I have disabled closed loop in order to beat surge (worked). I would like to just run an open loop tune but have read some debates in here that discussed the possibility of the PE vs RPM table not being accessed until closed loop starts. Well, in a case like mine timers may run out and what not but the enable temps have been raised through the roof so it can never enter closed loop. Am I safe to run this way or am I going to go lean due to the table not being used?

My plan is to stay in open loop but lean my MAF down until I see surge come back (02 feedback induced lean condition caused the surge ..fuel trims were overkill) ....then when it comes back I'll add fuel in small increments until it goes away again. This way the engine gets what it wants, and I don't have to tune with a wideband (cammed motors don't like 14.7:1 anyway ....too lean for cruise).

 

I believe it has been verified by several on the dyno that the PE tables are not used in open loop.

The open loop AFR enrichment table is probably the only relavant table in that case.

 

**** ...that's not what I want to hear. I do not know of any open loop AFR table, what are you talking about? I have LT1 Edit for OBD1 ...maybe you're talking about tunercat? It doesn't make sense to me that the table wouldn't be used ...I mean, why? Once you hit the throttle you're no longer in closed loop anyway.

I'd lke to run closed loop but this surge is impossible to get rid of with it enabled. I have heard of BLM lockers and stuff like that but have no idea how to do that ..it is not in my existing version of LT1 Edit, I am sure of that. My surge problem is related to too much fuel trim to be used with cam overlap.

You sure about this?

 

i don't know where this myth started but it ends here, The PE AFR WOT tables are used in either open or closed loop operation. The only thing that isnt used is the fuel trim correction. The AFR 10X table is also used but not to such a high degree.

 

Don't know. I guess this is why it's such a controversy. I recall several people on here posting that they did tests with a wideband and the A/F didn't change when they changed that table in open loop. Other people then came on and said that was totally wrong.

If anyone that did one of those tests wants to say something, that would be helpful. I'm just going off the info I've heard previously.

 

Yeah there is a table that controls the commanded AF ratio in open loop based on coolant temp. Didn't know lt1 edit did not have that.

That's really easy. It's another program (I have it if you want it) that you use and just select your .lt1 file and it makes some change to it that activates this.

No, I'm not. I've just heard the same as you I guess. Some say it does, others say it doesn't. Some people did a test on a dyno and said it didn't. That's the most believable evidence I've heard from anyone yet so I'm on the 'does not' side until I hear something more conclusive.

 

The consensus in this thread seemed to be that it does use PE for 93s, does not for 94-95s, and does for 96+. That makes no sense to me, so I don't know what to believe at this point.

 

I'm sticking with my story If you want to change AFR with an open loop tune just tweek the MAF calibration in those high airflow areas. Problem solved. This assumes a 94,95 car.

Steve

 

actually the easiet way to due it is to use the afr 10x table and set all the warm values to 147 which is 14.7 then adjust the MAF tables to achieve the 14.7 then use the 10x table which is load based to set the AF where you want it. then use the wot multiplier to tweak it in.

 

Another question is, regardless of closed loop or open loop; when it uses the PE vs RPM table does it wait until the MAF is maxed or does it start using it at less than 100 KPA? ...or ...does it start at 100 KPA and before and after the MAF maxes?

 

I noticed a PE vs coolant temp table, maybe that is the one you all are talking about. If you can shoot me that blm locker program that would be awesome and probably the smartest alternative for me. This way I'm not taking any chances and I can fine tune the fuel trim (like limit the trim to 120, or whatever it needs to get rid of the surge, for example). Can you shoot it to my e-mail? Thanks! Better safe than sorry, go lean once and that's all it takes sometimes.

 

I'm really interested in this as well..

Isn't there some way to make the car run in open loop only while cruising? I find that all of my crusing is done in cell 6 (set to 1200-2000 rpm and 30-55 kPa). There is no way to only use open loop there so you can fine tune the cruising without have fuel trims kick in? Is this what you are trying to do with the blm locker program? I am assuming by the way you guys describe it is that blm locker can specify certain rpm and map ranges where you want the blm locked to a certain value? If so I'd appreciate a copy too! (omarlcc@gmail.com)

 

You can't do that, there are no adjustable settings. It only locks it for wot.

 

No that's the PE coolant table. There are two PE tables, coolant temp and rpm.

The table I'm referring to is called Open Loop AFR enrichment vs. Coolant Temp vs. MAP in tunercats and the values in it are all fuel ratios (12.5, 13.7, 14.1, etc.).

 

??????????

I think we must be talking about two entirely different things. I wasn't aware of closed loop learning happening at WOT, never heard of such a thing.

I was talking about limiting the max fuel trim to say ~120 (instead of 108) in the cells where I see the surge (30-50 KPA at 1200-1800 RPM) .....or ....in the MAF AFGS where I see the surge (13-30) ....surely there is a way to specify a range, no?