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Old 09-06-2010, 07:36 AM
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N941WR N941WR is offline
Join Date: Jan 2005
Location: SC
Posts: 12,887

Originally Posted by apkp777 View Post
I am thinking about running some MOGAS in the near future. It seems to be that the "Restricted" "B" curve might be better (Jumper installed)?
The jumper forces the EPIs to run on the "A" curve. If you want to run the "B" curve, with or without changes, you will need to remove the jumper.

Originally Posted by apkp777 View Post
What are the advantages of using the full "B" curve? I assume better combustion, therefore more power and economy?
You are correct. My suggestion to cut back on the advance of the "B" curve is simply to start out conservatively and move up to the full curve, once you feel comfortable with it. There is no reason you can't start at the full "B" curve, many people have done that without issue.

Originally Posted by apkp777 View Post
At some point can you go to far with the advance and start getting in to danger?
YES! I would not play with the timing settings (beyond the "A" and "B" curves) unless you have a full EMS w/ CHT and EGTs for all cylinders. We talked about developing a knock sensor for the Lycoming engines but backed off. Cars typically use one knock sensor plugged into the engine block, which works fine for those quiet running engines. Our aircraft engines are very noisy and what we found is that we would require a knock sensor on each cylinder and then some serious computing power (hardware and software) to filter out the noise on each cylinder. Once we had that info, there isn't much we could do with other than display it since we don't control anything. Your rising CHTs are a good indication of pre-ignition. (I'm not talking about poor cylinder cooling here.)

We did work out a way to mount knock sensors on stock cylinders but that is a different story. Ironically, Lycoming's TEO-540-EXP twin-turbo engine with the integrated iE2 electronic engine management system also uses knock sensors mounted on custom cylinders.
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC

Last edited by N941WR : 09-07-2010 at 08:39 AM.
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