When can Auto gas be used?

s10sakota · Post by **s10sakota** » Thu Mar 22, 2012 1:15 pm

Everyone I talk to tells me something different. I've heard that up to about 180 hp a Lyco can run on mogas.

Yesterday an RV builder told me that anything higher than 150 hp has to use AvGas.

I just got my wing kit this last Friday so I won't be putting gas in my RV for at least a few more months...

...but fuel will determine my engine choice.

Is there anyone here that actually KNOWS when autogas can be used? Maybe I'll just put a Rotax 582 in my RV. 50 hp should be enough, right?

captain_john · Post by **captain_john** » Thu Mar 22, 2012 1:40 pm

Mark, a 4 engined RV would be AWESOME! Put them on the wings!!!

Hahaha If I am not mistaken my 180hp ECi engine can use MOGas. No alcohol... but MOGas nevertheless.

I have no plans of using auto fuel. It has never been worse or cost as much as it now does. I am using AVGas in my generator and in all of my engines that sit for a season or more (at the end of each respective season).

Horsepower does NOT have anything to do with whether or not you can use MOGas. It is compression. Low compression engines can use MOGas so long as it is at least 91 octane.

150 HP is low compression for a 360. I think that is 8.5:1 if I am not mistaken.

Does this help?

CJ

Vlad · Post by **Vlad** » Thu Mar 22, 2012 4:23 pm

s10sakota wrote:

Is there anyone here that actually KNOWS when autogas can be used?

I know when. On Monday afternoon. Yes I am off that day

paulie · Post by **paulie** » Thu Mar 22, 2012 9:35 pm

Check STC list for autogas-it'll show which engines have been tested for autogas use. No alcohol is ever allowed.

smithhb · Post by **smithhb** » Fri Mar 23, 2012 5:38 am

s10sakota wrote:Everyone I talk to tells me something different. I've heard that up to about 180 hp a Lyco can run on mogas.

Mark,

I have the ECI IO360 with 7.2:1 low compression pistons. This equates to about 177 hp. ECI and Lycoming both say this engine has a minimum rating of 80 octane (mogas). They also allow mogas in 8:1 standard compression engines (180 hp) but suggest using >90 octane (I can't recall the exact octane number).

Call ECI at 830-624-7671

I run mid-grade mogas (ethanol free) regularly in my plane and see no difference in performance. I only run it in the right tank and perform TO and landing on the left tank (low lead left).

Hope this helps.

s10sakota · Post by **s10sakota** » Fri Mar 23, 2012 2:37 pm

Thanks for the replies. I want to use Mogas just because it's less expensive than AvGas.

I have no idea what compression ratio I will have in my future engine, but I just know that I would like 180 hp. Nothing fancy.

Looks like it can be used. I will just have to find out the specifics when it comes time to buy an engine.

hydroguy2 · Post by **hydroguy2** » Fri Mar 23, 2012 6:06 pm

My engine is 9:1 piston. When I was motor shopping both Aerosport and Eagle Engines said I could run autogas...as long as I didn't run to much advance on the timing.

I've benn toying with the idea of running 1 side with autofuel and 100LL in the other side. But so far I've been running my engine hard and staying with the 100LL.

airguy · Post by **airguy** » Mon Apr 16, 2012 2:24 pm

Last conversation I had with ECI, they said 8.7:1 compression would be OK for premium non-ethanol autogas. That's what I'm planning on, with an IO360 in my 9A. The lower compression robs a little horsepower so I add the cubic inches to get it back, and save a buck and a half per gallon.

smithhb · Post by **smithhb** » Mon Apr 16, 2012 4:22 pm

Greg, that is exactly what I did. I built the ECI IO-360 with the Airflow Performance FI. With dual P-Mags it bumps the HP to around 179 HP.

Thee performance is outstanding. BTW, ECI told me I could run as low as 80 octane (that is how I have the tanks placarded). I run Mogas in the right tank only (Left is Low Lead). Even with the AFP 4500 screens I cannot discern any difference from 100LL.

Joe Parish · Post by **Joe Parish** » Mon Apr 16, 2012 8:03 pm

Is it the compression ratio of the engine alone that determines what you can run?

DaAV8R · Post by **DaAV8R** » Tue Apr 17, 2012 10:58 am

Joe Parish wrote:Is it the compression ratio of the engine alone that determines what you can run?

I'm not an engine guru but this has always been my understanding. Most often the carbureted engines were "stc approved" and the injected engines were not, but that is not always the case.

An example of an injected engine that was STC'd for autofuel was the 225 hp Debonair.

An example of a carbureted engine that wasn't approved was the O-235 in the C-152. I think the O-235 was approved in other applications so I suppose it is a function of airframe and engine. No doubt the installation of the same engine in different airframes may effect the likelyhood of vapor lock.

I realize we don't need STC's for what we are doing.

JOHN TIPTON · Post by **JOHN TIPTON** » Wed Apr 18, 2012 7:26 am

Is this what you are looking for:

http://www.lycoming.textron.com/support ... I1070Q.pdf

Bob Barrett · Post by **Bob Barrett** » Wed Apr 18, 2012 6:44 pm

This is the very information I have been struggling to get documented.

I have an Lycoming engine -320E2d 160HP Engine in my RV-6A N784TB. It used to be in a 172 that I used to rent and on flights to New Rockford ND I would top off the tanks with 91 Unleaded Auto gas without alcohol. It ran fine and I was planning to burn 91 Unleaded Auto without alcohol in the left tank and keep 100 LL in the right tank. Since most traffic patterns around here are left handed I figured I needed to reserve the 100LL fir taje if's and landings. So far haven't implemented that system yet but I think it might work okay. We would cruse on the left tank and keep the right tank for critial times.

This is very helpful information and I was just discussing this with a perspective buyer of my airplane.

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