Quote Originally Posted by JeepLab View Post
Ive been searching for about 40 min now, and cannot find a clear final answer about the inner working of the dynojet. Ive read arguments from both sides of this in other forums and there is no clear post that would settle this.

I will call dynojet tomorow and make them email me a response I can post.
It will depend on exactly which model of dynojet dyno. Some are inertia dynos, others are load bearing dynos.

Simple inertia dynos are only capable of acceleration sweep tests, and the load is simpy the mass of the dyno drum. This type of dyno is 100% guaranteed to have the problems I'm trying to describe with significantly different results with a turbocharged vehicle with different transmission and/or axle ratios. Rotational inertia of the drivetrain/tires/etc also affects the readings on these dynos, 100% guaranteed.

Load bearing dynos are capable of performing steady state dyno pulls, where it holds the engine steady at full throttle and records the amount of load (torque) was required to hold the engine at a steady rpm (rinse and repeat for many different engine speeds, and you get data points to form a cull rpm range dyno chart). This would give consistent results no matter what transmission gear, axle ratio, or tire size was used, because there is no torque lost to accelerating those components (so therefore no differences in the amount of torque lost to accelerating different configurations of those components), and the turbo lag would not be an issue either because the turbo would be allow to spool up at each rpm point and reach equilibrium before the measurement is taken.

Load bearing dynos can also perform acceleration sweep tests, but can be configured to perform the sweep in different ways. This is even more complicated than a sweep test on an inertia dyno, because at least an inertia dyno can only operate in one mode. The results of a sweep test on a load dyno can be affected by a combination of gear ratios, tire size/weight, AND how the dyno operator configured the dyno to operate (slower sweep with more load? faster sweep with less load? constant load? varying load to achieve constant rate of acceleration?).

Yes, it's a big mess