Educational by Chapter of the Powered Paragliding Bible

I: First Flight

01 Training Process

02 Gearing Up

03 Handling the Wing

04 Prep For 1st Flight

05 The Flight

06 Flying With Wheels 

II: Spreading Wings

07 Weather Basics

08 The Law

09 Airspace   

10 Flying Anywhere

11 Controlled Airports

12 Setup & Mx

13 Flying Cross Country

14 Flying With Others

III: Mastery

15 Adv Ground Handling

16 Precision Flying

17 Challenging Sites

18 Advanced Maneuvers

19 Risk Management

20 Competition

21 Free Flight Transition

IV: Theory

22 Aerodynamics

23 Motor & Propeller

24 Weather & Wind

25 Roots: Our History

V: Choosing Gear

26 The Wing

27 The Motor Unit

28 Accessories

29 Home Building

VI: Getting the Most

30 Other Uses

31 Traveling With Gear

32 Photography

--- Not in book ---

33 Organizing Fly-Ins

34 Places To Fly

35 Preserving the Sport

36 Tandem

Does Avgas run Cooler in a Paramotor?

Testing the difference in running temperature between car gas and av gas

There's a lot of dispute as to which is better to run in your paramotor, avgas or mogas (as in motorcar), especially with the higher ethanol content of mogas. But one claim is significant: that avgas runs cooler than mogas. That's big because excessive heat is an engine's mortal enemy. So I plan on getting some numbers together to see.

I consulted with Chris Bowles of Southern Skies, a long time proponent of Avgas, on the proper way to do the test for a fair comparison.

I've purchased the Digitron RPM/EGT/CHT temperature gauge for the test, mounted in according to the directions, and test flew it on my Black Devil paramotor mixed at 35 to 1.

The first test was to run the motor on mogas as it's running right now—perfectly. I adjusted the mixture for highest RPM, which actually allowed quite a range of settings so I opted for the rich side but no more than 30 rpm rich of peak. With the motor warmed up, I started doing readings.

Just after the first test, I noticed a muffler bolt coming loose. That would skew the results so I'd have to go back and do the mogas test again.

By the way, the idle mixture is best set rich for starting but that will make it run somewhat rough. It starts surprisingly easy when rich but I struggled until figuring that out. And I started it a bunch of times.

Results were: Mogas 91 Octane, Shell or equivalent

7570 rpm, 1030 f, until stabilized

7540 rpm, 1050 f, :60

7520 rpm, 1030 f, :30 cht from 330 - 393

Then I put the fuel pickup in a 5 gallon can of avgas, ran the motor a minute to clear out the avgas and did the test again. Importantly, I tightened the very loose exhaust bolts.

I went to full power and adjusted the mixture to peak RPM which was about 100 less than with autogas. Go figure that one out. It took a lot of adjustment to actually get the RPM to change, at least a half-turn.

7330 rpm, 1180 f, until stabilized

7260 rpm, 1190 f, 400 f after :60

7330 rpm, :30 second run starting at cht 330, it went up to 384.

Then, since the exhaust bolts had gotten tightened between tests, I ran it up again with Mogas to see what I got.

7450 rpm, 1275 f.

I didn't even go further because it was obvious the mogas was running hotter than the avgas.

So the verdict is out. At least on my Black Devil motor, Avgas does run cooler but also seems to get slightly less power when both are leaned to peak RPM.

We'll find out if, and how much, Avgas runs cooler than Mogas.

© 2016 Jeff Goin & Tim Kaiser   Remember: If there's air there, it should be flown in!