yep
L98 ignition timing
Drifting
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From: Brisbane Australia
C4 of Year Finalist (performance mods) 2019
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From: Mission Viejo CA
Yes, that's right. Your custom ECU ignition curve was set up for 0 deg. static "base" timing. The factory ECU ignition curve was set up for 6 deg. static "base" timing.
I run my L83 at 9 deg. advanced. I'm sure an analysis of my engines "knock counts" would help decide what's best for my engine, but my WAG must be pretty close. I reset my timing to 6 deg. for my bi-annual smog test, then return it to 9 deg. after the test. They DO test my engines ignition timing! Gotta love California! The smog guy must know what I'm doing, because my timing marks are so clean! They frequently comment about how well my engine runs, for a 35 year old car with 240,000 miles on it!
I run my L83 at 9 deg. advanced. I'm sure an analysis of my engines "knock counts" would help decide what's best for my engine, but my WAG must be pretty close. I reset my timing to 6 deg. for my bi-annual smog test, then return it to 9 deg. after the test. They DO test my engines ignition timing! Gotta love California! The smog guy must know what I'm doing, because my timing marks are so clean! They frequently comment about how well my engine runs, for a 35 year old car with 240,000 miles on it!
Last edited by Hot Rod Roy; Oct 15, 2019 at 11:52 PM.
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Yes, that's right. Your custom ECU ignition curve was set up for 0 deg. static "base" timing. The factory ECU ignition curve was set up for 6 deg. static "base" timing.
I run my L83 at 9 deg. advanced. I'm sure an analysis of my engines "knock counts" would help decide what's best for my engine, but my WAG must be pretty close. I reset my timing to 6 deg. for my semi-annual smog test, then return it to 9 deg. after the test. They DO test my engines ignition timing! Gotta love California! The smog guy must know what I'm doing, because my timing marks are so clean! They frequently comment about how well my engine runs, for a 35 year old car with 240,000 miles on it!
I run my L83 at 9 deg. advanced. I'm sure an analysis of my engines "knock counts" would help decide what's best for my engine, but my WAG must be pretty close. I reset my timing to 6 deg. for my semi-annual smog test, then return it to 9 deg. after the test. They DO test my engines ignition timing! Gotta love California! The smog guy must know what I'm doing, because my timing marks are so clean! They frequently comment about how well my engine runs, for a 35 year old car with 240,000 miles on it!
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My ignition timing on the prom has been set up by PCM of NC, along with the rest of the tune. I told him my initial timing and sent data logs of WOT runs for them to adjust properly.
I use a higher initial setting because back when it was a stock street car and I was racing it, the engine seemed to have a little more bite and response running the stock prom timing curve advanced a little. When I built the race car I just set it up like I had been on the stock engine and let the tuner take care of the rest. I could leave it at 0° and let the chip do more work, but I dont think it matters as long as the end result is the same.
I use a higher initial setting because back when it was a stock street car and I was racing it, the engine seemed to have a little more bite and response running the stock prom timing curve advanced a little. When I built the race car I just set it up like I had been on the stock engine and let the tuner take care of the rest. I could leave it at 0° and let the chip do more work, but I dont think it matters as long as the end result is the same.
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From: Hartford WI
My ignition timing on the prom has been set up by PCM of NC, along with the rest of the tune. I told him my initial timing and sent data logs of WOT runs for them to adjust properly.
I use a higher initial setting because back when it was a stock street car and I was racing it, the engine seemed to have a little more bite and response running the stock prom timing curve advanced a little. When I built the race car I just set it up like I had been on the stock engine and let the tuner take care of the rest. I could leave it at 0° and let the chip do more work, but I dont think it matters as long as the end result is the same.
I use a higher initial setting because back when it was a stock street car and I was racing it, the engine seemed to have a little more bite and response running the stock prom timing curve advanced a little. When I built the race car I just set it up like I had been on the stock engine and let the tuner take care of the rest. I could leave it at 0° and let the chip do more work, but I dont think it matters as long as the end result is the same.
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From: Mission Viejo CA
There is NO WAY for your ECU to know where TDC is. It is triggered by the pulse from the distributor, which may, or may not be correct for your eprom program.
Last edited by Hot Rod Roy; Oct 16, 2019 at 05:51 PM.
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From: Hartford WI
Just thinking out loud but if the EPROM hears detonation, it will pull back timing but if not, it should advance it to whatever is in the tables. IOW, stay safe. So if it were set up for say 6 degrees and you leave it be, it should have no detonation. If you set it for 12 and it hears detonation, it should "do more work" by backing off the timing 2 degrees at a time till it hears nothing then push it up a half a degree. So if you have it set for 0 at the time the data log was done and the chip was written around 0, leaving it alone would mean it runs whatever is in the tables. So why would the chip do more work at 0 than 6?
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From: Akron Ohio
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If you don't think it matters, have you tried it at 0*? Or 5* ATDC? What does PCM say about your base timing?
There is NO WAY for your ECU to know where TDC is. It is triggered by the pulse from the distributor, which may, or may not be correct for your eprom program.
There is NO WAY for your ECU to know where TDC is. It is triggered by the pulse from the distributor, which may, or may not be correct for your eprom program.
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From: Akron Ohio
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Just thinking out loud but if the EPROM hears detonation, it will pull back timing but if not, it should advance it to whatever is in the tables. IOW, stay safe. So if it were set up for say 6 degrees and you leave it be, it should have no detonation. If you set it for 12 and it hears detonation, it should "do more work" by backing off the timing 2 degrees at a time till it hears nothing then push it up a half a degree. So if you have it set for 0 at the time the data log was done and the chip was written around 0, leaving it alone would mean it runs whatever is in the tables. So why would the chip do more work at 0 than 6?
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From: Mission Viejo CA
The chip would need to be programmed based on the initial timing. If you set it at 0° and the goal is 36° the computer is adding more timing than if the initial is set at 10° and the chip is only adding 26°. Its not more "work" but the tune would involve more timing to make up for less initial.
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The timing table is set. If you change the initial timing it shifts the predetermined curve. Whether you program that curve to start at 0° or 10° it should reach the same desired end result. If you change the initial timing AFTER setting the table in the chip, no the chip doesn't know to compensate. I never said it did. YOU HAVE TO CHANGE THE PROGRAM TO MATCH THE INITIAL TIMING. It doesnt matter if you start the curve at 0° initial or 10° as long as the chip is programmed to have the same end result. How many different ways can I say the same thing so you understand??
Last edited by Kubs; Oct 17, 2019 at 03:27 PM.
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From: Hartford WI
I had an idiot that did just that. ECM just pulled out timing and I was never able to get it to idle steady after the intake manifold install. One day, I decided to check the timing myself and found out it was about that much advanced. Other than that idle, it seemed to run "just fine". Higher than it should be but did not die out.