How much timing on top end is best for power?
11-07-2004, 04:35 PM
#1
How much timing on top end is best for power? I bumped my timing advance in the mid-range, and it feels good there. Got rid of most of that upside down speed bump.
But I also increased on the top, and it seems that the top end is off a bit.
How much timing from 5500 and up is everybody with h/c cars running?
I'm running 30 degrees with no knock, all the way to 6900, but I'm thinking it would make more power back down around 27-28 or so.
So I'm looking for feedback on what levels everybody else is running...
(everybody that is getting around false knock and that have cranked it up)
But I also increased on the top, and it seems that the top end is off a bit.
How much timing from 5500 and up is everybody with h/c cars running?
I'm running 30 degrees with no knock, all the way to 6900, but I'm thinking it would make more power back down around 27-28 or so.
So I'm looking for feedback on what levels everybody else is running...
(everybody that is getting around false knock and that have cranked it up)
11-07-2004, 06:07 PM
#3
I guess I need to log that... 
I made the tune for some drag racing Saturday, and was going to tweak the timing and see the effect. But didn't get to make it out Saturday because of having to do on-call stuff for work.
Then I went for a couple of 20 minute track sessions today (first time ever by the way) on that same tune, and it just felt down on power on top. Like it didn't want to go past 110-115. The old tune was 28. I had thought about trying to log it there, but figured they wouldn't like a laptop flopping around in the car while whipping the car around the road course.
I made the tune for some drag racing Saturday, and was going to tweak the timing and see the effect. But didn't get to make it out Saturday because of having to do on-call stuff for work.
Then I went for a couple of 20 minute track sessions today (first time ever by the way) on that same tune, and it just felt down on power on top. Like it didn't want to go past 110-115. The old tune was 28. I had thought about trying to log it there, but figured they wouldn't like a laptop flopping around in the car while whipping the car around the road course.
11-07-2004, 07:25 PM
#4
Timing and A/F go hand in hand.You can run more timing with A/F rich or less timing with A/F leaner.KR is good to go by but a wideband A/F gauge is almost a must for the best tuning.Also do the WOT runs in 4th(m6) 3rd(A4) to get accurate results.
11-07-2004, 07:42 PM
#5
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I think as you go up in RPM, the mixture-timing slack
(run more timing and more fuel = power-neutral) will
start to break down. At low RPM you can just lead by
whatever it takes, based on the burn rate of the mix.
But as you get to shorter and shorter power stroke
times, eventually you will need the burn rate to be
faster than a fat mixture will be, if you want to
"git 'er done" before BDC. I have seen some people
actually start to lean out the higher end of their PE
tables presumably for this effect (and then you
would have to pull timing too).
(run more timing and more fuel = power-neutral) will
start to break down. At low RPM you can just lead by
whatever it takes, based on the burn rate of the mix.
But as you get to shorter and shorter power stroke
times, eventually you will need the burn rate to be
faster than a fat mixture will be, if you want to
"git 'er done" before BDC. I have seen some people
actually start to lean out the higher end of their PE
tables presumably for this effect (and then you
would have to pull timing too).
11-07-2004, 08:17 PM
#6
That's all true. I've seen people run way rich to "cover up" too much advance. Yeah they stay away from knock, but it's definitely not optimal for power. Coming off the timing would let them run a much stronger a/f ratio, since a/f typically trumps timing.
I'll have to redo all this anyway when my STS turbo gets here...
Just looking for a last killer run at the strip na.
(and wondering if it was just in my head that my top end was gone at the road race course today - those straights aren't really all that long - but it sure seemed like the car just topped out halfway through the straight.)
I'm going to start logging "transmission torque" too. It tracked pretty closely with my dyno runs back in August. Close enough to see if a tuning change affects the torque, and where in the rpm band it has an effect.
I'll have to redo all this anyway when my STS turbo gets here...
Just looking for a last killer run at the strip na.
(and wondering if it was just in my head that my top end was gone at the road race course today - those straights aren't really all that long - but it sure seemed like the car just topped out halfway through the straight.)
I'm going to start logging "transmission torque" too. It tracked pretty closely with my dyno runs back in August. Close enough to see if a tuning change affects the torque, and where in the rpm band it has an effect.
