COMPRACER

Can the stoich afr be changed to say 13.5 instead of 14.7 and run in closed loop as long as all tables are dialed in? Or can you only do this in open loop?

Texas_WS6

iTrader: (9)

The problem would be that you would be telling the PCM that stoich is 13.5, so the PCM would still lean out until it saw the NB O2's indicate the switch from rich to lean, and then it would continue to switch from lean to rich and back to lean at the stoich point. So it would still be running at stoich (14.68) and all of the tables (there is more dealing with this then just the VE tables) would be off. The NB O2 sensors only work at stoich.

My suggestion is if you want to constantly command 13.5 9Except at WOT/PE mode) then turn off the Closed loop function by maxing out the temp in the closed loop table. Then set your Open loop table up to command the AFR you want it to. You will have to tune the VE tables with the use of a WB. I am not sure the MAF sensor will be relevant at that point though. This is one of the steps you have to do to tune the VE. I personally do not use Closed Loop at this time, I am running my setup in Speed Density Open Loop. I do plan on eventually going to SD Closed Loop once I am finished tuning everything out.

So why do you want to command 13.5 instead of 14.68? There may be ways to work around this if you do not mind explaining the reason/issue you are having.

COMPRACER

Car is an 01 F body LS1, 229/239-600-600-114 cam , mast small bore L92 heads, L76 intake. I can get all my fuel trims +/- 3-5% running closed loop sd.
The engine just seems happier and smoother @ 13.5 instead of 14.6. Especially at idle.

Texas_WS6

iTrader: (9)

I know what you mean with it running happier at the richer setting. That is my main reason for not really wanting to go back to closed loop. I am running mine in OL targeting 12.5 and it does not even sound like it has a 230/240 cam in it. It is too darn smooth really. I have been told there is a way to run the PCM in a “Hybrid" way so that it is in OL when idling and low rpm like when driving around town, but it will go into CL once you reach a desired rpm, like when you are cruising down the highway. This way it will help with bucking and surging, but still get good fuel mileage when running down the road. Maybe some on here can inform us how to do this.

COMPRACER

That would be a great help.

ND2RACE

This can be done for sure by running one of EFIlive's custom operating system like I'm doing. You can command whatever AFR you want, and when you command stoich it'll use the STFTs. It really does work well. You may also look into your spark at lower RPMs, light load. With some spark tuning I'm back to running stoich without much problem down there.

jimmyblue

iTrader: (11)

You don't want to lie about the chemistry, which is what
the stoich ratio number is for.

If you want to push closed loop fueling targets, do it by
the O2 sensor switchpoint voltages (vs airflow / airflow
mode). You could raise the mV numbers for where you
idle, and watch how the wideband moves.

Realize that a big cam at idle can be spoofing your
wideband as well as narrowband sensors, so tuning to
an indicated AFR reading may not put you to best
idle quality or economy.

shoemike

iTrader: (25)

Changing EQ1 will have an effect on all the fuel tables.

slow

iTrader: (7)

changing EQ will not change the stoich point of the fuel, and in closed loop the o2 sensors find the stoich point of the fuel, regardless of the setting in the calibration.



Ryan

Gh0st

iTrader: (3)

bingo

WeathermanShawn

iTrader: (1)

I have heard of a few people who change the PE Enable percentage to 0% TPS to at lower Rpm's to stay 'open-loop' at idle.

I have no idea if it works. There are so many smarter custom tuning options now, that that idea may be antiquated.

As JimmyBlue stated, it is hard to trust a wideband or the narrowbands at idle, that determining your true AFR 'sweet-spot' is difficult to know. I stay closed-loop and just manipulate the idle O2 switch-points to make it work.

Hope that helps.

..WeathermanShawn..

white01ss

iTrader: (37)

I'm doing this exact same thing. Had my stock cam idling at 14.7, but after a cam swap it was running an average of 15.0 and bucking sometimes in parking lots. Time to fatten it up a bit.

Like JB says, raising the voltage of the O2 switch points does the trick. Make small changes at a time as just adding 5-10 mV can have a big impact on the average AFR. Also, you only need to change the lower 4 cells (CL 0-24) as they control idle and off idle.

Good Luck.