Whenever some body builds or buys an engine for some thing they claim gobs of horse power but no real data. There is a real easy and cheap way to build your own engine dyno. Moving or storing the engine after build can also be a problem. With this in mind heres what to do.
Get a secure 2 wheel trailer and hook it up to your pick up using 2" or larger ball. Chain it like a normal trailer but use a good chain. The bed is not important.
Build a good secure L shaped mount to bolt on the trailer using about 4-5 inch square tubing with a quarter inch wall. Cheaply loading your engine can be a problem but what works the best is a well protected prop to bolt to the out put of the engine. As the horsepower of the engine changes the load will have to change. If you want to use a water brake dyno you can but expect to pay more but keep in mind water freezes. The engine has to run WOT - wide open throttle when taking measurements corrected to RPM.
As the weather, temperature, and humidity changes the power output will change. Some people THINK it doesn't make a big differance but it does. I have run many engines on a dyno so I know. Because of these changes you have to correct your readings to a standard atmosphere. The CF or correction factor must be noted. This is 29.92 inches of mercury pressure, 59.5 degrees farenheit , and 0% humidity. Some body got the bright idea of opening the outside door in winter to see the power go up. It does according to the CF , exactly.
Because of this you will need an accurate barometer , thermometer , and a means of determinig humidty. The cheapest and easiest way to determine humidty is dry bulb versus wet bulb temperature.
As the engine is loaded it will try to twist on your mount. Easily allowing the engine to twist is done using a wheel rim and bearing. The engine can be mounted using the original mounts to the turnable wheel and bearing.
Measuring this twist force is the load on the engine. You can use a 1 - 4 foot bar monted some where on the center line of the engine. A 400 pound shipping scale from Office Depot can be used to measure this force. As the lever increases the load is increased.
Use your internet search engine and go to flycorvair to see a dyno like this. I use google search to get a lot of possibilities. Please ask me or who ever on this board to get more info. Lee
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Thread: Engine Dyno
11-20-2008, 08:32 AM #1
Last edited by leeschaumberg; 11-25-2008 at 12:33 PM.
11-25-2008, 09:30 AM #2
This sounds not only like a disaster in the making, but alot of work just to measure horsepower. I don't think I'd want to be near anything like that spinning a prop. I think I'll stick to the standard, professionally run engine dyno, inside a room designed just for that purpose.
11-25-2008, 12:27 PM #3
A test cell or a Dyno made to run an engine is better but it will cost near 1 million dollars. I cant afford a million dollars may be you can. Spinning a prop is not dangerous unless safety precautions are not followed. Being a pilot of piston airplanes a spinning prop is only dangerous if you try to grab it while the engine is running.
With out a dyno people can say they have a zillion horse power. People use a dyno like this to test the horse power accurately with out killing themselves.Think Alot
And Then Do It Again & Again
11-25-2008, 12:42 PM #4
I was not implying that someone go out and buy a dyno, which costs no where near a million dollars but probably more around 100k. I was saying that it would be cheaper and less of a hassle to go and "rent" engine dyno time by the day. I generally do this once a year at a cost of about $500 for the day, and if things go well, you usually don't need a full day. Going back to your weather vs. HP comparison, I can say that based on my experience on the dyno and at the track, vapor pressure(or grains of water) has the most bearing on horsepower. The humidity may be the same for 2 different vapor pressure readings, but the lower VP reading will make more power.
11-25-2008, 03:03 PM #5Voigt Precision Welding, Inc.
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11-25-2008, 09:09 PM #6
One Meeeeeeeellion dollars!
That'd be on heIIuva dyno, for sure!