How much timing we talking wot? What afr you at?
How much timing we talking wot? What afr you at?
i helped tune a 5.3 the other day. they really dont seem to like (or require) a bunch of timing, probably because they have a pretty damn efficient combustion chamber. 28 degrees wot all-in is sooo much for that engine imo
Shell/Chevron 93 is the only thing I recomeend people around here to use. Well E85 is better in a Flex Fuel.
The truck I tuned was 4.8 with milled ported 243s in a RCSB truck.
The 5.3s I have tuned are as you guys have said 24-26* total. I think the short stroke/long rod makes the 4.8 want a little more timing.
The old L31 engines do not like a whole lot of timing with the stock cams either.
We did however recently have some kind of gasoline reformulation. I had been running 89 octane, KNOCK FREE on 32-33* total timing in my Titan. Suddenly it was picking up knock activity at WOT, no actual timing retard yet though. Nothing more than a few months time and a noticeable change in gasoline quality. Computer even picked up the change and adjusted the ethanol % accordingly. I am thinking we are getting more than 10% in most batches here. I am glad that I logged it, moved up to 93 octane and retarded the timing 2*, before I hit it with the 75 shot.
89 K1500 Scottsdale 5.7L 5spd 3:42 RamJet cam Dart iron TBI heads 427 PCM swap
95 C2500 Cheyenne 6.5L turbo diesel 4L80e 4:10 DB2-4911 Manual pump conversion 0411 PCM trans control 2Bar COS
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I'd have to look at the calibration but it is the stock High Octane table timing... by rights it should not be knocking, on stock motors that have been running high octane I've seen no knock retard to 1*. At one point in a log it was only getting 10* and pulling 8* timing.
The GM.ASPARK PID is still at 70% as well, so thats 70% High Octane and 30% low octane table for spark advance. Don't think the knock sensors were over tightened, the owner of the rig is a certified tech and owner of the shop as well as aware of knock sensors being sensitive to torque. He checked today and the were not AC/Delco but Delphi replacement sensors.
AFR is about 12.5, I've set it up VIA EQ Ratio at 1.16.
The oil is interesting! We'll be pulling plugs tomorrow for a look. This is a brand new motor and maybe 500 miles on it. No notice of any oil burning or loss. Also going to try turning off the knock sensors and see if they are the issue...
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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