Why are dyno's diferent

[WILLSGTIR]

WTF Bob! Why is there such a diference in dyno's? my car has a 20hp- diference spanned over two days on three diferent dyno machines.264-256-278 .the variable were not diferent and other than about 10 degrees in outside temp, but it was still done on cold days between 40 and 50 degrees both days. boost was stable. how can the operator control the machine or is it all in the initial calibration? and no i havent rulled out that mabye the car is being bitchy but i feel sertain the operators have some control. the highest number was set at a shop that i vist from time to time and the other two are just pro shops for the v8 guys.

[Jason@JGY]

WTF Bob! Why is there such a diference in dyno's? my car has a 20hp- diference spanned over two days on three diferent dyno machines.264-256-278 .the variable were not diferent and other than about 10 degrees in outside temp, but it was still done on cold days between 40 and 50 degrees both days. boost was stable. how can the operator control the machine or is it all in the initial calibration? and no i havent rulled out that mabye the car is being bitchy but i feel sertain the operators have some control. the highest number was set at a shop that i vist from time to time and the other two are just pro shops for the v8 guys.

This is probably the in debth question and might be called the *smartest* question that we have had so far.

It is also the hardest question to answer correctly.

There are many factors that affect numbers.

1. Probably the most important is the brand of dyno. Realistically, all dyno's are a mechanical device that uses electronics to convert values into values that you and I want to see. When our first group of guys from MD came here to calibrate our dyno, they sucked......... We were dynoing cars with values that I knew were wrong. We ended up getting a review and had our entire system redone. Afterwards, the numbers were what they should be......or close. Here's the thing, it's still a subjective calibration. But after it is set, all the numbers that spit out are based on the same basis. This means that if our dyno is off by .0002 percent, then it is consistently off by that amount. Also, .0002 has a greater change on a 999ft/lb of torque truck than on a 200ft/lb car.

2. Different brands of dyno's calibrate and verify values in different ways. Our dyno uses a brake to make the numbers more realistic. Dyno's that don't, will have higher numbers. That doesn't mean you can't tune by the values, but that the values are not *true*.

3. Variables that you may not think are important, are. Alignment, interior motor temperature, and dyno temperature are very big variables and hard to catch. My rule of thumb is this................"6% rule" I mean, that a 6% variable is a fair enough value to call something even. Let's say that on a given day, you make 300HP up here. Let's say that later this year, you make 282HP. I'm ok saying that nothing *may* have changed with your car.......and that it may still make the same power. When you count a load bearing dyno like ours compared to a free roll DynoJet, that 6% would make you laugh.

4. Bottom line is that dyno's are tuning tools for JGY and comparing your 1/8th mile time in BFE to my 1/8th mile time in our awesome town is not comparable, unless I win.


p.s. Your wife wears the pants. She called and wants yours taken in.