Friends,
Over the years we've done a lot of thrust testing in order to compare the output of engines, the
thrust of different propellers, and the effects of systems installations. The method used to measure
thrust is a hydraulic cylinder attached to a remote gauge. It is easy to calibrate because you can
hang a known weight from it. In our case, the thrust is 1.54 x the number shown on the gauge. This is
because the piston in the hydraulic cylinder has more than 1 square inch of area. If you'd like to see a
lot more of our previous thrust testing work, visit
Mark Langford's Web Site from our Corvair College #3 in Daytona Beach.
A few days ago, we tested a lot of different combinations at the hangar for comparative purposes. All tests
that we've done recently are conducted on 100ll fuel. All of the Corvairs were tested with 32 degrees total
ignition advance. The only exception to the ignition was the turbo engine, which was set at 22 degrees total.
A $300 digital, optical tachometer was used to measure rpm. Weather conditions are measured on the spot with
digital instruments. Here
you'll see tests of certified engine and propeller combinations also. Over the years I've been working with
alternative engines, I've noted that many people who are fans of alternative engines know very little about
certified engines. Being an A&P mechanic, I have the greatest respect for certified powerplants. I like
everything about them except for the expense of obtaining and operating them. All my work with the Corvair
motor is patterned after the success of certified engines. I use their performance as a baseline, and
their level of reliability as a goal. Anyone who tells you that alternative engines have superior reliability,
or fantastically better performance than certified powerplants is either not telling the truth or has no practical
experience with them. In our case, we own, maintain and fly certified powerplants in addition to our work with
Corvairs. This gives me a greater range of experience and a more balanced view of the capabilities of
alternative powerplants, specifically the Corvair. The next time you hear somebody comparing alternative to
certified powerplants, either pro or con, ask them if they've owned and operated both and you'll find that
very, very few people have personal experience in both fields.
The Zenvair 601
Above is our 601's engine measured as installed in the aircraft. The only thing different about this engine
is that it has roller rockers and our modified cylinder head intake pipes. I doubt either one of these mods
would have a substantial effect on the output of the engine. The prop pitch setting of 11.5 degrees at the tips
would be an appropriate setting for a direct drive Corvair motor to move the 601 at 140-150mph. If the prop was
set flatter for a slower speed airplane, or used a slightly larger diameter prop, the thrust numbers would be
even higher.
Engine: Corvair
Displacement: 164cid, .060 over
Carburetion: MA3-SPA
Exhaust: Collected, open
Cowling: WW 601 Corvair Cowling, 13" spinner
Propeller: Warp Drive 2-blade HP hub and blades, stock tips, 66" diameter, 11.5 degrees pitch measured at tips
Temperature: 85F
Humidity: 35%
Pressure: 30.11
Density Altitude: -174
Wind: 4-9mph headwind
Performance
Thrust: 347 pounds static
RPM: 2550
MAP: 29"
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1946 Cessna 120
In the photo above is Gus Warren's 120 that he rebuilt from a basket case to 1998 Oshkosh Champion. It lives in our hangar.
The engine has about 100 hours on a first class overhaul. It has flow matched Superior cylinders.
Engine: C-85-12 Continental (85hp, redline 2575rpm)
Displacement: 188cid
Carburetion: Stromberg NAS-3, 1 3/8" Venturi
Exhaust: Stock 120
Cowling: Stock 120
Propeller: McCauley 71x46 Met-L, aluminum (This is a climb prop for a 120)
Temperature: 85F
Humidity: 35%
Pressure: 30.11
Density Altitude: -174
Wind: 4-9mph headwind
Performance
Thrust: 340 pounds
RPM: 2350
MAP: 29"
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Larry and Cody Hudson's Corvair Engine
This father/son team from Indiana built their own engine, in the photo above, from our Conversion Manual and components last year.
They dropped it off at our shop before Sun 'N Fun for a break in on our test stand. The prop installed is
appropriate for a 180mph airframe. This is why it has low static thrust numbers. It is good for comparative
purposes, and is the same prop used on some of the 2002 tests. This engine is not fully broken in, as it has
less than two hours of test stand time on it.
