Engine Dyno's

[woollymoof]

Hi All,

Those of you out there using engine rather than chassis dyno's, how do you drive the dyno?

Is it via a chain off the engine sprocket, or direct drive off the engine output shaft, or direct drive off the crank, or any other way?
Do you use any rubber torsional vibration and shock suppressors between the engine and dyno?

Photo's of your setup would be good as well if possible.

Thanks

[woollymoof]

Hi All,

Those of you out there using engine rather than chassis dyno's, how do you drive the dyno?

Is it via a chain off the engine sprocket, or direct drive off the engine output shaft, or direct drive off the crank, or any other way?
Do you use any rubber torsional vibration and shock suppressors between the engine and dyno?

Photo's of your setup would be good as well if possible.

Thanks

[DontAsk]

Normally you would want to find a way to drive it directly from the crank, but being that this is a motorcycle engine, you'll likely drive it off the output shaft.

If any of the gears are 1:1 that would of course be your best bet. On the 600F4I 6th Gear is 1.075:1 which will throw your numbers off by 7.5% plus the loss in the gear box. I would hope that the software on the dyno would be able to compensate but would not count on it. The only other option would be to drive the engine dyno directly off the crank but you would have to fabricate the appropriate adapter to accomplish this.

Too many people worry about the number, the number, whatever the dyno might spit out does not mean diddly. What really matters is that you get a repeatable baseline number and measure your improvements from there.

The key to successful dyno work is consistancy. That means in the environment and in the running of the tests. Failure to control the tests carefully will result in flawed data.

[B Lewis @ PE Engine Management]

We have used both direct drive off of the gearbox (u-joint) and chain drive to couple the dyno and engine together. My preference would be to use the u-joint although both methods gave reasonable results. I think that it is more important to have the dyno and related hardware (control valves, hoses, water supply if a water brake is used) sized correctly for the engine than the method to connect the two. The small 4-cyl engines run pretty smooth so I am not sure what advantage a soft torsional coupling would provide but I don't have any experience using them in this type of application. I worked on a project with Harleys and dynos at one time, and those definately need torsionally soft coupling.

Good luck

[Dan Deussen @ Weber Motor]

DontAsk's comment on gear reduction is not quite correct. There is also a primary reduction from the crankshaft to the clutch basket to consider. In top gear most 600cc sport bikes will have close to a 2:1 reduction crankshaft to output shaft.

Personally, I have used both ways to couple an engine to a dyno, and I prefer the straight coupling using a shaft.

[DontAsk]

You caught me sleeping there Dan. I forgot about that. I've primarily done work on automotive engines.

Thanks for keeping me honest. I totally forgot about the reduction prior to the gearbox.

[VFR750R]

Chain seems to me to be the easy setup. It allowed us to gear the dyno up and get back some torque advantage over the engine. (Our absorber is small) And like DontAsk said, measuring changes is what matters so it doesn't matter how you hook it except which way is easiest. If both are easy and changing gear ratios to the dyno isn't important keep this in mind; we smoked an 530 oring chain in 4 months of dyno testing, which means our readings were different at the end of those 4 months then at the beginning. Keep your sprokets big to keep chain tension down too. U jointed shaft may be longer lived and reliable.