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128 Posts
Discussion Starter · #1 ·
Ok, for this topic I'll be focused on the fiance's GT with L67.

Mods are:
xp cam
slp headers
no cat/res
Custom dhp commanding max 20 timing

That's the basic main power.

So I get it dialed in with the afc roughly 98% idle, 98% up to 6K, 100 7K, 101 8K, 103 9K, 103 10K, 103 11K.

LTFT's would always show -'s at idle and cruiz and I was able to get the trims almost 0 dead nuts all the time. WOT ltft's when static were -1.6 and 02's were 911-924.. never higher never lower. Obtained an average of 17.5 timing adv.. not to bad *no nock on stock timing, but with the added degrees we saw some* it would drop to about 14 by the end of the 1/4 in third gear, effectivly netting us only a 18mph gain in the back.. kinda hurts.

So In an attempt to try to bump it up I tried 105, 106, 108 on the afc, could never get the 02's to go over 924 and it would still lean out and actaully got WORSE and was hitting 8's on the 02's.

Fast forward to today.. the ltft's were way negative, supposedly telling me the car is rich, so I decide to give it a shot.. back the cruize/idles down to 97% and back 7-8K to 99 and try 9K+ at 101. 02's hung around 840... KR was 4-6 when WOT, LTFT's locked at -10.2 every wot run... but the weird part is it only ran 8-9 degrees of timing adv... so if I had no knock I'd only see 14 total timing???

Now for the part that scared me.. the car was HAULING A$$$!!!!! The car has NEVER felt this powerful the entire time we have had it.... Could it be that there is something hosed up with our 02 reading wrong and I actually have it dialed right??? I don't know what to do.. the scanner tells me by the ltft's the car is pig rich, but the 02's say I am very lean along with KR figures and I don't even break 9 for timing but it is just pulling SOOOO hard.. harder than it has when running 13.2's on 15 timing.

I'm just confused.. it seems running it at conditions that it should not be, it is a raped ape.. Even on these 850 02's I have the same knock we did when at 920's but timing is a lot less.

Need thoughts.. ltft's say rich, 02's say lean, power says perfect, timing says I should be slow, kr agrees with 02.

22 Posts
Sounds exactly what my car was doing....

MY problem was when I was using my ICCU, is it does not take adaptation into the equation. You have to retune according to ambient temp.

As far as the stock O2, I was showing 940s with my ICCU set on 104% at WOT, and the car would only allow 9* advance, and no KR or KC showed up.
Took it back down to 98%, and was able to get my 22 back.

I dont trust the stock narrow band O2 now....

Try taking it and dynoing on a wideband, it will be the only sure way to know how rich / lean the car is running :)


7 Posts
You could have felt faster with only 9° of timing if you were running lean, since there'd be a more agressive flame in the cylinders. Running richer would necessitate more spark advance to burn all the fuel completely.

That's just my theory.

Kind of like on my car running on 87 octane with ~23-24° total timing and 4-6° KR it's just as fast as it is running on 93 octane with 26-27° timing and little to no KR.
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