Anyone ever strap their cars down to both a dynojet....

[blykins]

Tony, I agree with your thinking.

Dynos are delta devices only, but it seems like a lot of builders get roped into the dyno wars debacle.

There was a post on my other thread about adding engine dyno results to my webpage, and a reply was made that it needs to be coupled with a chassis dyno report. However, there is no direct correlation, and with different chassis dynos even showing 10-12% differences between brands, I can't see how someone can put that constraint out there.

And....

There is no golden standard. Even on engine dynos. The only way you could even make an A to B connection would be to have both an engine dyno and chassis dyno in a facility, pop the engine off the engine dyno, stick it in the car, then put the car on the chassis dyno. And even then, the only thing you would be able to say, would be: "Here's a correlation between *my* dynos."

[Cobra #3170]

Originally Posted by blykins

Tony, I agree with your thinking.

Dynos are delta devices only, but it seems like a lot of builders get roped into the dyno wars debacle.

There was a post on my other thread about adding engine dyno results to my webpage, and a reply was made that it needs to be coupled with a chassis dyno report. However, there is no direct correlation, and with different chassis dynos even showing 10-12% differences between brands, I can't see how someone can put that constraint out there.

And....

There is no golden standard. Even on engine dynos. The only way you could even make an A to B connection would be to have both an engine dyno and chassis dyno in a facility, pop the engine off the engine dyno, stick it in the car, then put the car on the chassis dyno. And even then, the only thing you would be able to say, would be: "Here's a correlation between *my* dynos."

Agree on the delta factor, when my son was racing gokarts I built a dyno to evaluate different engines. My design used a power absorption unit with a calibrated load cell. That thing led us down the wrong path many times even though I was using accepted correction factors for density altitude. We finally built a standard engine that we only used for back to back comparisons when dynoing a new engine. That actually worked because it gave us a delta from the standard engine to the compared engine. We tested the standard engine from time to time under the same conditions of humidity, barometric pressure and temperature to make sure it remained a good standard and wasn't wearing out or getting better. The main thing I learned was that if you wanted to get a new track record (they charged $10 per attempt) you did it on a cool day with a very high barometric pressure. I tried making my own correction equations but the actuals were so non linear that it was never as accurate as back to back with our standard engine.