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zakkb787

<that’s not me...
Sep 29, 2014
2,151
6
38
Granite Falls NC
I’m not understanding how completely flat footing off the line would give the same speed at the end of the 1/4 than a launch would...
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
17,496
156
63
Phoenix Az
I’m not understanding how completely flat footing off the line would give the same speed at the end of the 1/4 than a launch would...


Flat foot, no boost launch will net you a higher mph and slower et. Boosted launch will net a slower speed but quicker et. Assuming no traction loss.
 

NC-smokinlmm

<<<Future tuna killer
May 29, 2011
4,640
16
38
At Da Beach
NA 5.3 with mods would make 450HPish at the crank, 14psi of boost with the parasitic loss of the supercharger should around 300-350HP gain, then 20% powertrain loss should put you around 575-625 Wheel HP.
It's around 625 wheel. The calculator I use says 586 awd hp. I was being careful how hard I ran it bc Zach and I drove it up there. Soo, it was heat soaked like a mofo, I believe IAT's were 135 once I got out of staging lanes and lined up and up to 165 to 170 at the end of the 1/4. I need to take it out on a trailer and see what it will do with a normal IAT of 80 or 85. The heat kills the power.
 

MAXX IT OUT

<<<IT WORKS
Mar 1, 2013
1,660
2
38
Des Moines, Iowa
Stock cam?
From back on the other page


I forgot about this thread. I built the top end with BTR stuff, added a stage 3 boost cam, no more AFM or DOD, got 105 ID injectors, pinned the crank pulley, did a few oiling upgrades and retuned it for 14lbs. Truck spun really bad on the rollers so I played with it at the track a little. No launch just flat footed it from a 700 rpm dig and it went 12.5 at 110 weight is over 5300. Tuner figures power is a tad over 800 crank with performance numbers and fuel trims. It's a blast to drive, I have put over 20k on it this year alone. :D
 

JoshH

Daggum farm truck
Staff member
Vendor/Sponsor
Feb 14, 2007
13,011
58
48
Texas!!!
Flat foot, no boost launch will net you a higher mph and slower et. Boosted launch will net a slower speed but quicker et. Assuming no traction loss.
I can tell you on a diesel, you will trap slower if you just flat foot launch off idle with no boost, but if you leave with too much boost and spin, you will typically trap higher. I have no idea how a positive displacement supercharger on a gas engine reacts differently compared to a turbo diesel in that test though.
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
17,496
156
63
Phoenix Az
Yup, dont disagree on that. there is almost a bell curve and it varys depending on setup. being hes not waiting on power/torque to come in, it changes the bell curve on the window for mph increase or decrease. waiting on the turbo to light can vary that as well, specially a large turbo.

the extremes to either side of the curve will cause a low mph. atleast this is what i have seen over the years at the track. You spin the shit out of your tires to the 330 or farther, mph will be low. But you only spin some with a "meh" 60ft, mph could be the best you ever had. you lag the heck out of the start, same thing. Its only when you start getting traction down and your launch down when you notice that a bad launch gave a crappy et but mph went up 2, maybe 3 mph (depending on how bad the launch was). Vise versa when you get that perfect launch.

So mph is not "fool proof" but its way more accurate than ET imho as you have more leeway to a bad launch or some traction issues. unless you are REALLY bad at getting it down the track, most guys dont see much more than a 5mph swing between good and bad launches.

id love to plot that bell curve theory though. could be interesting.
 

NC-smokinlmm

<<<Future tuna killer
May 29, 2011
4,640
16
38
At Da Beach
It's at my buddies shop for some paint touch ups and wet sand, once it get it back I'm going to bolt on a set of lighter 17's with a 29" tire, trailer it up there (it's an hour drive), remember to pull fuse for traction/stabiltrack, change my belt, clean it out and launch the **** out of it and see what happens...:D

And I should probally weigh it considering it's got a lot of extra crapp bolted on it, hard bed cover, sway bars, lift kit, bed mat, subs with amp, etc...
 

NC-smokinlmm

<<<Future tuna killer
May 29, 2011
4,640
16
38
At Da Beach
I said **** it and had it completely repainted. Had every ding and dent fixed and had it shot with PPG GM ebony black and a ton of PPG Mercedes clear. Full wet sand starting with 800 up to 3000, buffed then polished and ceramic coated. Replaced all plastics, wiper arms, grills, bumper, door handles and new tires. I've been looking for OEM take offs, but once I add tires and clean them up I might as well buy a set of used race stars. I've started looking so I can go to the track with out my 22's and 33" mud tires. :rofl:
 

NC-smokinlmm

<<<Future tuna killer
May 29, 2011
4,640
16
38
At Da Beach
My 6l80 is upset, time for a new one or maybe a build. I'm not sure yet going to trans shop in the morning. She is still going just upset on the 2 to 3 shift under boost. It's still shifting but free revved on me this week for a split second before jumping into gear and blowing the tires off at 60 mph. That wasn't cool, need to fix it before it blows everything up.
 

lutzjk913

Active member
May 5, 2010
1,314
14
38
groveport, ohio
My 6l80 is upset, time for a new one or maybe a build. I'm not sure yet going to trans shop in the morning. She is still going just upset on the 2 to 3 shift under boost. It's still shifting but free revved on me this week for a split second before jumping into gear and blowing the tires off at 60 mph. That wasn't cool, need to fix it before it blows everything up.
LOL. Been there done that

was out in my uncles f150 a couple months back. 2020 5.0 that is twin turboed. That 10 speed was on its way out and he didn’t tell me.

it skip shifted then missed a shift under 3/4 throttle. Immediate rev limited and then fireballs out the cutouts. Not a fun time. LOL
 

NC-smokinlmm

<<<Future tuna killer
May 29, 2011
4,640
16
38
At Da Beach
Ass puckering moment for sure...

I'm getting mixed signals about a built one so might go back with a reman from GM and drop a new converter in it and roll out.
 

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