VE Tune, shifting hard

[puckyou]

Finally started the VE tune tonight.......one thing though, when the MAF is disconnected I really shift hard or clunk into D from P? I am also pretty rough shifting from 1 to 2? Is this normal, and will it continue until the VE tuning stage is completed?

[Sprucegagt]

Yes. I would recommend finishing up VE tuning fairly quickly. I left my car in this mode for a month and now I have a 1-2 gear shift slip. Never had it before.

[puckyou]

Thanks, yeah this sucks.....

[Sprucegagt]

If you do it right, you shouldn't need more than a few hours to get VE tuning done.

[khellendrosxs]

Does the MAF stay unplugged only when scanning for the VE tune? From what Ive read on the DHP boards it can take hours or days for the PCM to relearn the fuel trims so in that time should I leave it without the MAF? I dont think I remember reading anything that specifically said leave the MAF unplugged...

[AaronGTR]

Yes, the MAF is only unplugged during VE tuning. It only takes 15-30 minutes for it to relearn the fuel trims well enough, then you do your driving and logging in VE mode so you can change the VE table using the scan data. After you are done plug the MAF back in. The reason it shifts hard is the pcm uses the MAF as part of the equation to determine engine load and how much line pressure to use when shifting, so when there is no MAF signal and it goes into "limp" mode it basically maxes out the line pressure. A short time like this won't hurt it. Just don't leave it like that for a month like Spruce said.

[lastyear4gt]

What is VE tuning. Is there a publication somewhere that someone can direct me to on all the meanings of tuning phrases?

[puckyou]

What is VE tuning. Is there a publication somewhere that someone can direct me to on all the meanings of tuning phrases?

Do you have a Powertuner? If so, log onto www.gmv6pcm.com

[lastyear4gt]

Nope, don't have a power tuner, Im getting HPT

[AaronGTR]

Good luck with that. VE tuning with HPT is much more involved because of the different parameters available, and the forum users there don't seem that informed about it. Basically though VE tuning involves driving and data logging with the MAF unplugged so you only get closed loop fuel corrections from the O2 sensor, then going back later with the data collected and making changes to the VE table to correct your base fueling values. This is to bring the fuel trims in line so they don't change as much between different trim cells (decel, cruise, part throttle, etc.). From what I've gathered this can improve fuel milage as well as increasing engine safety since the trims don't have to move as far to make adjustments when you make quick throttle changes. So the AFR should stay more steady instead of hitting lean/rich spots. At least that seems to be what I've read. There's probably more to it I've forgotten or haven't read yet.

[xonelith]

Don't let Aaron scare ya... VE tuning with HPT is quite easy. I just started doin it myself. I'm in the process of creating a how-to manual for it:) It's just displayed differently than DHP, so the DHP guys don't quite see it as easier.

I agree though, the HPT forums can really suck as the ppl there don't believe a GA V6 should need to do it. I hope to prove them wrong.

A question I have about VE tuning, wouldn't MAF tuning net the same results? ie balancing out your fuelt trims?

[geldartb]

since it goes into max trans pressure when you unhook the maf, what about turning the max trans pressure down from 90 to like 70 or something.

and then when your done just put it back up to normal. im not talking about dropping the whole trans shift presssure table just the max pressure. stock i think its like 90.

[AaronGTR]

Nope. The MAF table is a modifier of the VE table which is your base fueling, so there is always going to be a fuel trim inbalance between fuel trim cells unless you do Ve tuning. The reason for the trim cells is because there are different fuel needs at different throttle positions regardless of airflow. You can have the same MAF signal at two different rpm and throttle positions, but the load on the engine is different. That's what the VE table is for, fuel needs for engine load based on engine efficiency.

[AaronGTR]

since it goes into max trans pressure when you unhook the maf, what about turning the max trans pressure down from 90 to like 70 or something.

and then when your done just put it back up to normal. im not talking about dropping the whole trans shift presssure table just the max pressure. stock i think its like 90.

I'm not sure if you can do that. You can change the shift pressures with the tuner, but I don't know if there is a separate table for "limp mode" that we can access, so we might not be able to change that setting.

[xonelith]

Thanks Aaron, makes sense.

There's a table in HPT (probably in DHP too), that references the force motor current. The last column is maxed out. I don't know if that will correct the hard shifts or not, but once i get some time and finish up my VE tune, i'll let you know.

[2003SCT]

Interesting.....

When I installed my CAI, I forgot to hook the IAT sensor back up and it shifted REALLY hard for a day, like slamming the gear shifts. After that, I have the 1-2 slow and slippy shift. It was only for a day tho so I dunno but I wish I hadn't done that..my tranny must have just been on the edge.


CHRIS

[geldartb]

I'm not sure if you can do that. You can change the shift pressures with the tuner, but I don't know if there is a separate table for "limp mode" that we can access, so we might not be able to change that setting.

see if they can add the table or if theres another way to do it on the dhp site. dont remember seeing anything the last time i was using dhp. ill check later.
Interesting.....

When I installed my CAI, I forgot to hook the IAT sensor back up and it shifted REALLY hard for a day, like slamming the gear shifts. After that, I have the 1-2 slow and slippy shift. It was only for a day tho so I dunno but I wish I hadn't done that..my tranny must have just been on the edge.


CHRIS

mine did that when i forgot to hook the tps back up. i took it for a quick trip up the road and was like wtf its slamming into gear, pulled over and saw that i forgot to hook up the tps another 10 minute drive and she was normal.