The smt is like all things in a street going performance car is a compromise. The compromise is shifting speed vs. reliability. Ideally there should be 2 shifting modes one mode for longevity and one mode for speedy shifting. The actual shifting mechanism is quite quick in stock form what isn't is the clutch engagement.
There are a couple ways to make the smt up shift faster. The system works by monitoring crank speed (rpm) and Transmission input shaft speed (RPM). When those two shafts are within 500 rpm of one another the smt will release the clutch to engage it and the next gear. A good example is the smt down shifts faster than it up shifts because it can rev the engine faster than decelerate it. There are a couple ways to make those two shafts reach the appropriate speeds quicker.
Over the years smt owners have devised a couple ways to make the smt shift quicker. One is to time lifting off of the throttle with up shifts so the throttle body closes faster and the revs drop faster. This method works but can be inconsistent. I figured out a way (thanks to oilfieldtrash for letting me tinker with his car) to make this happen without the timed throttle lifting part. Lifting results in quicker up shifts because of the back up system the smt Drive by wire system uses. The back up system uses the actual throttle cable in the event the dbw motor or pedal sensor fails. None of the later model toyotas that use Drive by wire throttle bodies have this back up because the systems are very reliable. If you have taken the smt t/b off you will notice that the cable input spool will open the throttle body partially.
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The mechanical opening/back up system is the reason you need to lift throttle to get it shift remotely quick. With the throttle body fully closed the revs match faster. The revs will drop low enough with the t/b only partially open (not lifting your foot off of the floor) for the smt to shift it is just painfully slow. Remove this direct link to the throttle plate and you don't have to move your foot off of the floor to get the car shifting as quickly as possible.
So to get that perfect lift throttle timing every time all you need to do is take the throttle body off of the car. Pull the 4 bolts out of the pedal position sensor. Cut the tab off of the pedal position sensor to remove the direct link. Then reassemble and install the throttle body. Be advised this mod eliminates the mechanical throttle acutation backup.
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This is two different pedal position sensors. The one on the left has the tab removed the one on the right is stock.
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The other method to improve shifting speed is to lighten the rotating assembly (crank, clutch pressure plate, flywheel, rods, pistons, crank damper) so the revs fall faster. This allows the shaft speed to fall faster when the throttle plate is closed. Which in turn allows the smt to engage the clutch quicker? This mod is effective but costly. If you want to do this mod buy the absolute lightest flywheel and clutch combo possible. I DO NOT recommend using undampened crank pulleys to lighten the rotating assembly. Under driving individual accessories like the alternator will also improve this. Lighter rods and pistons would help but not worth the effort IMHO.
SMT Throttle body Removal and reinstall
There are a couple ways to make the smt up shift faster. The system works by monitoring crank speed (rpm) and Transmission input shaft speed (RPM). When those two shafts are within 500 rpm of one another the smt will release the clutch to engage it and the next gear. A good example is the smt down shifts faster than it up shifts because it can rev the engine faster than decelerate it. There are a couple ways to make those two shafts reach the appropriate speeds quicker.
Over the years smt owners have devised a couple ways to make the smt shift quicker. One is to time lifting off of the throttle with up shifts so the throttle body closes faster and the revs drop faster. This method works but can be inconsistent. I figured out a way (thanks to oilfieldtrash for letting me tinker with his car) to make this happen without the timed throttle lifting part. Lifting results in quicker up shifts because of the back up system the smt Drive by wire system uses. The back up system uses the actual throttle cable in the event the dbw motor or pedal sensor fails. None of the later model toyotas that use Drive by wire throttle bodies have this back up because the systems are very reliable. If you have taken the smt t/b off you will notice that the cable input spool will open the throttle body partially.
The mechanical opening/back up system is the reason you need to lift throttle to get it shift remotely quick. With the throttle body fully closed the revs match faster. The revs will drop low enough with the t/b only partially open (not lifting your foot off of the floor) for the smt to shift it is just painfully slow. Remove this direct link to the throttle plate and you don't have to move your foot off of the floor to get the car shifting as quickly as possible.
So to get that perfect lift throttle timing every time all you need to do is take the throttle body off of the car. Pull the 4 bolts out of the pedal position sensor. Cut the tab off of the pedal position sensor to remove the direct link. Then reassemble and install the throttle body. Be advised this mod eliminates the mechanical throttle acutation backup.
This is two different pedal position sensors. The one on the left has the tab removed the one on the right is stock.
The other method to improve shifting speed is to lighten the rotating assembly (crank, clutch pressure plate, flywheel, rods, pistons, crank damper) so the revs fall faster. This allows the shaft speed to fall faster when the throttle plate is closed. Which in turn allows the smt to engage the clutch quicker? This mod is effective but costly. If you want to do this mod buy the absolute lightest flywheel and clutch combo possible. I DO NOT recommend using undampened crank pulleys to lighten the rotating assembly. Under driving individual accessories like the alternator will also improve this. Lighter rods and pistons would help but not worth the effort IMHO.
SMT Throttle body Removal and reinstall
, that anyone would find out?
