Vortec MAX Posted November 25, 2006 Report Share Posted November 25, 2006 (edited) I'm new to this. I have always just pressed on the accelerator once the light turns green. I was riding with my friend in his Jeep Grand Cherokee and he put his left foot on the brake and revved the engine at the light. When the light turned green, he let off the brake. It really launched hard - I was impressed. So, does this hurt the truck. Is this how you guys launch? My truck seems slow off the line. I left in 20% of the torque management. I blame that . It just makes a WAAAAA sound off the line (CAI), but does not really launch too hard. Once it is rolling it is just on the verge of spinning the tires (I can feel it squirm). It hauls butt once it's rolling (at least to me). If I could get a better launch, my truck would be pretty fast. Advice please. Mike Edited November 25, 2006 by Vortec MAX (see edit history) Quote Link to comment Share on other sites More sharing options...
tonman316 Posted November 25, 2006 Report Share Posted November 25, 2006 I've heard several different methods. Try it in 4wd and switch into 2wd once your goin, see what happens. Quote Link to comment Share on other sites More sharing options...
Vortec MAX Posted November 25, 2006 Author Report Share Posted November 25, 2006 I've heard several different methods. Try it in 4wd and switch into 2wd once your goin, see what happens. <{POST_SNAPBACK}> But...do I just punch it when the light turns, or hold my left foot on brake and try to get RPM's up first? Mike Quote Link to comment Share on other sites More sharing options...
11H Posted November 25, 2006 Report Share Posted November 25, 2006 (edited) You say you "left in 20% of the TQM" ... Well, there are 3 phases/types of TQM ... 1. Abuse Mode 2. Upshift TQ Reduction Mode 3. Overall TQ Reduction Mode (Based on load, tps, temp, etc) The one that may very well be the culprit in YOUR description is #1 ... There is about a 2-3 second delay off the line to where the PCM won't allow open loop/PE (power enrichment tables) ... Once that timer counts to ZERO, then PE kicks-in and gives you a PE table ... In my experience, when you are doing a wot launch, with #1 intact, it can also pull some timing via KR (knock retard) as well due to the lean AFR targeted at the full load you are demanding ... REMOVE #1 and you will have a nice hard launch; however, bear in mind, you will then have about 30% or more shock loading taking up the driveline from a stand-still ... So my advice is to slightly load up the driveline with foot on brake (hard) and instead of slamming it to the floor, roll into it quickly as then the driveline sees a slightly more "progressive" torque delivery ... The goal is when you launch, to have all the slack taken up out of the driveline, have the converter near flash point, (about 1600-1800 rpm) and roll into it as to have a good launch with a balance of gradual but quick throttle application as to lessen the HIT ... (most street races are decided from the launch) Many people have a different approach however ... But with our 4L70E, having an upgraded reaction assembly, and many shot peened parts, OVER the 4L65E, I think this trans can tolerate quite a bit more abrupt input torque than the 4L65 and 4L60 because the hard parts that are sensitive to hard hits, have been upgraded ... (I have talked to a GM tranny perf builder, and all the 4L70 really needs up to about 400-450RWHP is friction material care in that you want to reduce shift times and have firmer application as to reduce slippage as to not glaze or over heat the surfaces) ... This trans has been in the 2005-up LS2/SSR for a while now and he has yet to see one come in broken or for a rebuild... And for the rear-end? ... Not a worry ... The 9.5 ringed 4.10 14 bolt can take a lot of abuse ... (as long as you are not hammering it around corners to put the G80 into activation and slam it too hard) ... Straight-line runs, our rear diff is well over sized to take it ... The SS for example has the 8.625 10 bolt which is a stout rear, but not like our's in the Vmax package ... my .02 Edited November 25, 2006 by 11H (see edit history) Quote Link to comment Share on other sites More sharing options...
dancar Posted November 25, 2006 Report Share Posted November 25, 2006 It's my understanding that if you launch from idle you will flash the tq converter to a higher rpm. This will put your engine higher on the horspower/ torque curve. If you're getting a slow throttle response from idle, you can do as your friend does, but only bring the idle up slightly to take the slack out of the drivetrain. The real answer to your problem is to change your tq converter to a higher stall unit, i.e. a trailblazer converter. You will then need to learn how to launch without frying the tires. Quote Link to comment Share on other sites More sharing options...
rivierakid55 Posted November 26, 2006 Report Share Posted November 26, 2006 being as i now have a 2wd and launching is just a tire roasting session im not sure. my last truck (4wd dakota with kenne bell s/c) i launched in 4wd then switched to 2wd as someone else mentioned. different game as no torque management in 45rfe trans but similar idea. even then i could spin all four for a short distance. Quote Link to comment Share on other sites More sharing options...
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