Joshboody

I've been reading a bit preparing to start logging/tuning once I get HPT. I believe my PCM understanding is ok to this point, but have a question.

When warmed up you are either in closed loop or PE and the OL table is not referenced (maybe in PE if richer). Can we use this OL table without completely disabling CL operation?

My understanding (if PCM chooses richer parameter) is to purposely make PE AFR leaner so PCM references OL during PE. Is this a tuning technique?

The reason for asking is thinking how to tune smoother transitions at part throttle instead of just stoich or PE AFR.

danieloneil01

Read a lot more, I think you are very confused.

Joshboody

Nice reply, I did find the answer... PCM can only be in CL or OL. If in OL it will take the richer of PE or the OL table.

directnosfogger

i think you are confusing what PE means. Power Enrichment is only leveraged when you trigger a variable to go into PE. Those are in your PE settings. OL or CL will reference PE.

Joshboody

You all may not have understood my question. I understand PE is triggered based on MAP and TPS. OL is only used during warm up (stock tune), BUT has some advantages in AFR control since you can set it based on MAP and RPM. With CL your only AFR set points are stoich or PE, which is 2D based on RPM... not as many options as OL. Using OL you can either disable PE or "override" the AFR by setting a richer OL. The latter likely being better considering PE may add additional fuel factoring acceleration.

Anyway, this is my understanding... of course I could be confused/wrong as I am new to the LS1 and haven't played with it yet.

directnosfogger

What exactly are you trying to tune your vehicle to do? Even in open loop you fuel based on coefficients. If you use open loop it will attempt to command an AF based on only maf/sd readings without use of 02's. When using closed loop you have a check factor of leveraging an 02 reading while getting the base fueling from the maf/map. I would never disable PE because it compliments an open loop configuration. You can reach the any type of fueling you wish through the use of a VE table with open loop and PE [OLSD].

Joshboody

Well the point was that PE is not disabled, but instead a combination of OL and PE based on MAP. Basically PE controlling fuel but substituting the richer OL AFR. It would make for a very smooth tune, but without the trimming parameters... thus my original question about potential of OL to be referenced in PE when in CL to have both trimming and more complete AFR control.

It was more for understanding. I have HPT in the mail and will be playing with a stock car to start.

Anyway, thanks for the discussion.

tblu92

The PE mode can be activated when running either a CL Tune or an OL TUNE---ONE IS WITH THE MAF AND ONE IS WITOUT--- TheMAF works excellent for any NA wngine with less than500 RWHP--

tblu92

Sorry for the typos---- Again---Only on highly modified engines or engines running over 6500---or large cubic inch motors you may benefit from running an other than stock CL/OL MAF tune--
YES you are right when running a CL tune the ECM will pick the RICHER of the PE AFR or the OL AFR----But this is ONLY as a safety --Not intended for a running tune
You can run what they call a "semi open loop tune" by disabling the MAF and running in true open loop--However the PE mode still works---The only time I have seen a benefit from this is in extreme cases like running LT headers and a super charger--
Remember when running without CL there is NO fuel correction at P/T at all--so when the weather changes or you change altitudes your AFR in PT is at the mercy of your tune-Which can be lean or rich---
In your case you are looking for an advantage that is simply not there--trust me--My 98 with 400 RWHP had excellent drivability and power-- 12.00 1/4 mi times running the STOCK MAF and CL/OP stock set up----I had LT headers Heads and Fast intake and an automatic
---and got 28 MPG on the freeway--


PS: If your goal is to smooth out the transition between CL and PE and get better throttle response ------ that that can be achieved by mapping logging and correcting your VE table--Must be done with a wideband----The VE table is used in a CL/OL tune only during "RAPID CHANGES IN AIRFLOW"--- The ECM will take the MAF signal and fueling and add the VE table then use the average of them all during the transition --Which smooths it all out and can add some HP--The VE table also can be used soley in a Speed Density Tune which is mostly intended for dedicated race cars and NOT daily drivers as again there are not only no corrections for weather or altitude at P/T but not any at WOT either--

Joshboody

Hey Blu, thanks for the comprehensive reply. Just trying to get an understanding of PCM logic.

Took my first scans of a stock car yesterday on 91oct at 90deg ambient and definitely time for some ethanol (excessive KR) which will be my first tuning exercise.

I'm at 1200ft elevation with only K&N filter system and getting about 10% LTFT across the board... which is surprising. I suspect the temp/baro corrections swing excessively and guessing LTFT will come down when cooler... we'll see.

Since my dyn air and MAF are tracking pretty close <4k, I'm going to attempt an easy peasy tune NOT isolating VE and MAF scans. Dyn air is greater in the higher revs, which I'll take LTFT-(dyn-MAF) for some of the VE table. Now to just get a handle on using histograms.

Can't wait to put some E in the tank.

EDIT: Just looking over HPT and doesn't seem to be any IAT compensation considering density... theoretically not needed for MAF I guess, but important for VE calcs. Its prob factored, but not defined in HPT.

romandian

"The VE table also can be used soley in a Speed Density Tune which is mostly intended for dedicated race cars and NOT daily drivers as again there are not only no corrections for weather or altitude at P/T but not any at WOT either--"

why would that be? doesnt map/iat correction take care of this? there are plenty of sd systems working very well.

enoniam

The statement you quoted is incorrect. You can get LTFTs in Speed Density. Some tuners however like to turn them off.