Track Tac

Prototype dynomometer

Dan Brown said:
I just bought a prototype dyno too, mine is set up for 4 cycles direct drive, but I build 2 cycles so I am going to add a sprocket drive to it so I can drop the rpm of the pump input for the higher revving engines. Your dyno.com has a great setup for under $1000. It comes with air temp and pressure sensors and corrects for weather automatically , plus they give you the correct load cell for your application. The unit runs of USB power, comes with software for your laptop and everyone I have spoken too that is running it is extremely happy with ease of setup, accuracy and customer support. Where are you located?
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I'm in ks. The guy I got mine from tested on 2 cycle engines also. I also build 4 cycle engines.
 
The manual that came with mine uses hydraulic pressure X gpm flow / 1714 = hp. You can use the correction factor app I found online and enter current weather conditions to get corrected hp. I have tried mine with several engines on completely different days and and the corrected hp is virtually identical for the same engine on a different day.
 
Dan Brown said:
The manual that came with mine uses hydraulic pressure X gpm flow / 1714 = hp. You can use the correction factor app I found online and enter current weather conditions to get corrected hp. I have tried mine with several engines on completely different days and and the corrected hp is virtually identical for the same engine on a different day.
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I get 6.56 hp uncorrected with that formula .
 
Dan Brown said:
The manual that came with mine uses hydraulic pressure X gpm flow / 1714 = hp. You can use the correction factor app I found online and enter current weather conditions to get corrected hp. I have tried mine with several engines on completely different days and and the corrected hp is virtually identical for the same engine on a different day.
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Really the manual I got says psi x gpm÷1400=hp. What does yours look like?
 
:cool: 14 hundred if your selling 17 if your buying .
 

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I just looked it up, it's pressurexflow/1714. And flattop and I are close in numbers, I did a predator I bought with a pipe on it, but it's stock otherwise ( to my knowledge, I haven't dismantled it) and I got 6.77 corrected hp
 

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Does yours have a hydraulic preheater on it? Mine does, and it says the oil should be between 100-130 degrees F for every run too, so results remain consistent
 
Dan Brown said:
I just looked it up, it's pressurexflow/1714. And flattop and I are close in numbers, I did a predator I bought with a pipe on it, but it's stock otherwise ( to my knowledge, I haven't dismantled it) and I got 6.77 corrected hp
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Dan Brown said:
I just looked it up, it's pressurexflow/1714. And flattop and I are close in numbers, I did a predator I bought with a pipe on it, but it's stock otherwise ( to my knowledge, I haven't dismantled it) and I got 6.77 corrected hp
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This is what came in my manual...
 

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Mikesims84 said:
Barometric pressure: 29.98
Humidity: 66%
Air temp: 53°
2250psi@5gpm
Comes out to 8.21hp before correction.
Msa corrected hp is 9.38 according to the calculator for flywheel hp.
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Correction factor comes out to .943, that means your corrected horsepower is less than your Indicated horsepower. Corrected horsepower is 7.76.


Most dyno software does their calculations assuming dry air. . The correction factor for humidity changes so little in a normal day, or period of time, it's of no consequence.
 
alvin l nunley said:
Correction factor comes out to .943, that means your corrected horsepower is less than your Indicated horsepower. Corrected horsepower is 7.76.


Most dyno software does their calculations assuming dry air. . The correction factor for humidity changes so little in a normal day, or period of time, it's of no consequence.
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The correction calculator I found on robrobinette.com says the correction factors is 1.0021882185336766. idk which one to go off of... Uhg
 
2250psi@5gpm
What does that mean? I understand psi, but I need the RPM at which set reading was taken. What correction factor did yoou use?
 
Was that test sheet in your manual? It appears to be something a previous owner put together, not sure why he used 1400 as the number. If you look up calculating fluid hp the 1714 figure comes up on all the equations. Using 1400 your hp is going to come out much higher than using 1714. I believe if you put the same engine on 2 different dynos, and th conditions were identical the results would not be the same. One pump could be slightly more wore than the other giving different pressure readings, etc. I am more concerned with comparisons between different setups like timing, squish, port heights etc.
 
Dan Brown said:
Was that test sheet in your manual? It appears to be something a previous owner put together, not sure why he used 1400 as the number. If you look up calculating fluid hp the 1714 figure comes up on all the equations. Using 1400 your hp is going to come out much higher than using 1714. I believe if you put the same engine on 2 different dynos, and th conditions were identical the results would not be the same. One pump could be slightly more wore than the other giving different pressure readings, etc. I am more concerned with comparisons between different setups like timing, squish, port heights etc.
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Not sure, it seems to be on the same paper stock as the manual so unsure. Am going to try to find more info on who built it and find out exactly I guess.
 
Mikesims84 said:
The correction calculator I found on robrobinette.com says the correction factors is 1.0021882185336766. idk which one to go off of... Uhg
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People publish dyno run numbers, RPM – torque – HP. When I put those numbers (RPM – torque) in my spreadsheet, it calculates pretty much exactly the same horsepower. I have the temperature and. Pressure set to the standard for a correction factor of 1.0. I'm pretty confident that the numbers I gave you are right. Still, I'm always open to suggestions and corrections if you can document them.

What I'm saying is; I'm right and the numbers you were given are wrong. Kind of a bold statement, true, but I am very confident in it!

I probably just lost a bunch of fans!
 
Looks to me like both can be correct, or both wrong.

Depending on which standard you set your correction factor to.

The J1439 SAE standard produces a number less than indicated hp.

The motorsports std and the std day correction factors produce a number greater than indicated hp, all using the numbers provided by the poster.

All 3 standards assume 0% humidity.

Which, by the calculator in question, indicates a measurable difference in correction factor.

Here is the calculator I used.

https://robrobinette.com/Dyno_Correction_Calculator.htm
 
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