NisTune and A/C

[Nuyskov]

Hello!
Sorry for my English!
I've already seen such topic, but it left unaswered...
With RB25DET NEO when I push my A/C on, the AAC valve opens more (also additional valva start pulsing vaccum), the MAF voltage become higher too, but injection time remains near... The A/C and fan are working, all the systems exept fuel (of course additional) work great!
So, my idle with A/C rise just a lot (only about 50-70 RPMs higher) and the AFR is too high - about 16-17.
Also when I start driving, there a lack of power and AFR is about 18-20 (till about 3000 RPMs, after car goes much better). And when I push A/C off, the car goes great and AFR is 14-15 on slow motion.
What can be wrong? Why there isn't enought fuel with A/C? And how can I add some fuel with A/C on?
Thank's!

[S14Phoenix]

Correct me if I am wrong but it sounds like you are also running very lean for a turbo motor anyway. But as long as you are not getting any detonation it should be ok. Just can't think those ratios being healty/safe.

I have a similar problem on my S14 74F01 ECU in a S14 with SR20. however when I put my lights all the way on the AFR goes from +/-14.7 to +/-13.5 any ideas? is there a place where this can be set? Is the idle control valve getting stuck and not opening enough or even not at all? Not hijacking just related I think.

[Nuyskov]

Correct me if I am wrong but it sounds like you are also running very lean for a turbo motor anyway. But as long as you are not getting any detonation it should be ok. Just can't think those ratios being healty/safe.

I have a similar problem on my S14 74F01 ECU in a S14 with SR20. however when I put my lights all the way on the AFR goes from +/-14.7 to +/-13.5 any ideas? is there a place where this can be set? Is the idle control valve getting stuck and not opening enough or even not at all? Not hijacking just related I think.

Hello!
No, my AFR is pretty good - 14-15 on iddle and slow motion, and 12-13 on high drive!
I think you should test your ground points - it seems to be you have not ideal ground near some sensors - try to measure voltage between + of battery and several points of car's ground points - near ECU, near sensors and etc. Voltages should be very similar...

[Eric]

may have something to do with the injector latency voltage correction variable.

when running non standard injectors then this variable should be adjusted (ideally), so the injector latency will be correct for any given voltage.
This is often overlooked though, causing rich/lean conditions when the battery/alternator-voltage is changing for whatever reason

Correct me if I am wrong but it sounds like you are also running very lean for a turbo motor anyway. But as long as you are not getting any detonation it should be ok. Just can't think those ratios being healty/safe.

I have a similar problem on my S14 74F01 ECU in a S14 with SR20. however when I put my lights all the way on the AFR goes from +/-14.7 to +/-13.5 any ideas? is there a place where this can be set? Is the idle control valve getting stuck and not opening enough or even not at all? Not hijacking just related I think.

[Matt]

Interesting, so when the A/C kicks in this causes a decrease in voltage which then affects injection? I havent seen this changed previously even through the value is there

This parameter is 'Volt latency change' inside Nistune

[Nuyskov]

Interesting, so when the A/C kicks in this causes a decrease in voltage which then affects injection? I havent seen this changed previously even through the value is there

This parameter is 'Volt latency change' inside Nistune

I'll try to change it and tell you if there would be better!

[Eric]

Interesting, so when the A/C kicks in this causes a decrease in voltage which then affects injection? I havent seen this changed previously even through the value is there

This parameter is 'Volt latency change' inside Nistune

I was actually referring to S14Phoenix post, where AFR's changed when turning all lights on.

Although the AC problem mentioned by Nuyskov could possibly also be battery/alternator voltage related, as the magnetic AC clutch is electronic and may draw a few amps when the AC is turned on.

[RomChip200]

Well, well, well

I observed the same on stock rom and tuned too.
On my Z32, TP is around 5-7 in idle (warm engine, 740cc, oem MAF). AFR is about 16 (this is a wanted AFR @idle on E85 in my case).
My oem lambda are disabled.
As soon as you kick the A/C in, TP rises up to 10-11., rpm rise too This has effect of leaning out the mixture and AFR raises up to 17-17.5 (not a problem for me). Raising above 18 would be a problem.
When A/C is on, rpm rises a bit, the engine sucks more air, and even if pulsewidth is adjusted (TP changed), this is not enough.

This is a multi-parameters problematic (rpm, TP, AAC valve, open loop ...) and I ended up keeping it like this.
FYI, when re-enabling the lambda, evrything goes back to AFR=14.7 @idle, with A/C on or off.
Lambda is the unique feedback available for the ECU to keep the AFR @idle in the good range, it introduces an additional mixture correction.

I did some tests, from TP=7 to TP=10, I jump into a new column in the map, I increased values from 192 to 212, even more, it has some effects but not so much. At idle, the maps are not always taken into account.
Moreover, it has some side effects, after a short stop follwing a run, the RPM rises a bit @idle to cold down the engine for a while, meaning AFR drops to 13 for a while (about 1 minute) to go back to 16 after (the wanted value).
Injector latency doesn't help neither as it affects indifferently normal idle and idle with A/C on.
I run 112 (1.12ms ?) for latency. I ran 108 before.
That matches more or less the values given by DW for their 740cc (re-drilled 370cc):
6v-17v in 1v increments: 3.36 2.63 2.25 1.94 1.71 1.57 1.40 1.30 1.22 1.12 1.08 1.00

Here are my current values, I found a compromise:

idle A-C.JPG

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