FAQ: Spark Advance (Timing, Retard)

deekster_caddy wrote:

Great! Keep it up, I would work on timing and fueling some more before you drop pulley sizes again. When you drop pulleys, you need even more fuel, etc.

My understanding of E85 is your ideal base A/F ratio should be around 9.8. So your setup sounds a bit lean. Maybe you want to work on that before you drop pulley size again. WOT should be a bit richer.

Did you change the Stoich setting to 9.8? Here's an article suggesting lambda is 9.9 and WOT A/F should be around 8.6-8.9 (and we are supercharged, so it may need to be even richer than that).

http://www.rockettbrand.com/downloads/tech_bulletins/Tech-Changing%20from%20Gasoline%20to%20E-85.pdf

I don't run E85, just basing what I'm saying here on what I've read online about it. That's another reason I'm not giving you specific advice, but again - the concepts are still the same.

Sorry, i am using the 14.7 stoich scale. You are right. I need to increase my fueling before i can drop pulleys. I am currently running ~80% IDC with 60#. Damn you Tyler for talking me into 60s instead of 80s!

I am confident with larger injectors I can run a 2.55" pulley with decent timing and 0 KR. But we will see in time!

Do your best to get things right on this pulley and these injectors. You have a lot of potential here if you can get your fueling right!

That's the hardest part I had tuning - I was running way too rich at WOT and was never really able to get it down to where I thought it should be, but then it wasn't my car anymore so I never got to finish the tuning the way I wanted. There was something in the PCM that kept making things rich when I thought I was making them leaner. I think I was fighting the 'WOT vs time enrichment' settings, but also didn't have a wideband O2 (this was many, many years ago now.

I've seen many, many people chip 3800 pistons from being too lean, so tread carefully until you work that fueling out.

Dang, i wouldnt even touch WOT tuning without a wideband.

I will update once I have more progress to report. Goal has been a 12.9 quarter mile since I got the car in 2011. So we'll see.

CharlieRobinson wrote:

Please show me which pages talks about timing advance while using E85. Or how the 3800 performs with different combinations of boost and advanced timing. It's not there but it can be found on the net by other tuners with documented dyno graphs. It's an interesting read but doesnt delve very deep into the world of supercharged 3800 tuning. It barely scratches the surface, really.

Charlie, you only know what you know. But what about what you don't know? You're looking for something very specific (and familiar to you) in a book with a broader scope. What about fundamental tuning knowledge that can apply to any car? Example: EGT. Does this book talk about exhaust gas temp in relation to timing advance? What I'm saying, there might be some valuable info in that book, even if it's not what what you're expecting to learn (E85, boost, E85 boost, E85...)

AA wrote:

CharlieRobinson wrote:

Please show me which pages talks about timing advance while using E85. Or how the 3800 performs with different combinations of boost and advanced timing. It's not there but it can be found on the net by other tuners with documented dyno graphs. It's an interesting read but doesnt delve very deep into the world of supercharged 3800 tuning. It barely scratches the surface, really.

Charlie, you only know what you know. But what about what you don't know? You're looking for something very specific (and familiar to you) in a book with a broader scope. What about fundamental tuning knowledge that can apply to any car? Example: EGT. Does this book talk about exhaust gas temp in relation to timing advance? What I'm saying, there might be some valuable info in that book, even if it's not what what you're expecting to learn (E85, boost, E85 boost, E85...)

I dont recall anything about EGT in relation to timing in the book. I read it two times cover to cover to absorb as much as possible. On a scale of 1(useless) to 10(mind blowing) I would rate it a 4.4.

$15 shipped if you want it!