advance - retard basic question

[Machnumber2]

To advance the timing that that mean that you want the spark to fire when the piston is closer to top dead center? Or is that to retard the timing?

Secondly, when you add higher octance fuel than the car was made for, do you want to advance or retard the timing in general?

Appreciate any comments, love this site, thx

[neileg]

If you advance the timing, you move it to a point earlier in the combustion cycle. Since ignition is usually triggered as the piston is rising on the compression stroke, then this means that advancing the timing means the piston is further from TDC.

In general, advancing the timing tends to increase the chance of detonation (knocking or pinging) and a higher octane fuel will help prevent this. In some engines, advancing the ignition will improve combustion, but this is not always the case. It's not the higher octane fuel that gives you more power, it's the ignition advance.

[mbdoc]

What car??
ON a 1988 190E 2.3 timing cannot be adjusted!

Higher octane fuel doesn't make for better running or more power unless the engine was designed for it!
The 1988 190E 2.3 has 9/1 compression & should run on 90-91 octane.

[Machnumber2]

Thanks for the info. Btw this is not for my car I just keep seeing the terms out there and wanted to check what they meant.