Attention: TDR Forum Junkies I am new to the TDR sight. I have Been looking at the website for quite some time, so I finally signed up. I have some thoughts regarding Fuel economy and injection timing that I would like to share. please keep in mind that these are My theories and opinions. I certainly cannot say much of it is fact, so I would like to get your feedback as well, to determine if any are indeed facts.
First the known facts:
1) our P7100 pumps have no provision for adjusting timing in relation to engine speed. If start of injection occurs at 14 degrees BTDC at 500 RPM, it is going to occur at 14 degrees BTDC at 2500 RPM. (this is in theory. reality may be a little different, but not enough to affect this dicussion)
2) timing and engine speed go hand in hand to provide best economy.
now for the theories:
1) Timing is generaly recommended to be set at 15-16 degrees before TDC. for folks that are doing high performance, you need best economy at high RPM's. For folks like myself, Economy cruising down the road is more important than a few tenths of a second at the racetrack.
A) there is a time lag between when fuel injection begins, and when the burn begins. this time constant will not change with RPM.
B ) proper timing at high speeds (18-19Degrees) will provide good economy at high speeds. At slow speeds, the burn can start before TDC, resulting in very high cylinder pressures, & all the bad things come with that.
C) timing set for slow speeds (12-13 degrees??) you will have an efficient slow speed, but the fuel will be late it high speeds, causeing inefficiency.
I propose that folks who have high gears, & drive at slower speeds might benefit from a slightly later pump timing. Maybe 12 or 13 degrees BTDC.
I am willing to give this a try, by turning my timing back to the stock 12 degrees BTDC To see what kind of results I get, but it will take me a month to put on enough miles to check.
Please let me know if any of you have knowledge with this sort of thing. Obviously the primary factors are cruising RPM, MPG, & Degrees BTDC Timing. I Don't want to waste time with this if My theories are Wrong!
Thanks in Advance, P.
First the known facts:
1) our P7100 pumps have no provision for adjusting timing in relation to engine speed. If start of injection occurs at 14 degrees BTDC at 500 RPM, it is going to occur at 14 degrees BTDC at 2500 RPM. (this is in theory. reality may be a little different, but not enough to affect this dicussion)
2) timing and engine speed go hand in hand to provide best economy.
now for the theories:
1) Timing is generaly recommended to be set at 15-16 degrees before TDC. for folks that are doing high performance, you need best economy at high RPM's. For folks like myself, Economy cruising down the road is more important than a few tenths of a second at the racetrack.
A) there is a time lag between when fuel injection begins, and when the burn begins. this time constant will not change with RPM.
B ) proper timing at high speeds (18-19Degrees) will provide good economy at high speeds. At slow speeds, the burn can start before TDC, resulting in very high cylinder pressures, & all the bad things come with that.
C) timing set for slow speeds (12-13 degrees??) you will have an efficient slow speed, but the fuel will be late it high speeds, causeing inefficiency.
I propose that folks who have high gears, & drive at slower speeds might benefit from a slightly later pump timing. Maybe 12 or 13 degrees BTDC.
I am willing to give this a try, by turning my timing back to the stock 12 degrees BTDC To see what kind of results I get, but it will take me a month to put on enough miles to check.
Please let me know if any of you have knowledge with this sort of thing. Obviously the primary factors are cruising RPM, MPG, & Degrees BTDC Timing. I Don't want to waste time with this if My theories are Wrong!
Thanks in Advance, P.
