Question on 454 Spark Timing

[N0DIH]

I am looking at the 454 spark map on a 2000 for the C3500 truck, mainly as a guide to my 99 K2500 454 Suburban (anyone have a OEM for this truck?).

Ok, there is the Optimal Timing Map (B1040), and then the Main Spark Advance (B5913), and then the ECT (B5910) and IAT (B5911) tables.

How is the Optimal timing map (B1040) used? From what I gather the Main Spark Adv map is the timing used, and the add/subtractions come from the other tables as needed. OR is the OTM the main one used?

I never see anywhere close to the timing on the OTM. Even mine is tuned by Jesse, (not sure what he programmed in) and timing seems quite low under power.

I would expect more like 32-36 degrees at WOT, but I see in the teens.

Is there any place I can do some more reading on how the timing is determined from the maps to actual?

[wait4me]

My programs use tables differntly than stock. What you are seeing in the tables in any of those spark ones are not even going to be used the same as a factory computer.

If you want to tune your own, i can send you a stock file to use. Then the tables will be working the way the software says it does.

[wait4me]

Another thing, you dont want to put 32 degrees in the timing tables at wot. you will eat a piston.

[N0DIH]

Maybe my datalogger (one of those ELM ones) doesn't show real timing? Maybe I am seeing it off more than the datalogger shows?

Maybe it is just me, but the 454 makes ok power, but honestly for a fuel injected 454, with OD and 3.73's, it gets worse mileage than a 76 Olds Delta 88/98 (EPA rated 12/18, which is actually pretty close to reality) with a carb'd 455, no OD and 2.73 gears. And the weight is within 600 lbs of each other 5000 lbs vs 5600 lbs. And aero for the 88/98 is not exactly great either, like the truck (A suburban). But the truck is worse, but is it really that much worse?

Why the mpg in the 10-11 range city/highway combined? I just feel it should be more like 15-16 highway with all the modern goodies the L29 has (OD, Tuner Port EFI, modern cyl heads, fat duals, streamlined exhaust manifolds). I have heard of an occasional 454 owner getting 15-16 but they are few and far between and I can't verify. But mine has never seen over 13.2 and that was stock tune, and that was the first tank of gas on it, pure highway.

With your tune (Wait4Me), it pulls like a freight train, but upper rpms aren't fantastic, but then again, probably cam restricted, heads flow good, manifolds are a decent design, fat 2.75" mandrel bent duals into one probably pretty restrictive muffler. So it has the makings that it should be better than it is.

Am I just expecting too much out of a Mark IV BB? Are they really that inefficient? I drove an untuned 350 Burb recently, same gears, tire size, etc, and there is no comparisson, I am not going back to an L31... No way..... Just not fun to drive compared to the 454.