Nistune Forums

Alright, well everything is running great in nistune now, and I'm becoming more comfortable with the program. I'm now stepping into tuning and need help!

Let me first say I have a type 2 board on my 1991 300zx twin turbo. I currently have the redline set for 7000rpm. The first thing I did was set the system to handle my 740cc injectors, double the size of the stockers (so half the K constant)

Next I looked at the rpm scales, and they only went as high as 6400 rpm, so I increased them as linearly as possible across the board up to 7000 rpm. At this point I took the car for a boosted run to see how it would datalog. At the high RPM's I believe I heard some knock (a quick "ping-tick-ting-ting") so I immediately let off the throttle. I have a data log of the run as a screen shot and I have quite a few questions which I have been unable to answer on my own. First, here is the shot.




Now, I have selected the highest rpm/boost sector I could. I heard detonation right about here. Clearly the car is running a bit lean or too advanced if detonation is occurring, so I ask,(1) is the shown AFR lean for a WOT boosted scenario? I believe people recommend it being closer to 11.7 or so at this point.

(2)Next question is the target AFR, clearly the engine is not reaching that (but fully has potential to with these injectors) so what is going on here?

(3)As for "closed" or "open" loop, can someone explain the difference? I have tried pressing "O" on a selected sector with flags on, and I cannot tell if anything is happening, and I also don't know if this is a necessary step.

any help is highly appreciated!!!

another q

(4) obviously my load scales are still off too, as they top out at 44, and on the log they are reaching around 55. This obviously needs to be adjusted, however this will only further lean it out if I am not mistaken. so what is my next step? should I toy with the K constant until I see the numbers getting closer to the "target a/f" ??

I'm no expert but I love sharing my opinion so I'll throw it out there..

Before I answer you questions..
Find the Nistune tuning guide and read it. Adjusting your K constant is just the first step in changing injectors. The second is to turn off o2 sensor feed back and fine tune the K constant until you get ~14.7:1. Then you turn o2 sensor feedback back on.


1. There is no "perfect" AFR for boosted cars, it varies.
12.14:1 is rich, but I believe you could running richer like 11.5:1 to help use the excess fuel to cool. No one can tell you anything here 100%. The only way to know is to get some EGT probes and see what your temps are..

2. Forget the "target AFR" map view don't use it PERIOD. It's not at all a representation of reality.
I switch between RAW view and COMPARE view.

3. First check the "flags" checkmark on the Fuel map window. This will show you the cells that are using o2 sensor feedback (close loop) generally these will be in cruising range, definitely not under WOT on our cars. Then you can see the "o" button doing stuff check you select cells and turn o2 sensor feedback on or off.

4. You shouldn't be hitting the last column in the map with a stock car, so I'll just assume you're not stock. After Adjusting your k-constant, you need to change your load-scales so that you never touch the last column.
You are correct that doing this might cause you to run lean, but just put a really conservative fuel value in all the high load cells after you do the load scaling.

I'd compare you bin with a stock bin. It doesn't seem like a max load of 44 is right, but I don't know.

modulation wrote: Before I answer you questions..
Find the Nistune tuning guide and read it. Adjusting your K constant is just the first step in changing injectors. The second is to turn off o2 sensor feed back and fine tune the K constant until you get ~14.7:1. Then you turn o2 sensor feedback back on.

modulation wrote: 3. First check the "flags" checkmark on the Fuel map window. This will show you the cells that are using o2 sensor feedback (close loop) generally these will be in cruising range, definitely not under WOT on our cars. Then you can see the "o" button doing stuff check you select cells and turn o2 sensor feedback on or off.

Okay, I've tried exactly this and seen nothing change on screen. I assume the car needs to be running and in tuner mode. I turn flags on, select a light blue box on the fuel map, and press the "o" key, nothing changes.

modulation wrote: 2. Forget the "target AFR" map view don't use it PERIOD. It's not at all a representation of reality.
I switch between RAW view and COMPARE view.

Can you tell me what the raw and delta compare numbers represent?

modulation wrote: 4. You shouldn't be hitting the last column in the map with a stock car, so I'll just assume you're not stock. After Adjusting your k-constant, you need to change your load-scales so that you never touch the last column.
You are correct that doing this might cause you to run lean, but just put a really conservative fuel value in all the high load cells after you do the load scaling.

I'd compare you bin with a stock bin. It doesn't seem like a max load of 44 is right, but I don't know.

The car is far from stock, but I have JUST stepped into the realm of tuning so I am learning boatloads. I've read the nistune users and tuning guides and they have helped, but these are the questions they have not answered. I adjusted the RPM scales first to get the highest RPM to be my rev-limiter as I saw that as fit, Now I assume I ought to adjust my load scales to the last row is around 58 or so (meaning it will not be accessed under most conditions).

When you say "put a really conservative fuel value", I do not know how to do this. do I increase the raw numbers (again, I do not know what these numbers represent)?


Thanks for all your help, I'm going to be re-reading the tuning guide to see what I can figure out of my own, but all input is appreciated!

Also check the 'Mapping guide' and the 'Software users manual' a lot of the answers are detailed in there along with pictures

Okay, I've tried exactly this and seen nothing change on screen. I assume the car needs to be running and in tuner mode. I turn flags on, select a light blue box on the fuel map, and press the "o" key, nothing changes.

Don't just select one light blue box, select all of them that are shown as highlighted when you click on the "flags" checkbox.

Can you tell me what the raw and delta compare numbers represent?

- Raw is just the raw values stored in the ECU table. It plugs in some mathematical formula which tells the injectors how long to stay open for.
- Delta compare is the difference between the two binaries you have loaded.

When you log/view logs use the "wide band input tracer" under the "operations" menu. Then turn on TPS decel cut so it's only showing your AFR's at WOT. You then load the map that is on your ECU as the "compare" bin, and load the same ECU map in "main" but save it as a different name. You think use the delta compare function and it'll be 0 on all cells in the fuel/air map. You then use the wide-band input tracer to view your actual AFR's in the cell, and adjust the Fuel/Air map cell "compare" value accordingly.

I.E. say the cell located at 5000 rpms and 44 load is show as having an actual AFR of 12.5:1 in the "wideband input tracer" screen. You want it to go down to 11.5:1. So you then goto the 5000 rpm and 44 load cell on the fuel/air map, highlight it and use the + key to increment fuel 4-5 units.
You then save that binary file, and then upload it to your ECU, log and then keep adjusting your AFR's until you get them perfect.

Now I assume I ought to adjust my load scales to the last row is around 58 or so (meaning it will not be accessed under most conditions).

This sounds good.

When you say "put a really conservative fuel value", I do not know how to do this. do I increase the raw numbers (again, I do not know what these numbers represent)?

The raw number is a variable that plugs into some equation and tells your fuel injectors how long to stay open for. Take the maximum RAW number you see on the last table and copy it over all the parts of the map. Then save the binary and upload it to your car. Start logging, and go into boost slowly. Log, hit 3500rpm's and look at your AFR's, if they look too lean then increase the numbers in the Fuel table so that all the numbers to the right of that cell are at least that RAW value if not higher. Then upload changes to ECU, log again until like 4000rpm's, rinse and repeat.
(As more boost builds, under high RPMS there will be more and more fuel, so the numbers in RAW value should go up from left to right, and from bottom to top.) You'll see some numbers that are like 192+ in the lower left, that high of number means o2 sensor feedback is enabled in those cells.