problem after 70mm tb install

[wb's87]

I installed a Accufab 70mm tb, plenum and 1" spacer. PROBLEM: Without adjusting the TV cable the car shifted much differently. 1-2 shift seems similar to before. The 2-3 is more drawn out. At 60 mph I have to let off on the gas to hit overdrive. I adjusted the TV cable as per instructions on GNTTYPE.ORG and now the car is shifting way too early in all gears. At very light throttle it shifts 1-2-3 at 25 mph and goes into overdrive at about 40 mph. I had previously marked the position of the TV cable so I moved it back towards the firewall where it was before. Now for my QUESTION: Did installing the Accufab tb, plenum and spacer somehow change the geometry of the throttle/TV linkage or what? It's fine to manually set the TV but as soon as I go WOT it pulls the cable out too far. any suggestions please respond.

TIA Bill

 

[wb's87]

bump.....can anyone help me??

 

[pacecarta]

you cant expect the cable length to stay the same when changing the throttle body but it still needs to be adjusted so it can go WOT
if its pulling out from when you set it manually then you have a bad tv cable adjuster
a simple fix ... adjust it then cut a short piece of 1/4 rubber hose , slit it and slide it on the cable behind the adjuster and then use a small hose clamp over the rubber , now the cable wont slide forward

 

[wb's87]

you cant expect the cable length to stay the same when changing the throttle body but it still needs to be adjusted so it can go WOT
if its pulling out from when you set it manually then you have a bad tv cable adjuster
a simple fix ... adjust it then cut a short piece of 1/4 rubber hose , slit it and slide it on the cable behind the adjuster and then use a small hose clamp over the rubber , now the cable wont slide forward

Thanks I will give that a try and report back.


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[David Husek]

I installed a Accufab 70mm tb, plenum and 1" spacer. PROBLEM: Without adjusting the TV cable the car shifted much differently. 1-2 shift seems similar to before. The 2-3 is more drawn out. At 60 mph I have to let off on the gas to hit overdrive. I adjusted the TV cable as per instructions on GNTTYPE.ORG and now the car is shifting way too early in all gears. At very light throttle it shifts 1-2-3 at 25 mph and goes into overdrive at about 40 mph. I had previously marked the position of the TV cable so I moved it back towards the firewall where it was before. Now for my QUESTION: Did installing the Accufab tb, plenum and spacer somehow change the geometry of the throttle/TV linkage or what? It's fine to manually set the TV but as soon as I go WOT it pulls the cable out too far. any suggestions please respond.

TIA Bill

Yes, when going to a larger throttle body, you will need to adjust the TV spring inside the valve body. Also, the calibration of the trans changes and does not give correct pressure for the extra air entering the engine with the lighter throttle openings. It has no effect on full throttle shift points. Very easy to hurt the trans with a larger TB unless addressed. A properly built trans will do better.

 

[haywire4130]

David, can you elaborate on this adjustment?

 

[nightrain]

Bump. I'm interested in this adjustment as well. I just installed a 70mm Accufab TB and I've gotten some bad 2-3 shifts (flashes to 6000+RPM when manually trying to shift at 5500). I never heard of having to adjust the TV spring (opening up the trans) when installing the TB. I do notice I can't hit anything over 4.15v at WOT now. It may be my imagination ,but I also feel like I'm not starting in first gear from a normal stop sign start.

The part I don't understand is it's the stock linkage going on the throttle blade shaft. How is the geometry changing with a stock linkage on the same centerline? Thanks!

 

[mikestertwo]

Bump.
The part I don't understand is it's the stock linkage going on the throttle blade shaft. How is the geometry changing with a stock linkage on the same centerline? Thanks!

The geometry hasn't changed but like Dave said the amount of air entering the engine for the same throttle angle has changed. You are making more power with the same throttle angle so you have to use a spring in the throttle valve with a different spring "rate" to compensate. In other words the pressure rise in the transmission has to rise faster to handle the extra power at the lower throttle angles.

 

[wb's87]

Thanks I will give that a try and report back.


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So..... My problem was that for some unknown reason my TV cable was pulling out way too far. Prior to the installation of the TB and plenum my TV cable when properly adjusted extended about 1/2" past the end of the bracket after adjusting the TPS sensor to .42-4.50 the TV cable was still in the same position as before. After some WOT pulls the trans started long drawn out shifting also the shifts were very lazy. Upon inspection the TV cable had pulled out to about 1" I readjusted it and all was good 1-2 is nice and crisp. 2-3 is back to normal and OD and lock up are as they should be. But after a couple more WOT pulls the TV came forward again. I did as Pacecarta suggested and it's been fine since??? I'm at a loss for answers. I consulted Richard Clark and he said that changing the TB and Plenum with all the stock linkage should not affect the trans. Idk. I'm sure my trans builder would love to go through it again $$$$ any other comments or help is greatly appreciated!!


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[wb's87]

Bump. I'm interested in this adjustment as well. I just installed a 70mm Accufab TB and I've gotten some bad 2-3 shifts (flashes to 6000+RPM when manually trying to shift at 5500). I never heard of having to adjust the TV spring (opening up the trans) when installing the TB. I do notice I can't hit anything over 4.15v at WOT now. It may be my imagination ,but I also feel like I'm not starting in first gear from a normal stop sign start.

The part I don't understand is it's the stock linkage going on the throttle blade shaft. How is the geometry changing with a stock linkage on the same centerline? Thanks!

The TB I bought had a TPS on it. It was new so I just left it on. As you said I couldn't get anything above 4.2 while trying to adjust it. I swapped my old stock TPS onto it and it easily adjusted to specs. We had a problem with a friend of mine's car that we couldn't adjust TPS. Rattail file on the rear side mount of the TPS cured the problem.


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[David Husek]

I install a longer spring in the TV when a larger 70mm TB is installed. It is one of the questions asked to my customers. Geometry has some to do with it. More air enters the engine at less throttle opening. You have to adjust for the extra air. TV should always be set for full throttle and adjust TV spring length for proper pressure rise. It is wrong if you adjust the TV for proper driving/shifting and when floored the TV cable pulls out. Easy way to toast a 200-4R.