Timing advance

[OH71RRunner]

I'm somewhat confused about timing advance.
I understand that as your RPM's increase, you want the timing to advance to keep up with the RPM's.
What I don't understand is what determines how and when your timing should be ALL IN. Is it a preference?Wouldn't you want your timing to continue to advance the higher the engine revs? Is there a certain point that the advance makes no difference?

Thanks in advance.

 

[Ranger16]

Don't quote me on this as I am far from an expert, but my understanding is that 35 or 36 degrees is max for any engine (if that's what you are asking).
I once read a very good explanation, but can't find it now.

 

[RJRENTON]

Timing depends on many variables: compression ratio, valve timing, cylinder head/combustion chamber design, and of course fuel being used.
Many new cars use GDI (gasoline direct injection) where the fuel is injected micro-seconds b4 the spark occurs. Wiith high compression for efficiency, the principal of latent heat of vapor vaporization occurs, actually cools the combustion chamber temperature to below the auto ignition point (detonation), while the knock sensors keep the spark advanced to the maximum tolerable. How much dpark advance is correct? .... it depends on the individual and engine.
Bob Renton

 

[Yatzee]

I'm somewhat confused about timing advance.
I understand that as your RPM's increase, you want the timing to advance to keep up with the RPM's.
What I don't understand is what determines how and when your timing should be ALL IN. Is it a preference?Wouldn't you want your timing to continue to advance the higher the engine revs? Is there a certain point that the advance makes no difference?

Thanks in advance.

When you purchase better distributors they come with spring kits and instructions to delete the vacuum pot if you want only mechanical advance. They also have instruction sheets showing the advance curve ( based on rpm ) that you can achieve by utilizing the various colored spring sets. My engine has all timing in at about 3200 rpm. If I planned to run at really high rpms I would want my timing all in at about 4500 - 5000 rpm. But alas it all depends on the build of the engine as stated above. Best performance is a trial-and-error thing that gets it roots from the way the distributor is set up. You can see various advance curves by viewing instructions from MSD, FireCore and others online - it really is a bit of an art.

 

[dieseldazzle]

Timing depends on many variables: compression ratio, valve timing, cylinder head/combustion chamber design, and of course fuel being used.
Many new cars use GDI (gasoline direct injection) where the fuel is injected micro-seconds b4 the spark occurs. Wiith high compression for efficiency, the principal of latent heat of vapor vaporization occurs, actually cools the combustion chamber temperature to below the auto ignition point (detonation), while the knock sensors keep the spark advanced to the maximum tolerable. How much dpark advance is correct? .... it depends on the individual and engine.
Bob Renton

Damn, beat me to it. Exactly what I was gonna say.


Lol j/k Bob. Great explanation.

 

[OH71RRunner]

Is there a time that you would want your advance to come in sooner? Is it best to have the curve throughout your given RPM range?

The reason I'm asking about this is because I was having timing issues. I have an MSD distributor and trying to follow others' setups but my timing seemed to be coming in too soon. I've switched to one heavier spring and one lighter one. It seems to be running better but might try two heavier springs.

So I'm trying to figure out how to determine where and how to set a timing curve for any ideal setting.

 

[Fran Blacker]

http://www.onallcylinders.com/2014/09/05/ask-away-jeff-smith-basic-guide-ignition-advance/

http://www.onallcylinders.com/2015/...rstanding-vacuum-advance-and-why-you-need-it/

 

[OH71RRunner]

It sounds like I need to experiment with different spring combinations to figure out what my engine prefers. As long as I figure out what my total is, then I can figure out where my curve should be based upon how my engine responds while driving.

Thank you all for your input.

 

[miller]

I've always prefered mechanical advance, so I can get exactly what I want. But, the guys are right...no two engines are alike, unless bone stock. Usually, but depending on the build, full advance is around 2000.
You choose advance springs, yeah, even different ones, to adjust the advance rate, or how slow/fast the advance comes in. Also, think of this, while the spark advance is at rest, timing is 'retarted', that makes it easier for the engine to start. Advance comes in, peaks at given RPM, and timing is good for the remaining RPMs. If that makes any sense.
Your engine will let you know!

 

[RJRENTON]

Looks like good old Jeff Smith works for MSD and drives a GM product. Does that make him correct (right) or incorrect (wrong) or is it just an opinion....and I'm sure everyone has heard about opinions.
Caviet emptor definitely applies....or paraphrasing, what you do to your own car is up to you.....if it fixes the issue..great, if not, blame it on someone else.
Bob Renton