bunker what did you change in order to make that open loop idle?? PE?

 

what I did is altered the MAF table first in the idle stages so actualy 9-18 AFGs I brought them down by about 5%, this made the BLMs go to 147 or so kinda like what I did before, but this time I put the BLM block at 140blm and the intergrator value (stft) to 138 because it adds about 2 on its own, so the LTFT and the STFT can't go over 140 and you can see the o2's are reading low while both trims max out at 140, the computer sees its lean and can't compensate and throws lean code and goes to open loop, as soon as you start moving, in 2 seconds it immediately goes to closed loop and the ses light disappears, I'll show you all my scans later today or early tommorow its awesome

 

Is it safe to assume that cams with larger LSA's would suffer less from the false lean at idle?

 

Bunker,

I have had mine set up exactly the same as yours and it works pretty darned good. You just have to kinda ignore the SES light if you idle too long. Also. make sure that the MAF table is in good shape up in the higher Flow area. Since we're limiting BLM corrections on the top end we want to make sure all BLMs outside the idle area are 128 or below. We don't want lean cruise or WOT.

Steve

 

No because the reason you lean out between 9-18 AFGS is so you don't run into any WOT issues, you also do this to make sure the BLM within that range is scaled way off so that anything after 18 afg's doesn't get effected by the 140BLM limit, make sure you never hit that before you do it. The SES light yeah you just lear to ignore it who cares, kinda reminds me that its too much traffic and to find another way to get to work LOL.

On mine at cruise anything about 1% throttle already goes past the 18 afg's at anyting about 2k RPM.


Also, yes, the narrower the LSA the more problems with lean idle, same with durration, the more durration the more o2 at idle.


Did you just lean out your whole MAF table? Make sure you only lean out the idle areas depending on cam size say a GM847 I'd have 8-14 AFGS I'd subtract 5% or so and limit BLM, I'd also get the Integrator set where the o2's would show 300mv on an 847 and anything bigger 100-200 I'd say. But until you put her on a gas analyzer you can't tell, I'm going to go to my buddies shop and make sure I'm idling at 1% CO which should be around perfect.

 

Yes correct. I just reduced the MAF in the idle area (about 12GPS) and let the rest of the table alone. What I was saying is that the rest of the table has to be in good shape ie BLM's 128 or so. If someones running a different table or ported MAF, they have to be sure that "off-idle" areas of the table are good so that they don't accidently peg the BLM at 138 and start to go lean in those areas also. I'll be very interested in your CO tests. Did you start to get surge at idle when you got too lean? I'm idling at about 17:1 AFR on the wideband but as we know, those numbers become a bit meaningless.

Steve

 

Sorry to dredge this up, but I'm exploring the option (or rather fact) that my car isn't going to closed loop idle.

When you guys are saying "large cam" what would large be?? FYI, I'm running a mid 23X low 24X Joe O cam in a 355, speed density 93 car.

After reading this thread end to end, what was the final outcome?? Did the PE Idle setting work, or was an open loop idle the only way???

 

As for large cams, I believe they are referring to cams in the 24X/25X area. I know my big Joe O. hyd. roller cam is in that area

 

And I thought MY Joe O Hydraulic Roller was big.

 

My CC306 is only a 230/244 on a 112LSA and there's a ton of reversion and smelly idle problems associated with it. So this problem isn't necessarily for the huge cam guys only. At the end of the day, PE idle works. You can lean your idle out as far as you want and not affect a good 14.7 cruise AFR or a 13 WOT AFR. The only downside that I can see is an intermittant Low O2 code being thrown during longer idle periods. Tap the throttle and the code clears right away. All that being said, Going leaner at idle with my CC306 didn't necessarily clean up all of the nasty smells at idle. I think it improved things somewhat but it still doesn't smell like a stocker.

Hope I've helped some,

Steve

 

I hate to bring an old post up, but im going through this right now, and Im just about done pulling all my hair out. Thanks to TurboZ, I have gotten my STerms limited to about 135, and the LTerms are pegged at 128 at idle due to the IDLE PE. However, when the car is warming up(open loop), the IDLE AF is great. Once it goes into closed loop, it richens up, and stays at about 12.8. This is with -19.1 in the PE vs RPM table. It seems that no matter how much I pull, the AF goes right back. PLEASE SOMEONE HELP ME! im begging...

 

WOW. I can only read so much. I've skimmed over this some and it appears the best way to lean the idle out some is add some timing and disable closed loop at idle only. I have OBDI and LT1 Edit, can somone summarize how to disable the closed loop at idle only and how to tune it for open loop (or power enrichment ...not sure I understand how PE can be used to tune idle though)? Man, the things you all went through to try to force closed loop to do what you want ....just crazy!

and Bunker, for God's sake ....it's tuning, not "tunning" lol

Well, if anyone can summarize what I need to do I'd greatly appreciate it, the timing is easy but not sure on the closed loop being disabled only at idle ....raise the "minimum map for blm update"? ..shoot I don't know....I'm at work right now, maybe I can use common sense and just figure it out when I'm actually looking at it

 

I just wanted to add that I've tried forcing the computer into open loop at idle in order to be able to manipulate the air-fuel ratio. Well, the end results were pretty good, a smoother idle (due to running it richer) but it burned out my cat converter. If you don't run cats or have to pass emissions, this would be ideal. Otherwise, forget it.

Also I would like to mention that my CC 224/236 blower cam has given me zero problems with emissions or weird smells. I haven't even tuned it yet either, very impressive cam IMO.

 

So what you tried was with another cam? (since you said you haven't even tuned the 224/236)

My cam is milder than yours @ 220/226/112+6/.544 w/1.6 and idles rich, but not to the extent of causing any real problems. Should I leave it alone or is it worthwhile to disable the closed loop (still not clear on how to do this on my OBDI LT1-Edit, the more I've read the more I'm lost in a way) at idle only? I think my timing is already bumped at idle, maybe that's why it runs decent. Still, if I could get it a little leaner it would be nice. I have no cat so no worries there.

 

Actually I tried that trick several years ago (running the engine in open loop at idle). My tuning now is just stock, with the exception of increased idle speed and an adjusted injector constant for the bigger 42 lb injectors.

I would like to eventually get the LM air-fuel meter with the Bosch wide-band 02 sensor to monitor the air-fuel ratio (which is so important on a boosted engine).