Timing in chip doesn't match datalog, '92
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Timing in chip doesn't match datalog, '92
Why would the car not reference the proper values in the chip for spark advance? IE my data log shows that at WOT, a MAP value of 101, and RPM's ranging from 3000 to 5800 RPM's, that it is producing a spark advance of 32 degrees.
Now according to the chip, it should be at 35-36 degrees in this range. The only value I can find in tunercat that would otherwise affect this value is the Coolant Temp Compensation Spark vs Load table, which happens to be at all zeros for the operating temperature in question.
I was drawn to this area of the data log due to a very slight amount of timing retard over a fractional part of this range, which naturally drops the spark advance even lower. My concern is though, while it is not detecting any knock, why is it not trying to run at the commanded advance value?
Now according to the chip, it should be at 35-36 degrees in this range. The only value I can find in tunercat that would otherwise affect this value is the Coolant Temp Compensation Spark vs Load table, which happens to be at all zeros for the operating temperature in question.
I was drawn to this area of the data log due to a very slight amount of timing retard over a fractional part of this range, which naturally drops the spark advance even lower. My concern is though, while it is not detecting any knock, why is it not trying to run at the commanded advance value?
Melting Slicks
Joined: Aug 2003
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From: Lakeville MI
Was there knock retard present earlier in the run? The spark retard decays over time ( a few seconds). You could increase the decay rate, or zero out the knock retard to test.
In my case I have the knock retard zero'd out at wot, and during scans I see the advance that matches the main spark table = 34.1 degrees.
In my case I have the knock retard zero'd out at wot, and during scans I see the advance that matches the main spark table = 34.1 degrees.
Melting Slicks
Joined: Oct 2002
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From: Cincinnati Oh
if there was knock 1-2 sec before it [the timing retard] could still be "decaying..."
You should have a power-enrichment spark adjust table as well as the coolant vs spark table, and that could be where the other 1-2 degrees of retard are coming from. This is the one I would look for - depending on your definition and software it may read differently.
Secondly, there is also a "highway mode" spark advance that increases timing under very stable part-throttle conditions - if accelerating or under 55mph this should have zero effect.
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Here's a screenshot of what I'm seeing.
There is no spark retard at all before it starts pulling timing. It is flat out running at 33 when it should be at 36.
The LT1 computer does not have a PE spark advance or a highway mode spark advance.
There is no spark retard at all before it starts pulling timing. It is flat out running at 33 when it should be at 36.
The LT1 computer does not have a PE spark advance or a highway mode spark advance.
Thread Starter
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I was actually just looking at the data log, I was going to investigate the knock. I was going to see about backing down the spark in the computer when I found out that the commanded value does not match the actual value.
I'm not really tuning for anything yet, I'm just trying to understand what is going on. It's gonna be a little bit hard to tune when the computer doesn't do what it is commanded to do.
I'm not really tuning for anything yet, I'm just trying to understand what is going on. It's gonna be a little bit hard to tune when the computer doesn't do what it is commanded to do.
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Originally Posted by Alvin
or low octane mode.
Short of zeroing this table and testing, how would one know if it is referencing this table?
I mean if the computer is running in "low octane mode," shouldn't there be some kind of flag to let us know that's what it's doing?
FWIW Brian always gets 93 octane fuel, I believe from Shell.
