Re: Top 10 Dsm Dyno Numbers
 

Are you talking SAE atmospheric correction or an SAE standard on one dyno brand to another? The numbers I was giving are SAE corrected vs SAE corrected from DD to Dynojet.

Even the most basic SAE atmospheric correction has problems on boosted cars.

Re: Top 10 Dsm Dyno Numbers
 

Either. I have zero knowledge of correction methods.

Re: Top 10 Dsm Dyno Numbers
 

Correction factors are used to try to correct to a common weather condition. When it works correctly then you can go an compare your HP number from one day to the next without there being huge differences and it can help you compare to cars in other parts of the country.

SAE correction works off of an environmental condition of 77 degrees F, 29.235" Hg barometric pressure, 0% relative humidty and 0 feet above sea level

SAE corrects the run to the following atmospheric conditions: 29.235" Hg, 77 deg F, 0 % relative humidity, 0 altitude. So when it is hot out, the dyno adds in a calculated perfect more power/torque to similate what it would make in a perfect SAE environment. On normal nice cool fall days here in MN, we might see 0 - 3% of additional correction, in the summer when it's hot and humid it will be more like 5 - 7+%. If you are dynoing when it's cold enough out to drop the dyno room temp down then your numbers will actually get corrected downward, since the car should be making more power with the cold temps.

There are other correction types(STD, DIN, EEC, ???). The most common non-SAE settings you see are uncorrected and STD. A lot of times people confuse STD with true uncorrected numbers. STD works like SAE, but it is an older formula and it has a tendancy to inflate the HP number more than SAE, so you will often see dyno charts still posted with STD correction, since people want to see higher numbers.

Normally SAE correction works very very well, but it is designed around naturally aspirated cars. At lower altitude, this isn't a problem at all, but at high elevation, like Denver, Salt Lake City, Albuquerque, etc you can end up with very inflated HP readings on forced induction cars. At higher elevation, you still have the same ~21% oxygen in the air as at sea level, but you are starting from a lower barometric pressure. So a naturally aspirated car will never even get close to 0psi at Denver altitude. SAE correction then does it's job by factoring in the lower barometric pressure and giving a HP number close to what it would make at sea level. The problem is when you add nitrous or boost, you no longer in the saem playing field. Spraying a 50 shot of nitrous at 5000ft gives exactly the same amount of power as doing it at sea level, so the ~25% correction that SAE normally gives at Denver altitude overcompensates too much. The same problem happens on boosted cars. If, on your pressure sensor in your AEM EMS or whatever, you have 30psi of boost in your intake manifold, then it's just like having 30psi of boost at sea level. You have the same 21% oxygen content air at the same pressure. But the dyno just treats it as a pressure challenged all motor car and way over corrects. So, usually using totally uncorrected numbers at high altitude on boosted cars is much more accurate than SAE or STD in those places. You have more lag at high altitude because you are starting from a lower pressure environment to begin with.

Re: Top 10 Dsm Dyno Numbers
 

There isn't any standard that I know of for chassis dyno calibration. So every dyno manufacturer has a bit different numbers that come out of their dynos. And some dynos can be calibrated differently too.

You will see general conversion numbers online from one dyno company to another, but from personally experience with Dynojet, Dyno Dynamics and Mustang Dyno, the usual quoted numbers are a bit off.

Uncorrected from highest reading to lowest dynos:

Dynapack
Dynojet
Superflow
Mustang
Dyno Dynamics

The Mustang dynos are hard to compare though. They can and often are calibrated differently from one to another. The one at Sound Performance in Chicago is calibrated to read like a Dynojet, while the one at RS Motors seems to read a little lower than most Mustang dynos I see online.

I don't know if any of the dyno numbers are the "real" numbers. Buschur had posted a short article on why the Dynojet numbers were higher. It had to do with how after careful calculations and building thier first dyno, the HP numbers seemed too low compared to the factory HP rating at the engine, so they ending up adding in a fudge factor to make the numbers seem more reasonable.