The operation of the dyno is fairly simple. Below this article is a picture of my dyno control panel. I have numbered the parts that I will make reference to in this article. Item number 1 on the panel is your dyno oil temperature. You will want to keep an eye on this. I keep my oil temp around 125 degrees. This is important because cooler oil will show slightly higher pressure numbers. Make sure you stay consistant with your oil temp.
Item number two is the tachometer and cylinder head temp guage. I used a single display on mine because that was all I had but a dual display would be much easier to get the readings from.
Item number three is the outside temperature and humidity. You will need this info along with the current barometric pressure to make your corrected calculations.
Item number four is your system pressure gauge. This is where you will get your raw PSI numbers from to make your calculations.
Item number five is the needle control valve. This is used to control the RPMS of the motor once the dyno run has started.
Item numer six is a flow gauge. If you are using the pump I mentioned in the parts list you don't need to use this. I put it on mine to test the calculations and my calculations were correct so I don't even look at this anymore. It just adds one more thing you have to look at while you are making a dyno run.
The way I am going to tell you to make a dyno run may or may not be the correct way. Everyone develops thier own formula that works for them. I'm going to tell you how I do it and then you can take it from there.
Mount the engine up on a motor mount then mount it all to the dyno just like you would a kart. Keep the chain fairly snug but not too tight. You will want it tighter than you normally run it on your kart. Once you have the motor bolted down and the chain tight you can attach your throttle linkage, CHT, and tach sensors. Once you have all this attached go ahead and fill it up with fuel (to the seam) and put your oil in.
Go to the control panel and make sure your needle valve(item 5) is backed all the way out counter clockwise, this will take all the restriction off of the engine. Make sure your throttle is at or near idle position. Go ahead and start the engine now.
Once you have the engine started you will want to rev it up to about 2500 rpm's and put about a 100-200 pound load (by turning the needle valve clockwise) on the engine to get the motor and the dyno fluid up to temperature. Now, you won't be able to get the motor temp up to normal racing temp until you actually start putting a load on it at full throttle. What you are looking for is to get the engine up to 250-300 degrees on your CHT(item 2). You may have to put a little more than 100-200 pounds(item 4) if it's not up to temp in about 2-3 minutes. By the time the motor comes up to temp your oil should be in the 100-110 range(item 1), if not don't worry it will warm up as soon as you start your pulls.
Once the motor and the oil is up to temp you are ready to start your pull. What I do is get the motor in the 2500-2800 RPM range(item 2) and start turning in on the needle valve(item 5) until you see the motor RPM's drop about 200 rpm. You are now ready to start your run. Go ahead and start opening the throttle and closing down (clockwise) the needle valve until you have reached full wide open throttle. You want to make all your test with the motor throttle all the way open. You control the target RPM's with the needle vavle. The more you turn the needle valve in the lower the engine RPM's will be. I usually start at the low end and work my way up. I usually start an unrestricted engine about 3500 and work up in 500 rpm increments. If you have someone to help you write down the data you can go right through the test without stopping and just writing down the pressure from the gauge at your desired RPM. I usually do mine on my own so I have to get it to the target rpm and let the load off so I can write down my data then move to my next test point. I input all my data into a Excel spreadsheet that does all the calculations for me. That's pretty much it. If you have any questions drop me an email.
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You can reach me at phinishline@yahoo.com for comments, questions, and suggestions.