I have been trying to find the answer to this question for some time now. If you have an airplane that has a STC for Mogas, and it has a Ray Jay turbo can you still run Mogas? I have been trying to find a copy of a Ray Jay turbo STC to see if it has a requirement on it for 100ll, but I can't find one. The Mogas stc's specify that an airplane must have X engine installed but I don't think that the Ray Jay stc changes the engine identifier ( a O-360 with a Ray Jay turbo doesn't become a TO-360, its just a 0-360 that happens to have a turbo on it)?

Octane is Octane........ if your turbo is just 'normalizing' the motor then 91 auto fuel should work.. if you are boosting the motor for higher HP then 100LL is , or should be required.. IMHO.

That's what I was thinking. Is there anyone out there with a Ray Jay turbo that can confirm this? I have no doubt that you could do it, but I wan't to know if you can do it legally.

try here
http://www.rajayparts.com/rajaystc.htm

SA 153 SO

I gave RayJay parts a call and I didn't get to fare. The person I talked to didn't know if the stc had a fuel requirement on the paperwork.

http://www.airweb.faa.gov/Regulatory_an ... 4-1638.pdf

Found this on the FAA website. The STC pertaining to the aircraft installation does not specify any fuel. However the STC for the installation of the turbo on the engine requires aviation fuel. So if you have a rayjay turbo = no Mogas. Unless the fed isn't watching

With several hundred hours of turbo ops in my logbook, I'd have to say don't run mogas in any turbo'd airplane, whether it's legal or not, whether you're going to be caught by the feds or not. The risk to the engine is just too great, especially if as occasionally happens with the 3rd throttle of a Rajay, you forget to pull it out before pushing the primary throttle in on a go around. Overboosting is one thing; overboosting combined with pinging from too low an octane is something else, and very destructive. The amount you save per gallon will never pay for the potential damage to the engine.

BTW, have you considered how little you really save, running mogas? If you burn 14 gph, you're saving roughly $2/gallon or $28/hour. If you run 100 hours a year, that's $2,800. That's a lot in beer money, but not so much when it concerns engine maintenance. In my case, burning 9.8 gph, it would be less than $2,000 per 100 hour year, but I run closer to 60 hours per year, or only $1,200; is that enough to replace valves and cylinders that might be damaged by running too low an octane fuel? Add to your cost the equipment necessary to fuel your airplane (assuming mogas isn't pumped at the airport), consider the added risk of a fueling disaster, and the time it takes to do the mogas fueling, is it really worth it? If I could knock off $2/gallon without any of those issues, I'd love to do it, but for now, I'll stick with 100LL.

Cary