My 385 LT1 Dyno Graphs need some input
09-20-2008, 05:29 PM
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My 385 LT1 Dyno Graphs need some input Whatsup everybody. I'm trying to get my car in working order asap since the track is about to close soon for winter. I took the car to the dyno so I could tune WOT. Well I had one god run 453 rwhp and 405 tq. The other runs I was playing with the timing to see where I made the most power. However they all looked like the second graph. The car started to fall on its face at like 5K. Anybody know what might be causing this? Both graphs below had identical tunes.
09-21-2008, 12:29 AM
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custom grind comp cam and some crane springs. not sure on the exact part # and installed height on the springs though. i bought some springs that didn't fit properly and my builder then got me some crane springs with about 130lbs of pressure on the seat. going to them on Friday to get the exact specs and get my valve lash adjusted.
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09-21-2008, 06:52 PM
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maybe. when i take the car to my builder im going to have him check the whole valvetrain. any way to test to see if my coil to see it is still functioning properly?
i did notice that even though my tune was set for a certain amount of timing datamaster was showing 3 degrees more.
i did notice that even though my tune was set for a certain amount of timing datamaster was showing 3 degrees more.
09-21-2008, 07:21 PM
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so when you removed the msd opti and replaced it with the stocker you had better results? also does the fact that datamaster was reflecting 3 degrees more timing than my tune lead you to believe i have a opti problem?
09-22-2008, 01:58 PM
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alright all i should have looked at the obvious. The car's afr was rich throughout all the runs. However the car likes to run reall rich. All 370ish pulls the afr was 12.2-6. On the 453 run it was 11.4-8. This is consistent witht the very first time i tuned the car myself last year with the 355 & same cam. Car made in the 350 range at any afr around mid 12s. When I set it at 11.8 it made 396hp.
I've read in books and online that NA cars should be around 12.7-13.0 at WOT but seems like mine likes a lot more gas. like i said i only messed with tming this time around so i don't know how it got so rich on that one particular run. I'll be back at the dyno to play with the afr to confirm my findings right after i get the valve las adjusted and make sure the springs are okay.
I've read in books and online that NA cars should be around 12.7-13.0 at WOT but seems like mine likes a lot more gas. like i said i only messed with tming this time around so i don't know how it got so rich on that one particular run. I'll be back at the dyno to play with the afr to confirm my findings right after i get the valve las adjusted and make sure the springs are okay.
09-22-2008, 03:57 PM
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yes the OEM Opti took place of the MSD and we never seen any other issues
now I'm sure some have had good luck with the MSD, but we have not and no longer chose to use them
now I'm sure some have had good luck with the MSD, but we have not and no longer chose to use them
09-23-2008, 02:45 AM
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I had a similar problem like this with my stroker--it fell in its face anytime I got into full throttle.
I had a GM tech go through everything and discovered I had a bad mass air flow meter. It's something you can rule out in a few minutes if you can borrow one for a quick test.
I also had a similar problem several years earlier. The same GM tech discovered both my plug wires and optispark were bad. Once replaced, the car ran fine.
I had a GM tech go through everything and discovered I had a bad mass air flow meter. It's something you can rule out in a few minutes if you can borrow one for a quick test.
I also had a similar problem several years earlier. The same GM tech discovered both my plug wires and optispark were bad. Once replaced, the car ran fine.
09-23-2008, 06:19 AM
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sounded like a fuel issue to me.. only other thing i was thinking was valve float but leaning torwards the running way too rich
lol imagince this happening???? WOW!!!! such a shame that these optis that are almost a third more the money suck worse than an original part haha...
if you go with aftermarket you should prolly hit up dynaspark not ACCEL or MSD....BOTH CRAP and will make your car on its face after about 5000 to 5500rpms...or they will just fail on you..lol
if you go with aftermarket you should prolly hit up dynaspark not ACCEL or MSD....BOTH CRAP and will make your car on its face after about 5000 to 5500rpms...or they will just fail on you..lol
