jhelms

iTrader: (2)

Hey guys, I just had a chance to GTech my 2003 Yukon after installing the HPP3, !MAF screen and UPD intake (modified lower stock box). 3.73 gears, 2wd, 11k miles on the motor.

Weather was 50 degrees, took out the 3rd row seats but no other weight saving mods, me and a 200+ pound passenger, 1/4 tank of gas.

Did two runs, one level to slightly downhill, the other noticeably uphill and I had to cross 3 lanes of traffic right in the middle of my run.

1) 0-60 7.15, 15.44 @ 96.6
2) 0-60 7.26, 15.54 @ 92.3 (uphill and lane changes killed mph?)

HPP3 is set to 93 octane tuning, 6200 rev limiter, tranny shift firmness on, +4/+12/+0 shift settings, and I think that's about it, top speed limiter deleted of course.

What do ya'll think? I know from my fbody days that the GTech is considerably high mph-wise, but my 1/4 mile times have always been fairly accurate with it. My 94 M6 bolt on Z28 went 13.39 @ 109 on the GTech compared to 13.402 @ 105 at the track.

Even with the skewed mph, what do you think I would see at the track? If I yank the spare tire and the 2nd row captains chairs and ditch the passenger would low 15's be in the cards? What do I need to do to break into the 14.9's? I have a few gallons of 104 unleaded at the house? Would that help? What about a cutout?

Oh yeah, tires were at 24psi (cold) all around, so I know I need to air up the fronts some more and probably the rears too, as the truck did not spin at all power braking it off the line (concrete expressway launching pad).

F8L Z71

MPH is always jacked with those things. The new G-Timer by Escort is much more accurate. But yeah ET was always about 2 10ths fast on my G-Tech

I was running 15.6 on the G-Tech on the way to the track but when I got to the track I ran 15.9

jhelms

iTrader: (2)

Cool, I guess my avg of these two runs is 0-60 = 7.205, 1/4 = 15.49 @ 94.45 - getting it to the track will provide a more accurate assessment of course, but how does this compare to other Yukons/Tahoes/etc. on a GTech?

Anyone else run theirs stock or with similar mods?

What do Denali's and Stock XL's with 6.0's and/or 8.1's run?

Scream

iTrader: (6)

That mph seems kinda high...I would think that you would be running mid-high 15's somewhere in the 90-93mph range.

jhelms

iTrader: (2)

MPH seems high for a GTech run or seems high altogether? I know the GTech normally shows a few mph's higher than a true 1/4 mile run, as noted by my 94 Z28 comparison of running 109 on the GTech compared to 13.402 @ 105 at the track.

Scream

iTrader: (6)

MPH seems really high altogether. My cammed 4.8 was pulling 95-96 mph, and ET with a little better traction would have easily been a full second over what the GTech says your ET should be.

I hate to be a naysayer, but take it to a track and find out what it REALLY does. I don't trust GTech's at all.

jhelms

iTrader: (2)

No problem, we'll be going to the track for sure (as I have with all 4 of my previous fbodies, the last one went 10.8 @ 129).

Even if we take the 'low' (uphill) mph and guess that it is high by a few, that puts me at 90mph, is that more realistic?

I don't understand this part of your post though: and ET with a little better traction would have easily been a full second over what the GTech says your ET should be. Do you mean that your 4.8 with traction would have run 14.4 or 16.4? Or that if I get traction (which I did have, BTW) I should run xx.4 at the track?

Like I said, I knowthe mph on a GTech is always high, but if I could compare it to other Yukons/Tahoes/Denalis that have also run on a GTech that would be a fair comparision I would think. At least until I have a chance to go to a track.

I'm a pretty good judge of how a car feels via seat-of-the-pants since I've generally run all my fast and not-so-fast cars at the track (in addition to my 2 supercharged LT1s, more sane cars like 98 S70 Volvo T5, 14.9 @ 98 at the track, Legend GS M6, 15's @ low 90's at the track, 2003 S10 4.3 no-options-base-model, 16.3 @ 92 spinning like crazy with weight reduction mods and bolt ons). So I feel like that gives me a pretty good indication, since the Yukon feels just as peppy as my old Legend did, and feels a good bit stronger than my S10 on a diet, I feel pretty good about the times.

We did test one other Yukon, an '01 with 5.3, 4wd, and 3.73's, ran 15.9 @ 89 on the same GTech, same road, with no mods and 30 degree weather.

KeukaZ71

on a G-Tech my truck runs around 15.6 without the yank and eaton. it is around 5400lbs. how does that compare to the weight of your yukon?

Scream

iTrader: (6)

I'm sorry to confuse...I have a RCSB truck. I was just giving an example of why your mph seemed high to me.

My truck is lighter, and my truck ran a consistant 95mph. BUT, I had zero traction, so I was saying that my truck *with traction* should have pulled 14.4 or better with the 95mph trap speed.

I don't think that a Tahoe/Yukon with your mods should pull anywhere near 95-96 mph. I'm guessing low 90s tops. Might even be more like 88-89.

jhelms

iTrader: (2)

Good question, I hope to weigh it and find out soon. Mine is an SLT 2wd with 2nd row captain's and 3rd row removeables. Took the 3rd row seats out for the run but had a 200+ # passenger.

Ahh, ok, that makes sense. I agree if I run 90+mph at the track I will be pleased with that.