Engine/Transmission (1998.5 - 2002) Launch procedure for drag strip with auto

[jebia]

I took my truck out (24 valve) to the local drag strip with 3 other truck owners (a 12 valve, a new duramax, and a new super duty).



I made two runs, and ran 16. 1 with a 1/4 mile speed of 91 mph. I lost both times to a super duty that was almost stock (he maybe had a fueling box).



Both times he off the line and had a good truck length and 1/2 lead, but I would gain on him hard once my turbo spooled up.



He was running his truck in 4 Hi, and holding the brake and bringing his boost up and then releasing the brake.



I was just basically doing hitting the gas at the green light (and having to wait for the turbo to spool up like normal).



What is the proper technique for launching at the strip (I was scared to run the truck in 4 hi, especially since the top speeds ast the end of the track was 90 mph).



thanks in advance,

 

[LOtero]

hey jon, sorry i couldnt make it. i believe that guy in the superduty had a 120hp fueling box. with the dtt and the comp what you need to do is hold the brake build about 10psi and launch that way. i launch my truck that way and believe me it rips! what you do have to learn is how to find your threshold traction where you hook up the hardest without spinning the tires. it takes some practice, but it isnt too hard. when launching in 4 hi, just slap it back into 2wd at about 30mph. let me know when you wanna get together and i will show you all this in my truck. i just went through all the same with a girlfriend of mine who wanted to learn this stuff (a. k. a keeper) gimme a call or post 263-5903 luis

 

[RacinDuallie]

This was better suited for the Competition forum.....

But, 4hi- pre-stage build up some boost-5-10 psi- more if you have the turbo for it, when you have built up some boost- stage and usually you'll want to mash the pedal on the last amber, when truck shifts into 2nd is when you want to put it back into 2hi..... let the trans do the shifting, you worry about shifting out of 4hi... ... ... and concentrate on the last amber- when it starts to lite is when you mash for better reaction times... ... and above all practice, practice, practice.

 

[jebia]

Thanks guys. I remember reading that max speed in 4 hi was 50-55 mph, I guess the manual can be ignored?

 

[paulb]

What Racing said...



Your sig doesn't say if you have billet shafts. If you have stock shafts keep the launch boost below 10psi or the input shaft will fight the output shaft, on which is going to break first. :{



I turn on the pre-stage light, and then build boost, and then the stage light. If it's an NHRA track with the auto start system, you have 10 seconds once the other guy is fully staged, and you have the pre-stage light on, before you have to be staged. 10 seconds is longer then it sounds... .



Paul

 

[JasonCzerak]

"for safety" yeah. 55mph. . I always ran my jeep in the snowy road well above 55. My truck has stock tires on it, anything above 55mph on slick roads would spin all 4 wheels anyways under stock power!!! so it's was rather pointless. New tires this winter!



Also, you automatic guys, electronic 4x4 or manual 4x4, the transfercase _WILL NOT_ shift out of 4x4 mode untill a load is released from the driveline. It's all spring loaded in some form or another. Once you get moving, drop the lever to 2x4 mode, but at some point you will have to back off the accelerator for a moment to get the T-case to drop out of gear. The force of acceleration on the gears will hold them in place. For example on a manual trans, try to pull it out of gear at WOT? not easy huh?



I know for a fact on my 6-speed (and 5 speed 93' xj), both manaul T-cases, you can drop it to 2x4 via the shift lever and she's still in 4x4 untill you grab the next gear. I find if you quick, you can do this between 2nd and 3rd gears on the CTD, better yet, do so when you 3rd -> 4th shift.

 

[JasonCzerak]

What Racing said...



Your sig doesn't say if you have billet shafts. If you have stock shafts keep the launch boost below 10psi or the input shaft will fight the output shaft, on which is going to break first. :{



I turn on the pre-stage light, and then build boost, and then the stage light. If it's an NHRA track with the auto start system, you have 10 seconds once the other guy is fully staged, and you have the pre-stage light on, before you have to be staged. 10 seconds is longer then it sounds... .



Paul

Hey, I'm going to be dropping in a SBC in my truck, should I be considering upgrading the input shaft while I have things apart? I know a 4x4 2nd gear 2000-2500rpm launch is a bit more aggressive then a little torque converter.

