Can't seem to find the answer to this

[98Camarod]

When you have a lean afr, and you multiply the error % to the VE table, why does it increase the value rather than decrease the value?

Also, does changing the timing affect the afr? If so, which direction is required to richen a cell?

[Dozer]

You increase VE to increase fuel so if your error is 10% when you multiply VE by % it will add 10% more fuel in that cell. Small Timing changes will affect AFR very little but extremes could affect it a lot more. - timing richer, + timing leaner. Use the VCM controls to and play with the timing at idle and watch your wideband for examples.

[talsayed]

Small Timing changes will affect AFR very little but extremes could affect it a lot more. - timing richer, + timing leaner.

In addition,Exhaust gas temperature sensor (Pyrometer) will show the same way in relation with timing.More timing=less EGT,Less timing=More EGT.

[98Camarod]

You increase VE to increase fuel so if your error is 10% when you multiply VE by % it will add 10% more fuel in that cell. Small Timing changes will affect AFR very little but extremes could affect it a lot more. - timing richer, + timing leaner. Use the VCM controls to and play with the timing at idle and watch your wideband for examples.

I thought the VE was the airflow that is required in that cell to operate at your commanded afr for that cell, not fueling.

My fueling is constant due to the boost ref reg

[Atomic]

More air = more fuel

[98Camarod]

More air = more fuel

I realize that, just trying to make sense of it all.

[Atomic]

I apologize if my previous post came off as harsh. The actual numbers you see in the VE table are airmass per cylinder. Basically, how much air is entering the engine per given MAP and RPM.

The engine always tries to maintain a constant ratio (14.68 at stoich) of air to fuel. What this means is when you see 5% error in the scanner, the vehicle is having to add 5% more fuel to get the right ratio. Since air and fuel are in a constant ratio, you can correct this 5% fueling issue by increasing how much air the vehicle thinks is there by increasing the corresponding cell in the VE table by 5%.

Hope that helps.

[98Camarod]

I apologize if my previous post came off as harsh. The actual numbers you see in the VE table are airmass per cylinder. Basically, how much air is entering the engine per given MAP and RPM.

The engine always tries to maintain a constant ratio (14.68 at stoich) of air to fuel. What this means is when you see 5% error in the scanner, the vehicle is having to add 5% more fuel to get the right ratio. Since air and fuel are in a constant ratio, you can correct this 5% fueling issue by increasing how much air the vehicle thinks is there by increasing the corresponding cell in the VE table by 5%.

Hope that helps.

But the value was negative and it added more air to the VE table. At cruise it was lean at about 15.3 afr and had a negative AFR Error %, and when I paste special-multiply by percent, the value went up.

I was under the impression that the VE values were for the air in the cylinder for that particular cell. Then uses a fueling and spark tables to execute combustion.

Also it will change if you are past the PE or BE threshold to a corresponding commanded ratio.

[Atomic]

If you WB is showing 15.3 and you are commanding 14.7, you should have a positive AFR Error of [(15.3-14.7)/14.7] which is ~4%.

I have a feeling you have your AFR error equation backwards where you are doing [commanded - actual/ commanded] instead of [actual - commanded/commanded].

Mine looks like this: 100*(([USER.9008]-[SENS.121])/[SENS.121])

[Frost]

But the value was negative and it added more air to the VE table. At cruise it was lean at about 15.3 afr and had a negative AFR Error %, and when I paste special-multiply by percent, the value went up......

This is where you are mixed up. Lean is positive error, and the VE value is added to for correction.

[98Camarod]

This is where you are mixed up. Lean is positive error, and the VE value is added to for correction.

I'm a moron. I guess I was thinking red as negative and green as positive, even though there is a clear negative sign right in front of it.

Off topic: are the stock offsets and pules fine for lucas 42.5 injectors? I have a hanging idle, I'm not sure if its my iac causing it or what.

[Atomic]

Think of it as green= safe=rich, red=bad=lean.

[98Camarod]

Think of it as green= safe=rich, red=bad=lean.

lol. Me=Moron

I just needed for someone to point it out I guess. I still have a sputter if there is too much throttle applied. I re gapped the plugs to .028 and I'm on my 3rd 30 min log to change the VE table. Big AFR % errors still, about an 11.4ish when slowly accelerating and after lean after I get to about 50mph cruise.

What is a good afr to shoot for on part throttle acceleration?

That's what I'm working with right now.

[Atomic]

What kind of wideband are you using? I am using a plx and dont totally trust it, so I use the stock o2s at 14.68 for part throttle, and just use the plx when in PE.

If your running closed loop you should be at 14.68 until you enter PE.

[98Camarod]

Sorry, I'm running OLSD right now.

[Atomic]

Ah, any particular reason?

[EaglePerformance]

You should shoot for 14.7 in steady cruising, any acceleration enrichment is a separate adjustment, (if available). The way I look at the VE issue is that if it is lean, then more air is going through than the "brain" expects, so the # is increased to correctly reflect what is really happening, and like what has already been said, more air, more fuel.

i

Ah, any particular reason?

In OL, you don't have to fight the STFTs.

[98Camarod]

Ah, any particular reason?

Trying to get the VE good before I enable the fuel trims.

[Atomic]

Ah, well I suppose my philosphy is a bit different. I trust the stock o2s at stoich more than I do my wideband, so I like to tune by them at stoich. To each his own.

[RoDan]

Off topic: are the stock offsets and pules fine for lucas 42.5 injectors? I have a hanging idle, I'm not sure if its my iac causing it or what.

I have been using the injector offset tables from an 05 Silverado with the 6.0. They are disc-type injectors like the Lucas 42's, and I swear they are behaving more natural now that I changed to that over the stock table.