When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I wish it were so easy, but these results will be all over the place with or without the exhaust. I hit 278 rwhp with SAE corrections when I was still stock. There are way too many variables, the biggest of which is the car. Some are factory monsters, and some aren't. Actually, the dyno machine itelf may be an even bigger variable than the car.
Here are my stock runs with the hood up vs down on a DynoJet. I don't know where I got the 278, but 274-276 for a stock IS350 on a DynoJet is a pretty significant variance from 265.
I'm trying to remember what SAE stands for ... I should know this since I'm an engineer ... ah forget it ...
SAE sets all kinds of standards for all kinds of engineering and scientific "stuff". They have derived correction factors that supposedly compensate for changes in temperature, barometric pressure, humidity, etc. so that a car would theoretically have equal dyno numbers in Denver Colorado during the summer as it would in Houston, TX during the winter.
All dyno's read differently even the same make/model. Best to use one dyno for all comparisons. There are way too many things that could be slightly different from one dyno to the other such as placement of the weather sensor and the correction factors in the software. But for the sake of this thread i'll vote.
Last edited by caymandive; Nov 16, 2007 at 02:35 PM.
"The Society of Automotive Engineers (SAE) has created a standard method for correcting horsepower and torque readings so that they will seem as if the readings had all been taken at the same "standard" test cell where the air pressure, humidity and air temperature are held constant.
The equation for the dyno correction factor given in SAE J1349 JUN90, converted to pressure in mb, is:
cf = the dyno correction factor
Pd = the pressure of the dry air, mb
Tc = ambient temperature, deg C
The pressure of the dry air Pd, is found by subtracting the vapor pressure Pv from the actual air pressure. For more information about pressures and calculation of the vapor pressure, see Air Density and Density Altitude.
The relative horsepower is simply the mathematical reciprocal of the correction factor."