Timing Advance

[phatdaddymackc]

How do I know what is a good number when looking at timing advance in the torque app? Mine is so random I am not sure what is good or bad?

[MattStrike]

If you're cruising, only enough to maintain speed, look for 40+. Beyond that, I can't really help.

[Jrs3800]

Timing advance changes with load, air intake temps, TCC lock so on and so forth... Like stated its really variable unless cursing at a very steady speed with low load..

[phatdaddymackc]

So then what exactly is it for then? I read somewhere about timing something and if it was off causing big problems.

[MattStrike]

It is so that the explosion in the cylinder happens exactly at the moment it needs to to be most effective given the driving condition. Basically, you're getting good mileage whenever it's above 40, as you are getting more of the burn while the exhaust valve is still closed - more efficient. Some engine drop to 10 degrees (or less) off idle when you go to WOT, increasing to 20-25 near redline. But to make the WOT power you have to waste some of the burn during the exhaust stroke.

A good simple way to understand this, though not critically accurate, is to think of the force applied from the fuel explosion as a bell curve (area under the curve is the amount of power), and the power stroke as a smaller window on that curve that is your 'useable power' (it shrinks as RPM increases too). The curve length never changes, fuel always takes the same amount of time to burn, but Spark timing controls where the window is on the curve. Injector pulse width determines how tall the curve is.

Dyno tuning come in and measures the area under the curve, to tell you if you're hitting the 'sweet spot'

[phatdaddymackc]

I am just going to admit my brain has just be fried lol. But thanks for that info.

[MattStrike]

You're not the first person to say that. Maybe mine is wired backwards?...

[phatdaddymackc]

I would pay to go back and take half the time I spend on computer, to learn more about my ride lol

[95naSTA]

Just remember.. suck, squeeze, bang, blow. The timing number is how far (in crank degrees of rotation) before the top of the squeeze the spark plug lights off. It's a head start on burning as much as possible.

Too much timing will cause pre-detonation (bang before the spark plug, aka knock). The more load and the lower the rpm, the less timing you'll have. The highest numbers you'll see are at cruise on the highway with the torque converter locked up and the EGR functioning.

Make any more sense?

[phatdaddymackc]

Some what. I have the knock detector plug in for torque, do you know how accurate that is? Is says get to third gear then floor it and it takes a few seconds and tells you if you have knock mine said it didnt but idk how much I should trust it you know?

[phatdaddymackc]

So I was tracking and at cruising my timing advance was like 30, didnt really go over 40. Could that be bad?

[95naSTA]

I'm not sure I ever saw over mid 30s at cruise on the highway with my L36. You should be fine there.

Does the Torque App show KR (knock retard)? That's what's really going to tell you if there's anything going on with your timing.

[MattStrike]

It really depends on a lot of things - fuel grade, climate, altitude, how well the engine is running, etc... My LG3 reported 54 degrees of advance once, but usually closer to 46. My L67 is fairly consistent at 42 degrees during lean cruising.

If you're getting a little KR then bumping up to the next grade of gas (89 instead of 87) may help. If not you may benefit from a tune to push the timing a little further.

[phatdaddymackc]

I get the premium unleaded gas, because that is what it says it takes. Also yes the torque app has the knock retard thing, and it said I didnt have any but I am not sure how much I can trust it.

[MattStrike]

Premium 91 or 93?

[Jfridge92]

I trust the KR on my torque app. It's pretty accurate for the most part on everything else, and as long as your knock sensors are functioning properly, the readings should be correct.