General Question on AutoVE

[NewV]

I've read the tutorial and this is my understanding: When completed your VE table will be accurate, LTFT should be virtually eliminated and AFR should essentially be 14.7 at all times.

Assuming the above is correct, how have I really benefitted myself?

Does this gain me anything performance wise?

[SSpdDmon]

I've read the tutorial and this is my understanding: When completed your VE table will be accurate, LTFT should be virtually eliminated and AFR should essentially be 14.7 at all times.

Assuming the above is correct, how have I really benefitted myself?

Does this gain me anything performance wise?

Close. The AFR won't always equal 14.7. Assuming the VE table is correct, a car in speed density will always have an AFR equal to the AFR that is commanded. In closed loop operation, a car in speed density with a correct VE table will have 0 LTFTs (in a perfect world).

What you have gained is the reliability and consistency of knowing the commanded AFR equals the actual AFR without having the need to log the WBO2 all of the time. Because the stock NBO2 sensors are only good for part throttle, open loop operation is kind of up in the air in the PCM's eyes. It assumes actual AFR equals commanded. Post tune, you know and not just assume. Also, people report better throttle response and over-all better daily performance. Get the MAF dialed in the same way and fueling tuning is done.

[Doc]

Ditto ^

[NewV]

So in the {B3605} Commanded Fuel in Open Loop table 1.0 is stoich or 14.7 AFR.

Is 1.5 lean or rich?

Correct me if I'm wrong but at higher throttle AFR < 14.7 is rich and increased timing typically means greater power/torque? I understand this can only be validated on a dyno.

Just wrapping my mind around the whole thing. Thanks for your help.

[Tordne]

It depends what your display units are?

1.5 in EQ is VERY Rich, in Lambda is is VERY Lean

[redhardsupra]

I've read the tutorial and this is my understanding: When completed your VE table will be accurate, LTFT should be virtually eliminated and AFR should essentially be 14.7 at all times.

Assuming the above is correct, how have I really benefitted myself?

Does this gain me anything performance wise?

this is a very good question, i'm glad someone is trying to understand what it is that VE tuning is actually about, not just how to do it.

1. without VE being perfect, you'll never be able to find out proper timing. when computer detects the tiniest tendency to run lean, it will be very trigger happy to pull timing with usually no good reason. thus, if your VE is on the lean side (and it usually is, afterall that's what adding better flowing parts is about--flowing more air) you will get a lot of knock in random spots, and no amount of pulling timing yourself will cure it, causing your car run like poo
2. sudden transitions are hard to get right. without VE being dead on, you are making it almost impossible to get right. bad transitions cause knock, which lingers around, doesn't last just when going over the areas that aren't perfectly tuned. i've seen knock last over 5 secs. if you're a drag racer, that's deminished performance for half of your run. that's why it's also important to tune not just some of the VE, but ALL of it.
3. when your car develops a problem, you will notice it. if your VE is well done. airflow numbers will be down, knock will appear, but you know it's not the fault of the bad tune, but a result of some hardware component failing.
4. when VE is perfect, it is meaningful. if you add a part that supposed to improve engine's breathing, your VE will go up, and if you get it tuned perfectly before and after, you will know just how well the part works, and for what map/rpm range.
5. with perfect VE, your airmass and airflow numbers will be meaningful as well. with their close correspondence to tq and hp respectively, you can optimize your powerband.
6. perfect VE enforces other tables to be meaningful as well. for example, to obtain the same proper fueling with wrong VE, you will have to hack either your IFR or PE numbers. with all of them perfect, all of them will be meaningful, when you want a 12.9AFR, you can just command it in PE and it will happen, instead of taking stabs in the dark hoping that some arbitrary PE will make it happen
7. since VE dictates airmass and airflow, everything based off such tables will work better as well. shift tables for automatics need to know how much power you're really making. if you're lying about VE, then this power estimation is also wrong, making the trans misbehave.

in general, VE in itself is important. a lot of other things are derived by calculations based on numbers calculated from VE. so it really ends up being a domino effect. if VE is meaningful and proper, then it forces other things to meaningful and proper as well. but if you botch/ignore VE, then the bad effects will propagate, making the entire tune a major hack, making the car drive horribly, and sending the tuner chasing his tail.

in the long run it's really just easier to do it Right

[joecar]

Everthings "cascades" down from two tables: IFR and VE.

And do not use Lambda units, these will create confusion.

[NewV]

Thanks for the help guys, I'm sure I can't be the only one out there that doesn't understand this stuff. Now how about some actual definitions of the following terms, tons of info on how to do it but not what it means:

Speed Density
Open Loop
Closed Loop

[joecar]

SD = airflow is calculated from engine speed and air density; MAF-less.

Open loop = not using feedback from the NBO2's.

Closed loop = using feedback from the NBO2's to contrl air:fuel to 14.63.

[Josho]

Thanks for the help guys, I'm sure I can't be the only one out there that doesn't understand this stuff. Now how about some actual definitions of the following terms, tons of info on how to do it but not what it means:

Speed Density
Open Loop
Closed Loop

Dude im in the same boat as you only i probably know less than you. Im still waiting to get my scan tool so i can start to understand all of this. I have no idea wat the VETable is lol. I have to start from scratch