Is my thinking correct, when I am thinking that the TV adjustment should be fairly easy to get "right on", as I have the pan off, I should have the plunger on vb all the way depressed at point of someone using their foot to push pedal down to floor (= WOT) or is there more to it that I am not accounting for?
TV adjustment - correct thinking?
- Thread starter tomard
- Start date
Junior Samples
Walk Away
- Joined
- Aug 3, 2007
push cable all the way back, open throttle by hand and wiggle the cable a tad, should get close. Once i got close I turned back in a notch to tighten up shift a little
You're correct. When doing a factory adjustment, pulling the cable back and then stepping on the pedal (going WOT) to set the cable, it's the bottoming of the internal linkage arm against the TV plunger sleeve that forces the cable adjustment block to ratchet. That is what is considered a base adjustment. Fine tuning may be necessary after doing a base adjustment. Every car is different about the fine tuning.
Making sure .....
Should the TV linkage be as far away from TV plunger as possible with NO throttle or min idle ..... and as you give it some throttle it goes closer until it actually touches the plunger and starts providing pressure as rpm's go up, until it is fully depressing plunger at WOT ???
Or should there be some TV pressure provided even at idle/no throttle ?
Should the TV linkage be as far away from TV plunger as possible with NO throttle or min idle ..... and as you give it some throttle it goes closer until it actually touches the plunger and starts providing pressure as rpm's go up, until it is fully depressing plunger at WOT ???
Or should there be some TV pressure provided even at idle/no throttle ?
The later is correct.
You need to realize that TV pressure must rise with engine torque. TV pressure modifies line pressure and counteracts governor pressure. This needs to start occurring right off of idle. This is paricularly important with a setup that spools quickly with relatively little throttle opening. Engine torque increases quickly, but is the line pressure keeping up if low throttle openings are being used?
TV starting pressure, rate of rise relative to throttle position are both tied to the geometry of the linkages at both ends of the TV cable. If you study the linkages, you'll see that the rate of pull on the cable changes as you go through the full arc of travel from idle to WOT. And the rate of pull changes at different points in the arc. Changing where the cable starts its pull in the arc and the length of the arm from the throttle shaft center line, will change the characteristics of the starting TV pressure (idle) and the rate of increase at different points through the travel of the arc.
One example. Let's say you want to increase the starting TV pressure because your engine now makes much more torque at lower throttle settings because of your turbo and torque converter stall setup. You want TV pressure to ramp up quicker to max relative to throttle position. And you want the quickest increase rate to occur at the earlier throttle opening part of the arc. You would start the pull of the cable at a point closer to 90 degrees to the shaft c/L. And you would shorten the length of the arm. This would give you less total pull on the cable. You would still have max pull at WOT, but now as you relax the linkage and go to idle, you'll notice that the linkage rests at a higher TV pressure at idle because of the less total travel. There are some other things to take into account when doing linkage geometry changes like how much line pressure will there be at idle and how will that higher line pressure affect the feel when dropping into gear. P to R, P to D, N to R, N to D, but hopefully this has given some of you food for thought.
Could you type up a little tutorial on fine tuning a TV adjustment?
The fine tuning is really not a big deal. Most cars will do fine at the base adjustment.
After the base adjustment is done, the car needs to be taken on a test drive. If the shifts are obviously occurring too late, for instance you have to lift off the accelerator to get an upshift to occur during normal stop light to stop light acceleration, you will need to lower the TV pressure a little. Go back to the adjuster block of the TV cable, push in the button while holding the inner cable in position and move the cable carefully to the front of the car, one notch at a time until the shift timing is reasonable. A modified transmission might increase part throttle shift points and lowering TV pressure too much to make up for late part throttle shifts could cause damage to the transmission. Consult your transmission builder first, before playing with the TV pressure.
