I saw mentioned that the PE tables are not used with an open loop tune. Is this correct that neither the PE vs. Coolant and PE vs RPM tables are used in open loop? I'm tuning a 93 LT1 and was considering an open loop tune, but this would seem to make it harder.

What tables are you open loop guys adjusting to get the WOT fueling correct?

Thanks,
Rob

 

No they don't seem to work at all, I tried it on dynoday, either way, for 94 guys you can use the MAF table, for you just use the VE table.

 

Ok, so now I'm wondering if it would be better to set the min and max blm's to 128 in the chip. That way you will still be in open loop, but the blm's can not change or affect fueling. I guess you would have to lock the INT's ant 128 too. Can that be done with TC??

-Rob

 

Tried that, locking BLM's doesn't do anythig, the Long Terms get locked but the Short terms still wonder off doing their corrections, only thing is does is not let the computer learn past say the locked 128 over a long term, but driving around it'll still correct, it'll just run like the PCM is being reset all the time to 128 when you let off the gas. Been there done that bud.

 

Well, I just got an updated definition file from TunerCat and I had him include the constants for max and min Integrators (short term fuel trims) so now I can lock them at 128 also. This should now allow open loop type tuning while retaining PE mode for WOT.

-Rob

 

No what you need is a BLM blocker for WOT, the max/min integrator in Tunercat only locks the LTFT not STFT so the PCM will still correct for it just it'll always keep relearning instead of learning it & storing the info as long term. what we need is a short term fuel trim locker.

matt.

 

The PE tables are used regardless of closed or open loop operation.

 

What?

I think you may be mistaken,
PE tables are NOT used during WOT in OPEN LOOP mode

 

Changes in the PE tables most definitely affect AF ratio whenever WOT mode is entered. This has nothing to do with Open Loop v. Closed Loop.

Rich

 

then I must have a special PCM, PE is not used in OPEN LOOP mode. The scan tool may SHOW PE is enabled due to the TPS % exceeding the preset % to enter PE mode. but in an OPEN LOOP tune, PE tables are NEVER referenced for fueling. Changing my PE tables does absolutly NOTHING for my AFR, however the pcm shows the car entered PE mode.

I think you and a few other people may be mistaking this for the car READING the PE tables, which it does not in open loop mode.

 

http://carprogrammer.com/Z28/PCM/Ana...OT_testing.txt

This is off Christian Millard's site on LT1_edit forum by Schube. He seems to agree with me.

 

I just wanted to update this thread. I received an updated definition file from Tunercat that includes settings for min and max INT's (short term fuel trims). I set my min and max BLM's to 128 and my min and max INT's to 126/130 and burned a new chip. My car now runs in closed loop but does not allow the computer any correction other than the 126-130 range of the INT. This is letting me run what is basically an open loop tune yet still retain PE at WOT since the computer is still able to go into closed loop, but it can not make any fueling changes. I still have some work to do with my VE tables (speed density car) but so far it's running better than ever.

-Rob A.

 

Sorry Rich but I think your wrong on this one. Cost me a full 2 hours on the dyno trying to adjust PE in OL and no change at all. Let her go CL and I could put AFR anywhere I wanted it. This was not a subtle thing either. I made massive massive massive PE changes while in OL and all to no avail.

Steve

 

Also to add to the post, Open loop AFR is way different from Closed loop even if you locked the STFT to 128, if you tuned your car well & you were at 128blm at all times durring driving/idling, when your in open loop with blm at 128 its way off, closed loop doesn't not look at the open loop temp vs. map tables at all, the way fuel is calculated in closed loop & in open loop are totally different.

Matt.

 

I understand the difference between open loop and closed loop AFR's. The reason I wanted to be able to run with locked BLM's and STFT's was so I could have a tune that could not be modified by O2 feedback yet still allow the use of the PE tables for WOT tuning. With the cam I'm running, I can not rely on the stock O2 for idle fuel adjustments since it reads lean from the overlap in the cam and unburned oxygen. The way I have my tune now, it is similar to an open loop tune but still allows PE mode at WOT. I can now use my VE tables to lean out the idle areas and not have the computer richen it back up and still use the PE vs. rpm and TPS tables for WOT tuning....

-Rob A.