MustangWorks.com : Ford Forums - View Single Post - Total Timing or Computer Timing. What is the deal once and for all!

PKRWUD · 01-27-2002, 06:13 AM

That means your base timing is about 11 degrees advanced, which is just about stock. You could improve things.

To answer you questions:

An engines total timing is the combined total of it's base timing (where you set it at idle), it's maximum vacuum advance (if equipped), and it's maximum mechanical advance (if equipped). You will usually find the engine has reached it's total timing by 3000 rpm. For a stock engine, the average total advance is about 34 degrees.

Your Mustang is electronically fuel injected, which means the ECM (the "computer") takes over the job of advancing the timing for you, so you no longer have a vacuum or a mechanical advance. This leaves you with the base timing. The factory recommends it be set at 10 degrees BTDC, so the ECM is programmed to respond like the timing at idle is set to 10 degrees advanced. If you try and change the base timing, the ECM will try and correct it, and you'll end up with a lousy running engine. So, in order to trick the ECM by advancing the base timing, the signal from the distributor to the ECM must be disabled. This is done by removing the spout connector. When the spout connector is removed, the timing you see at idle with a timing light is the real timing, not computer controlled timing. After the timing has been set, you MUST reinstall the spout connector, so that the ECM can control the advance for you. If you leave the spout out, the timing will not advance when the rpm's do, and you will lose power.

Most people set their base timing to 14 degrees to start, and test and adjust it from there. With 14 degrees of base timing, the total advance is around 38 degrees. An important note to this is if you have a 1986 5.0, and you convert it to MAF, you CANNOT exceed 14 degrees of initial advance (base timing) due to a unique head change that year.

Take care,
-Chris

01-27-2002, 06:13 AM	#2
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	That means your base timing is about 11 degrees advanced, which is just about stock. You could improve things. To answer you questions: An engines total timing is the combined total of it's base timing (where you set it at idle), it's maximum vacuum advance (if equipped), and it's maximum mechanical advance (if equipped). You will usually find the engine has reached it's total timing by 3000 rpm. For a stock engine, the average total advance is about 34 degrees. Your Mustang is electronically fuel injected, which means the ECM (the "computer") takes over the job of advancing the timing for you, so you no longer have a vacuum or a mechanical advance. This leaves you with the base timing. The factory recommends it be set at 10 degrees BTDC, so the ECM is programmed to respond like the timing at idle is set to 10 degrees advanced. If you try and change the base timing, the ECM will try and correct it, and you'll end up with a lousy running engine. So, in order to trick the ECM by advancing the base timing, the signal from the distributor to the ECM must be disabled. This is done by removing the spout connector. When the spout connector is removed, the timing you see at idle with a timing light is the real timing, not computer controlled timing. After the timing has been set, you MUST reinstall the spout connector, so that the ECM can control the advance for you. If you leave the spout out, the timing will not advance when the rpm's do, and you will lose power. Most people set their base timing to 14 degrees to start, and test and adjust it from there. With 14 degrees of base timing, the total advance is around 38 degrees. An important note to this is if you have a 1986 5.0, and you convert it to MAF, you CANNOT exceed 14 degrees of initial advance (base timing) due to a unique head change that year. Take care, -Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!