ORIGINAL: AndyW
Lawrence,
The Norvels were all made without a means to adjust the mixture at idle. The result was that at a low idle of 6,000 RPM, if you left it there for even a minute, the engine would load up with too much fuel and transition to full throttle would be poor.
Norvel's solution to later engines was to design the throttle so that it would quit if you tried to idle it below 8,000 RPM. But at this speed, your airplane would not land. You had to kill the engine to land the plane.
The fix to that is to bore the throttle body out so that the bottom hole is the same as the top hole in the throttle body. From there, you need to install an adjustable airbleed.
Here,
http://www.youtube.com/watch?v=1wZc7...e=channel_page is the stock engine converted to diesel, illustrating poor transition.
And here,
http://www.youtube.com/watch?v=57WTJUxV0DM is the same engine with the modifications mentioned.
Hi Folks,
Managed to have some experiments with the mod on Norvel AME .061 RC as mentioned by Andy on earlier post.
First, I fully screwed in the custom made adjustable air bleed and started the engine. It will die at low idle with a good top needle setting.
Keeping the same top needle settings, I opened the air bleed and keep all other settings the same. The engine started, and was able to idle well without dying.
However, one thing I found out was that the engine idle well, and will continue at same pitch/rpm even when I further closed the throttle. The main benefit has since been concluded as keep the engine running, rather than achieve a (much) lower idle.
Of course, I think fine tuning will let the engine idle lower rpm and the fact that I did have a proper tachometer at hand means no accurate numbers.
But one thing for sure, this mod is highly recommended for its preliminary results.
Will keep posted if further number/experiments come up. Thanks Andy!
Lawrence