GOod info ...

Not challenging, but would you please elaborate on the last statement about FI and steady throttle positions.

 

Empirical data shows that.

When in SD mode (as I am now with 2 bar map sensor) and a nailed down VE table, rapid throttle increase (eg, 30% throttle increase to 80%) will result in a temporary lean condition before the PCM catches up to the physical occurence going on within the engine.
Rapid pop off the throttle will show a very rich condition temporarily til the PCM catches up. This is due to the PCM not sensing the increased load until it has already entered the intake manifold and is available for the engine to take in.

When in MAF-ONLY mode (EFI Live allows you to effectively disable the VE table completely), a rapid increase in throttle from steady state will show a very rich condition immediately before leveling off. A rapid decrease in throttle will go lean briefly (assuming you don't have you PE ramp out rate set too high). This is due to the PCM sensing the increased load before it actually enters the intake tract (Throttle blade opens, more air flows through MAF before actually entering the engine).

With both systems in play, these lean and rich conditions are not nearly as pronounced, effectively showing us that a blend of the two systems occurs.

And to know that MAF fueling is the significant factor in relatively steady throttle, you only have to look at a stock radix or whipple or any FI tune for that matter. MAF table is completely unaffected, yet VE only handles non-boosted situations. You can run the stock maf calibration in boost with the commanded AFR being almost dead on to what a wideband would measured while the corresponding VE calculation is SIGNIFICANTLY lower.
I can actually show what this would look like right now if the MAF was not key, as something is amiss with my Custom OS installed right now wherein it is locking the airflow calculation to the 105kPa column while in boost when I am running a MAF/MAP combo, but works properly when in either MAF-only or SD mode exclusively.

Hope that makes sense, it's too long for me to go back and proofread effectively

 

That makes perfect sense.

In other words, the VE table is what *should* be happening by a series of calculations, and the MAF says the hell with that, this is what's going on. I guess this elaborates the need for both, VA and the MAF.

I do have a question however ... if one wanted to do away with PE mode, say for instance WOT will be going out of range for the MAF, therefore fueling will rely on something else, and doing away with the MAF all together will disable PE mode, how would one richen the fueling up for that, changing the VE table?

 

AWESOME explanation!!!

Flyer, I tried no-PE and only had VE give all fueling commands. You are battling 2 things in my opinion. As justin states, without the pre-manifold calc you are exposing yourself to some "catch up" play by the pcm and I found they're plenty of situations I am in a spot in the ve table that I don't want PE but sometimes I would. The only way for me to get what I want (I am married so I am sure you know that doesn't happen much) is to enable pe/be. So I can set the tps, kpa, ect switches. Obviously you don't need pe/be at 160kpa, if your not in extra fueling then you are in trouble any way. I have read that a few have 2bar tunes with no pe/be. It's all in the ve table. Not me though.

This probably one of the reasons dc_justin prefers to have the maf up to a point. He gets the best of both worlds. I certainly have HUGE lean spikes going 30% to 80%. That would almost be eliminated if I let the maf read the beginning transition.

 

Doing away with the MAF won't disable PE mode. PE mode is based on whatever airflow calculation is available to the PCM at the time.

If you went to a 2 bar setup with no MAF, it would rely on the VE table as the sole source of airflow calcs to base PE mulitplication on.

Think of it like this.
First step, PCM senses engine load (airflow calc). It can do this by MAF-alone, a blend of MAF/VE or by VE alone (SD).
Next step, inputs from other sensors that can affect air density come into play. IAT and ECT primarily (if not solely).
PCM then references all applicable fueling adders or reducers and sets commanded AFR to the richest of all applicable possibilities.
PCM then uses that commanded AFR and fuels according to the sensed load vs air density adjustments.

 

doh, i didn't read the question well. Yeh what justin said! LOL but FWW I did try making my pe/be multipliers "1" and doing just the ve table. Yikes!

 

Why is it then ... if the MAF is unplugged, the PCM will not fall into PE mode?

 

I've never encountered that phenomenon...

 

I've never been able to get mine or 2 other trucks I've tuned to go into PE with the MAF unplugged. If I remember right, I even read something about that too.