At what point do we run out of timing? Would I be better off tuning at 8psi or running 12 like I want to? With the stock cr ratio of 10:1 on 93oct. I've read that we have limited resolution for tuning timing on the jbody. So would tuning timing on 12 pounds pull too much timing for it to be of any gain? I'm sure it will still be a gain but is it enough to be worth it?
I'm confused by what your asking.
BUT I have tuned on a stock ECU for 10psi, 16psi, 18psi, 20psi, and 25psi.
FU Tuning
Sorry, I was reading an article about compression and boost. It was talking about how if you have too high of compression and too high of boost at a certain point your fuel will become insufficient in preventing detonation. its probably more info than I need to be worried about but I was just curious.
When that point is reached you need to run a higher octane.
That's why I was wondering about 93oct's capabilities but then addicted said he's tuned a stock one to 25 psi so I guess I have nothing to worry about haha
The fuel itself staving off detonation is a multi-part equation, octane, and AFR being the primary two. Higher octane equals more resistant to spontaneous combustion which will cause the fuel to burn more evenly under increasing compression and allowing you to step up your timing. Running a lean AFR will raise your combustion temperature and increase the likelihood of detonation, while running a more rich AFR will decrease the combustion temperature and thus decreasing the likelihood of detonation. There is a balance to be managed with the AFR as running too rich will cause power loss, which is where a suitable octane comes in. If you still cannot reach the timing advance you are aiming for, then other options can be explored like better incoming air cooling, fuel cooling, or methanol injection.
I am currently running 14psi on 93 octane with no issues. Don't recall what my timing is. The mentioned Resolution issue comes from running a 2 or 2.5BAR MAP sensor since our tables can not read that high. To get around it we rescale the 1BAR tables numbers to match where they would be on the new sensor (ie: 50% signal moves to 25% and 100% to 50% on a 2BAR MAP since the same signal spans twice the MAP). I am also running the 1BAR MAP.
How did this turn out? I found(on the dyno) that going from 13 to 15psi and losing 2-3 degrees of advance was worth it on my l61. Curious to hear your experience.
"In Oldskool we trust"
Not sure if your talking to me but I have not yet messed with it all though I've decided on 12psi when the time comes. I feel that I would be pushing it to go 15psi on a stock motor with 110k on it... I'm not sure I'll have enough money for that much dyno time to mess around with different power levels.
I push 17psi threw a stock eco with 106,000 miles on it. No worries.
Kyle's running a tvs, I'm running an m62. I think 12 is a good place to be for you.
"In Oldskool we trust"
With the standard disclaimer that every set up is different, only a dyno can tell you if extra boost at the expense of spark advance is worth it. For a TURBO car, I'd say as long as you are not maxing out the turbo (redlining the compressor wheel), you should benefit from more boost at the expense of spark advance. A roots supercharged car can be different when heat becomes a factor from spinning the blower too fast, or faster than the existing cooling system can take. In other words, as soon as it gets hot, your spark advance tanks anyways (at least it should if you care about the motor). On either set up, the more you tweak and work towards the ragged limits of the fuel you are using, the less forgiving it will be to a lower quality.
You can start with the old rule of thumb that you pull one degree advance per psi of boost, but I think on the ecotec platform (designed for 87 octane) that's extremely conservative (mild supercharger set ups run MORE timing than stock with good cooling)
Just my two cents.
I guess the only way for me to find out is to do a couple pulls and see what needs to be changed. I just think it's kinda weird that hahn would suggest the stock timing curve is fine for boost. They claimed they didn't change it early on with their first setups. But hey who knows maybe the stock timing is conservative.
Akizzem wrote:I guess the only way for me to find out is to do a couple pulls and see what needs to be changed. I just think it's kinda weird that hahn would suggest the stock timing curve is fine for boost. They claimed they didn't change it early on with their first setups. But hey who knows maybe the stock timing is conservative.
Hahn also says 14:7:1 AFR is perfectly fine on 8psi.
FU Tuning
The stock spark advance is conservative from a performance perspective - it's designed to run on 87 octane year round for it's life. If you throw good 93 octane in it, it makes some sense that you can get away with a few pounds of boost without adjusting them down a whole lot. The motor will not tolerate fueling, however, at stoichiometric at 8 psi for long. Aim for high 11s-low 12s, maybe a little leaner if you want to push it.
oldskool wrote:The stock spark advance is conservative from a performance perspective - it's designed to run on 87 octane year round for it's life. If you throw good 93 octane in it, it makes some sense that you can get away with a few pounds of boost without adjusting them down a whole lot. The motor will not tolerate fueling, however, at stoichiometric at 8 psi for long. Aim for high 11s-low 12s, maybe a little leaner if you want to push it.
I agree.
Ecotec seems to like 12.2, but 11.7-11.9 gives you some safety.
FU Tuning
I know this is a hella old post. On the hahn kits what did everyone find best for timing and or ve. Hahn doesnt mention changing any timing from stock for a stage 2 kit just something about changing the ve down but it was pretty vague.
