I have bumped the O-200 in my KR up to 8.5:1 compression, and have the O-320 in my SuperCub also at 8.5:1 compression to make it 160 HP. I run both on 91 octane premium Mogas. Since I carry a 110 Gallon fuel tank in the back of my truck, it allows me the luxury of doing a custom fuel mix. Most tanks of fuel I will mix in 10 - 20% 100LL to add a bit of lead for the valves to prevent valve recession, and about a pint of Marvels Mystery Oil to keep the valves and guides clean, but performance wise, 91 octane Mogas works just fine in both of my engines. I can't tell any difference in performance or temperatures either summer or winter. It should also be noted that I run Emags on the O-200 in the KR, so that engine sees the timing advance as high as 39° BTDC depending on the RPM and manifold pressure.
The problems referenced were in my SuperCub and was not alcohol related. However, there is another additive in most of the alcohol free premium fuels in my area that reacted rather badly with the epoxy resin tanks that were in my SuperCub essentially dissolving the tanks. I don't know what the additive is, but did discover how to test for it and found one local fuel that is still acceptable for use in my planes. My KR also has epoxy resin tanks, but they were sloshed with the Hirsch coating available through Aircraft Spruce some 23 years ago. That prevented the fuel I was using in both planes from damaging the tanks in the KR. When I rebuilt the tanks in the SuperCub, I did them with VinylEstr, then sloshed with with a compound from KBS Coatings. If you want more information on what I found with the local fuels and photos of the damage it caused, it's on my web site at <http://jeffsplanes.com/Cub/MOGAS/mogas.html> -Jeff Scott Arkansas Ozarks > Sent: Sunday, February 02, 2020 at 8:43 AM > From: "Flesner via KRnet" <[email protected]> > To: [email protected] > Cc: Flesner <[email protected]> > Subject: Re: KR> Avgas - UL94 > > On 2/2/2020 8:15 AM, Joe via KRnet wrote: > > I tried in and have seen no difference in performance when I had my > > O-320 with low compression. > > +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > As a non-engineer, non-chemist, I understand the issue to have two > concerns. One is octane rating and the second is what effect alcohol > has on the fuel system. I ran a great deal of auto fuel in the Tripacer > and the KR before they added alcohol to boost octane rating when the > lead was removed and it worked great. The engine ran very clean. > Octane rating on lower compression engines is not the problem. My > concern is what the alcohol will do to my epoxy fuel tanks and > secondarily, to the rest of the system. We're all familiar with the > problems Jeff scott had. Each concern must be considered separately. > > Larry Flesner > > > _______________________________________________ > Search the KRnet Archives at > https://www.mail-archive.com/[email protected]/. > Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. > see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change > options. > To UNsubscribe from KRnet, send a message to [email protected] > _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/[email protected]/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to [email protected]
