Total timing
Team Owner
Joined: Jul 2004
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From: Hartford WI
What are you trying to achieve?
Team Owner
Joined: Jul 2004
Posts: 28,356
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From: Hartford WI
Even if you could change total timing, how would you check it if it runs best? If you had a dyno and a wideband O2 sensor, probably. If you want to optimize it, best get a dyno tune. When they did my chip, they would see what the dyno read, tweak it, rerun it till the power drops off and use the O2 sensor to check the rest. IIRC.
Team Owner
Joined: Jul 2004
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From: Hartford WI
Depends. Have you done any substantial mods? If not, I don't know it will be worth it unless you have more money to burn than brains. With a stock system, it has been said to not have that much effect. Say you throw in a much better intake and headers, your curve has changed so it is somewhat justifiable. If you throw in heads and cam, definitely.
Safety Car
Joined: Sep 2004
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From: Mission Viejo CA
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Race Director
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is the 36 degrees governed by the ECM? to me, that would make sense IF the initial timing is set at the factory specified 6 degrees BTDC.
Race Director
Joined: Apr 2002
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From: Anaheim CA
The ECM assumes the initial timing is 6°. You can change the 6° in the tune if you feel compelled to change the initial timing. The ECM adds the appropriate value it looks up in the timing tables to the initial advance. The ECM also has a maximum advance parameter and will not advance the timing more than 42°.
Race Director
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Yes.
The ECM assumes the initial timing is 6°. You can change the 6° in the tune if you feel compelled to change the initial timing. The ECM adds the appropriate value it looks up in the timing tables to the initial advance. The ECM also has a maximum advance parameter and will not advance the timing more than 42°.
The ECM assumes the initial timing is 6°. You can change the 6° in the tune if you feel compelled to change the initial timing. The ECM adds the appropriate value it looks up in the timing tables to the initial advance. The ECM also has a maximum advance parameter and will not advance the timing more than 42°.
Last edited by Joe C; Jan 6, 2016 at 10:35 AM.
Team Owner
Joined: Jul 2004
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From: Hartford WI
IF I am reading him right, the ECM assumes you started at base based on the program you wrote. If it advances a max of 42, your total advance is (6+42) 48. Whether you reach that point or not depends on your KS and whether it is picking up knock. IIRC, it will retard timing till it hears no knock.
Melting Slicks
Joined: Jun 2013
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I'll try to break it down. Stock BASE timing is 6*. In the tune, if you were to set one cell in the timing table to 36*, then the ECM would do the following formula. 36 - 6 = 30, advance timing by 30*.
You can change the base timing in the tune from 6 to whatever you want it to be, but it's kinda pointless unless you are tuning your cranking timing, in which 6* is perfectly fine from what I have experienced.
You can change the base timing in the tune from 6 to whatever you want it to be, but it's kinda pointless unless you are tuning your cranking timing, in which 6* is perfectly fine from what I have experienced.
Race Director
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IF I am reading him right, the ECM assumes you started at base based on the program you wrote. If it advances a max of 42, your total advance is (6+42) 48. Whether you reach that point or not depends on your KS and whether it is picking up knock. IIRC, it will retard timing till it hears no knock.
Melting Slicks
Joined: May 2013
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From: Sacramento California
Besides the KS feedback, I understand that RPMs, engine load, throttle position, MAF feedback, fuel injector pulse, and other parameters are also factored into the amount of timing advance given by the ECM. May be inconsequential to the discussion at hand, but wanted to chime in.
Safety Car
Joined: Sep 2004
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From: Mission Viejo CA
How can it know what the initial advance was set to? There's no way it can even know TDC (L83 & L98. LSx engines may be smarter.)!
So, if you've set initial advance to 6*, and the program says +30*, you get final advance of 36*.
With initial advance of 10*, and the program says +42* (max, per Cliff Harris), you get final advance of 52* (less knock, if detected).
If the ECM was smart enough to know I've set initial advance to something other than the stock 6*, why can I feel the difference in performance of 6* vs. 8* (SOTP test)? If the ECM was smart enough to know the initial advance was something other than the recommended 6*, it wouldn't even care where you set the initial advance! It's just not that smart!
Last edited by Hot Rod Roy; Jan 6, 2016 at 07:08 PM.
Melting Slicks
Joined: Jun 2013
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Besides the KS feedback, I understand that RPMs, engine load, throttle position, MAF feedback, fuel injector pulse, and other parameters are also factored into the amount of timing advance given by the ECM. May be inconsequential to the discussion at hand, but wanted to chime in.
Injector pulse has no influence.
KS has influence when there is a signal, and the TPS has influence at WOT where it can either retard or advance timing, however the tuner chooses.
At least this is what happens for an '85.
Race Director
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From: moraga ca
In reading this thread, I think some of the posters are not differentiating between wot timing and timing at cruise. The 6 degrees initial plus 30 that the ECM adds for a totL of 36 is for wide open throttle parameters. At cruise, the motor can easily see 45 degrees of total timing. Think of it as a vacuum advance added timing
Last edited by 383vett; Jan 6, 2016 at 04:29 PM.