Here is a look at a classic testing story from our days at the Edgewater Florida hangar . The years we spent there (2004-2008), maked the sucessful completion of many planes and hosting a number of outstanding colleges. The pace of testing was going into high gear then. The story notes that we had previously run 50 engines on the run stand before it was converted to a dyno. In the years that followed, we ran more than 100 engines on the dyno, most of the in public or at college where we invited people to study the system and verify the conclusions.
Today, the run stand we use at the college is made from many of the same parts we used on the dyno. It has been simplified to allow much faster engine changes required to run many engines at a college. If you look at the engines in all the tests, you can see that they are all 2700s that pre-date any of our Gold system components. (Gold oil systems eleminate the need to verify the stock oil bypass as shown in the story) The engines we build today, the 2,850s and 3,000cc power plants, are even more powerful than the engines in the tests, with no sacrifice in reliability. As we have extracted more power, we have done it largely by increasing the displacement of the engine, so the power output per cubic inch has stayed about the same, keeping the stress on the engine to very conservative levels.
Torque, Horsepower and Thrust Testing
September 21, 2004
Here’s the second engine being run on our dynamometer. We ran this a few hours ago. In the photo above, Gus is checking the timing with a light. We spent some time this week upgrading the dynamometer in its details. Visible is its new paint job, but it got a lot of detail work to facilitate rapid engine changes, and multiple tests. I contacted Darryl at Warp Drive Propellers today, and he’s sending us down a matched set of smaller diameter blades which will allow us to graph the horsepower at high rpm settings. These blades will become part of the permanent setup. The engine shown here in the test is a virtual clone of our 601 engine. The only significant difference is that this engine has GM steel rockers, while our 601 engine has roller rockers. I built this engine to represent our standard engine configuration, and use it as a test engine for the dynamometer. It’s fully airworthy and has many nice details like ARP close tolerance through case studs. After the break in and dyno runs, this engine will be for sale.
Here’s a side view of the same engine running, above. This engine has the inward leaning, welded on aluminum intake tubes that fit in our 601 Nosebowl. The intake manifold has four rubber slip joints in it that allow it to mate to many different intake pipe configurations. In photos below, you’ll see the PC Cruiser engine, which has a different intake pipe configuration. The adjustable intake manifold for the dynamometer quickly mated to both motors with a minimum of fuss. These types of details will allow many engines to be evaluated on the dyno. There are 5/8″ and 3/8″ tubes welded into the left valve cover. These mate up to the readily available and highly effective air/oil separator sold by Wick’s and Spruce. The gauge measures mechanical oil pressure. Temperature and rpm are measured remotely. We’ve painted the heavy duty baffle box green. The exhaust system is currently stock iron manifolds with 1 1/2″ down tubes. Shortly, we’ll have mufflers in place.
Above is the front and right side of the engine. The right valve cover has the oil filler neck welded in at the back. The starter motor is the Ultra Low Profile configuration, which fits inside the 601 Nosebowl. The alternator is not yet mounted, but the corner of the front alternator bracket is visible at the edge of the Ring Gear. The Pulley to drive the front alternator is just ahead of the Ring Gear. Pushrod tubes on all of our production engines have always been painted white. While many people believe that oil returning to the crankcase through the pushrod tubes is cooled by airflow through the motor, our testing has shown that just the reverse is true; the pushrod tubes run significantly hotter than the oil in the sump. We paint the tubes white to help them reflect heat.
The photo above shows a very important piece of test equipment that we use on all the motors we build. We use this to evaluate the condition of the oil cooler bypass in the engine. The cooler bypass performs a crucial function in the Corvair. It has a tradition of trouble free operation, even in engines 30 years old. The Corvair’s oil system has a very good track record, and the design of the cooler bypass contributes to this. However, in the interest of truly knowing its condition, we built this tool. The bypass is a pressure sensitive check valve set to relieve at 7 to 8 psi differential. When operating correctly, it allows the motor to warm up the oil quickly. But if it leaks or has a weak spring, the engine will have hot oil temperatures no matter how big a cooler you put on it. This tool, made from a modified oil cooler mount, bolts on to the stock cooler mount and allows me to measure the exact pressure at which the bypass relieves. This is done when the oil pump is being primed with a drill motor, long before the engine is ever run.
Above is the cooler bypass tool in action. Although the photo is a bit blurry, you can see an 8psi differential on the two gauges. The engine is sitting on the dyno being dressed out. What’s driving the oil pressure is a half inch electric drill using a dummy distributor housing and distributor shaft without a drive gear on it. You’ll see this priming tool in many photos. It’s painted orange like many of our shop tools. I primed this motor for 20 minutes with the drill turning the pump at a speed that would be comparable to a high idle on the engine. During this time, I turned the propeller over slowly by hand a bunch of times, allowing the oil to flow through all the passages in the engine. This technique is very effective. This motor has Sealed Power hydraulic lifters, and these, combined with priming, did not let out a single tick when we started the engine an hour later. These hydraulic lifters will maintain their adjustment for the life of the motor. It’s attention to detail like this that pays rewards no matter what type of engine you’re building.
