TH400 kickdown TPS%

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Frankenchevy

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hello.

just trying to gather information on programming my sniper EFI. it can be programmed to control kickdown on my TH400. voltage is applied to the circuit just as oem switch would do, only you set it to be applied based on a chosen parameter.

my question is what do you guys think would be a good tps% to start with? what would most replicate factory throttle position percentage? my truck didn't come with a switch for me to look at/experiment with, so I would downshift at the column when necessary. I was going to start at 85%...is this too high, too low, am I even in the ballpark?

side question should I program the radiator fans to come on at the same temp as my thermostat is rated at? i.e. 185 degree thermostat, trigger fans at 185...

thanks!
 

4WDKC

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85% seems high, I would think 50% would be closer to right.
 

Frankenchevy

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85% seems high, I would think 50% would be closer to right.
so the stock switch energizes around 50% throttle travel? I'm only asking because I've seen a lot of guys use a nitrous switch on the linkage and it seems to require close to WOT for the contacts to complete the circuit.

edit: so if you're going up an incline and have the car at say 55% throttle and the grade is causing your vehicle to decelerate under throttle load, your 700r4 will downshift for you? I want it to act as close to stock as possible, but I don't want it jumping down a gear too often. I guess I can always start low and move the percentage up from there. it only takes a few seconds to change..
 

CSFJ

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So try it at 65%. That'll give you a little extra throttle for hills before the downshift. I don't think you would want nitrous at less than wide open.
 

bucket

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85% seems high, I would think 50% would be closer to right.

Agreed. I was thinking in the 50-60% range.

Nitrous trigger points really have nothing to do with it.
 

Frankenchevy

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Are you sure you don't have the kick down switch under your dash and it's not hooked up or broken?

Look at post #3 of this thread if you you need to see what it loks like or it's location.

http://www.gmsquarebody.com/threads/kick-down-switch-or-vacuum-leak.12029/
I looked when I got home. it was under there, hooked up. the problem is the top half of the pedal arm when fully depressed still won't make contact with the rod on the switch. I noticed in the picture provided by @chengny that they put a piece of black hose over the rod, possibly to make the pedal arm come in contact with the switch sooner. my bracket isn't modified in any way and the throttle pedal rod looks just like the one in the picture. I pulled the switch apart, cleaned and lubed everything then tested for continuity with the switch closed and it is good. the top of the pedal arm just won't come far enough to touch the switch, let alone throw it far enough to close the contacts. I checked travel of the throttle cable and it is definitely traveling from fully closed to fully open without a problem. I was thinking of k.i.s.s. with utilizing the factory switch, but maybe the simpler solution is to use the sniper ecu to trigger the kickdown, that way is is fully adjustable.
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Frankenchevy

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Nitrous trigger points really have nothing to do with it.
I agree about nitrous trigger and kickdown trigger aren't one in the same. however, when searching the internet for a remedy, this seems to be a popular solution for the th400 for people without a factory switch.

my factory switch has less than an inch of travel, the switch has to travel the full distance before it closes. that tells me the kickdown isn't activated until the last half inch or so of pedal travel.

I think I'll stick to triggering it with the sniper ecu since it is fully adjustable and can be changed in a minute via the touchscreen.
 

rpcraft

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You definitely do not want to have your trans shifting down too high a percentage. It will break driveline components as well as the inside parts of the transmission. I'd start off at 50 % and adjust from there. Like you said, keep it with the Sniper setup, after all it is adjustable relatively on the fly. You can drive, test it, make your changes, save the file and then test again in relatively quick succession.
 

Menace1357

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Curious Frank, what was your final percentage you went with? Currently I'm looking to do the same thing and planning out my wiring/setup.
 

Matt69olds

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There is a reason the kickdown switch only has an inch or so of travel. The switch is only activated at WOT.

I would think 85% would be a good starting point.
 

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