Advancing Your Base Timing - Why Do It?

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Dec 14, 2005 | 08:10 AM

90Indy

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From: Forney Texas

Advancing Your Base Timing - Why Do It?

I was thinking the other day, I know a very dangerous practice, about the setting of base timing. I have a 90 L98 and I understand the reason for disconnecting the ESC wire. I know you need to set the engine up at what the ECM sees I'll say as "0" so it can work from a known starting point to adjust the timing according to current operating conditions. What I don't understand is why set the base timing from what the ECM sees as "0" (6 deg ATDC) to say 8 deg ATDC. Is this 2 degrees of timing advance carried forward when the ECM makes its timing corrections? Or does this 2 degrees of advance only help with getting started from a dead stop until the ECM begins to see and adjust the timing based on demands being placed on the engine?

I have my base timing set at 8 deg ATDC but I really don't know if I am doing any good or bad.

90Indy

Dec 14, 2005 | 09:00 AM

mseven

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From: The Motor City

It was my understnading that the timing is then carried up globally.
What I know is that when I had it apart, the dampner was not exact to TDC as measured w/a piston stop and a dial indicator mine was 2* off. Because I belive in a good tune on the chip I set after the re-build to what was 6* on mine and let the computer do the work.
Before this was done I had tried a few different different settings and 8* seemed to work fine (FWIW 8* actually is 6 on mine after later examination of TDC).

Dec 14, 2005 | 09:10 AM

rick lambert

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From: seattle WA

My 87 just seems to run better at 8, 109,250 miles on her stock engine.Haven't checked but I imagine total timing starts at this point and would advance an additional 2 degrees.

Dec 14, 2005 | 10:53 AM

vader86

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Its carried forward from 8* advanced, and the L98 likes timing.

Dec 14, 2005 | 11:09 AM

Grenkepr

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From: Lewisvlle NC

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Dec 14, 2005 | 11:12 AM

hippy

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Quote:

Originally Posted by vader86

and the L98 likes timing.

I don't necessarily disagree with this statement BUT my old car didn't care where the timing was initially set at. I tried up to 12 degrees on the dyno and showed virtually no HP improvement. I stuck with 6 on that car or close to it.

Last edited by hippy; Dec 14, 2005 at 11:16 AM.

Dec 14, 2005 | 02:32 PM

RacerX70CC

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From: Cape Coral FL

Indy,
I think you mean BTDC (Before top dead center) ATDC is AFTER top dead center and at 8 ATDC, you'd have a slug of a ride.

Dec 14, 2005 | 02:46 PM

CFI-EFI

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From: The Top of Utah

Quote:

Originally Posted by 90Indy

I have my base timing set at 8 deg ATDC but I really don't know if I am doing any good or bad.

90Indy

First, if you are setting your timing at ANYTHING after top dead center (ATDC) you are running severely retarded and the performance should be super crappy. I hope that is a typo for BTDC. The problem is that you used it too many times to be a pure typo. Also, 8° ATDC is not advanced from 6° ATDC, it is retarded.

Your ECM has no way of reading or sensing the timing of the engine, unlike the fuel mixture or the idle rpm. The amount of advance for any given set of circumstances is programmed into your prom. The prom was programmed from the specified 6° BTDC base setting. As previously stated, any deviation from the specified base timing affects all the timing numbers, "globally".

Whether you are, "doing any good or bad" is based on YOUR testing, experimenting and YOUR results. If you "really don't know if I am doing any good or bad", then I'm guessing there is no point in leaving it different from the specifications.

RACE ON!!!