test advance, timing light and ref and sync

[yotamhks]

i got around intresting info and i am confused.
i tuned about 40-50 cars but so far i only did this with ref only mods. i havn't used anywhere the sync option.
currently i have three cars that are ref and sync mods in them.
i alaways set up test advance through 0, 10 , 20 deg. i use a very reliable snap on timing light with digital advance
set up.

i heard that when you test advance with ref and sync, you shouldn't test with nothing other than 0. if you set it
up in ecu to be 20, your timing light should read 10, but in the engine itself it would be like 20 deg of advance.
any true in all of the above?

[RossB]

There is no difference with the use of test advance on a mode that uses a sync sensor. The important thing to look out for is that sometimes a timing light with a dial back function may not give an acurate timing value so you should use a light without this feature or set the timing light to zero and rely on the timing marks on the engine to determine if the CRIP is correct or not. There is no need to check more than one test advance value, if you check it at 20 degrees there is no need to check it at 10 degrees. Check the CRIP at idle speed and then at high RPM, if the CRIP is not the same at high RPM you can correct this by adjusting the Ignition Delay Time in your ignition setup.

[yotamhks]

just another kind of question,
from your experiance ans knowledge,
what is the differance in crank index teeth when synced and not synced modes are used?
would it vary alot or small numbers?