Timing measured with timing light does not match Powerlogger timing. Why?

[10SECV6]

So a few weeks ago I posted about my car not really running the times and mph expected given the number of mods. Here is the thread: http://www.turbobuick.com/forums/th...-why-is-my-car-not-quicker-than-it-is.406377/.

Following some of the advice received, I started creeping up on WOT timing. I added 2 degrees of timing over what was in the Turbo Tweak alcohol chip already. The car did not knock at all at 26-27 psi with the added timing, so I added 2 more degrees of timing at WOT for a total of 4 degrees over what is in the tune already. Still no knock. So I added more timing for a total of 7.7 degrees over what is programmed into the chip, which I believe is around 21 degrees for an alcohol tune. Finally I got a slight bit of knock. The Powerlogger file showed 31 degrees of timing with 27 pounds of boost and 2 degrees of KR, which went away quickly. Obviously, something is not right...

So I decided to check the base timing with a timing light. I jumped the A & B pins at the ALDL connector to put the car into ALDL mode. Timing measured at the balancer with a timing light showed a perfect 15 degrees, but spark advance measured at the same time with the Powerlogger showed 25 degrees.

Why would the ECM/Powerlogger see timing as 10 degrees higher than actual timing measured with a timing light? Is this normal? If not, what do I need to do to correct it?

Thanks.

 

[Jerryl]

Deleted. Don't need to post info. that's inaccurate. :-(

 

[pacecarta]

y

 

[TurboBob]

module timing is 10 degrees.

aldl test mode timing is 15 degrees, and the software in the ECM overrides the chip calculations. The powerlogger is reporting the chips "normal mode" calculations.

stick a dime in the throttle stop, the RPMs should wind up around 1000 or so, see what the PowerLogger shows, and compare to the timing light. (no ALDL jumpers for this test)


Bob

 

[earlbrown]

Keep in mind, the #1 journal can be a little bit off, the snout keyway can be a little bit off, the balancer can be a little bit off, the regulator ring can be a little bit off, the crank sensor bracket can be a little bit off, the crank sensor itself can be a little bit off.....

.......and the timing tab can be a little bit off.


That's a whole bunch of 'little bit offs'

 

[10SECV6]

module timing is 10 degrees.

aldl test mode timing is 15 degrees, and the software in the ECM overrides the chip calculations. The powerlogger is reporting the chips "normal mode" calculations.

stick a dime in the throttle stop, the RPMs should wind up around 1000 or so, see what the PowerLogger shows, and compare to the timing light. (no ALDL jumpers for this test)


Bob

I'll give that a try to see if the ECM is seeing a different timing number. Thanks.

 

[10SECV6]

Keep in mind, the #1 journal can be a little bit off, the snout keyway can be a little bit off, the balancer can be a little bit off, the regulator ring can be a little bit off, the crank sensor bracket can be a little bit off, the crank sensor itself can be a little bit off.....

.......and the timing tab can be a little bit off.


That's a whole bunch of 'little bit offs'

Makes sense. It certainly seems that something is off. Thanks.

 

[greeneyegi]

ive been searching for the sticky for checking the timing with a light......anyone got a link?

 

[87-WE2]

It's the top sticky in this section (general tech).

 

[we4Mateo]

http://www.turbobuick.com/forums/threads/verifying-ignition-timing.377617/

 

[greeneyegi]

Wow, I was tired or just blind, thanks guys...