Nistune Forums

Hi all,

I have an S13 Sileighty with an zenki S14 SR20DET transplant (previous owner). EDU is 74F01; JDM MT. I bought the car already fitted with RB25 MAF and 740 cc injectors, and tuned Nistune board.

I've just fitted a bigger turbo and new, genuine) Z32 MAF. The car is being dyno tuned on Monday. I hate to start a new thread but I've been reading the forums and guides non stop for weeks and am running out of time to nut this out over the weekend.

When using the original 74F01 image, the stock K value is about 33k. I adjusted for the Z32 MAF and then 740cc injectors using the operations in the menu. I only adjusted cranking tables, not load scalers. This puts the K at around 31,000. The car starts and drives very well. I have the timing wound back and the mixtures rich pre-tune and only external wastegate spring pressure (14.7psi). I am using a wide band AFR gauge to monitor the fuelling with my testing. At idle, the TP is on the far left and under load about two thirds across. If I up the boost it goes close to hitting the load cut. The main problem is the ecu holding onto closed loop as it comes onto boost in high gears at lower rpm as described here. I thought upgrading to feature pack firmware would be the answer.

Today I received my base image programmer and flashed the 74F0F feature pack image. I changed the MAF as usual which puts K at around 62,000. I then resized injectors using TIM which halves it from 512 to 256 but leaves the K constant about double factory. I wrestled with this perceived issue for a while but then understood that K is only used to determine the TP and that the changes in VQ map should cancel out the doubling of K and deliver a TP in the usual range.

Unfortunately the car starts fine but the TP at idle is in the middle columns and on the far right hand side at low boost in low gears. The car hesitates when slowing and going back to idle and drives worse than ever before. The load scaling is all mucked up.

Currently I feel I'm missing something and that the TIM aspect of the feature pack is not all it's cracked up to be, despite being mentioned in any posts as the solution to keeping load scaling at factory levels for things like 02 sensing to play nice. I'm sure it's something I'm doing but I've done a lot of reading an am stuck.

Tomorrow I intend to adapt to the z32 MAF and 740cc injectors the old way without using TIM, but then confidently alter K with TIM automatically being changed (auto mode) to fine tune.

What I am missing and what might be a better approach?

I'd prefer if someone more experienced answers so I don't give you wrong information, but since no one else has commented I will.
I recently started to redo my map from scatch after some mods. I went round in similer circles thinking I should not be touching K manually in FP1, until I realised that is not the case.

This is how I did it FP1:
Move TIM to get fuelling corrected
Move K to get load scales corrected

To elaborate
Move TIM so fueling gets close estimated AFR on medium to high load.
To get K close, move K so TP at idle lowers down until it matches the load at first column, 8 for me.
Then adjust K until max load is just touching the last two load columns

Tune as normal from there, nice not having to mess with load scales anymore.
If your going off the scale to the right and hitting boost cut, I don't know about why it's holding onto closed loop.

Hi immy21,

Thanks for the reply. It is much appreciated.

I prepped the car before tuning by changing the injectors and MAF using only the K constant and not the TIM. Only the cranking tables were changed automatically in the functions.

The tuner started by adjusting these values to get the short term trim within 1% at light load. He then held the car in open loop at load and adjusted the TIM and the K a bit more until the dyno's wide band was very close t the predicted afr in the fuel tables. Finally, he increased injector latency until the low load mixtures were correct.

Once this was done, almost no tweaking was required with fueling because the target afr had already been set. The car repeatedly matched the numbers.

immy21 wrote:...This is how I did it FP1:
Move TIM to get fuelling corrected
Move K to get load scales corrected

To elaborate
Move TIM so fueling gets close estimated AFR on medium to high load.
To get K close, move K so TP at idle lowers down until it matches the load at first column, 8 for me.
Then adjust K until max load is just touching the last two load columns...

Thanks for writing this! I tried this today, because I have a fresh and new feature pack map.

Here you can see load is too high:


Adjusted it by moving K from 58657 to 40727:

Yes looks correct. I've commented on multiple threads about setting the load up after the auto resize to trace within the factory scales but missed this one

When you resize MAF it adjusts the K constant to the maximum capacity of that MAF. But if you do not use the full capacity it will need to be scaled down

Thanks Matt, now I understand why, and that I didn't made a mistake but needed to adjust the loadscale. I see you also replied in my topic viewtopic.php?f=11&t=3439#p25171.

One more question related to adjusting the load scale. Adjusting K from 40728 to 40727 will result in changing coloms. So the loadscale goes from "16-20" to the first colom "8-16". Now when hitting gas, the entire map (load) will be used, until end. Do I need to set K lower than 40727 or leave it like it is now?

For example 40728-40828 is loadcolom 16-20. A difference of 100. The middle of the second colom is 50, which is 40778 (40728+50). Do I then also need to adjust K until it goes to the first colom and lower it then again with 50 so it's in the middle of the first colom? Otherwise it is only one K left of the next colom. Hard for me to explain, but I hope you can understand.

Have a look at your TP index guage (or in the log) since this is TP/256 which is used to access the load columns going across

If you are going over the last TP load column value then scale it back. Some tuners make the last column a safe column for overboosting (add more fuel, and reduce timing) so if you plan to do that then pull it back further