77f250diesel
Full Access Member
I was looking to get a better understanding of the advance/retard on the db2 inj. pump and came across this on the 6.2/6.5 forums.
In regard to timing with the pulse-adapter - it's really meant for a relative reading of timing advance - more than a specific reading. It WILL tell you how much the advance is travelling. If the advance wasn't working at all - the engine would skip and smoke when you revved the engine - especically when cold or no-load.
Ford doesn't give general timing specs for the 6.9 or 7.3 - it all depends on what the engine is installed in, specific cetane of the fuel being used, and the altitude the engine is being run at. Actual timing inside the combustion chamber (as seen by a luminosity probe) can be set anywere from 8 degrees BTDC at 2000 RPM, to 7 degrees ATDC at 1400 RPM. Using a pulse-adapter is going to be quite different since it reads earlier than the actual time of combustion. Often 6 to 12 degrees earlier than timing with a luminosity probe. A good ballpark though - with the pulse adapter is 13-15 degrees BTDC at 1600 RPM.I remember awhile back Mel telling me a properly timed idi [6.9/7.3] will be at 19 deg. at idle when timed at 8.5 @ 2000 rpm.
I checked my timing after reading this and it's 8.5 @ 2000 rpm but only 13 deg. btdc at idle, 650 rpm. using my pulse adapt..
So obviously if we're using a pulse adapt. we have to adjust for the difference between the "pulse" and actual ignition.
I was going to try advancing mine to the 13-15 deg. btdc as quoted but what I didn't understand is why 2000 rpm/luminosity and 1400 rpm/pulse ?
Sorry for the long post but there are some of us that thought we were timing our trucks right and I guess we're still retarded.
Dennis
