Any Guesses to HP Loss With Emission Control?

[K5lwq]

It was tested before and after.

Weather conditions very similar both days.

First dyno was showed 35 HP and 345 ft lbs of torque. This is stock with filter and 9 hrs on the tractor.

Today it was 36 HP and 415 ft lbs. It actually hit 438 ft lbs before falling completely off at 500 PTO rpm. Tractor has 15 hrs after test was complete.

The dealer does not have the printer for the dyno so no print out to share. They only use it for loading tractors while diagnosing issues. They never use it to rate HP so it has never been calibrated.

If you use the formula HP=torque x RPM / 5252 you get a 7HP gain. That would put the tractor at 42 PTO HP and more in line with advertised rating of 40 PTO HP.

There is another thread in the Branson forum where I documented the process. This thread was intended to be fun to see who could guess the change. However, the results to me are questionable as the dyno contradicts itself.

I monitored the readings and RPM as both test were done by same tech. It held power down to 500 PTO RPM then fell off quick. This was a computer monitoring dyno.

 

[finn1]

Dealership pto dynamometers are notoriously inaccurate. They are not equipped with laboratory grade instrumentation, and you really can’t really can’t rely on a simple back to back pull for good information.

I spent thirty five years in an Oem engine lab environment, with upwards of forty engine test cells and a half dozen chassis rolls. The instrumentation had a calibration program with traceability to the National Bureau of Standards.

At the very least you would have to do a number of back to back to back to back (A-B-A-B) tests to establish test to test reproduce ability with such a crude setup, and even then, the absolute numbers would be garbage.

Our test cells cost upwards of several million dollars each, and had a dozen or more support staff, something no dealership service department could afford.

The torque reading disparity between the two runs is particularly questionable if you understand how back pressure affects airflow. I assume the engine you are dealing with is naturally aspirated. Airflow is pretty much a function of engine speed, so back pressure is nil at low to mid engine speed. Eliminating a restriction in the exhaust would have little effect at peak torque compared to rated, so there would be little effect at peak torque compared to your reported results.

Garbage information.

Also, remember that a dyno measures torque only. Horsepower is a calculation of torque and engine speed, or in this case, pto speed. (HP= TorquexRPM/5252)

 

[K5lwq]

Dealership pto dynamometers are notoriously inaccurate. They are not equipped with laboratory grade instrumentation, and you really can稚 really can稚 rely on a simple back to back pull for good information.

I spent thirty five years in an Oem engine lab environment, with upwards of forty engine test cells and a half dozen chassis rolls. The instrumentation had a calibration program with traceability to the National Bureau of Standards.

At the very least you would have to do a number of back to back to back to back (A-B-A-B) tests to establish test to test reproduce ability with such a crude setup, and even then, the absolute numbers would be garbage.

Our test cells cost upwards of several million dollars each, and had a dozen or more support staff, something no dealership service department could afford.

The torque reading disparity between the two runs is particularly questionable if you understand how back pressure affects airflow. I assume the engine you are dealing with is naturally aspirated. Airflow is pretty much a function of engine speed, so back pressure is nil at low to mid engine speed. Eliminating a restriction in the exhaust would have little effect at peak torque compared to rated, so there would be little effect at peak torque compared to your reported results.

Garbage information.

Also, remember that a dyno measures torque only. Horsepower is a calculation of torque and engine speed, or in this case, pto speed. (HP= TorquexRPM/5252)

Thank you for the information. At least I tried. Lol

What does surprise me is understanding that the dyno measures torque and calculated HP, how can the computer hooked to the dyno show 415 ft lbs of torque and only 36 HP at 540 rpm? Makes no sense.

None the less garbage information is correct.

 

[LouNY]

It was an interesting test and now your tractor is feeling better to you and pulling a bit better,
with no filter to plug up and cause issues.
enjoy her