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Old Today, 05:18 PM
Twistaholic AMA 134406
Dad_Roman's Avatar
USA, TX, Teague
Joined Jul 2007
5,211 Posts
Okay....you got me....THAT one I have never heard of before....
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Old Today, 06:13 PM
I HATE GLOW PLUGS!
SrTelemaster's Avatar
United States, NY, St Lawrence
Joined Feb 2012
997 Posts
Quote:
Originally Posted by taildragger1589 View Post
But if the timing is too advanced for the load, doesn't that lead to pre-ignition and
lots of heat? (keeping in mind that I don't adjust the timing more than 3 or 4 degrees either way)
Therefore when I put on a larger prop and hear the rattling noise (or knocking if you prefer) I retard the timing until it goes away, this in turn reduces temperature.

This is the way I timed and ran my Super Cyke, Thor and GHQ
(Yes, I actually got all of them to run, my dad was a maintenance chief in the AAC and gave me some tips)
and never had overheating or excessive wear. I flew all of them in the late sixties, but only have the GHQ now. But the reverse pitch aluminum prop, (around 18 inches I think, not sure) made it very sensitive to timing errors. (I flew it in a control line ship built around a Smoothie wing. Granted, I only had about 30 feet of line out on the Ureely and had to swing it a little)

Nick

If the timing is set correctly, the advance should be correct throughout the RPM range regardless of load.

If the engine is overheating, then the load is too much for that particular RPM/throttle setting. It is better to prop so that the engine runs near maximum torque RPM static. Detonation will not occur if the A/F ratio is correct.

Ever see the chrome burn blue on motorcycle pipes? That is often due to retarded ignition timing.
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Old Today, 06:55 PM
Lookin' up at the centerline
taildragger1589's Avatar
Lawrenceville, Georgia
Joined Feb 2005
1,967 Posts
Quote:
Originally Posted by SrTelemaster View Post
If the engine is overheating, then the load is too much for that particular RPM/throttle setting. It is better to prop so that the engine runs near maximum torque RPM static. Detonation will not occur if the A/F ratio is correct.
While the above is very true, what we are trying to ascertain is the possibility of turning a prop that's much larger than recommended without overheating the engine by manipulating the A/F mixture like we can on non ignition engines.
I have already put many hours on overpropped nitro engines by merely running them rich enough to stay cool, although at a greatly reduced efficiency and rpm.
Thus sacrificing power for scale effect.
Thus far I have no practical experience in extending the technique to ignition engines, mainly because I haven't had one to experiment with and no need to do so (yet). So I'm mainly just talking it out to see if it's possible. I know it is with the non throttled GHQ, I ran it with a large O&R prop, (think it might have been a 16x6) that was very light and it ran much faster and could take a more advanced setting than the slower turning aluminum prop and I thought this may apply to the new four stroke gassers.

Quote:
Originally Posted by epoxyearl View Post
And as you already know the pickup location is immaterial, as long as the magnet is located properly in the rotating mass, relevant to the timing desired.. But you still need a reference point-a degree wheel-if you will, for knowing exactly what the timing is....
I always did prefer the degree wheel with a bamboo skewer in the plug hole. but the picture below is the total ignition info in the Saito manual.
No hard numbers just this pic and the words that moving the pickup ccw makes it easier to hand start but lowers the max rpm.

Ah well. We may never know for certain until Dad makes an attempt, unfortunately, I have no projects lined up that could use the big slow prop effect.
at least not the next three planes I have planned.

Nick (come on Dad, show us how it's done)
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Old Today, 07:04 PM
I HATE GLOW PLUGS!
SrTelemaster's Avatar
United States, NY, St Lawrence
Joined Feb 2012
997 Posts
Quote:
Originally Posted by taildragger1589 View Post
While the above is very true, what we are trying to ascertain is the possibility of turning a prop that's much larger than recommended without overheating the engine by manipulating the A/F mixture like we can on non ignition engines.
I have already put many hours on overpropped nitro engines by merely running them rich enough to stay cool, although at a greatly reduced efficiency and rpm.
Thus sacrificing power for scale effect.
Thus far I have no practical experience in extending the technique to ignition engines, mainly because I haven't had one to experiment with and no need to do so (yet). So I'm mainly just talking it out to see if it's possible. I know it is with the non throttled GHQ, I ran it with a large O&R prop, (think it might have been a 16x6) that was very light and it ran much faster and could take a more advanced setting than the slower turning aluminum prop and I thought this may apply to the new four stroke gassers.


I always did prefer the degree wheel with a bamboo skewer in the plug hole. but the picture below is the total ignition info in the Saito manual.
No hard numbers just this pic and the words that moving the pickup ccw makes it easier to hand start but lowers the max rpm.

Ah well. We may never know for certain until Dad makes an attempt, unfortunately, I have no projects lined up that could use the big slow prop effect.
at least not the next three planes I have planned.

Nick (come on Dad, show us how it's done)

Richening up the mixture (to a point) will prevent detonation even on gas engines.

True, it won't retard the timing like W/GI, but it will still prevent detonation.

Retarding the timing a few degrees won't make the engine run any cooler but won't do any harm as long as you do not overdo it.
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