TriPinTaZ

Well I am going to have to disagree, PE mode is not used in OPEN LOOP. I use an OPEN LOOP tune on my car and there are ZERO Long Term or Short Term fuel trims. Changing the PE tables on the dyno results in ZERO change of fueling at WOT.
And VE tables changes DO make a difference in OPEN LOOP tunes, but people are under the misconception that changing the VE is going to drastically change the fueling, but this is not the case. But I have experience in OBD2 tuning, not OBD1. However I am pretty sure PE is NOT used in OPEN LOOP on OBD1 either.

97Z-M6

if i change my ve tables with the maf pluged in, my blms will drasticly change. so why do people say that the ve tables are not used when the maf is fuctioning properly.

97Z-M6

Simply adjust you WOT vs TPS to 0 at the lower rpm range


where is this table in tunercat. i have "kick down mode enable tps threshold" and "kick down mode disable tps threshold" in the constants tables.


i found the wot rpm table

cmillard

Open/ Closed loop is a separate boolean variable from power enrichment/ non-power enrichment boolean variable. Closed loop indicates the O2 sensors are warmed and can be used for feedback adjustments. Power Enrichment causes target AFR to switch from Stoichiometric 14.7:1 in closed loop, or open loop table value to adding extra fuel as per the PE vs RPM and PE vs Coolant temp.

Changing the PE tables is exactly how you dynotune WOT. That's the purpose of having the tables there. Yes some people alter the MAF tables to misreport the airflow, but that's a bit of a rough hack to put it bluntly. Tune with the PE tables allows me to dial in WOT AFR dead on usually within three dyno spins. It allowed me to nail the AFR like this:

http://carprogrammer.com/Z28/dynos/C...FR20030801.gif

Here's where it's inportant to know the differences between OBD1 and OBD2. OBD1 (94-95) doesn't use the VE tables unless the MAF fails tests. OBD2 includes the VE tables in the fuel calculation to verify MAF readings, both in Open Loop and Closed Loop operation. Again think of Closed loop as the O2 sensors being warmed up for a feedback system.

Hope this helps,
-Christian

cmillard

VE tables are used in the fueling calculation for OBD2 cars, that's all. What you've seen is normal.

cmillard

On the OBD1 $EE definition Tunercat calls this table: %TPS Threshold for WOT vs. RPM (low cool) - ( High cool isn't populated or used)
stock values are 66% TPS to enable PE all the way up to 3200 RPM.

Hope this helps,
-Christian

TriPinTaZ

on OBD2 cars, PE tables are not used in OPEN LOOP. Instead the pcm refers to the OPEN LOOP vs KPA vs TEMP AFR tables. I have data logs that even show the PCM refers to this table for target ARF under WOT as well as part throttle fuel while in OPEN LOOP.

I run an open loop OBD2 tune. There are no fuel trims happening, and the PE tables are not used at WOT. And the target AFR always matches the values I have set in my OPEN LOOP AFR table.

cmillard

Interesting, I have dynotuning experience with OBD2 LTx's and LSx's that has shown otherwise, that's all I'll say. If the PE vs. RPM table isn't referenced, then how do you control AFR at different RPMs? Yes, the open loop table is a starting point for fuel calculations, but hitting WOT in open loop does cause a lookup to the PE tables for calculation. Again, just my experience.

Here's a quick way to test if the PE vs RPM table is referenced. Max out the values in the table, forcing lots of fuel to be added at WOT. Take the car for a spin around the block, floor it and watch how pig rich it runs after the change.

Not saying what you've observed is wrong, just sharing my experience, that's all,
-Christian

Highlander

I am still skeptical about the roughness when entering from open loop to closed loop, which was i have not used this method...

Christian, can you post your feedback on if you feel the car surge, kick or give ANY indication that has changed modes?

on 94-95 cars VE tables are not used if MAF is working correctly, VEMaster never worked for obdi with maf...

97Z-M6

but im running a obd1 conversion.





so udjust this table to 0% at what ever rpm i idle at. and this will set pe mode at idle, and when i go off idle it will do as normal. correct

bunker

correct, only problem is if you idle at 1000rpm, the next bracket is 1200rpm, if you set that to 0% then if you cruise between 1200-1600 you will be going in & out of PE mode depends on your TPS position which would kinda suck

Highlander

Why not idle at 900rpm?? what kind of cam are you guys running to have such a high idle.. i just hope i dont have problems with my new cam

cmillard

Yes, other than datalogging, you can hear the engine sound change when closed loop is entered (depending on setup, cam, displacement, etc.)
Open loop tends to be a bit smoother sounding than closed loop, it's a slightly richer mixture, not as erratic as closed loop (again, depending the build, a hotcam sounds much different from a CC306)

-Christian

Highlander

im over a cc306 already...

cmillard

Okay, then I have done the experiment for you (with my car even.) I can promise you PE mode can be enabled during open loop.

[/QUOTE]

yes, and you might want to adjust the neighboring cells like bunker was saying. If you idle at 900 rpm (like most do) then set 800 and 1200 cells to zero.

It isn't a drastic change if you've calibrated the PE idle to a reasonable mixture (say 13.5 - 14.0:1) I did it for a long time with my Ultradyne cam, no problem whatsoever.

-Christian