Engine Dyno's

[XTRMEASURES]

Me and a buddy was talking about dyno's and the question came up that are all engine dyno's the same. Do differnt dyno's give different hp rating's. If you use the same engine and test them on multiple dyno's will you get a multiple hp numbers.

[Pro Stock]

Me and a buddy was talking about dyno's and the question came up that are all engine dyno's the same. Do differnt dyno's give different hp rating's. If you use the same engine and test them on multiple dyno's will you get a multiple hp numbers.

Most engine dynos will give you different numbers, some by a small amount and others by larger amounts. First of all is the difference in the quality of their water brakes and the strain guages used in the manufacturing of their products. Another big factor is how well the air supply is delivered to the engine in order to ensure a consistant quality air supply to the engine, and then there is the accuracey (sic?) of their data acquisition system. The answer to your last question is, yes, you will get different numbers with the same engine on different dynos. The best way for you to test is to go to a facility that has dyno'd engines for the people that your trying to compare your stuff to, that way you will have an apples to apples baseline to compare to, all of these rules will apply to a chassis dyno also.

Dale

[wmhjr]

Also, remember that dynos actually measure torque. HP figures are nothing more than a math formula being applied to torque/rpm data. Dynos can be very different, with even different software versions of the same dyno or different configs of the same software delivering different results. They can be deliberately manipulated as well by the operators.

One example I had was a dyno sheet I got after building a harley V-Twin motor. I looked at the graph and instantly realized that the shop in question was pulling some funny business. The torque and hp lines did not intersect at 5250 rpm. I wonder how many people they "tuned" that are walking around with clearly invalid graphs.

As I recall, the formula is Horsepower = Torque x RPM x (1 min / 60 s) x (2pi rad / 1 rev) x (1 hp / 550 ft-lb/s) = Torque x RPM / 5252. It's because 1 mechanical HP = 550 ft-lbs per second. There are a bunch of ways to manipulate a DynoJet or Mustang for example, to generate different results.