aseer

I have seen a number of discussions about stabilizing idle AFR's and addressing heat soak of the IAT where using the EGO control to help manage the idle is mentioned.
I have been using the MSPNP default which is not to do it but is there any reason I shouldn't turn it on at idle RPM's rather than >1500 (the MSPNP default).
{my idle AFR's could be more stable over temperature and I thought as long as the LC-1 is reading true than it would not hurt to use it to keep a stable AFR}

Can anyone point me to a discussion that would list the pro's and con's of using EGO control when idling? (or better yet, just tell me what you think?)

Joe Perez

iTrader: (8)

Suggestion: try it and see.

I have run both ways, and I think in the end I found that my idle was just a tad more stable with EGO turned off. I relocated my IAT sensor to cut down on heat soak (it's in the intercooler end tank now, instead of in the up-pipe right behind the radiator) and that helped a little.

aseer

Yeah, I switched it on last night. I'll keep an eye on it and also think about relocating the IAT (I have it in the same spot you did). My turbo leaked a fair amount of oil prior to a rebuild recently and the IC piping and IAT were coated. I cleaned it as best I could but it might be getting coated again (which could reduce its air temp sensitivity I assume).


Thanks again for responding. I am trying to get the car ready for some road trips in So. Cal and want to be sure everything is as tight as I can get it (especially if I drop by Shawn Church for a dyno tune while I am down South).

aseer

Tried it, short run moderate boost (10psi max then some cruising and then idle). By the end I was running 12 AFR at idle instead of the set around 13.7. I assume that was because I was outside the EGO controller authority range (assuming I get what that means). Right now I am set to +-5% (the MSPNP default), should I try another setting (I don't have a feel for this variable)?

(log/msq attached)

Update:
Just tried 10% and it seemed to work a bit better, what do most people run?

(the attached log is the 5% setting)

ScottFW

iTrader: (4)

If you switch one of the traces in MLV to show "Gego" then you can see what EGO is doing. In your case, at idle it steps down 1% at a time until it gets down to 95%, at which point your AFRs are still a little richer than 13.7. Assuming that's your target, you need to either give EGO more than 5% authority, or go a point or two leaner in the idle cells in your VE table (how much time have you spent tuning idle?) or both, and then see where you are.

As far as AFR stability, I've never gotten the LC-1 to read one rock solid number at idle. It always seems to drift around a few tenths so I wouldn't worry about that at all. It will also be more stable without EGO adjusting things. But EGO can help keep you closer to your target AFR (assuming you give it enough authority for how close your VE table is tuned) with varying under hood temp or if you have a mild case of heat soak, compared to no EGO.

Assuming you fix your IAT/heat soak issues and the VE table is pretty good, EGO on or off shouldn't make a dramatic difference because it usually won't be adjusting much. FWIW, I usually do have EGO enabled above 700 rpm. It's also easy to be overly obsessed with idle because often times there's nothing better to do when stopped at a red light than stare at your AFR gauge.

aseer

Thanks, I'll take a look at the Gego variable, that should give me a better feel for what is going on wrt EGO correction.

My original plan was to use the LC-1 for tuning the VE table across band and then not depend on it going forward (I would leave it in for logging and cruise but turn off EGO correction for idle and in boost).
I had been seeing some pretty large AFR excursions at idle over temperature which got me thinking about EGO corrections, IAT heatsoak, and possibly even a problem with my Easytherm settings. (and when I took data logs at night v. day, the VE analyzer gave different results, at idle and across band.)

Finding the inside of my IC piping coated with oil did not help the IAT sensor I expect.

Setting the controller authority to +-10% and activating it at idle has helped, I was not sure what range most people use so thanks again for the response and the explanation.