Defuel during shifting mod
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Lead Driver
Joined: Jan 2006
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Defuel during shifting mod
Is there a tappable wire anywhere, from the PCM, that has a voltage or signal when the PCM sends the shift command to the tranny?
And second, is there a common ground for the injectors, so that someone could wire a relay in so that the injectors paused for a brief second allowing the transmission to grab the next gear without as much strain?
Can a chip do this?
And second, is there a common ground for the injectors, so that someone could wire a relay in so that the injectors paused for a brief second allowing the transmission to grab the next gear without as much strain?
Can a chip do this?
Post Fiend
Joined: Feb 2006
Posts: 11,892
Likes: 2
From: Middle Tennessee
I think this is why the tranny uses hydraulics and clutches and a TC. Keep the engine in the power band and shift. I am sure we are not going down an uncharted road here and experience says keep the engine in the power band and make shifts crisper. Pull the power out and you have no power.
Post Fiend
Joined: Jun 2006
Posts: 9,714
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From: White Mnt's,New Hampshire
any time you defuel your loosing HP and jurking the trans...the bts or john woods VB takes care of the shift..jody's tunes takes care of the line pressure after the shift..you also want a triple disk TC...you want all power on the ground at all times...
Post Fiend
Joined: Feb 2006
Posts: 11,892
Likes: 2
From: Middle Tennessee
I am not a auto tranny expert, but look at it this way: The tranny shifts via demand from the rpms and throttle position commanded via the PCM table, along with the MPH. So the shift happens smoothly via bands and clutches actuated by line pressure from the front pump in the tranny. This pump is operated off of the crankshaft. So if we cut fuel around the shift, pump/line pressure falls off right then and in short, it sucks.
I know this is layman's terms, but I think this is the general idea. Someone feel free to correct me if this is wrong.
I know this is layman's terms, but I think this is the general idea. Someone feel free to correct me if this is wrong.
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Cargo Master
Joined: Sep 2007
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From: Chandler, AZ
Some gasser computer controlled engines retard timing to reduce power during shifting to prolong trans life.
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Butt-Head
Joined: Apr 2004
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From: Reed Point, MT
Not that I'm an expert, but I'd love to know how a glorified 10K mod (Edge juice) knows when the PCM commands a shift or when the throttle is pegged (the idle validation switch does not give APP). Yes, I have installed them and noticed the option.....
A lot of tuning tables will show a "Torque reduction on 1-2 (or 2-3, 3-4) shift". It is possible to reduce torque during a shift using these tables, but nothing but actual "tuning" is going to allow you to do it.
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Lead Driver
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Lets say the truck is pinned, and the engine is putting out 500 ft/lbs of power. When the tranny shifts, it has to hold 500 ft/lbs PLUS the inertial forces of the engine spinning, .
It would be nice to cut the injection events, just for a split second, to eliminate the tranny having to absorb the engine tourque and tourque involved in slowing the RPMS down. Just about a 1/4 of a second, and that would keep the stress down on the tranny quite a bit, I think...
Butt-Head
Joined: Apr 2004
Posts: 9,457
Likes: 2,938
From: Reed Point, MT
Except that you've got an inefficient torque convertor absobing a lot of the "bang" you're speaking of. If it's locked, even if you were to "defuel", there is so much inertia there (60 lbs. worth of spinning flexplate and TC) that won't slow down very much in that 1/4 second......
FWIW, the factory programming DOES defuel slightly during a shift...usually anywhere between 85%-100% torque output (according to the tuning tables) depending on APP.
Besides, have you driven a newer Duramax? Those shifts are downright ANNOYING because they do exactly as you say on a much larger scale.....
FWIW, the factory programming DOES defuel slightly during a shift...usually anywhere between 85%-100% torque output (according to the tuning tables) depending on APP.
Besides, have you driven a newer Duramax? Those shifts are downright ANNOYING because they do exactly as you say on a much larger scale.....
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