Can someone please explain how timing effects performance, and in what situations one would advance or retard timing? Generaly speaking a N/a engine. I realize it goes hand and hand with cam specs just not sure about what to look at to optimize performance.

Thanks. Jason

 

Id like to see some responses on this subject too. But Id also like to add that it be LT1 or 23 degree head specific.

 

anyone?

 

You may want to try Ye Olde search function. But in short, optimal timing is determined empirically using a dyno (preferred) or trap speeds. It varies according to a large number of variables including:

1. fuel used
2. design of the combustion chamber (size, shape, quench, etc.)
3. design of the piston crown
4. materials used (such as coatings, etc.)
5. fuel used (especially octane and burn rate and type of fuel (gas v. alcohol v. nitrous, v. nitro, etc.)
6 air:fuel ratio
7. operating conditions such as load, rpm, air density and temperature, engine temp., etc.
8. compression ratio
etc.

Rich

 

Timing is all about complete combustion. The goal is to use least timing possible to achieve COMPLETE combustion. By complete combustion that does not mean taking out timing from stock. Stock uses "safe" timing that is not prone to knock.

Many people fall into the trap that you should use the MOST timing possible before knock happens. Also, dont confuse knock with pre-ignition. They are two different beasts. Knock is bad, pre-ignition is REALLY BAD. Knock happens after the spark when you spark too soon and there is a secondary flame created in the cylinder and combusts too soon. Preignition happens when the mixture combusts BEFORE the spark. You can actually lose power by adding too much spark as well. Its best to get it on a dyno and see how the timing works for you.

The purpose for timing is to spark the plug before the piston gets to top dead center. This is necessary to allow for complete combustion to happen at the precise time when the piston is at top dead center.

 

disco... that is what I was after. If anyone wants to add to it feel free. I'm sure alot of guys don't fully understand it. Ye Olde search function only helps one, not the masses that come to advanced tech to learn further.....

Jason

 

Elaborating on disco...

Generally speakign you want the combustion to end at about ~23* ATDC because combustion doesnt do much good past that point. So the earliest you can start pressurizing the cylinder without pushing the piston back down the bore (detonation), the better. Its kindof a balancing act between doing one or the other of the above, the combustion occuring in an engine is always fighting the piston from coming up in the bore to turn around and get its *** pounded back down the bore, but as long as there are other cylinders or a flywheel to keep the inertia high enough, it wont let it work too much against itself that it shuts off.

jon

 

Good stuff... So, say your running an after market ignition such as an MSD box. Does that effect timing at all?

 

It can, when paired with wider gapped plugs. It would allow you to run less lead on the spark to burn up the whole mix, Not much though. Timing is just something you have to play around with to get it right, you could have identical engines and run sligthly different timing on one or the other just because of maybe small imperfections in the CC or a spot of carbon or the way the fuel mixes.

jon

 

Thanks... I got a pretty good grasp now...