Power Fc Air Conditioning

[edizio]

I've had the skyline a while now and I've been tuning the powerfc myself with fc edit/datalogit over the seasons to keep the AFRs where I want them. I've recently overhauled the fuelling as I wasn't using the throttle position vs injectors functionality. Supposedly a lot of amateur tuners will set the TPSvINJ to 1.0 and directly place values into the inj adjustments tab, which I believe is all you can do if you're using the commander.

Anyhow, I've set up my throttle position curve and I've now been using the recalc base and have now got a much more accurate tune across the power band as I no longer have to add enrichment to areas that were once overly rich as the area would be touched when coming onto boost as well as cruising.

Something I've never really got right though is the air conditioning! It's a right pain, my fuel map is perfect for what I want. I'm sitting at 14,7 on cruise and 14,3 at idle as my cams are 264s and don't seem to like sitting at stoichiometric. I come onto boost with AFRs of 12,5 and sit around 11,8 on max boost. The problem is if I'm just driving around normally at stoichiometric and then decide to turn air conditioning on, everything goes nuts! The AFR jumps to 15-16.. It seems calmer when in driving at steady throttle at high rpm, I,e, 100km/h / 62mph but still a lot leaner than I would like.

So, with that said, and apologies for the wall of text above, can anyone help with the following: -

1. I've been led to believe that air conditioning is temporarily disabled when on boost, true or false

2. Is there any sensor value that I can use to determine when air conditioning is on and add enrichment to the mixture? I've looked at battery voltage, temperature, etc and just cannot seem to get it right.

3. Is this just a limitation of power fc and is the air con a problem for most people? Most tuned cars I see have had the air conditioning removed

Edited October 4, 2014 by edizio

[GTSBoy]

If there's any de-activation of air-con it will just be WOT that does it.

[89CAL]

Yeah you will find that if anything turns the A/C compressor off it is the switch on the accelerator pedal when at WOT

The Air con shouldnt cause that many problems under heavy load, if you are having AFR's go weird at higher loads then I think you have a more serious issue

As for the AFR's on cruise, its been a while since I have played with FC Edit but I think there is only provision to adjust the idle RPM when the AC comes on. I cant recall if there is any fuel correction for AC but im fairly sure there isnt.

To be honest though, if your leanest AFR at cruise is 16:1 then I wouldnt have a problem with that (assuming you are running on 98 octane). I usually aim for 15.7:1 at cruise and havent had an issue.

[edizio]

Yeah, no problems at all under load; just as you say, on cruise.

Yeah nothing higher than mid 15s usually but I thought that 16:1 at cruise would cause exhaust gas temperatures to get really high?

I can adjust the idle rpm when air con is on and the mapping cell for idle air con also falls in a different zone so I can easily tune both values to idle nicely.

Edited October 4, 2014 by edizio

[edizio]

I guess air conditioning correction is just a shortfall in the power fc ecu. It's somewhat strange to me though that there is such a difference between the air conditioning being on and off. I had to correct idle by enrichment to a load cell by quite a lot which can give me quite a rich condition on startup of the vehicle. Without the correction, idle would surge at around 17-18 AFR. I have cleaned the AAC but I don't believe that has much to do with air conditioning.

It's just strange behaviour in my opinion. It's almost as if there is surging when driving with the air conditioning on, as it seems to fluctuate between 14.7:1 and 16:1 when cruising in sudden movements. The whole air conditioning side is something I don't really think I can tune if there is no way to make corrections.

[89CAL]

have you got 02 feedback on still?

If you have 02 feedback on and your tune goes a little leaner then the sensor can see, it sends the AFR's a bit crazy, tend to fluctuate 1AFR or more

[edizio]

Hey, no the O2 feedback and ignition timing adjustment for idle is off as apparently it is buggy. I guess the fluctuations I'm seeing could just be the compressor turning on and off when regulating the temperature.

I may take the AAC off, give it a clean and see if I can play with the screw for a bit. It could be worth me re initialising the power fc and doing the idle relearning again too. Theoretically there shouldn't be this much difference between the AFRs.

[Dose Pipe Sutututu]

Just as a sanity check, see if there's a massive voltage drop once hour AC is running.

That could be a possible reason to why your combustion is leaning out.

Also it's advisable to run O2 feedback on to allow the ECU to trim the fuel mixtures to stoich on idle and cruise with/without the AC on.

If your factory narrowband is dead just use your wideband and connect the "simulated" narrowband direct to the harness. Works a treat!

[89CAL]

I used to run my power FC with o2 feedback off and just watch it on my wideband while driving. Just needed a quick tune up as the seasons changed but way better than what it was doing with o2 feedback on. I would get it fluctuate constantly and fairly quickly between 14.1:1 and 15.5:1. Simulated narrowband using the wideband would be the go but It never phased me too much. It was easy enough to adjust a couple of cells for cruise if needed ( and honestly didnt have to change it that often

[edizio]

That is exactly what I do 89cal, I tune up all the time and pretty much drive with my laptop on the passenger seat. It's fun, I didn't known anything about tuning when I first got into Japanese cars but now I just enjoy monitoring it on the wideband. I'm not that bad at getting the AFRs right and I've got somewhat adept at tuning the ignition advance/retard too.

