advanced timing timing too high?
07-10-2005, 09:45 AM
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advanced timing timing too high? Hi Folks
Engines (L98, etc) that you manual adjust the timing, I would set see the max timing is about 36 to 38 degrees under different engine conditions. I played with the timing table on 02 LS1 with a max of 28 degrees but as I was logging data, I noticed that there is max timing of 40 degrees. The engine runs a little rough under partial throttle. That appears to be very high - I was using HP Tuners - histogram. Am I forcing the timing to be that high and causing the engine to run rough??
Thanks - Any help would greatly be appreciated
Bill
Engines (L98, etc) that you manual adjust the timing, I would set see the max timing is about 36 to 38 degrees under different engine conditions. I played with the timing table on 02 LS1 with a max of 28 degrees but as I was logging data, I noticed that there is max timing of 40 degrees. The engine runs a little rough under partial throttle. That appears to be very high - I was using HP Tuners - histogram. Am I forcing the timing to be that high and causing the engine to run rough??
Thanks - Any help would greatly be appreciated
Bill
07-10-2005, 09:51 AM
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Just like old school, you have your "centrifugal"
flyweight / spring advance and you have your
vacuum advance. Flyweight is your X axis and
vacuum is your Y axis (more vacuum = up) in
the table.
If you're curving a distributor you do it with the
vacuum line off to see the base mechanical
advance. That would be like the 0.8 g/cyl line
in the table (more for heads & cam, way more
for power adder, less for choked-off stocker).
If you're messing with spark you want to log
the Dynamic Cylinder Air and RPM which are the
table indices.
Part throttle with higher spark may want you to
loosen up the PE enable criteria to let it come in
quicker, or else you will have to respect the spark
limits of stoich mixture up to the point where PE
currently kicks in.
Watch the knock retard and Knock Learn Factor
to see whether you are getting current knock,
or worse yet being penalized for history.
flyweight / spring advance and you have your
vacuum advance. Flyweight is your X axis and
vacuum is your Y axis (more vacuum = up) in
the table.
If you're curving a distributor you do it with the
vacuum line off to see the base mechanical
advance. That would be like the 0.8 g/cyl line
in the table (more for heads & cam, way more
for power adder, less for choked-off stocker).
If you're messing with spark you want to log
the Dynamic Cylinder Air and RPM which are the
table indices.
Part throttle with higher spark may want you to
loosen up the PE enable criteria to let it come in
quicker, or else you will have to respect the spark
limits of stoich mixture up to the point where PE
currently kicks in.
Watch the knock retard and Knock Learn Factor
to see whether you are getting current knock,
or worse yet being penalized for history.
07-10-2005, 11:09 AM
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Suprisingly my car made more hp when taken timing out. I ended up at 24 degrees at wot. There was no knock when going up to 28-29 but it didn't make any more hp until we dropped it.
Eric
Eric
07-11-2005, 02:04 PM
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When I scan at mid and WOT, I'm surprised to see 38 degrees. It usually happens at low TPS, when you are coasting or decelerating. Most of my WOT runs are at 28-29. These LS engines don't need a lot of timing. I have never seen a knock, even with 11.5 to 1 compression on Chevron Supreme gas. That is amazing. After I get everything tuned (VE, PE) I am going to try adding 1 degree at a time until I see a knock.
07-11-2005, 03:37 PM
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Originally Posted by racecar
When I scan at mid and WOT, I'm surprised to see 38 degrees. It usually happens at low TPS, when you are coasting or decelerating. Most of my WOT runs are at 28-29. These LS engines don't need a lot of timing. I have never seen a knock, even with 11.5 to 1 compression on Chevron Supreme gas. That is amazing. After I get everything tuned (VE, PE) I am going to try adding 1 degree at a time until I see a knock.
The last scan I did, yesterday showed the knock sensor detecting a knock at TPS under 20% but not all the time. I think I will take out some timing for RPMs under 2500. WOT appeared to be OK - temperature was about 92 degrees.
Bill