Engine: Corvair
Displacement: 164cid, .030 over
Carburetion: MA3-SPA
Exhaust: Cast iron manifolds, automotive muffler
Cowling: None, cooling baffle only
Propeller: Sterba 62x58
Temperature: 82F
Humidity: 51%
Pressure: 30.05
Density Altitude: -122
Wind: 5-7mph headwind
Performance
Thrust: 225 pounds
RPM: 2445
MAP: 29"
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Cessna 150
Pictured above is our neighbor Arnold's 1959 Cessna 150. The engine in this aircraft is one that is the
subject of the AD that requires the timing to be reduced to 24 degrees. The engine is a mid-time engine that
just came out of a 100-hour inspection. It can be considered to be in good working order. Contrary to what
most people think, O-200s in 150s are only certified to use propellers up to 69" diameter. No 150 left the
factory with a propeller diameter of 72".
Engine: Continental O-200, 100hp, 2750rpm redline
Displacement: 200cid
Carburetion: MA3-SPA
Exhaust: Stock 150
Cowling: Stock 150
Propeller: McCauley Clip Tip 68" diameter, aluminum, standard pitch
Temperature: 82F
Humidity: 51%
Pressure: 30.05
Density Altitude: -122
Wind: 5-7mph headwind
Performance
Thrust: 335 pounds
RPM: 2332
MAP: 29"
Shop Test Engine
We built up a test engine, below, from parts in our shop. We built it up to use in potentially destructive ground
testing. Since it's made of used parts, it is not only dirty, but also fully broken in and has very low internal
drag. I believe this is why it will turn slightly higher numbers than the Hudson engine. We utilized the same
distributor, intake, carb and exhaust on this engine and the Hudson engine. The only difference would be the
status of the internal assemblies.
Engine: Corvair
Displacement: 164cid, standard bore
Carburetion: MA3-SPA
Exhaust: Cast iron manifolds, automotive muffler
Cowling: None, cooling baffle only
Propeller: Sterba 62x58
Temperature: 75F
Humidity: 71%
Pressure: 30.06
Density Altitude: -133
Wind: 2-3mph headwind
Performance
Thrust: 231
RPM: 2520
MAP: 29"
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Turbo Test Engine
The engine above is the same as the test engine, with the addition of a new Garrett turbocharger, which we
had specifically sized and set up for a drawthrough condition. I wanted to test this on a junk motor with a
mild steel exhaust to evaluate the sizing of the turbo, and to ensure that it produced boost in the rpm range
we wanted. Turns out that the sizing and the trim of the turbo are nearly dead on. We're going to run a lot more
ground tests, and then develop our flight installation package. Based on early tests, we should have absolutely
no problem getting 100hp at 10,000 feet on a 164cid engine. While the installation looks very Mad Max,
it gave us the data we needed. Keep in mind that everything on this installation was less than optimal, and it
has already met my expectations. Despite being told by armchair experts of the antiquated nature of drawthrough
installations, and the requirement for an intercooler, this simple installation of a modern, efficient
turbocharger worked exceptionally well. At full output, you could reach up and put your hand on the steel intake
manifold, and it was not too hot to touch. While it would be hotter at altitude, I think the installation's off
to a great running start. A little practical testing has once again shown that you can learn a lot more by testing
rather than talking.
Engine: Corvair
Displacement: 164cid, standard bore
Carburetion: MA3-SPA
Exhaust: Cast iron manifolds to Garrett T04B turbo, 2.5" outlet pipe 18" long
Cowling: None, cooling baffle only
Propeller: Sterba 62x58
Temperature: 74F
Humidity: 62%
Pressure: 29.92
Density Altitude: -1
Wind: 3-4mph tailwind
Performance
Thrust: 331 pounds
RPM: 2950 (there was more power available, but I did not want to boost the motor past 45" without working
EGT in place)
MAP: 45"
Conclusions
We have more testing lined up on the turbo engine, and we're going to maintain a separate
Turbo Testing Page on www.FlyCorvair.com for it. We have a 72" Warp Drive propeller we'll be installing
for a maximum thrust test, which will give fans of 80-120mph aircraft a better idea of the potential of the
powerplant in their speed range. Please keep in mind when you read these statistics and look at the pictures
that all the data is factual. I frequently read stories where people claim to have VWs which produce 500 pounds
of thrust and Subarus which produce even more. We professionals in experimental aviation get a good chuckle out
of inflated numbers from advertising brochures and press releases. But, people new to sport aviation should
know that you can come down to my hangar any time and I'll gladly duplicate these tests.
Thank you.
William Wynne
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