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

[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.