crewchef

iTrader: (6)

3rd Gen LS1 conversion, running Kumho street tires. On the street hitting second hard can be fun but at the strip it's slowing it down. Son's first pass on Saturday he had it sideways on the 1/2 shift. Logging data I can see it spin every time on the 1/2. That one time was worse than normal.

A normal run shows shifting at (MPH) 45, spike to 57, settle back to 52 and climbs from there. Until I get some better tires I want to try to take some of the hit away from this shift to avoid the tire spin.

Question is, which table should I be tuning? To soften this up just enough to keep from spinning should I decrease base shift pressure and/or increase force motor? Other option I was looking at is extending the desired shift time, currently set at 0.250.

SSpdDmon

iTrader: (10)

I'd make sure the Force Motor Current table and all the base pressure tables are set to the stock settings for their model year. In my experience, an '00 shifts differently than an '02. Once all of the trans tables are set to stock, you can begin manipulating the tables in 5% increments to get it the way you like. Shift firmness lies in the base pressure shift tables. Increase for a firmer shift/decrease for a softer shift. Shift timing lies in the desired shift time tables. Decrease for a faster shift/increase for a longer shift. Typically, I wouldn't recommend increasing the base pressures more than 15% over stock or decreasing the desired shift times more than 20%. I got my buddy's '02 shifting decently with only reducing the desired shift times by less than 10% from stock.

SMOKINV8

iTrader: (6)

Is there a shift kit in the car? Converter? Is the MAF hooked up and working properly?

Shift time and Force Motor Current is what you want to look at. Lowering the force motor current increases the shift pressure, so you will want to raise those values in order to lower the pressure and soften the shift. Just make sure you don't lower it so much the tranny slips.

crewchef

iTrader: (6)

No shift kit or converter (yet) MAF is functioning properly, thankfully the shifts aren't that hard. I have tweaked on the FMC and Base Pressure tables as well as the shift times. All of this tweaking was done based on street driving preferences and some assumptions about what would happen at the track. Day to day driving shifts are firm and crisp and feels good. On the street at WOT it will always break them loose on the 1/2 shift which as I said can be a little fun. My assumption, the track would hook a little better and I wouldn't see any 1/2 traction problems, bad assumption.

I think I'm going to try working with the Base Pressure table and pull it back midway between current settings and what stock was. From 300 ft.lb on out I've got it set to 90. May also slow the shift back down a little bit, maybe 0.350

I think it will pick up a little on the ET if I can get rid of the spin. Of course still trying to figure out how to get the 60 down too but I don't think there's any gain to be found in tuning. The real fix for both will be some sticky tires.

Russ K

iTrader: (1)

Don't make the trans into some kind of traction control, if the the tires spin on the 1-2 shift put on sticky tires. The front band won't live long other wise.

Russ Kemp

crewchef

iTrader: (6)

I agree with what you're saying Russ but I think I may have gotten a little over agressive with my initial tweaks. I think there's a happy median in here somewhere until I can get a set of track tires for it.

Do any of you guys adjust air pressure in a normal street tire when running at the strip? We were running these at their normal 34/35 lbs. I know you wouldn't want to run them real low but is there any advantage to letting them down some?

joecar

Keep the pressure tables up (don't let the trans slip or it will die) and instead add some TR back in.

SSpdDmon

iTrader: (10)

I don't agree with the concept of changing the force motor current table. That to me is like changing the injector flow rate tables to get your AFR in line when you didn't swap injectors. You didn't change the internals of the trans. You just want to increase pressure. So why not just change the base pressure tables and leave the force motor current table stock??? Again, I get some nice crisp shifts by adding between 20~30kPa to the base pressure tables and dropping the desired shift times some. I'm sure you could do the same...

As for tire pressure....the stock settings for our cars is 30psi when cold. That's the only time you should really be checking them if you want the tires to wear appropriately. When you're at the track, I'd run them close to 25psi to help with traction. But, they're still street tires in the end and you'll be lucky to pull a 1.8 60'. Just make sure to reinflate them before you leave and check them the next morning when they're cold.

Just my $0.02...

SMOKINV8

iTrader: (6)

Agreed. I'm a bit doped up on pain meds this morning, maybe I shouldn't be giving tuning advice right now.