Fordmods Logo

I6 J3 Tuning: VE vs AFR tables? 

 

Page 1 of 1 [ 4 posts ] 

 
 Post subject: I6 J3 Tuning: VE vs AFR tables?
Posted: Fri Nov 09, 2012 9:23 am 
Parts Gopher
Offline
User avatar

Age: 38

Posts: 82

Joined: 24th Jun 2009

Ride: EF XR6

Location: Bendigo
VIC, Australia

galapogos01 wrote:
The VE table is the base volumetric efficiency the ECU starts from when calculating how much fuel is required at a particular load point.

The stabilised table is the AFR the ECU will aim for when calculating fuel requirements in Closed Loop mode (i.e. not used during open loop, WOT, etc).

KAM fuel trims are stored when the EEC finds that the calculations based on VE used to aim for the AFR in the stabilised table are out by X percent (X being the trim value stored).

If the VE table is correct for an engine there will be no trims stored.


So can I just use the AFR table for tuning target AFR's and let the computer compute the VE trims for me?
From memory (hah) KAM trims aren't used and so this won't tune open-loop but open-loop is used only during warm-up, is this right?

The reason I ask is because while AFR tables make sense to me, VE tables don't. I just don't get VE figures vs fueling at the load points. Maybe I could open up different tunes to understand the differences.

I've got an EF XR6 Auto to tune, and while I've done a WBO2-less 'tune' in the past (for less thirst and more advance with ethanol) this car I'd like to do properly. It's got an unknown grind cam from Herrod's which was used with a Unichip but the car got burnt out so the recently rebuilt head is being rescued and reused.

Any tips would be appreciated, especially about using just AFR and spark tables without touching VE.
Cheers
Top
 Profile  
 
 
 Post subject: Re: I6 J3 Tuning: VE vs AFR tables?
Posted: Tue Nov 13, 2012 8:40 am 
Getting Side Ways
Offline
User avatar

Age: 28

Posts: 4326

Joined: 30th Oct 2006

Gallery: 18 images

Ride: Envi EF

Location: Grafton
NSW, Australia

If you can understand how to tune the AFR table you can tune the VE table. Only touch the AFR table when you need more fuel and the VE table is maxed out in that cell.
All you need to do is compare your log referencing load vs AFR and you can tune the VE table to suit.
eg AFR log at 3000rpm, 10inhg reads 15:1 - find the same cell in the VE table and adjust it to suit. You'll probably have to slightly tweak the surrounding cells as well.

Everything you need to know can be found on the TI site, theres a doco showing you how to set up excel to compare tables for you.

 

_________________

>>>EF Futura T build<<<

Top
 Profile  
 
 
 Post subject: Re: I6 J3 Tuning: VE vs AFR tables?
Posted: Sat Nov 17, 2012 5:24 am 
Parts Gopher
Offline
User avatar

Age: 38

Posts: 82

Joined: 24th Jun 2009

Ride: EF XR6

Location: Bendigo
VIC, Australia

thanks mate, that 's helped somewhat.
It still frustrates me that I've read all the docos (EEC docs, tuning guides etc) and still can't really get my head around the VE table the way I can "see" the way spark and AFR tables..
Wish there were some 'hot' tunes I could open up to compare :)
Top
 Profile  
 
 
 Post subject: Re: I6 J3 Tuning: VE vs AFR tables?
Posted: Sat Nov 17, 2012 10:39 am 
Getting Side Ways
Offline
User avatar

Posts: 1140

Joined: 27th Feb 2005

Ride: Supercharged EF Fairmont

Location: T.I. Performance HQ
VIC, Australia

Have a read around online of what Volumetric Efficiency (VE) is, and what the table is meant to represent.

My summary is that the engine is an air pump, and the VE table represents how efficient the pump is at that cell. The ECU uses the calculation to work out how much fuel is required to be mixed with the air volume in order to target the AFR you are aiming for.

When you change the camshaft, you change the profile of the engine - you generally sacrifice low-end efficiency for top end - so you have to drop the VE in some cells and may have to bump it in others. The factory tune is very rich at WOT - which is why often they do not need a huge change in the VE at WOT even with a cam (unless it has massive lift, duration or porting). The bottom end and midrange are the areas where there the biggest gains are when tuning a mild modified I6 - and it benefits the drivability and wallet the most too.

TLDR; in a N/A 6 Cyl, you should only ever have to touch the VE table for fuel, unless you swap injectors (unnecessary unless you are making 180rwkw+).

Cheers,
Jason
Top
 Profile  
 
Display posts from previous:
Sort by  
 Page 1 of 1  [ 4 posts ] 

Who is online

Users browsing this forum: No registered users and 11 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

 

 

It is currently Mon Dec 18, 2017 7:56 pm All times are UTC + 11 hours

 

 

(c)2014 Total Web Solutions Australia - Australian Web Hosting and Domain Names