GMTU Boost fluctuations
02-14-2014, 06:46 AM
#1
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Thread Starter
Join Date: 12-04-2009
Location: Port St Lucie, Florida
Posts: 463
I've had the IC moved Fwd so the sensor isn't hitting and I've got a new lower charge pipe and Forge bpv with the green spring. Whether I have the stock bpv or Forge I'm still seeing some "bouncing" of boost when I hit 15psi if I'm say in 2nd or 3rd and moderately applying throttle. Not all the time. It seems it's when the tranny wants just a tad more gas to downshift but I'm just easing into it. The Forge definitely has increased throttle response and the green spring is holding 23-25psi. I really get the feeling it's the way the GMTU still has some safeguards. I know pretty much trifecta you get 23psi right away no matter how fast you're already going or rpm and the GMTU is more conservative to save the tranny I.E. The boost kicks in and climbs differently going from 40mph-wot vs 30mph or 50mph-wot.
Just curious, anyone else with the GMTU see this?
Just curious, anyone else with the GMTU see this?
02-14-2014, 10:36 AM
#3
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Join Date: 12-04-2009
Location: Port St Lucie, Florida
Posts: 463
That's what I'm thinking. I haven't noticed it in "i" mode. Man, this tune has awoke since the faulty charge pipe was replaced. If this GMTU is fun I can't wait to try Trifecta when my warranty is up.
02-14-2014, 06:14 PM
#4
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Join Date: 10-09-2010
Location: Tacoma
Posts: 14,420
Yes the auto will do lots of weird stuff. Like only boosting 15 when u floor it at 60 or 70. But.....
if you lift all the way off the peddle and plant it again, pulls 26, mine is tuned so it is not supposed to do that, but there are all kinds of protective stuff still at work in the background.
If you are getting 25 on stg-1 don't think you need a tune, just my opinion but I don't think we should be boosting these stock internals more than 26.
if you lift all the way off the peddle and plant it again, pulls 26, mine is tuned so it is not supposed to do that, but there are all kinds of protective stuff still at work in the background. If you are getting 25 on stg-1 don't think you need a tune, just my opinion but I don't think we should be boosting these stock internals more than 26.
02-14-2014, 10:59 PM
#6
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Join Date: 12-04-2009
Location: Port St Lucie, Florida
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02-14-2014, 11:14 PM
#7
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Join Date: 10-09-2010
Location: Tacoma
Posts: 14,420
That's about the lowest stg-1 boost I have heard of, but like I said these auto's have a little Christine in them at times.
Like when I installed the Ic and hotside pipe the first key stroke it ran at 29lbs with no hesitation or lag at all, don't know how much power that was, but it was big fun. Next time I started it, back to 25...
Like when I installed the Ic and hotside pipe the first key stroke it ran at 29lbs with no hesitation or lag at all, don't know how much power that was, but it was big fun. Next time I started it, back to 25...