Stay tuned for the test data and horsepower calculations. We’re going to run this motor for a few more hours before we give it full power runs on the dyno.
September 9, 2004
Here is the first run on our newly built engine dynamometer. There are many types of engine dynamometers. One of the most simple and easily made measures the engine’s torque reaction. Our own stand has a motor mount which is free to pivot along the crankshaft axis. This is restrained from rotating by a hydraulic cylinder. It is a simple calculation verified by a simple test, and you can ascertain the amount of torque the engine is producing at any given instant by reading the hydraulic pressure. It is accurate, and if you have the capability of measuring the rpm of the engine very accurately at the same moment, a simple calculation will give you the exact horsepower that the engine is producing. Shown above is the very first run we did on the dynamometer. Its details are still being finished, but it works very well.
Above is the view of the dynamometer with the engine removed. Its operation is very simple. Everything seen in blue rotates on the crankshaft’s axis. If you look closely, you can see that the bearing is the front spindle, hub and wheel removed from a late model Corvair. The bed type mount is slung low so that the crankshaft centerline lines up exactly with the spindle. The reinforcements below the engine contact a bearing at the bottom of the stand for additional support. This is a Corvair blower bearing rolling sideways on a steel plate. It effectively has no drag. Below the spindle is the mounting point for the hydraulic cylinder. The green oxygen bottle has been converted to a gravity feed fuel tank on the test stand. It hold 2.5 gallons of fuel, and has a very accurate sight gauge on it which allows precision measurement of fuel burn.
Another view of the first run is above. Just ahead and above the battery is the hydraulic cylinder. A stainless braided line running out of the picture goes to the remote gauge. Our rpm measurement is by digital optical tachometer. This is one of the few types of tachs accurate enough to give good test information. Many people will recognize the chassis of the dynamometer as our previous engine run stand. The old stand served us well, and broke in many famous Corvair engines, such as Mark Langford’s 3100. Although we never kept count, I’m pretty sure 50+ engines were run on it. The new dynamometer is capable of everything that the old run stand could do, plus its obvious new function of measuring horsepower. In the coming year, we’d like to run as many engines as possible and anyone converting a Corvair for flight reading this is certainly welcome to bring their engine for a run. We took the time to manufacture a very special intake manifold for the dynamometer which is compatible with any style of cylinder head used in Corvair flight motors. Details like this will make installing and running engines a quick and simple process.
Gus monitors the engine run, above. Note the newly constructed heavy duty baffle box to provide cooling air to test engines. I’ve said it many times, but it’s worth repeating that you should not run your motor even briefly without a cooling system in place. The carburetor in this run is an MA3-SPA from an O-200. This will be the dedicated carburetor on the dynamometer, although we will be able to evaluate others. The propeller is a 72″ 2-blade Warp Drive. In the background in this photo is the Corvair Trimotor fuselage.
Above is another view of the running engine. The baffle box is made of 50/1000″ aluminum, although 25/1000″ would be plenty for a box you’re only going to run for a few hours. We plan on getting a lot of work out of this, so we built it heavy duty. You’ll notice that the 12-plate oil cooler is outside the baffle box. Engines run on the test stand traditionally have very cool oil temperatures. I kept the cooler outside the baffle to give the oil a chance to warm up. When set up for flight inside a cowl, the engine will have normal oil temperature and it will be appropriate to have full air flow over the cooler.
Here is the same engine pictured running on this page. We built this engine specifically for the Corvair Personal Cruiser, a single seat aircraft designed for Corvair power. This engine will be installed on the prototype, now under construction. In the photo above, the engine is sitting on the mount for the Cruiser. Shown in silver is the intake manifold for the aircraft. We built this from mild steel tubing. The horizontal inlet is built specifically to mate with an Ellison EFS-3A. Also of interest, note the layout of the sparkplug wires. When oriented like this, the cap can be removed for inspection without removing the wires. Additionally, the distributor can be rotated to set the timing without the wires becoming slack or taut. Doing dozens of engine installations over the years has allowed me to perfect small details that allow the operation and maintenance on the motor to be done far more easily.
Very shortly, we’ll provide the next batch of photos sharing the test data and the calculations. Additionally, we’ll show you the calibration procedure, which allows everyone to understand how accurate this simple machine can be.
About William Wynne I have been continuously building, testing and flying Corvair engines since 1989. Information, parts and components that we developed and tested are now flying on several hundred Corvair powered aircraft. I earned a Bachelor of Science in Professional Aeronautics and an A&P license from Embry-Riddle Aeronautical University, and have a proven 20 year track record of effectively teaching homebuilders how to create and fly their own Corvair powered planes. Much of this is chronicled at www.FlyCorvair.com and in more than 50 magazine articles.