VersaTune User Forum

While I'm still struggling to figure out why my tunes run lean at WOT and I can't seem to get more than 2 load....I have noticed the ECU takes forever to transition to OL fueling. If I;m not mistaken, this is when LTFT goes to 0.

Seems like it'll change right around the 1.9 - 2.0 load mark.

Anyone else experience this? Any suggestions?

If you're running lean or even rich at WOT, then your MAF calibration is off. When you're WOT the car is in open loop, so the MAF cal needs to be spot on.

Polish_Eagle wrote:If you're running lean or even rich at WOT, then your MAF calibration is off. When you're WOT the car is in open loop, so the MAF cal needs to be spot on.

No it's not the MAF cal Trust me, this is not my first tuning rodeo. Been struggling with this for over a year. Hence me looking at other possibilities, like this one.

I've made a few different maps with just WGDC changes the only thing changed between the various maps - 0%, 30% and 43%. With each increase, it keeps going leaner at WOT.

Then I decided to borrow a friend's Access Port. Made a map that was spot on in under 2 hours. The MAF cal copied from my VT maps made it run rich like a motherfucker. So I quickly dailed that back in. Then targeted 24 psi boost. Which I managed to hit with around 50% WGDC, Load of around 2.2 and SPOT ON AFR.

I've sent the VT support guys an email with my findings with a follow up mail again yesterday. They've read it but haven't responded yet. Either they're also stumped, or don't give enough of a shit to investigate and resolve this.

Dolfius wrote:If I;m not mistaken, this is when LTFT goes to 0.

The fuel trims are not an indication of when the ECU goes into open loop.
Usually there's a PID you can monitor and see when the ECU is in open loop.

The reason you still see non-zero fuel trims in open loop is because in your tune the Closed Loop Load Limit tables have values above the load you normally hit.
The only thing different in your case is that you still have MAF adjustments and fuel trim based corrections in open loop. That is something useful especially when your MAF cal is not perfect.

Usually on the tunes I make I ditch the fuel trims anywhere above load 1.063 or 1.125.
The fuelling and ignition tables should match above that area to speed up the transition and also for consistency, because otherwise you may end up with a faster car on closed loop at high partial throttle than it was in open loop during similar conditions. Or even feel the car landing on its nose during the CL-OL transition on a high-PT or WOT event.

mituc wrote:

Dolfius wrote:If I;m not mistaken, this is when LTFT goes to 0.

The reason you still see non-zero fuel trims in open loop is because in your tune the Closed Loop Load Limit tables have values above the load you normally hit.
.

If you're referring to the 3 Closed Loop Load Limit tables at the top of the Absolute Limits section, then no. Can't be. I may have left them at the default value of 2.5 in the maps I shared. But specifically for this test I purposely lowered them to 1.25 because I knew it would be mentioned.

The description of what the tables also suggests that we're not exactly sure how it affects the tune as well.

Dolfius wrote:The description of what the tables also suggests that we're not exactly sure how it affects the tune as well.

I just described how it affects the tune...

mituc wrote: Usually on the tunes I make I ditch the fuel trims anywhere above load 1.063 or 1.125.

Would you mind explaining a bit more here? I'm not sure I understand how you would ditch the fuel trims above these load points?

mituc wrote:

Dolfius wrote:The description of what the tables also suggests that we're not exactly sure how it affects the tune as well.

I just described how it affects the tune...

This is what I was referring to, BTW. See the screenshot attached. The table description should ideally then updated to say how this tabe affects the tune.