Topic: I spec'd my 2008 today... very pleased

[Mike Mercury]

Was wanting to put down a baseline - if I ever decided to mod later on (though I have no plans on modding my Av; it's my daily driver).

Surprising that a 5900+ lb vehicle could give these numbers:

left - best run with T/H off; right - best run T/H on

info:
2008 AV 4wd with 5.3l 3.73 rear, 20" factory tires
100% stock; 4100 miles
50 degree air temp
1/4 tank 87 octane "every day" gas

how I ran:
*6 runs total
*All in 2w-Hi
*TC was always turned off, but I doubt it would of mattered.  I was never able to spin the tires anyways (as to be expected on a prepped drag track and the factory optional 20" tires).
*Three runs were with T/H on... three with T/H off.  All three T/H off runs were slightly better than with the T/H on. 

Most of the guys at work guessed "mid 17's at best".  But I'll take low 16's !!!!

a note to the GM readers:  I did not race my truck today; instead  I simply verified that your published 1/4 times were realistic.  This was at a real track and not on the street.  These runs were no different than a WOT dash on an interstate entrance ramp.  In the voice of Bart Simpson... "don't have a cow man".   

[oHIobellboy]

Thanks for posting those. Now we'll have a comparison when you start modding it.    Did you take the vette also?

[Mike Mercury]

  Did you take the vette also?

no; but it's been "spec'd before.  Since you asked though ....



I do have some bolt-on mods on my 2002 LS1 Corvette. But in 100% factory stock trim it would run consistant 13.3's.
But the '02 Vette weighs-in at  around 3400 lbs  - that alone makes a big difference.  Then add the 350hp stock LS1 and lower CoD; that matters some too. 

But I am amazed with this 5.3l in the Avy.  I could tell it pulled-hard; but that can sometimes be deceiving.  The numbers seem to verify my SOTP measuring device 

[MyBigToy]

I assume you're still active on Corvetteforum? I don't visit much since I sold my 03 MY vert.

[Mike Mercury]

sorry to hear you sold your '03.

Yep, i've been on CF for 7 years and have over 50k posts there  !! (though, I don't know if that's a good thing or a bad thing... HA !!!)

I still have the 2002 I bought new; and Yvonne recently sold her 1973 and purchased a 2003 Anniversary Vert that had 5400 miles on the ticker:





I tell ya (something you apparently already know)... these Avalanche guys are as "god & country" as the Corvette folk.  Great group of people.

[boilers94]

Must have been at Kil-Kare, eh? 

[Mike Mercury]

Must have been at Kil-Kare, eh? 

yes; and where were you ???  HA !!!!!!!

I was first in line, & first down the track at this opening season "Test and Tune". 

The first two T&T's are being held on Saturdays; todays...  and another next Saturday the 28th.  From then on it will be  Thursdays till the end of the season.  I'm there almost every week at the T&T; but I rarely run... usually just spectating.

[boilers94]

I was at baseball practice.........again!! 

[Main One]

Comparing your slips to some times/speeds I've seen for the older AVs, the times are similar, maybe a bit better, but the trap speed for those times is considerably higher.  Although, it's never been as cool as 50 degrees when I've been to a track - I'm sure that helps overall.

[Mike Mercury]

I did hear occasional pinging during the runs; probably due to the cheap gasoline I buy.  Does the 5.3 have an engine knock detector similar to the LS1 ?

[Main One]

Yes it does have knock detectors which pull timing.

You either need better gas or a better tune.  (Less timing and/or tweaking MAF calibration and/or richer power enrichment mixture.)

[Mike Mercury]

Yes it does have knock detectors which pull timing.

You either need better gas or a better tune.  (Less timing and/or tweaking MAF calibration and/or richer power enrichment mixture.)

there's a poor mans method to detect a rich AFR during WOT; and that's to back off the accelerator a small amount to where the system goes back into closed loop (but still accelerating heavily).  If the SOTP registers more thrust, then generally that means the WOT tables are set too rich.

I've come to believe that the factory  errors to the rich side under WOT.  Better that than lean.  But I'll tell ya; I have tried this with my new Avy and I don't sense any increase in pull when backing slightly off WOT throttle mode.  Yea; I know this isn't very scientific; and I do have an Innovate Wide Band O2 setup.  I guess I should get a bung installed upstream of the cats and check out the WOT AFR.

