2017 GMC 1500 6.2 1/4 mile run data

[Volkster]

First off the facts......

 

My truck is a 2017 GMC Sierra 1500 All Terrain crew cab short box with the 6.2L/8-speed

 

I had my truck weighed on a certified scale which was 5680lbs. That included a 30lb soft tonneau cover but I had recently swapped out to a hard trifold cover that added 20lbs. so we'll call last night's weight 5700lbs plus my 220lb fat a*#

 

Mods: Flowmaster American Thunder cat-back exhaust, S & B cold air intake and a Hypertech tuner with the 91 octane performance tune w/ throttle response set to "sport"

 

The runs..... Truck ran very consistent between the 5 runs ranging from a best of 14.05 @ 98.7 to 14.14 @ 98 flat. 60 foot times ranged from 2.05-2.14  I did a ~6 second power brake burnout before each run. I launched off idle by jumping on gas ~3/4 throttle then quickly to full. Matting the gas peddle would spin the tires even warmed up on the prepped track surface. Oh, the elevation was around 300 ft above sea level, 60 degrees low humidity.

 

Overall very happy with those numbers given the amount of weight. For reference, there were two stock 5.7 Ram hemi crews cabs running 15.3's @ 86mph which surprised me a little on the difference between these trucks. Back in late 80's, my stock '86 Mustang GT did a best of 14.68 @ 92mph.

 

[Denali34]

Did you feel much difference from the Hypertech "canned" tune?

[Volkster]

Clearly in throttle response. Can't really feel any difference up top. It would be hard to feel even a 10hp gain when you already have 420. My main purpose of the tuner was I set the AFM to not kick in below 30mph because driving through my development it would sound like crap on 4 cyclinders with the Flowmaster exhaust. I also raised the top speed limiter to "T" tire rating setpoint (118mph) as once passing a couple of cars it hit the 99 limit which came real quick. Unfortunately I never ran the truck before these mods so not sure of the impact on results

[SILVER SLED]

Nice.  What was the DA that day?

[Roscopcoletrain]

all runs in 2wd? 

[Volkster]

Not sure on DA last night and yes in 2wd with T/C off

[Roscopcoletrain]

2 minutes ago, Volkster said:

Not sure on DA last night and yes in 2wd with T/C off

always wondered how much slower an auto run would be 

[Volkster]

Even with the tune, I previously found that in auto mode the torque management really kicked in giving it a noticeably lazier launch (probably to protect all the extra drivetrain involved, or to give time for the clutches in the transfer case to lock up once rear slipage is detected). In 2wd the truck instantly boils the tires on the street. Last night it pretty much hooked up and launched hard

[2017Darkness]

Did you not try loading the converter to about 2500 to 3500 and matting the gas on green?

[SILVER SLED]

I've chirped all four (or three) tires launching in 4wd, then quickly shifting into 2wd.

[truckguy82]

 

1 hour ago, Volkster said:

Even with the tune, I previously found that in auto mode the torque management really kicked in giving it a noticeably lazier launch (probably to protect all the extra drivetrain involved, or to give time for the clutches in the transfer case to lock up once rear slipage is detected). In 2wd the truck instantly boils the tires on the street. Last night it pretty much hooked up and launched hard

Well you have a bad tune then, because tune + 6.2 + auto4 = beast mode

[SILVER SLED]

5 minutes ago, truckguy82 said:

 

Well you have a bad tune then, because tune + 6.2 + auto4 = beast mode

  Keep in mind, no hand held will tune a 17-18 8 speed transmission, at least as far as I know.  Hopefully that will change soon.

[Racindave]

Thats pretty impressive for that heavy of a truck. Did u lower the rear tire pressure to maybe help with the traction?

[Volkster]

I did not try loading up the converter. The off idle launch was leaving real hard (probably has to do with the throttle response from the tune)

 

I lowered the rear tires to 30psi, again, traction really wasn't an issue as I did a powerbrake burnout then rolled out of water box spinning each run. Lots of smoke!

 

I thought about leaving in 4wd then switching. Not sure under full load it would switch back into 2wd until you let off the gas? Again, my truck was already launching hard plus I didn't want to add anymore powertrain loss that you would get in 4wd

 

If anyone here that's suggesting different launches, please post your 60 foot times. My 2.05 is very good given the weight and in 2wd on OEM tires with no traction issues

 

And yes it's true, there currently is no support for transmission tuning. Curious once available what impact that may have

[Volkster]

I probably should have added I was a mechanic for many years and spent lots of nights drag racing at the track for years with an assortment of vehicles. My 2.05 sixty foot time last night was better than my stock '15 392 6-spd Scat Pack and that car had ~65hp more and weighed 1400lbs less. That car had serious traction problems though.