overshooting rpm limit

[morepowerjoe]

Hey guys so I've been dabbing in tuning world a little bit lately. Since I already had hp tuners from my remote tune from GPI I thought I would pull my tune and have a look at it. Now I must say since GPI I have had a dyno tune. I've been researching the hell out of tuning for a few months getting to know all about vcm editor and vcm scanner and how to use them. I have been getting my shift scheduling, torque converter lock up, and pressures dialed in as well as things like idle settings, fan control, and have tried messing with the torque reduction which both my tuners have disabled it. I tried enabling it and do not like the way it pulls timing at every shift. It chokes the heck out of the engine at every shift. Now someone on hp tuners says my shift timing is way to fast so I took a look at it and have set it all almost back to stock but haven't driven the car yet. But the one real problem I have is blowing past my wot rpm limit. I have it set at 6k rpm in 1st, 62k rpm in 2nd, 63k rpm in 3rd, and so on. But after the shift it goes up to like 66k rpm in every gear until it gets to 5th. I was losing traction in all those gears until 5th.

So would this be the reason for my overshoot of rpm? What do you guys think? Thanks

[Ashen 6.2]

Is it possible that its shifting by MPH rather than RPM's? Im just learning this tuning stuff as well and noticed that it has settings for both.

[morepowerjoe]

No that's what I was thinking too at first. But in my data log it shows the over rev happening after the shift has completed.

[hunter1660]

Compare the tunes and see what differs from I’m assuming not hitting rev limit vs. hitting it tune wise..just running thru the gears in drive,mine shifts mph..not rpm…not sure what happens at wot but it doesn’t fall on its face …

[gtstorey]

Originally Posted by morepowerjoe

No that's what I was thinking too at first. But in my data log it shows the over rev happening after the shift has completed.

If the over-rev is on an upshift, then I don't see how it could be after the shift is completed. It may be while the shift is taking place, but it would have to be slipping if after the shift?

It's my understanding that the transmission tune is hard to set up properly.

[morepowerjoe]

Originally Posted by gtstorey

If the over-rev is on an upshift, then I don't see how it could be after the shift is completed. It may be while the shift is taking place, but it would have to be slipping if after the shift?

It's my understanding that the transmission tune is hard to set up properly.

In the log I created the over rev happens right after the upshift. I tried setting it at stock and now it doesn't over rev but it doesn't take it to the wot rpm setting. So I'm just gonna try and raise the mph a little bit until it reaches the set rpm that I want. Maybe that'll work but shouldn't need to do it this way because everything I've read online say just raise the wot mph higher then the wot rpm range and it will shift at wot rpm.

But you got me thinking about slip. I don't know if it's supposed to be revving higher after the upshift or not? It's only for like a second of over rev but enough to blow past the wot rpm that I set.

[Tajefe Couple]

For what its worth mine does the exact same thing on the upshift. Doesn't seem to matter what I have the WOT setting at RPM always blows way past it up to 7400 depending on the gear. Like you I tried multiple changes between MPH and RPM for WOT nothing seemed to matter. Did find it always shifted at the MPH I have set and not so much the RPM. Always figured it had something to do with the rest of the trans tune that I had done by someone who is known to be really good at tuning these things. Just thought I'd share it happens to more than just you. GL and will be interested to see what you find.

[morepowerjoe]

Originally Posted by Tajefe Couple

For what its worth mine does the exact same thing on the upshift. Doesn't seem to matter what I have the WOT setting at RPM always blows way past it up to 7400 depending on the gear. Like you I tried multiple changes between MPH and RPM for WOT nothing seemed to matter. Did find it always shifted at the MPH I have set and not so much the RPM. Always figured it had something to do with the rest of the trans tune that I had done by someone who is known to be really good at tuning these things. Just thought I'd share it happens to more than just you. GL and will be interested to see what you find.

Oh thank goodness. I was thinking that my trans was toast. lol. Thanks for posting. Today I reset the wot mph back to stock and it did shift real early like around 55k or so and then the rpm shot up to almost 6k on the money. So now I think I'm on to something. So I raised the mph around 4-6 mph to see if that changes anything.I also reset all my shift speeds back to stock and logged the shift times and had from 1-4th. a shift time of .3, .4, .2, .3's so then I decreased the shift time on the 2nd gear and increased it on 3rd. We'll see if that helps. Thanks for the replies though I really appreciate it and I'll report back next time I go out.

[gtstorey]

I'm still curious on how it can over rev after the gears have engaged on an upshift. I guess maybe there is slip in the torque convertor?

[1JEWLDSSRS]

Maybe the converter was briefly "unlocking" then locking back up. Check those settings and see what's up...

[morepowerjoe]

Well I think I got it about nailed down. I put all my wot mph to stock and started from there. It revved to about 6k rpm right where the stock rev limit was set. So I raised each gear a little bit at a time depending on what gear it was and what rpm I wanted it to shift at. So now I got to go out and does some more wot pulls to see where I'm at now.

As far as the rpm raising after the shift, it's because the tcm is commanding the shift and it takes a while to complete the shift after it's initiated and that's why the rpm is still climbing after the tcm is asked to shift if that makes since. Basically then ecm / tcm is faster then the actual mechanics of the transmission.

[gtstorey]

I guess we were using the terminology a little different. You were talking about shift initiated and I was talking about shift completed. Some of you problem may have been caused by slowing down the shift. One thing I've learned as I've dipped my toe into tuning is to be careful on who you trust on HP Tuner forums. Is easy to find conflicting info. I'm saying this without having looked at Transmission tuning at all, just from the basis of older auto transmissions being better to shift quickly since the time during shifts things are having to slip (bands and clutch plates).

[morepowerjoe]

Yeah the guys over at hp tuners there are a lot of arrogant pricks that's for sure. I don't really mind saying that because of the way they've treated me on there so far. There's only one guy that is trying to help me but he doesn't reply very often.

Yeah so after I set the shift speeds back to stock I raised the max pressure, max pressure b, clutch pressure, max line pressure, the base pressures, and oncoming pressure preset based on what the two tuners have had them set too with my opinions on what they should be at. And then I re-enabled torque reduction and now it finally shifts the way I want it too. It even shifts faster then before.

The only thing I don't understand is that the tcc slip was around 250 rpm before I made the changes but now after the bump in I'm assuming the max clutch pressure, now when the converter locks up the tcc slip is negative numbers like -50 rpm. But on the freeway it feels way better and I think I'm getting better gas mileage.

[102SS]

Originally Posted by gtstorey

I'm still curious on how it can over rev after the gears have engaged on an upshift. I guess maybe there is slip in the torque convertor?

That would be my best guess