Dyno'd it - not happy at all....

[DZEE'S LX]

My Mustang club rented a day on the dyno so I finally got some #'s to chew on.

Best number was 252 which is way lower than I expected. At 18% loss that puts me at 297 at the crank. The dyno operator said the number is already calibrated for our 4200 ft elevation but I'm not completely convinced of that because the correction factor on my printout was 1.15 while other cars on the same day were 1.16. I'm wondering if that might have been a correction for temperature or humidity? This is all wishful thinking cause I'm just looking for an excuse to add more to the number.

What was strange to me is that I was running too much fuel pressure. After the 2nd run he said my a/f was way fat and told me to take the pressure down. I had guessed at 48 psi thinking that with my mods I could use the extra fuel at top end. I asked him what to set it at and he said 38. I didn't really believe him and set it at 42 cause I had it stuck in my head that I MUST need more fuel. Anyway, I went from 247 to 252 on that last run. He said I probably would have picked up 10 - 15 if I let the engine cool. It sat there on the dyno idling for a good 5 minutes while I got my tools out and adjusted the pressure. He said the whole engine was probably completely heat soaked during that 3rd run.

So my question is, how can it be that lower fuel pressure means more power? The guy running the dyno is a longtime 5.O dude and he says his highly modified (no pwer adder) engine puts out the best numbers at 44 psi. (and I'm sure he tunes all the time on the dyno since he is a part owner).

??