modified 502mpi intake on 502 dyno session at my shop
01-25-2016, 10:30 PM
#11
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Well so far ths is what we have, day 1 started out in the 520 hp range/540 ft lbs of tq, , tuned afrs/timing etc and ended at 536.8 hp at 5500 and 563 ftlbs of tq at i think 4200 (on 93 octane shell that I tested at less than 4% "other" ie- ethanol, additives etc) the hp peak however was close at 5600 at 534.4 and 535.8 at 5400, the tq peak was similar. Being less than 2 or 3 hp and ft lbs of tq/hp from the peaks slight tuning changes moved the numbers around these flat peaks. Day 2 we cleaned up some part throttle stuff doing steady state pulls , made the mistake of NOT doing a base run in the morning with previous days tune to see where I was at, big mistake. Motor was going on a rev limiter somehwere in software at 5750 that doesn't show anywhere on mefi burn , we werent sure if it was ignition breaking up or what so before we turned the key on day 2 I swapped in a DUI ign module into the TBI style distributor for the stock mercruiser one in the distributer. I have had good results in past with these and expected the same. Also switched to shell 89 octane as this is a 8.6/8.7 to 1 motor and really should not need 93 Made pull, motor was down about 20 hp and ft lbs tq, pulled all plugs looked perfect, checked and re-checked everything, checked weather data input to depac, nothing wrong. made second pull still down, tested alchohol content of the 89, surprising lt was under 6% other so not loaded down with ethanol. Drained all 89 out, put 93 back in from same batch as original, made pull, no real differnece, not the fuel. Swapped dui ignition module back out for 16 year old mercruiser, bam, made 534-536 again.
01-25-2016, 10:50 PM
#12
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So day 3, base lined around 535hp, went to 38 degrees total timing on 93, no real change, switched back AGAIN to the 89 octane, surprisingly had 1.7 degrees of KR on 89 octane at 38 total (remember this motor is ONLY 8.6/7 to 1 and has bigger cam then stock 502 mpi which merc says will run fine on 87 octane with more compression). Keep in mind other than base testing day to day/chasing bad components I was also tweaking on part throttle fuel tuning and wot afr's. The tuning (other than first day getting it to 536 hp) didnt really increase peak numbers but did get motor fuel safe and widen the curves.
AFTER seeing KR on the 89 I reduced total timing to 36 degrees on the 89 octane and bam we made 540 hp/564 ft lbs of tq, outr best numbersyet, the motor makes best hp on 89 BUT is timing sensitive! Funny thing is the 540 hp was at only 5300 but we still made 536 at 5400 and 534.7 at 5500. I also attached a STOCK 2000 gen 6 502 mpi flame arrestor and hp nose dived to 510 at 5400 and tq dropped to 537 ft lbs at 4100. Now , keep in mind ALL of this testing was with my biggest throttle body, a tpis with 58 mm throttle blades. I will be doing more testing at end of this week with smaller bored out throtlle bodys and stock throttle body, home brewed flame arestor mods, try to solve thd dui ignition module mystery and will post, Smitty
AFTER seeing KR on the 89 I reduced total timing to 36 degrees on the 89 octane and bam we made 540 hp/564 ft lbs of tq, outr best numbersyet, the motor makes best hp on 89 BUT is timing sensitive! Funny thing is the 540 hp was at only 5300 but we still made 536 at 5400 and 534.7 at 5500. I also attached a STOCK 2000 gen 6 502 mpi flame arrestor and hp nose dived to 510 at 5400 and tq dropped to 537 ft lbs at 4100. Now , keep in mind ALL of this testing was with my biggest throttle body, a tpis with 58 mm throttle blades. I will be doing more testing at end of this week with smaller bored out throtlle bodys and stock throttle body, home brewed flame arestor mods, try to solve thd dui ignition module mystery and will post, Smitty
01-26-2016, 09:18 AM
#17
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As mentioned in beginning, no custom cam since motor is for my old 272 im selling, its a used stock hp 500 efi roller cam , which im told is a crane 129621. 230/236 at .050 598/610 lift on 114, it was chosen becaue it was the smallest used cam i own and had to idle with gil manifolds once in boat. The dyno headers are a set of 2 1/8 chassis headers for a 62 chevy drag car, i extended the collectors a foot
01-26-2016, 10:03 AM
#19
