trans tuning.

[mustang_gt_350]

Originally Posted by Power Hungry

There are 2 switches which control the trans and converter states.

Switch 1 will turn on or off the ability to lock the trans into a specific gear. There is a values that is used in conjunction with this to select the gear in which to stay locked (1, 2, 3, or 4).

Switch 2 will turn on or off the ability to lock the converter. On 94-97 this is simply an on or off state. On 99 and later, it is used in conjunction with with a value that determines the pulsewidth in which to lock the converter. Normally, this would be set to 100%, but if you're really curious as to how fast you can fry your converter clutch you could set this to 25% or 50%.

We frequently do "sled-pull" applications on a chip that goes something like this...

Pos 1: 2nd Gear, Converter Unlocked, Fuel Curve modified to spool and light turbos
Pos 2: 2nd Gear, Converter Unlocked, Pulling Fuel Curve
Pos 3: 2nd Gear, Converter Locked, Pulling Fuel Curve
Pos 4: 3rd Gear, Converter Locked, Pulling Fuel Curve
Pos 5: 4th Gear, Converter Locked, Pulling Fuel Curve
Pos 6: Normal Operation, Light Fuel Curve

Instead of 1st gear, we can also set up to start in 1st gear.

These types of strategies work really well because they completely bypass most of the delay circuits in the shift strategies and just grab the gear desired. The only drawback is that you have to be very careful when switching or you could accidentally skip a position and jump 2 gears instead of 1. In a bouncy truck it's quite easy.

Anyway, just some thoughts.

Great post. So you would actually be switching tunes as you go down the track? So position 1 would be the spool/off the line tune then once rolling you would hit the next position? Then if you want to lock the converter just go to the 3rd position. Also what would be your thoughts about pulling with the converter not locked vs locked? I know the heat would be very high but do you think there would be a benefit to it?

Edit: SO also if i'm reading this correctly that means you could have the truck in Drive, and if you burn a position on the chip that when selected you would be starting out in 3rd gear?

[cleatus12r]

I would assume you'd like Bill to answer those questions but I can give some insight as a transmission tech.

Yes, you'd be switching tunes as you run down the track. One hand on the wheel, one on the hand throttle, and one on.......wait a minute!

Whether or not the converter is locked depends a lot on the truck itself. With a lower power rig or one with a huge, laggy turbocharger I can assume that having a locked converter (especially early in the pull) would be a detriment. Heat shouldn't be too much of an issue because you're not running for 15 minutes with an unlocked converter....more like 15 seconds. The problem lies in the torque multiplication characteristics of the torque converter. Once the input shaft speed gets closer to the engine speed, the torque multiplication factor goes away. Once you reach redline (not hard to do with an unlocked converter) and the torque multiplication goes away, the input torque to the transmission input shaft is very low.....and so is the power to the wheels at that point.

Your best bet is to try out Bill's suggestion and practice with shift/TC lock points.

[Power Hungry]

Yes, you could have the trans switched to third gear and start out in third. For a pulling truck this may, or may not, be a big deal.

My personal preference is to have the converter locked once the RPMs hit 2400-2500 and then keep it locked form there. Some folks prefer to start out in 1st, and some in 2nd. It seems a little easier to spool in first, but maybe that's just me.

Hope this helps.