Thanks Kurt!Kurt Bozarth wrote:Hey Tim,
Here are my only two cents worth:
$0.01: I don't think anyone needles to peak on the line and then backs it off.
$0.02: Motor set-up and airplane (tank height) can dictate how much to be off of peak on the line. Different set-ups unload differently.
Kurt
Now that's something I can work with...
Yes, peaking on the line, then backing it down doesn't sound right to me either. I was probably misunderstanding something there.
So then, to your point no. 2 (determining how far below peak to launch), you need to know how the engine behaves in your plane and read the plug after a flight to determine where to set it for launch.
And apparently, the procedure of peaking the engine on a test stand on location before the race lets you know the peak rpm at that point in time. Given that, and your prior knowledge of how far below peak to launch, you will know where to launch that day.
Sounds like one of the first things you do before you fly is to peak the engine on the ground to see where peak is then and there.
In my case, my Nelson in my Sweet Vee that Sunday morning peaked at 25,300rpm. I'm running a Jett oval tank as high as it will go, so the plane does not have a tendency to lean as the flight progresses - it seems to remain pretty much consistent through the 10 laps. We were launching it at around 24,300 and even "eeked" it up from there a bit. As the heats progressed the plane seemed fast (after my last race with Danny Coe he said "man, you got some speed!") and the plug looked good, so I'm there - I guess.
Given the above, for practice I might launch about 1000rpm below peak, read the plug and go from there. I can get into shimming later once I have a better understanding of a good launch rpm.
Thanks again.
Tim