Page 28 of 2008 Performance Parts by Ford Racing Performance Parts

ford racing calibration dynamometer testing and ford racing calibrations why do certain companies claim to make more power with their power upgrade kits than ford racing does with their kits to address that question properly it is necessary to understand some of the intricacies of chassis dynamometer testing as well as some of the compromises that must be made in order to simultaneously meet performance emissions durability and safety objectives chassis dynamometer testing there are two types of chassis dynamometer dyno in widespread use today · an inertia dyno uses a large spinning drum that is accelerated by the drive wheels of the test vehicle power is then computed by knowing the inertia of the drum and how quickly it was accelerated torque can then be calculated by knowing the speed of the drum · an eddy-current dyno absorbs and measures power by rotating a metallic disc through a magnetic field without getting into which dyno is more correct under what conditions and why we will simply say that these two types of dyno typically do not always give the same result even with all else being equal it is generally not possible to accurately compare numbers from one type of dyno with those from the other type of dyno each type of dyno has its own advantages and disadvantages but as long as all the tuning work is done on the same type of dyno it doesn t really matter which one is used with any dyno testing there is a need for correction factors that are applied to the raw numbers the dyno actually measures these correction factors are an attempt to correct for varying atmospheric conditions such as humidity barometric pressure and air temperature the two most common standards are sae j1349 and sae j607 sometimes known as std on some dynos how correction factors are calculated is given in the crate engine section of this catalog for this article understand that these correction factors will give results that are different from each other with sae j1349 typically about 4 lower than sae j607 oems will almost always quote j1349 corrected numbers when advertising horsepower and torque whenever comparing dyno results always be sure that the numbers are corrected to the same standard despite these correction factors atmospheric conditions can play an additional role in terms of ignition timing the correction factors account only for the change in the density of the air due to atmospheric conditions and cannot account for things like engine borderline spark sensitivity as inlet air temperature increases the pcm will generally retard spark to prevent detonation using the particular octane of fuel for which it was calibrated correction factors cannot account for this because different engine designs can have different spark sensitivity and different sensitivity of torque relative to ignition timing basically this means that the closer the actual conditions are to the sae j1349 standard 77 deg f inlet air 29.31 inhg barometric pressure the more comparable the results are to those quoted by the manufacturer most horsepower numbers in the ford racing catalog have been determined by using the sae j1349 standard when testing a particular calibration or performance enhancing part by performing back to back dyno runs it is critical to keep test conditions as similar as possible between the runs this sounds obvious but is very commonly overlooked by many aftermarket companies who frequently publish dyno charts depicting large gains but fail to give all the necessary data to show the tests were run under similar conditions in order to be certain that the test conditions are as similar as possible the following data is mandatory and needs to be collected for each run · ambient air temperature · barometric pressure · inlet air temperature on a forced induction car this is usually downstream of the power adder · air/fuel a/f ratio preferably upstream of any catalyst truly meaningful power numbers cannot be collected without this data 26 techline 800 ford788

[close]