

the car pulled great for a full boost (16psi) run up to red line. The numbers look to be pretty good and I'm pretty happy with myself for a first try.

I've attached a *.bin and some low end pulls along with the one high end pull.

MODS:
1991 300zx TT 5spd

Rebuilt engine due to 0 compression
XTD flywheel and clutch
87.5mm Wiseco forged pistons
GT2860rs Turbos (z1 gt675 kit)
z1 5 bolt divorced DP's
Megan's racing testpipes
Specialty Z catback
Nismo 740cc new style injectors
Godspeed intercoolers
JWT single pop intake