But, again... I really  was just curious to see what it ran in the 1/4 mile as-is; and have no plans to performance-mod the truck at all.

[MyBigToy]

I tell ya (something you apparently already know)... these Avalanche guys are as "god & country" as the Corvette folk.  Great group of people.

I've been on the Av forums longer than CF and I agree. Many of us are as mod nuts as the Vette guys, myself included. Most of my mods have been towards the performance side. I plan to get back into a Vette once the kids are gone from home. I've got college costs coming up in another year and then will have them continuing for at least the next eight years.

[Mike Mercury]

as much a surprise the lower-than-expected ET numbers... was that the Tow/Haul mode runs were -roughly- .075 slower than with the system inactive.

I had imagined the T/H mode should of made enough shifting improvements to where it would of given quicker times.  Though, I realize .075 isn't all that much; but there was a consistant pattern of slower ET's with T/H activated.

Any ideas why ?

[MyBigToy]

as much a surprise the lower-than-expected ET numbers... was that the Tow/Haul mode runs were -roughly- .075 slower than with the system inactive.

I had imagined the T/H mode should of made enough shifting improvements to where it would of given quicker times.  Though, I realize .075 isn't all that much; but there was a consistant pattern of slower ET's with T/H activated.

Any ideas why ?

I don't know for sure but maybe there is more torque management in t/h mode.

[Main One]

as much a surprise the lower-than-expected ET numbers... was that the Tow/Haul mode runs were -roughly- .075 slower than with the system inactive.

I had imagined the T/H mode should of made enough shifting improvements to where it would of given quicker times.  Though, I realize .075 isn't all that much; but there was a consistant pattern of slower ET's with T/H activated.

Any ideas why ?

I don't think there is a difference in TM for T/H.  Most, if not all, of the differences related to T/H are in regards to how the transmission is programmed.  It is probably due to different line pressures during the shift and/or programmed shift times.

[Main One]

there's a poor mans method to detect a rich AFR during WOT; and that's to back off the accelerator a small amount to where the system goes back into closed loop (but still accelerating heavily).  If the SOTP registers more thrust, then generally that means the WOT tables are set too rich.

I've come to believe that the factory  errors to the rich side under WOT.  Better that than lean.  But I'll tell ya; I have tried this with my new Avy and I don't sense any increase in pull when backing slightly off WOT throttle mode.  Yea; I know this isn't very scientific; and I do have an Innovate Wide Band O2 setup.  I guess I should get a bung installed upstream of the cats and check out the WOT AFR.

But, again... I really  was just curious to see what it ran in the 1/4 mile as-is; and have no plans to performance-mod the truck at all.

I haven't looked at any stock Corvette tunes, but my 03 Avalanche stock tune was programmed to peak richness at 4800 rpm, 11.0 afr.  I'm now running 12.5 at that rpm range.

My peak is 11.5 at 2400-3600 rpm.  I'm richer there than anywhere else do to my experiments with timing on a couple of dynos.  Those show with my 89 octane tune, I can give up a little timing at the high end, but in the mid range where I am richest, more timing helps.

Power enrichment doesn't just give you a rich air-fuel mix, it also, at least in our trucks from the factory, bumps up timing.  The stock tune with the 11.0 afr at 4800 adds almost 10 degrees of timing.  Down lower where I've added fuel, my add over stock is giving me nearly a couple extra degrees of timing.  There is a separate table that by rpm adds timing based upon how much extra fuel you are adding.  I have not changed that table, so I have indirectly affected how much timing I add in power enrichment though my changing my afr.

[Mike Mercury]

Comparing your slips to some times/speeds I've seen for the older AVs, the times are similar, maybe a bit better, but the trap speed for those times is considerably higher.  Although, it's never been as cool as 50 degrees when I've been to a track - I'm sure that helps overall.

Heck; if I could get the 60' down to 2.0, the ET would be in the mid/high 15's with no other mods.  A higher stall converter would do the trick;   but I'm  really not eager to mod my AV.