My local shop just installed a brand new 2006 model Mustang dyno. We wanted to make some baseline pulls before we installed the EWP to compare to any gains after the install. Here's where it gets interesting and forgive me if you know this already...You can manipulate the numbers significantly by changing what the dyno computer thinks the rollers weigh...The standard is around 1550 lbs...If you change to higher numbers, meaning the dyno thinks the rollers weigh more, your numbers increase tremendously...We made one pull at 410rwhp with the rollers at 2050 lbs and then changed to lower numbers, around 1550 lbs and got 366!

Those who have followed my posts know that I don't have a whole lot of faith in dyno numbers. I think dynos are a great tuning tool and I let the track mph be my hp dyno...Anyway, just putting it out there. I can see how easily it is to manipulate the numbers very substantially. This opens the doors for overinflated numbers for people who like numbers but may end in disappointment at the track. This may explain why my friends Corvette dynos at 420rwhp but has 119 mph..and my numbers are way lower but trap 118..mmmm...Anyway, just passing along an interesting observation that I was not aware of...Going back today to do the "after" dyno pulls to see EWP gains...

 

true but when a dyno is properly set up it should be dialed in to the weight of the rollers.

 

I believe this was already stated in the original post. (in the dictionary, under the word "redundant", it says, "see 'redundant'")

 

I was just saying that while the dyno is/was properly set up, all it takes is the operator to simply change the "weight" of the rollers to a higher number and you'll have a much higher rwhp figure than it really is. It took a second to change and you would never know unless you asked to see what the effective weight of the rollers was...Just passing along info I thought was interesting...Maybe this info is only good for the new Mustang dynos which allow for roller weight adjustment..didn't mean to be redundant...

--Alan

 

You weren't redundant. I perfectly comprehended what you were saying.

 

Maybe your findings explain why a aftermarket mass-air flow sensor adds 20 horse to the wheels.

 

This might explain why you may get different numbers on different dynos, not to mention if they set the SAE correction and simulate the same barometeric pressure/altitude and humidity. Yes, the weight would alter the numbers because the hp/tq is computed based on how quickly you accellerate the dyno wheel, so weight is very important in that calculation.

So, yes, make sure you always use the same dyno when testing/tuning and make sure the weight and the SAE factors are set the same for each test and each time you return to that dyno. And brand does not matter, its this way for all of them as the same software can run of most of them.