RPM WS6

iTrader: (3)

I've been doing a lot of fuel related tuning lately, trying to dial in the setup as best as possibile on the street. I know that PE tables are only supposed to be used for WOT opperation, but I have read that some people have seen changes to their LTFTs when making changes only to their PE table. This lends to the possibility that the fuel multiplier in the PE table might have some kind of effect on part throttle FTC fueling, correct? Probably not too many people would be willing to buy into this theroy at the moment as it contradicts the whole point of where PE is supposed to be used, but I have a condition that might be connected to this.

I'm having a couple issues that might be due to a lean condition at lower rpms, and it seemed to start right after I made changes (leaned out) to the PE vs RPM table. I'm wondering if richening up the lower rpm parts of this table would help that problem without effecting WOT fueling. For example, can I give everything from say 1600rpm and down a bigger multiplier without effecting WOT fueling?

Is everyone else changing the whole PE vs RPM table as a unit, or was I only supposed to change the higher rpm areas in the first place?

Please give me your thoughts......

RPM WS6

iTrader: (3)

I learned during the tuning of my VE table that when I went too lean, I would get idle surge while stopping and coasting at low speed/low rpm even if it wasn't lean enough to cause hesitation. I am having some of that issue again, and I'm thinking it's the PE vs RPM changes I've made. The only other change I've made is riching the IFR table a little further than before, but I don't think that's it. Going richer on the IFR should only help if anything, plus I have negitive LTFTs at idle.

I'm really thinking that it's the PE table change I made. I multiplied the whole table by 96% which brought the across-the-board number down to 1.19, and I'm really thinking that I should bring the 0, 400, 800 and 1200 rpm ranges back up to 1.24 as they were stock to make this issue go away. My concern is, what will that do to WOT fueling? I'm guessing nothing as 1200rpm and under changes are well below anything the car sees at WOT. My other concern is, since the table was a straight line stock (all columns were the same number), is it bad to have different multiplier numbers in different rpm columns (for the 1200rpm and under range)?

Has anyone had this issue?

Has anyone ever tried what I have proposed?

I'd love to go do it right now but I can't do any more reflashes till I take my emissions scan test, I'm having some trouble getting some tests to complete so I gotta get past that first......

In the mean time, anyone have any comments or experiance on my issue? Thanks.

RPM WS6

iTrader: (3)

Anybody? Anything?

jimmyblue

iTrader: (11)

PE "decision" is separate from WOT "decision"
and they overlap somewhat. WOT is just TPS
threshold, PE is mainly MAP (vacuum). At low
RPM you can get PE active with a fairly low
throttle angle. Then you have closed-loop
cells trying to trim back the PE-added fuel.
Bumping PE will just change your LTFTs a
bit as the loop has final authority at level
cruise. But on throttle transients the true
tune is exposed and you might get a stumble
or bog if PE is way off.

PE is the main enrichment available to WOT.
You could be more "surgical" in changing
PE vs RPM, and avoid idle issues from that
(just as people usually only change VE in the
at/near-idle cells, change PE only in non-idle and
maybe non-idle-adjacent cells).

RPM WS6

iTrader: (3)

Thanks for your reply. It makes perfect sense, and I'm almost positive that my issue is due to an overly lean PE number in the low rpm cells.

Now my only question is, what rpm range should I go back to stock with? At first I was only going to do 1200rpm and under, but maybe I should go higher? What would you recommend? 1200 and under? 1600 and under? or maybe something more drastic like the 3000 range and under?

The only VE table columns that I ever changed were up to 1200rpm, so I'm thinking that maybe I should only put the 1200 and under range back to stock on the PE table?

Thanks again for your help.

RPM WS6

iTrader: (3)

Ok, after doing some more research, it seems to me that most are only modifing the PE tables for above 3000rpm. So I think I'm going to put everything below 3K back to stock and see what happens with my recent low rpm driveability issues and LTFTs. Sound like a good plan?

Any more opinions are more than welcome.

deezel

Sounds like youre getting there. Let us know how it works...

Some comments on PE tables. My truck's stock PE table is not a straight line. It starts out very lean (AFR ~13.2 at ~2000 RPMs) and ramps down to its richest (AFR~11.9 at 4400RPMs). However, my stock WOT tables were set at 90%tps. From my logs, I only see PE enrichment when I enter WOT mode. I currently have my WOT set at 45%tps above 3000 rpms and a little higher below 3000.

SS SLP2

iTrader: (8)

Running stock heads, all bolt ons'-over, under and inbetween, set VE @ 70-80-90 @400-800-1200, to help idle ( now at 675-700 ) changed PE -RPM several times to get o2's @ 890 so I do not know how far from stock PE-RPM was set but after install 231/237 begain to have jerk and snap at 36-41 mph, Jason @ TEXAS-SPEED suggest try 101 @ 1200-1600-2000 in PE-RPM only, did great
good luck Johnny

RPM WS6

iTrader: (3)

Odd that it's different like that. My table was 1.24xx across the board.

I've read from a few sources now that the PE tables for F-bodies definitly have an effect on part throttle fueling. Seems that everyone notices a change in LTFTs in cruising FTC ranges when making only PE adjustments. I beleive this to be 100% true and correct based on what happened to my low rpm driveability after leaning the low rpm range PE.

I'm still struggling with exactly what rpm ranges I want to return to stock. I only changed the 400-800-1200rpm ranges on the VE table, so part of me says to only put those ranges back to stock on the PE table. But then I've read while searching in a couple places that we should only be leaning the areas above the 2800-3200rpm range on the PE tables, so I really don't know.

Put 0-1200rpm back to stock? Or put 0-3200rpm back to stock?

I have to take an emissions scan before I downlaod any more tunes (might be a while before I can get to the test center), but I'll take all the opinions I can get in the mean time so I have ranges to consider/try when I start trying to fix this issue.

Again, thanks for the replies guys. Keep 'em coming. The more the better.

RPM WS6

iTrader: (3)

back up