 

[EBung]

I wouldnt be scared to run my truck 100mph in 4hi but at the strip you want to run as fast as you can so once you get off the line and no longer need the traction assistance why keep it in four wheel drive?Why abuse the front end and rotating components any more than necessary?Just common sense. I think the reason you lost was probably the same reason I would of and thats because of the stupid defueling that takes place on our '00-'03 automatic trucks. I tried a Comp box on mine and it ran better but still couldnt even do a burnout. My truck off the line is a pooch but try me at 20mph+ and look out!I want one of those BD Race. Anti. Defuelers and then maybe I would need to be in 4wd at the track. I envy you guys with traction problems!

 

[RacinDuallie]

I've run mine out in 4hi to the tune of 12. 98 @ 105. 49- forgot to shift it back to 2hi, no problems though... ..... got too busy looking at my mirror to see where the other guy was... ...

 

[SLangegger]

Racing,



When you forgot to take it out of four wheel, did you run a better of worse time? It makes sense that the transfer case would not unlock with a load on it. When you take it out of four wheel, does the light go off right or does it stay on until the end of the track? Im just wondering if it comes out or not. Thought I'd ask someone with experience cause i don't know.

Thanks

Steve

 

[RacinDuallie]

My indicator light goes off... ... ... ...

 

[RacinDuallie]

Here's how I do it:



I pay attention to the guy waving the next pair up- when he waves us in I proceed to pull around the water, and then back into it. There's no need to just drive through the water and carry it to the line with your front tires soaking wet... ...

Then since I don't run slicks ( YET ) I like to really put some heat into the rear duallie tires- with a very healthy burn-out..... I like to roll through the burnout and gradually back off the throttle when rolling thru it- I have a Full-Billet Suncoast so I'm not worried about the trans, but I do worry about tossing a U-joint/ or driveshaft. Rolling thru the burn-out will not shock the drivetrain... .

Then when I have rolled thru my burn-out- and stopped I qwickly throw the trans in neutral- then pull the transfer case into 4 hi. then back to Drive. I wait for the indicator to light to tell me that my vaccum system has engaged the front axle, Then I slowly roll to the Pre- Stage bulb.

When you light the prestage bulb look and see where you competition is- before you start to build boost- there is no sense to sit there building boost if you don't know that your opponent is pre-staged or if the Starter is ready or if there is any problems ect. ect. If opponent hasnt broke and has pre-staged also: START BUILDING BOOST!! (5-10 psi in your case) I build up more- (I'm BOMBed for it. )

When you have your boost you'll want to bump in, to light the Stage bulb, or if you like to Deep-Stage you do a double bump..... Just make sure the second bump is shorter than the first... ... .

Watch the tree- Keep you eye on the 3rd amber when it has lit- lift off the brakes and MASH IT ! ( practice will net in better reaction times..... )

When my truck pulls through first gear I have my hand on the transfer case shifter- when the trans shifts into second gear is when I push the case into 2 hi- then I hit my lock-up switch- (depends on if I use the preprogrammed setting in the lock up controller- or I can over ride it and Lock it up on my own)

Then I let the trans do the rest of the job and look around to see where the competition is... ... ... ...

All this talk here about this has me all itchy now-Oo. thanks!

 

[SLangegger]

how much difference between 4x4 then 4x2 and 4x4 all the way?

would you rather not say at all?

 

[RacinDuallie]

Hard to tell the difference between them as I only made that mistake once

Some say it could be about 2 tenths difference... ... ..... and I had lifted slightly when I was at the 1/8th- I was cursing at myself for forgetting to shift it out... ... ... But we won't go there ... .....

 

[pwerwagn]

I thought you ran a 17. 1 Jon??

The psd he was against was a 04 F-350 dually with a 130hp quadzilla box. This truck moves pretty good. He ran a 15. 2@88mph.

Jon, I was launching in 4-wheel saturday. mine is a 5-speed, though. I usually try to take mine out in 3rd (if I have time) but normally I dont manage to get it out until 4th.

Eric mills run the same basic setup as you (hp wise), except he has an ats auto and a B-1-2 turbo. His doesnt have billet shafts either. He launches around 18psi, but he has broke the output shaft one time.

Practice in 2wd at a few stoplights. try it at 2psi, then 4, then 6, and keep going up until you loose traction in 2wd.

oh yeah, where did you say you got that steering wheel cover thing at???

--Jeff