Voltage is not changing when air con is on. I checked that as I can make adjustments to the injectors based on the voltage

[nicksamaniac]

Im running a power fc on my RB30DET, I dont have the a/c switch or the power steer pressure sensor connected, ive got my idle set to 800rpm (sounds high but thats where its happiest idling)

and I have no problems with idle when a/c is on or at cruise, afr's stay solid and I csn only just feel when the a/c comes on @ idle but not at cruise speed.

Maybe try disconnecting these inputs to test?

[edizio]

Eek, 800! This makes me feel really bad about the current idle. It sits at 1100rpm typically and I can't seem to get it any lower. I assumed this was because I was running 264 cams which I thought required higher idle and a richer idle condition.

There's definitely not any vacuum leaks as I've tested this with a smoke test.

[edizio]

I might pull the throttle plate this weekend and see if there is anything wrong here as even if I set a lower idle in datalogit, it still sits higher won't idle.

I suppose that's a bit off topic but may explain why I have to add so much fuel at idle to hit stoich with air con on.

[nicksamaniac]

Big cams will disrupt cylinder pressures at idle speeds hence the "lumpy idle" this is due to reverberation back past the inlet valves, the more overlap the more lopey the idle is.

So its really hard to get afrs right at low engine speeds, I learnt this after buliding a cammed up v8.

[edizio]

Anyone have any further explanation for the air con causing such strange jumps in AFRs?

It's literally, switch air con on whilst driving -> jumps from 14.7 to 15.1 -- sure, that's fine, but then it'll jump up to 16:1, then a few seconds later, back down to 15.1, then a few secs later, up to 16:1 again. I've kept an eye on the voltage and from what I can see, there's no noticeable change when air conditioning comes on. Still tends to just float around (13.9-14.1volts).

As I wrote earlier, I guess the reason the AFRs are jumping is because of the compressor coming on and then going off to ensure the temperature inside the cabin remains stable but surely there's a way of stopping this ludicrous behaviour. I don't really like suddenly hearing the engine change tone every 5 seconds with air con on when it decides to run strangely lean. The issue is not apparent on boost as explained already but most certainly is apparent when attempting to just drive the car normally, i.e. not on cruise/boost.

[89CAL]

Your A/C compressor should not be cycling every 5 seconds

Can you turn your idle down a bit and then see what the car does when you turn the air con on then? Lower revs should exagerate the problem, Just wondering if the compressor is putting more parasitic load on the engine then a normal one.

Anyway, a few things to check -

* Have you looked at the injector (and timing) maps when this happens. Might pay to do this as a passanger while someone else drives etc. I feel like this is something you would have checked but it doesnt hurt to ask

* Your TPS is functioning 100%? i.e set right and the digital (on/off) input to the ECU is going on/off when you go from closed throttle to any sort of open throttle

* Can you log when it does that and post a photo of it. Best things to log would probably be IGN, Inj duty, airflow (V) + anything else that might help

Lastly, have you absoloutly made sure that all your sensors appear to be working correctly in your sensor/sw screen? It may be hard to monitor this while driving so again get someone else to drive while you watch. I'm not 100% on this but I think in your sensor SW screen there is AC and ACR. one is the signal to turn your AC on and the other is a feedback to tell the ECU that the AC is ACTUALLY turned on. Maybe someone else can confirm, I'm a bit rusty with Power FC

[edizio]

My idle is 1100 due to the 264 cams but does idle with a little instability at times.

I will check the timing maps and re-check fuel cells although I can confirm that the fuel cell doesn't change when this happens. Infact regardless of whether the air conditioning is off/on or doing it's strange AFR behaviour, the cell stays constant if at the same load/rpm. I'll capture the following and post the results: -

• TPS value at throttle off and on and post the results
• Screen capture of the graph when the problem occurs

I think there is something larger to blame here though as I'm finding that if I'm driving for long periods of time, the AFRs become leaner overall which brings the air conditioning spikes to 17+. Talking maybe driving for 50 miles+; air intake temperatures seem to be reading fine though so I can't attribute it to that.

[GTSBoy]

Watch your battery voltage carefully when it is happening. In fact, probe the 12V lines at the ECU to find out what the power is like there. Report back.

[edizio]

Alright, I'll have to get the multimeter out on this then. Datalogit is showing it sitting around 13.9-14.1, never anything more alarming than that so I never bothered. Are you suggesting there could be an earthing problem?

[GTSBoy]

Maybe. When current flow is high then earthing problems show up that were previously hidden. What we want to see more than anything is that it is changing. If it's changing by large enough amounts it can/will change mixtures. If it's not changing much, we have to look elsewhere. So look at the 12V lines and probably also look at the earths to see if they pop up to non-zero voltages.