Dyno horsepower loss

If I remember correctly you should see no less than 80 percent of hp on the dyno. Its prolly a 600hp.

 

~15% is a rule of thumb. It really depends on how it was dynoed. In brake test, which used to measure total power at the wheels and diagnose problems at certian RPM, you see less loss than an acceleration test. A brake test, also known as a step test, puts a full load on the engine by holding at a specific RPM and measuring how much braking power is needed to hold it there. They do that at several increments to give a curve, usually 250 or 500 rpm increments.

An acceleration test is a little different and often used to diagnose a miss or sputter under accleration. It's also popular to show customers estimated flywheel HP In that case, the dyno is programmed for an acceleration rate, 200 RPM/sec, for example. It shows less power because it is measuring while the driveline is accelerating, which takes power to do. But, an acceleration test also allows them to do a run down test, which just lets the driveline freewheel to slow down. By measuring the run down, it can calculate parasetic driveline losses fairly accurately to figure flywheel HP. There is a margin of error with the run down, heavier tire's wheels, driveshaft etc. have mroe inertia, so is acts similar to a more efficient driveline becasue it freewheels longer. They have correction factors that off set this, but it depends on the skill of the operator. A skilled operator can fudge the #'s to a certian extent too if he changed correction factors, so a trustworthy shop is important.

I'd guess, if your truck is all stock and rated at 500, they did an acceleration tests, then calculated flywheel HP based off run down. This is popular because customers are happy when they see #'s close to what they're "supposed" to be. It also saves a lot of time explaining why they are lower than they're "supposed" to be.

There are also inertia chassis dynos, but are more for racing applications. They have no brake at all and can only do acceleration tests. They are just a big drum with an known moment of intertia. The dyno calculates power based on the drums acceleration rate and engine RPM. They are very accurate, but lack the abilty to hold an RPM to diagnose problems.

 

We used 82% as the total driveline loss. That was with the fan on, no AC, none of the BS rev it up and jam on the load, it had to be able to pull the load for at least 5 minutes, then we would back off the load about 5%, and see if it would pick it back up.
Just a thought!

 

The dyno that I use to run we would see a loss of 25% on it from advertised horsepower. We would run the truck at 100% throttle and let the dyno control the rpm of the engine. We would do this at peak horsepower rated speed and then do the same at peak torque. Each run for one number would last between 20-30 minutes.