CAS sensor and BOVs

[caribougtr]

Well I had the CAS out this winter to do the timing belt ect. Have her all back together and just eye balled it in position to where I remember it. The car drives fine and no timing light.

There is a cracking noise at high boost. Asked my dad in which is a mechanic and he says it does not sound like knocking. I did put new blow off valves and and loosened them way off and have been tightening them one turn at a time. The noise does seem to be getting better...

Question is do I need to do the timing with a light? My Toyota mechanic friend and my dad say if I get it close the computer should compensate if the CAS is out a bit...

Thanks

C

[nimblestix]

Do it with a light! It can change base map by as much as 40°.
Good luck

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[Skym]

You need a timing light to set CAS correctly.

If sounds like nails inside engine at higher rpm, CAS is probably too advanced. If CAS is adjusted wrong (too advanced), engine could start knocking. ECU probably will then compensate by pulling ignition timing. But it depends where engine starts knocking. ECU doesn't look for knock at higher rpm (engine is too noisey), so probably won't compensate.

The CAS is used to get a base timing figure BTDC. ECU via ignition map adds ignition timing to that figure to get ATDC where it fires the sparkplug. Also CAS tells ECU when to open injectors. If pull CAS off and turn key to 3, then turn CAS shaft, you'll hear injectors click.

BTDC (Before Top Dead Centre or before piston reaches top of cylinder and stops moving)

ATDC (After Top Dead Centre or when piston is moving downwards in cylinder)

[caribougtr]

Ok great guys thanks I will search out a timing light next week when I am off shift!

And thanks for the in depth explanation SKYM!

C

[caribougtr]

Anyone know the name of the timing light I need? I understand its not the conventional on that clamps on the spark plug wire on #1 cyl. Crap tire sell them?

Thanks