2005 LLY 1/4 Mile trans settings

[03sierraduramax]

going to be taking my truck to the track this weekend. so I'm looking for some info on shift settings for 1/4 mile. shift point, lockup, Etc. looking for strictly track settings. I will reflash when im there.

truck is a 05 2500hd crew 4x4 stock tire size, 4 inch exhaust no muffler, no cat, intake, trans go shift kit. tuned for power no towing.

any advice on dragging a duramax in general would help. ive tuned and raced dozzens of gas cars and trucks just never a duramax.

thanks

[ajamesbond007]

Another Dmax owner looking for trap times, my kind of guy!

First things first, do you have tie rod sleeves and/or steering linkage upgrades? This will determine if you can do 4x4 launches. If you don't have any upgrades, stick with RWD only. 4x4 could bend your tie rods like tooth picks.

Second, trans tuning can be very complicated on the allison. When shifting gears, the allison actually goes from in gear, to neutral, and then into the next gear. This is due to one clutch pack disengaging a gear, and then another clutch pack engaging a gear after the previous clutch pack is disengaged. If you command for a shift with a much shorter duration, the allison will actually try and engage the 2nd clutch pack while the 1st is still engaged, which can result in being in 2 gears at once. When making changes, always go very small. I would not decrease the time by more than .050 seconds until you are extremely comfortable with going further. Also you will need to up the clutch pressures. again, start small. I change mine to mm3 for the volumes and change by 500 mm3.

Third, each time you reflash the truck, the adaptive shift pressures are cleared, and the default pressures you set in the tune are used until after so many shifts. This is why it is so important to take the truck out and run it up and down thru the gears multiple times at various throttle positions to allow it to relearn the ASP's. Start out slow and work your way up.

If I were you, I would flash the truck with the settings the day or two before and let the allison relearn before you hit the strip, or else lots of flaring can occur on your first run. As for speeds and lock up points, you will have to play with that. I would recommend not going into 5th on the track, OR letting up before it shifts. DO NOT REDUCE TORQUE MANAGEMENT! Otherwise, the engine will still be making massive amounts of torque when the clutch plates are engaging which will most indeed cause slip, potential and most likely burned up clutches, and limp mode.

When lining up, I would watch your boost and try launching at different boost levels. start at like 2 pounds, then 4 pounds, etc. See what boost you can achieve the best ET at and stick with it.
Also, I know you already know this but WATCH YOUR TEMPERATURE LEVELS!!! Dragging is hard on transmissions and will heat your oil quickly, especially when stalling the converter before the green light. Also watch your coolant temp as the LLY usually has trouble with overheating. Granted, this is usually prominent when towing heavy loads, but it still wouldn't hurt. Both the transmission cooler and radiator is slightly undersized on LLY's, so keep the gauges in your line of sight...

Wow I just wrote a book... and still didn't get you any firm numbers. Hope this helps, and let us know your ET times when you go this weekend!

[03sierraduramax]

thanks, lots of great info. I dont have tie rod sleeves yet but they are on order. I will be launching in 2wd. ive been fighting with my allison to get clean shifts from day one. I put some torque management back into it and it helped. I'm trying to figure out how not to go into 5th at WOT, would setting 4-5 shift RPM and MPH extremely high work?. as in it would just rev to limiter in 4th unless I back off a little?

again thanks for the help. I'll come back with some numbers after the weekend.

[ajamesbond007]

Yes, just set the throttle position of 70% and more to like 150 mph and 4500 rpm, that way it won't command a shift.... unless you are crazy fast lol

[ajamesbond007]

How did you do?!?!?!?!

[03sierraduramax]

never made it out, had a few minor problems, still dont like where my tune is. I have been slowly adding more fuel and think I may be running into fuel pressure problems. not really seeing any power gains past the 80-90hp level still have yet to limp trans.

[ajamesbond007]

Can you get us any logs? How are you adding fuel? Thru pulsewidth or commanded fueling rate? What is your FRP doing? Are you adding boost in addition to your fueling? I just put on lift pumps and decided to up the power a bit by adding more pulsewidth to see how much it would gain. It seems that if I want to add the first 100 hp, about a 20% increase in pulsewidth is needed, but if I want to add the second 100 hp, it seems that I need about 2-3 times as much (or at least it feels that way since I haven't gone that far yet).

[03sierraduramax]

I'll see if I can get some logs havent been logging lately, my pulsewidths are getting about 2400ish and ive increased fuel in commanded fuel rate also, boost is up but not in line with fuel. ive basically been increasing fuel and wating for some smoke under WOT, I get a large puff of smoke when I go wot from low rpms but it dissapears as soon as turbo builds boost. truck feels sluggish off the line but pulls well after a second or 2 of boost.

I'll scan some logs soon and see what fpr is doing.

in the meantime any good ideas to reduce turbo lag?

[ajamesbond007]

Have you used the timing calculator in your tune?

To help with your intial turbo lag, what is your turbo vanes setting for under 1200 rpms?

[03sierraduramax]

yeah ive got the few low colums set at 55 and 50% then when it gets into fuel there all 40%

as for vane position its all stock settings, dont have much experience with the tables so I just left them alone.

baro low vane position table is 80-90 under 1200 the baro high table is 77 at 1200 66 at 1000 and back to 76 at 800rpms.

thanks again for the help

[ajamesbond007]

Just for the columns under 1200, set those percentages to 95. Also will have to change the max vane table as well. It will help with your smoke, but won't eliminate it complete. Your higher rpm columns are fine.

Another tactic it to reduce the timing in your heavy throttle and low rpms to build heat to spool help spool the turbo. Try the vane tables first, then try and reducing timing some.

[03sierraduramax]

tried changing the vane positions under 1200, made a bit of a difference off the line but still have huge lag if I go wot too fast while cruising. ive included my tune which is a work in progress. theres tons of messed up things in it so dont laugh too hard when you see it lol.

I tried uploading a log but its long theres a good WOT run a third of the way through, log looks messed to me, fuel says 79.7 but its definatly higher because my pulsewidths at 79.7 are way smaller. so it must be my config

you can see it takes a few seconds for pulsewidths and boost to come up

[ajamesbond007]

Do you have your config file as well? I will need that to look at your log

[03sierraduramax]

this is what I used, if you have a better one please let me know, this one always tops out at 79.7 mm3

[ajamesbond007]

Okay I'll take a look at it tonight and see what I can come up with. In your cruise area for your boost tables' up the boost by 10% and see if that helps with some of your lag going to WOT. It's not going to be snappy, but it should help some. When you watch your logs, look at your TPS, your RPM, Fueling Rate, Speed, Vane position, and boost. The higher the boost is before you go into WOT, the quicker and snappier your truck will be. For example, lower your boost to 0 (15 psi in the table) at cruise, flash it, then run it. It should be smokey and laggy until the turbo spools. Then, retune your truck with 5 pounds in your cruise area, the smoke should be relatively gone, and your truck should be pretty quick in response.