That's why I say I watch for less throttle effort, when I log, I compare the tps and kpa readings before/after and try to get the timing where it minimizes the amount of throttle it takes to accel vs before. On the kr, u usually only see kr on transient cells under low rpm high map load so, when I see the kr I will come back a few degrees from that.

 

And I agree about wot timing, the better the head design the less timing needed. I usually never run over 29*on an ls engine. I haven't seen where they make any power past that. But all setups are different with different variables. if you tune a gto, you probably will find yourself with about 23 to 26* at wot, wheras most fbodies will like 26 to 28*

 

<--- tuning noob here, but damn there's some good information in this thread...definitely gets the ol' noggin moving.
I read in one of the stickies here that the 4.8 seems to be a freak of nature when it comes to WOT timing, i.e. makes gains at 30-34 degrees. Rhino, can you confirm or deny?

 

Mine has about 28-30* pre converter swap. I havent really dialed it in since the swap, was going to play with it at the track. I have ran as high as 32 in some spots with mine, but it didn't feel any quicker on the butt meter or on the log files measuring time between 0-100 pulls. I have heard of people running crazy timing like that with sucess and maybe even more believable with the 4.8 being so low on compression (mines advertised at 9:1). I will play with it some and post up some results. Btw, I am running on 89 octane.

 

Not sure, but you might be referring to my thread:
https://www.performancetrucks.net/fo...d.php?t=469718

If you weren't, then sorry for the confusion on my part.

If you were, I'd like to clarify some things about what I posted. I didn't just leave my PT transmission settings alone. I actually had spent quite a bit of time trying many different little tweaks to the PT shift parameters, yet as I said in my thread, it never quite felt "right" to me. Stock Part Throttle shift speeds/rpms is what I ended up with for MY best results. I do have slightly higher shift pressures, which firms up the "feel", but the shift timing is perfect for me. I concentrated on WOT upshifts AND downshifts, so (in my opinion) I have the best of both worlds, and a transmission tune that does exactly what I want it to do, when I want it to do it.

Since my Camaro is long gone, I've also spent quite a bit of time datalogging and re-flashing MANY different timing tunes on my truck, and I believe that I have the tune about as perfect as it can be. It runs great at any rpm, pulls pretty hard for a stock longblocked 4x4, and even gets respectable gas mileage as well. Generally speaking, I've added (or even subtracted in some areas), anywhere from 1 to 6 degrees of timing to end up with what I feel is an optimum tune for my truck and it's diet of 87 octane gasoline exclusively.

Experimentation is the key IMHO. What John Doe's engine likes, yours may hate. Trial and Error is the only way to find out what YOUR combo likes. There's plenty of different ways people go about optimizing their tunes. Just keep reading and soaking up the info, and then use a tuning method that you're comfortable with....

 

No I don't think it was you. I'm completely **** about how my trucks shift and what I like probably wouldn't feel right to most people. I tend to like a performance shift all the time as far as shift speed vs tps as well as shift firmness but at the same time at very light throttle around town I like for it to be able to grab a gear at a fairly low speed and get the converter locked so I'm not using too much gas. It must work because I got a solid 17 mpg last tank with a mix of highway and around town driving back and forth to work for a week (about 10 miles a day around town) and idle time and some mild spirited driving and thats on 33s. Stock it wouldn't see 17 mpg going down hill with a tail wind.

 

Don't get me wrong, I've played with part throttle timing. However, it's one of those tuning parameters that will make you insane as measurable improvements are not the easiest to attain. For what I do on my own stuff, near stock works perfect. I don't give a damn about fuel mileage and I don't race part throttle.

I definately agree with you about the part throttle shift points though, especially with cams and loose converters.

 

At the OEM level they spend a good deal of time on each calibration carefully and diligently finding MBT timing for the base spark maps. What they end up with is a pretty well developed spark curve for each engine and application and their isn't a need to go way out there making HUGE changes with amounts of timing or to the curve itself particularly in the part throttle regions. Adding say 8-10 degrees to part throttle and cruise areas of the spark map which I have seen done on some tunes in most cases is just working backwards because you can end up way past the point of MBT at part throttle especially, before you ever see any knock at all.

 

MBT-Mean Best Torque

 

Word!