htrdbmr

I seem to have created an "idle surge" condition, 700 to 900, on a 800 rpm command, which is triggering an AE (Map) event. Or is the AE event triggering the surge? How can I disable map ae at idle, 0% TPS? I'm using SAUJP v5, and at a hot idle my IAC counts are 8-15 in park.
383 W/ Superram, 226/231 @ 0.050, 112 lsa, .540"

ULTM8Z

Did you already disable the spark advance/retard vs idle speed correction? That typically helps "hunting" and "surging". You typically set all these to zero with modified engines.

The thing about zero-ing the 0% TPS on the AE Delta MAP vs %TPS is that it the "0% "is really a range from 0 to 12% (if you look at the table).

So if you zero that out that value, you'll get no Delta MAP AE for any delta MAPs occurring when your TPS is within 0-12%. That may cause driveability issues elsewhere besides idle, like a throttle tip-in stumble at small throttle changes.

How much is your MAP fluctuating during the surging? I think a factory AUJP requires a ~3kPA change in map before a "delta-MAP" is actually triggered. I think the threshold table for that is called AE Delta MAP Threshold vs TPS or RPM or something like that.

RPM fluctuations by themselves will not trigger a delta-MAP event. But if you think the RPM fluctuations are causing sufficiently large MAP fluctuations, then simply set the Delta MAP threshold value to something like 15-20kPa or something ridiculous like that and see if it improves. If it doesn't improve, then you know it's not a delta-MAP issue.

Other than the spark timing thing I mentioned above, you could also try richening up the O2 threshold constants at idle. I have mine set around 650 mV with my Miniram and 212@.050 cam. Seems to like idling around 13.5:1 AFR on the WB. With the more overlap you have on your cam, a richer idle AFR target may help.

htrdbmr

Thanks for the quick reply Mike. The spark retard/advance is set to zero, no joy there. I'm going to do an IAC idle reset and see where that goes. My WB is showing a rich idle, 13-13.5

ULTM8Z

Was it running good before and this a new problem? Or was it never running properly and you're trying to figure it out?

Is it good at certain coolant and/or MAT temperatures? Closed and/or open loop?

htrdbmr

Months ago there were issues with a cold surge, but I added fuel to the AFR/Temp tables and sorted it out. Then last week I was bored so naturally I started fooling with the computer again. Now the surge is back, but mostly when warm, closed loop. I noticed the AE-Map being set, and that got me curious. What you explained cleared that up, so as I said I'll reset the idle stop and see where it goes. Thanks

ULTM8Z

Just noticed you're running a miniram... lol... ahhh the joys of tuning one of those things at idle...

Have you swapped the O2 to the other side to see how it's running on that side? You may be running into the dreaded split BLM issue... may be running "ok" rich on the current O2 side but could be running even richer on the other side or possibly too lean. Remember, All the Tunerpro data on BLMs and stuff is only looking at the side with the O2 sensor. Changes based on that may actually make the other side run worse.

Also what did you do in terms of MAT tables since minirams require a relocated MAT sensor?

htrdbmr

The O2 is on the driver's side, and the WB is on the pass side. The WB reads a little rich, and the narrow band says the VE's are good (126-131). I have to change my sig data, I'm no longer using the Miniram, I have a Superam now.-Much easier to tune, and more suited to my application. I haven't done anything with the MAT tables, it's in stock location. I have an extra bung on the driver's side so I could put the WB on that side for checking if need be.

ULTM8Z

You may want to consider relocating the MAT sensor and updating the tables to match.

htrdbmr

I've considered that, I have a rubber 90 elbow on the throttle body that might be a good location. In stock location my MAT runs about 60 degrees less than coolant temp on a 95 degree day. What would be the benefit, and why didn't GM do it?

ULTM8Z

That's a subject worth a good a search! Lol...

htrdbmr

Aren't they all! Thanks Mike

gp90gta

iTrader: (1)

Does this happen in closed loop and open? Or just one or the other?

htrdbmr

Seems to be when warming up in close loop

htrdbmr

Seems to be when warming up in closed loop

gp90gta

iTrader: (1)

You should datalog it and if you have an old datalog from before the issue to compare, I like to look at kpa, pw, rpm, iac steps, ign timing, usually idle surge is from running to lean or ign timing jumping around.