The stock ECU uses the idle valve for three things:

1) Warmup - raises the idle while the engine still cold
2) Normal idle
3) AC idle bump

Has anyone managed - so far - to get items 1 & 2 working "almost" like stock? Ie warmup while cold and normal idle after that?

I understand that so far no one has managed the AC idle bump so far except for Jerry (FoundSoul) but that's just with the PnP unit and I guess Jerry would like to keep that trick to himself - it's business after all! Am I correct here?

Jim

Ps. I just don't give up, do I?

 

I have closed loop idle working pretty well on my 99 engine except when I have the headlights on, then it idles a lot lower for a few seconds before picking up again. I'm playing with the settings and it is slowly getting better but I really do mean slowly....

 

to get the AC to work correctly tune the row under idle RPM, and below and the same as your idle kpa's abit richer this way it won't die on you. Also to get the cold start to work right turn down the warmup compensation, and aftrestart enrichment.

 

Actually I posted my maps which have all my settings in them-- you can snag my settings if you want. Sure it's business, but the first three letters of our company name is DIY right? We're here for the DIY guys forever . http://www.megasquirtpnp.com/mspnp_downloads.htm

Note your min and max DC settings will likely be different with whatever IAC transistor you're using (TIP12x I'm betting) as we're using a different solution there. But the frequency the same and other settings should be the same/similar.

 

Jerry,

doesn't the MSPNP unit bump the idle to ~1000rpm when the AC activates? Ie ~800rpm when the AC is off, ~1000rpm with the AC on?

Jim

 

Actually the way the code works is it's aiming for a stable idle speed regardless of load, and adjusts the idle valve to get near that. 900-950rpm is the target.

 

I see, so it runs in closed loop, aiming for ~900-950. I get bad oscillations when the A/C kicks in (MS controls fuel and spark, stock ecu controls the idle valve) and Im pondering whether its worth switching the idle valve to the MS.

Jim

 

I would agree that its alot in the tuning. When I had MS running on my car when it was turboed I didn't even plumb the IAC into the intake tract. At the time I had no idea what it was. My car ran great though without it because I tuned it to compensate for any shortcomings.

 

i ran for 5-6 months and 14K miles on my setup with no AIC it is not necessary but it helps to compensate for real cold start AC/alternator etc. It is like a auto choke valve more or less.

 

There are still oscillations sometimes but it does a pretty good job when properly tuned. The documentation on tuning the closed loop idle control isn't as strong as it's officially experimental code, but it seems to work pretty well. It is reactive as opposed to the stock system which is proactive, so it responds to the drop in idle speed and opens the valve, if it overshoots it will close the valve a bit, etc. In the process there can be a bit of oscillation sometimes but it usually gets there pretty quick.

 

That sums it up pretty nicely, thanks Jerry! I just need to know in advance what to expect. Since I have tons of Innovate dataloggers on the car, I will connect the idle valve to one of the dataloggers and have a look at what the stock ECU does - base frequency, cold DC, warm DC, dashpot etc.

Jim

 

seems like it would be easy enough to add a few lines to the code to allow for a 12V/GND switch to identify when the compressor clutch is engaged and effectively bump the idle speed like the stock unit does. I haven't looked at the MS unit code myself yet, but if this feature doesn't get added sooner or later I'll have to do it myself.

 

That's one of the wonderful things about the MS, eh?

 

I've been playing with this a fair bit lately and I've got my idle sorted fairly well, but I still get stalling problems with the air con on when coming to a stop if I push the clutch in before the revs drop below 900rpm. It's like I have to wait for the IAC to start compensating, then push the clutch in.

Another problem is when the air con kicks in and the car is at idle, the revs will drop to about 650rpm and take literally 8 seconds to come back to the 900rpm target.

Without the air con on it's pretty much as good as stock.

Any suggestions?



Cheers

 

There are two different things going on here... The 'coming to a stop and putting in the clutch with the AC on' thing is challenging without fitting a variable TPS to the car and setting up the ECU to use it. I see you have a BMW TPS though so you're on the way there.... The Dashpot settings are your friend for this. Set the TPS ADC to about 3 ADC above closed throttle. Set the Idle Activation Adder to maybe 400 rpm. Set Dashpot settle time to 250. Dashpot Adder of 1 or 2 dc is about right. You should then start seeing the idle come down, and as the throttle drops below the ADC threshold you've set, and at the same time the RPM drops below the Adder RPM plus the average of your low/high rpms set just above these settings (in your example above, 900+1400/2=1150. Add your Idle Activation Adder to this and that's what it's watching for the RPM to cross)

So as the RPM threshold is crossed as just defined, and the TPS ADC threshold is crossed, that's a 'dashpot event'. When a dashpot event occurs, the MSPNP will open the idle valve an additional X dc, whatever is programmed into the Dashpot Adder setting, and then it will settle back down to normal.


If you didn't have a VTPS, I'd recommend bringing up your idle at the throttle body with the screw just a little bit, maybe one turn at a time at the most, and then adjusting the targeted 'Slow idle speed' to match more or less, with the goal being a slightly higher idle, maybe 1100rpm, but with the idle valve not doing the work but still having it's full range of use. So you'd want the idle valve to be 1 or 2 dc from the minimum/closed setting (which appear to be mucked with from default above) so if minimum/closed is 19, you want the car to idle at it's new idle speed with the idleDC still at 20 or 21.

This same procedure may still help you a bit for your second issue, if you'd like to idle the car up just a bit to attempt to help it to not be effected as much by turning the AC on when the car is idling. It shouldn't take 8 seconds to recover, and doesn't on a stock Miata here in testing, not with the base map. But there may be some differences with your car, or some differences in your map, that could have effected this. The car will recover best idling a bit richer, close to 13:1, and with a touch more ignition advance, maybe 17degrees. you may not need to idle at this all the time (AFR and/or advance I just mentioned) but you could setup your table to change a bit at lower RPM to bring in a bit more torque for recovery. I wouldn't think you'd have to do this based on my experiences, but it's another tool for the toolbox...

 

Jerry, you are a machine!

I will let you know how how the new settings work, cheers!