HPTuners trying to reset fuel trims

Shdwdrgn

Original poster
Member
Dec 4, 2011
568
Anyone else had issues with resetting the fuel trims in VCM scanner? The options are all greyed out, so I assume this means our PCM doesn't allow the trims to be reset... or am I just doing something wrong?
 

ScarabEpic22

Member
Nov 20, 2011
728
I havent tried with HPTuners, EFILive cant do it either. With EFILive, I can connect to the PCM using LS1 controls and a few of them work. Dont know if this is a possibility with HPTuners, I havent tried it.
 

jbacklund

Member
Dec 16, 2012
118
Never got it to work, option is just greyed out as you say. I just write the tune again to reset it.
 

Shdwdrgn

Original poster
Member
Dec 4, 2011
568
jbacklund said:
Never got it to work, option is just greyed out as you say. I just write the tune again to reset it.

Actually that reminds me, that was something else I was wondering about... if the trims get reset every time you write a new tune? I guess it doesn't pay to be making shift mods while you're waiting for the miles to rack up after changing the VE tables. :smile:

You know what's really annoying? I've been trying to smooth out my low-speed 1-2 shift. I have two areas of construction on my way to work. Without fail, if I update my shift tables before leaving, the traffic through the construction area will be non-existent, so I won't know for a couple of days if my changes made any improvement. Maybe I can sell this as a service -- "Need to get to work fast? Pay me to make sure traffic is smooth today..."
 

jbacklund

Member
Dec 16, 2012
118
A new write to the PCM reset the LTFT, mine is always 0% after a flash.

I don't like the hard 1-2 shift either, but it's only there when the transmission oil is cold. Let us know when you come up with any good numbers.

Another thing I'd like to fix is the double downshift it does when giving it WOT.
 

ScarabEpic22

Member
Nov 20, 2011
728
Low speed shifting is a combination of shift time, line pressure, and torque management. You have to play with it until you get it how you like, I spent quite a while dialing my P10 tune in. The SSs were even worse.

For the double-downshift, do you not like that it doesnt drop straight from 4->2 and goes 4->3...3->2? Hint: make sure your up and downshift points are all set correctly and DO NOT OVERLAP. Again, takes a little time but really cleans the shifts up. There are spreadsheets on both EFILive and HPTuners forum.
 

Shdwdrgn

Original poster
Member
Dec 4, 2011
568
So far, taking the stock tune, I have multiplied my force motor table by 0.90 (slightly firmer shifts) and multiplied my normal shift time table by 0.40.

In order to smooth out the low-throttle shifting, I had to manually update the 1->2 shift row, but I wanted to maintain the stock curve. I settled on a progressive adjustment... Starting on the left, I multiplied the first field by 0.68, the next field by 0.70, and so on, so I ended up multiplying by 1.00 on the last field. This gave me a starting point of 7.9. Originally my low-throttle shift was happening at around 18mph, but now should be closer to 12mph. As I play with it more, I may adjust the curve so that a heavier throttle holds off shifting longer.

Additionally, I modified the 3->4 shift row to a higher RPM. It seems rather silly to be shifting into OD at all while driving around town, but I had to find a balance where a low-throttle acceleration didn't cause the same hard shift as we're seeing in the 1->2. I applied another progressive multiplication to this row, so now it starts out at 38.6, and I am rarely seeing OD in town now.

I have not played with the downshifting at all yet, but there are some very strange values in the stock table at the end of both the 3->4 shift and the 4->3 shift... Why are the last several columns maxed out instead of having smooth numbers applied? And looking over the values I have now, I need to make suitable adjustments to the downshifts to stay well under the upshift points.
 

ScarabEpic22

Member
Nov 20, 2011
728
Stock these wont shift into OD at WOT, thats why those values are higher than reasonable from the factory.

For the shift points, thats removing a lot of MPH. In the end it's up to you, usually there no need to reduce them that much. Especially with the I6, holding a lower gear longer helps get these things moving, the I6 loves to rev whereas a V8 just wants to grunt along.
 

Shdwdrgn

Original poster
Member
Dec 4, 2011
568
Oh I agree, I don't want to drop it too much, that's why I only dropped the left end, and not the entire curve. I want to make sure that by the time I get into some real throttle, I'm getting close to the normal range again. It's just a matter of playing with the slope. I'll drive it around like this for a few days and see how it reacts to different traffic conditions, and probably make more adjustments from there.

I also found some tables for adjusting DFCO today and tried out those values... Wow what a change that makes! You can sure feel when its cutting in, but by the time I got home I was getting a feel for feathering the throttle to control the cutoff when I didn't really want it. I'll have to look around a bit - it would be nice if there's a value to control the rate at which the cutoff occurs. Right now its a bit of a jerk when it happens, almost makes me feel like I'm trying to learn how to drive a stick again.
 

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