2003-04 Mach 1 Registry Owners Club - View Single Post

Ricksterman · 01-06-2005, 07:52 AM

CY-Mach1,

Certainly the torque curve is flatter. I still have the "dip" in both HP and TQ but not much. The only change between the two runs is the custom tune, so timing would be the most likely possibility, since there wasn't much of a temperature change between the runs.

Yes I've also heard that 13.1 is the best ratio for power, but most of the time the AFR is measured after the cats, so the actual engine AFR is lower (0.5 point is one estimate I've read). 13.3-13.5 is consistant with what I saw on the dyno. I've tried lower AFR's (12.1-13.0) and I've lost both HP and TQ. I say you're in the right ballpark for AF.

If you look at my last post, you'll see my timing curve(s) (with the latest tune) now go up (too much really). Timing is adjusted based on a number of parameters. My knock retard is disabled, and temperature has been pretty constant for most of my runs. I would expect different timing for 3rd and 4th since the calculated load would be more variable. I did all my datalogging WOT in second gear to avoid that, so very good point btw. The tuner has this data also, and hopefully will get back to me as to why my Predator cant retard the timing between 2.5-3.5 K.

I am debating doing one more dyno pull now that I have 28+ degrees through redline, but that's another 50 bucks, so I may wait until I get the ported intake installed.

01-06-2005, 07:52 AM	#17
Ricksterman Registered User Join Date: Aug 2004 Location: Albuquerque NM Posts: 253	Re: Predator revisions and timing PART DEUX CY-Mach1, Certainly the torque curve is flatter. I still have the "dip" in both HP and TQ but not much. The only change between the two runs is the custom tune, so timing would be the most likely possibility, since there wasn't much of a temperature change between the runs. Yes I've also heard that 13.1 is the best ratio for power, but most of the time the AFR is measured after the cats, so the actual engine AFR is lower (0.5 point is one estimate I've read). 13.3-13.5 is consistant with what I saw on the dyno. I've tried lower AFR's (12.1-13.0) and I've lost both HP and TQ. I say you're in the right ballpark for AF. If you look at my last post, you'll see my timing curve(s) (with the latest tune) now go up (too much really). Timing is adjusted based on a number of parameters. My knock retard is disabled, and temperature has been pretty constant for most of my runs. I would expect different timing for 3rd and 4th since the calculated load would be more variable. I did all my datalogging WOT in second gear to avoid that, so very good point btw. The tuner has this data also, and hopefully will get back to me as to why my Predator cant retard the timing between 2.5-3.5 K. I am debating doing one more dyno pull now that I have 28+ degrees through redline, but that's another 50 bucks, so I may wait until I get the ported intake installed.