ECMlink VE table question

[blktalon3]

Quick question about the ve table. My wide open throttle area on the VE table ended up around the high 80's low 90's. Does this mean anything or is just what it is.

 

[curt-s]

I would figure your global fuel % is a tad low. That is, you're adjusting for injectors sized smaller than what you actually have, causing excess fuel to be added. That, or you're not able to clear out your cylinders at higher RPM and load, lowering your actual VE. Based on your profile, I would doubt the latter.. unless you had a small rodent crammed in your pipe.

How are you throughout your range in hitting your target AFRs?
Can you provide a pull log ?

 

[blktalon3]

I just got my injectors back from ECMTuning and they flow tested them on their bench, so I'm pretty sure the global is right. That's the main reason I was asking. I haven't actually made any pulls yet just idle and cruise but I had to drop my VE table down quite a bit in those areas. So I'm sort assuming that WOT will be the same, of course I could be completely wrong. I'll try and get a pull in today and post

 

[BoostedBeaver]

I would suggest posting a log and actually filling out the provided template of required information when asking for tuning advice. The template is presented when you post a thread in this section.

 

[blktalon3]

I really wasn't wanting tuning advice. Just wanted to know is it normal for the VE table to not hit 100 at WOT

 

[curt-s]

The max VE is a result of many factors, some controllable by you directly.. so, really, you can make it whatever you want if you try hard enough.

If you absolutely believe your fuel parameters are spot on, then I would say generally not for a turbocharged vehicle with a free flowing exhaust front to back. If ECMTuning provided you the deadtime and global adjustment, they should be pretty trustworthy numbers provided the rest of the system is working correctly.

Another method that comes to mind is an improperly calibrated or otherwise reading wideband you're relying on to tell you your actual AFR vs target could be telling you that you're rich when you're really not. This would result in you pulling numbers from cells when you shouldn't be.

I wouldn't be estimating WOT VE off idle and cruise, though.. especially if deadtime is out.

 

[OGDSM1989]

Just my thoughts ..100% VE would represent 100 efficiency and be a 100 efficient motor. I would think that something around 95% would actually be reall hard to achieve, so something around 89-92% would actually be really good, but I have not ever really used the VE tables. I dont think I ever really payed much attention to them ...

 

[curt-s]

In an ideal world and literal translation of the term "volumetric efficiency", yes.

However, in the real world, it does not work quite so well. It is used to modify a formula's output which assists in calculating how much fuel should be injected at a certain rpm and manifold pressure to achieve a desired AFR.

This formula has various inputs, only one of which is your global fuel adjustment. If your global is off, you can end up with artificially small or large VE values for a given cell.

For instance, I can overstate my global fuel and pretend my FIC 750s are 950s. That would cause the global fuel to result in a lean condition. To reach my target AFR, I would then have to inversely increase my VE cells to compensate for an incorrect global fuel adjustment.

So I could wind up with a VE of well over 100.

Similarly, I could do the opposite and state my 750s are 550s. I would have to decrease VE cells to compensate and not run wickedly rich, ending up with VE of 90 or under at maximum.

Global, deadtime, exhaust leaks pre-O2, a wideband that reads improperly, these will all point you at making nonoptimal VE adjustments at various places amongst other causes.

Exhaust leaks general result in VE increases to compensate for extra oxygen being read, just a note.

 

[Lester B]

Great explanation curt! Thanks man.

 

[jakelandry]

There is no "normal number for VE. Its just a numerical representation and has no impact on anything really. Your VE and global directly effect one another. You can make either whatever number you want and just compensate with the other.

Literally you can make your VE table read 180-200 if you want, compensate for it with global, and have the car run the exact same as it would tuned with a "normal" VE table.

A lot of people on DSM forums really don't understand what global is even because its so well integrated into ECMLink but on other universal tuning softwares it doesn't really get used like we use it.