Went to the local 1/8 track last night for a little T&T before going to a little mustang/buick get-together tomorrow. Car was running good, but I noticed a problem with the timing advance. DS showed timing slowly advancing as I staged/built boost, but as soon as I launched and the revs came up, it dropped back to 21.8* from 45*.....Any idea what could cause it to do that? Car only ran 93mph with no K/R, and 4-5 knock counts. O2's were kinda high (830-840) with A/F as bad as 8.3-1. I was running a RA93 chip, which is 26* initial. Any thoughts on the matter would be much appreciated.
Timing advance acting up...
- Thread starter Slo86GN
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Steve Wood
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- Jul 18, 2001
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I would think this is the way it is programmed. Are you saying that it has not done this before?
There are two timing tables in the 86-87 code. One for normal driving, and then a second when the ecm thinks it's in boost. While not all tuners use both, more often then not, they do. Anyway, if they are using both there are some qualifiers for when then ecm switches tables, GENERALLY if you see the timing jump when you see the BOOST field highlight (on DS) then they are using both tables, and you can see huge jumps when the ecm switchs tables.
Nope, it hasn't acted like this before. I took it out for a late night run earlier in the week and DS showed 45-46* at WOT in high gear. Dunno why it decided to act up like that. Would have been interesting to see what full advance woulda made the car run like. .
Guess I'll try pulling and re-installing the chip to see if that helps.
Guess I'll try pulling and re-installing the chip to see if that helps.Steve Wood
Active Member
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I think Bruce is probably on the right track.
There is a part throttle, cruising timing and a wot timing when it falls back to whatever the programmer limited timing to under that condition. Some chips will show quite a bit of timing while spooling up but will fall back to wot upon launch.
There is a part throttle, cruising timing and a wot timing when it falls back to whatever the programmer limited timing to under that condition. Some chips will show quite a bit of timing while spooling up but will fall back to wot upon launch.
Hmmmm....I still wonder what would cause it to run full timing one night, but then drop back so much another? One run I saw 1 frame where it jumped from 21.8* to 46.7*, but the next frame it dropped back to 21.8*. TPS doesn't vary much, stays around 4.70-4.74......Dang car is acting strange. Maybe it's just track shy...LOL.
What's normal is to see the timing drop off to the 20-22 degree range when at WOT.
What's NOT normal is to see timing in the 45 degree range at WOT
Normall when you see single fram timing spikes (as you described) it's an issue with connections on DS, Or even more likely is MAF dropouts. Use the graphing mode to display graphs of "timing", "MAF", "LV8", and "O2's" and look at the run. Look for those single fram spikes. You'll notice that when timing spikes, LV8 will usually be spiking also, and somewhere in the vacinity there may be some falling spikes in the MAF graph.
Got those??
What's NOT normal is to see timing in the 45 degree range at WOT
Normall when you see single fram timing spikes (as you described) it's an issue with connections on DS, Or even more likely is MAF dropouts. Use the graphing mode to display graphs of "timing", "MAF", "LV8", and "O2's" and look at the run. Look for those single fram spikes. You'll notice that when timing spikes, LV8 will usually be spiking also, and somewhere in the vacinity there may be some falling spikes in the MAF graph.
Got those??
