I have looked through the tuning articles but the fuel table in my ECM doesn't look right to me. Probably because I have a different ECM than what any third gen would use. Every article I ready talks about adjusting the VE tables based on the BLM to get the fueling just right. Attached is the fuel table for my truck and those values look way too high to be VE (especially for my motor), so what exactly is it?

 

It looks like a VE table. VE can go from 0% to 100%.

RBob.

 

i realize that it can theoretically go up to 100, but the fact that this chart shows it even getting close to 100 doesn't sound right for a 93 suburban 350, i doubt my motor is really that efficient

 

Ahh, the VE in the table is not relative to atmosphere. This is different then what is used for carb'd engines. Which is why a lot of EFI VE tables taper off as they approach 100 KPa MAP.

RBob.

 

The VE table is likely rich to cause the engine to run richer at high loads and not melt down the cat. The PE AFRs in some of the calibrations are hovering around 12.5-13.0:1, and leaner at lower MAP/RPMs when transitioning into PE to improve performance from what I can tell. Obviously at high loads and RPMs these would damage the cat, so they probably richen the engine up to some acceptable AFR through the VE table. Also note the 400 RPM/100 kPa cell. This cell, and the one in the closed throttle table are the ones that the engine transitions into when coming off of the engine cranking pulsewidth tables, so use care when editing these as they could also effect start-up

 

Dim says: Also note the 400 RPM/100 kPa cell. This cell, and the one in the closed throttle table are the ones that the engine transitions into when coming off of the engine cranking pulsewidth tables, so use care when editing these as they could also effect start-up.

Question: are you refering to startup on warm coolant in CL? on cold engine would not the OL vs coolant tables be used untiil it flips CL?

i never realized that on a startup it would see that cell but it sure makes sense now as it is at atmospreric pressure on startup. no way to log that is there. would it not be better to be certain that cell has ample fuel?

 

I look at the VE table more as an injector duty cycle table, makes more sense to me. I know that a stock/mild TBI engine will not have anything near 100% VE efficiency. What I am trying to say is that the VE table value really has nothing in common with the TRUE VE of the engine.

FWIW, here was the table (very close to BJYM $OD) that ran my stockish bolt-on L05 very well. This is with 61# injectors at 16 PSI and the corresponding BPWC. The PE air/fuel ratio was set for 13:1 with a slow decay down to 12:1 after several seconds, observed on the wideband was very close all the way through the RPM band.

 

Startup is always open loop. Closed loop is not entered until the approapriate(cold, warm, hot) timer has timed out. In the later truck PCM's there are two VE tables, near idle and off idle. Coolant fuel compensation is done via an "Open loop AFR vs. coolant vs. vacuum" table. Startup can be datalogged by connecting to the PCM with key on, engine off, then start a log and start the engine. This is the only way I know of to troubleshoot startup problems. HTH

 

Hallin: how low does a warm engine stay OL on startup before the timer allows CL? are we talking sec or msec? i never logged warm start with WB. might be interesting to look at. always had good luck with cold/warm start with my tune(cept when i found out one of my IAC's was kaput). i suspect there is a constant in TC for decay.

 

The CL timer is in seconds and can be anywhere from 10 sec to 2 minutes or more depending on the application. The timers function is to allow ample time for the O2 sensor to warm up before allowing closed loop. Applications that have a heated sensor can enter CL sooner and therefore have shorter timer delays than those applications that do not use a heated O2 sensor. HTH

 

Look here Ron...

 

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If your using a C3 ECM, then those dont have the cranking PW tables like the PCM does. The startup is straight off of the VE table. That 400 RPM/100 kPa cell is in use while your cranking, so that along with all the other startup stuff will effect how much fuel the motor gets while cranking.

 

My truck is running the E6 PCM, which doesn't seem to have as many options as many of your's do.

Main Fuel Table vs. RPM vs. MAP, open throttle
Main Fuel Table vs. RPM vs. MAP, closed throttle < this only goes to 1800 RPM
WOT AFR vs. RPM (PE mode?)
TPS threshold vs. RPM for WOT (PE mode?)
TPS threshold vs. RPM for WOT fast
Accel. Enrichment vs. differential TPS
Accel. Enrichment vs. differential MAP
Open loop AFR vs. coolant vs. MAP
AFR at startup
Crank BPW vs. coolant temp

i'm guessing that WOT means PE mode. the first thing i did was change the Crank BPW by the percentage injector size changed because it was idling up very high off startup, now it does not idle too high but it takes a little longer to start. The next thing i did after datalogging some was change my open throttle VE tables i took them down by 3 % because it was running a little rich all across the board (and sometimes a lot rich, like 105 BLM). most of the time it hovered around 120. after another datalogging session it ran more consistently at 124 or so, but would get lean spikes where my knock counts would go up (i'm guessing that ECU counter from last loop means knock counts, its the only thing that sounded close). also something funny i noticed it when i did a WOT run my BLM went to 131.

 

There are alot of options, but theyre probably not shown in the def. file. In the PCMs and some of the ECMs, the BLMs are alowed to move in PE if the O2 volts fall too low, like around 14.7:1 and leaner AFR wise.

 

i know there are more options available with this bin because i've seen what other ppl have done with it in related topics, is the bin definition file my problem?

 

Ok it has been many moons, but I know how to read a hack now, and have added a few tables of my own to this xdf file. I have a couple of new q's though. Here are my mods:

Holley direct replacement TBI (65 lb/hr injectors)
Stock Fuel pump
Performer intake manifold
E-fans
Hooker comp long tube headers -> 2.5" true dual with H-pipe and high flow cats.
E6 PCM 16168625

Here is my problem, its leaning waaaay out in the upper KPA range - starting at 135, sometimes hitting 150ish BLM's. richening waaaay up decel. Just about right at idle and normal acceleration. it doesn't matter when the decel is, on the freeway, neighborhood, as long as my foot is not sustaining or accelerating the truck its rich.

Can I fix the rich-ness by playing with DFCO and decel enleanment?

The problem with the lean-ness is that my VE is maxed out in the upper KPA. What other values should I be editing to fix this?

 

what is your MO on your logging routine?

are you on a level road with easy on the throttle movement? if not you are involking AE which will skew your results. are you logging steady throttle in every gear at various rpms?

i once logged upper kpa with PE set so as to not to be used. i found it to be lean BLMs compared to underlying kpa. then i moved all upper kpa cells to enrich similar % as not all cells were hit. not recommend you do this as you cant forget to reset or big thouble.

running third gear of 5 at 85-90 mph with hooker aerochambers got attention of other drivers on xway as well as any police in county.

 

What does MO stand for?

I guess I haven't been perfect in my datalogging techniques, but I'm not doing any of it in PE yet, and AE is on but I didn't think it would affect much, as its only enabled for such a short period of time. i guess i should find a nice straight road somewhere around here and do the multiple gear thingy, don't want to blow the tranny though!

 

PE can be logged with a WB02 setup. onset of AE will skew the datalog somewhat if you hit AE just prior in that cell(s) it was logging. i think i read "whatsup" in EBL disregards AE in the logs. nice feature. among many.

 

Yeah I'd like to go EBL, but I'd have to run two computers, 1 for transmission and 1 for engine. I know it can be done, but I need my truck on a daily basis and can't afford the down time (until I get my LS1!)