Spark advance?

[tmsbandman]

I am playing around with my "Transmission Only" stock tune to see what I can do for max fuel economy. What is a "normal" amount of spark advance at 87 octane? It's at 1.25 right now and seems fine. Do I keep bumping it until I get valve rattle, then back down one notch? That's pretty much the drill I remember from adjusting a distributor long ago.

Thanks.

[Longshot270]

Originally Posted by tmsbandman

I am playing around with my "Transmission Only" stock tune to see what I can do for max fuel economy. What is a "normal" amount of spark advance at 87 octane? It's at 1.25 right now and seems fine. Do I keep bumping it until I get valve rattle, then back down one notch? That's pretty much the drill I remember from adjusting a distributor long ago.

Thanks.

Unlike the distributors, these modern vehicles are able to retard timing if it becomes over advanced.

Have you tried running the other tunes? For me, the tow tunes get me by far the best fuel economy.

[tmsbandman]

I have. I ran the stock towing tune until I got my 87 Custom Performance. I have run the 87 Performance for about 8 weeks. I'm just playing around with it. Initially it looked like I was getting better MPG. but it was because my wheel size got whacked when I switched tunes. I've just about got that dialed in so I can make a good comparison. I must remember to WRITE IT DOWN this time. It seems that the tranny only tune is doing a hair better on gas, but I can't tell until I get the tire size right. I guess then I could do a tank on each (all three) and compare. Is there a "normal range" on the spark advance?

[Longshot270]

What kind of mileage were you getting on the tow tune?

What do you mean by range?

Also, which programmer do you have?

[tmsbandman]

Seems like the tow was about 14-14.5 (about 70%city/30%highway.) Seems like Custom 87 Performance was a shade better. Truck is on '04 SCrew 5.4.
Tuner is the Gryphon (original, not CTS) I'll be doing a little more highway driving this weekend. Curious to check it there. I once (only once) got 18 an an all highway trip. It was before the Gryphon, but I had fresh oil/filter. I'd love to see that again.

[tmsbandman]

Oh....range. I mean "what degree of spark advance is normal/acceptable with our trucks?" Mine's at 1 or 1.25 right now. Just curious if I should advance it more, leave it alone, or back it down some.