Dyno’ing a manual transmission car is easy. For those with no experience on a dyno, the general idea is to get the tires rolling, slowly shifting up through the gears until you get to the gear that is closest to 1:1. Most cars, this is 4th in a manual transmission. Once rolling in 4th at about 2000-2500 rpm, you press start on the dyno and floor it. Once you get to terminal engine speed (whatever you have chosen as max RPM), you let off, and the dyno slows down.
If you try flooring an auto trans car at 2000-2500 rpm, the car will downshift, no matter what gear you have selected. Many dyno shops will simply floor it and let it run through the gears. The problem with this is that you don’t get a good idea of the hp/tq curve below about 5000 rpm. You will get peak HP and depending on turbo / engine setup, maybe peak TQ as well, but, like everything else we do on this website, there is a better way.
Our a650e automatics are 5 speed transmissions as well. That in mind, the 4th gear is the gear we want to be in to dyno. It is exactly 1:1, which is ideal. So, follow these steps to get the most accurate dyno possible. Select manual mode and downshift as far as possible using the steering wheel buttons – you will be limited to 2nd gear. Put the car in snow mode. Power mode will make no difference on the dyno. Get the tires rolling, up to about 20 mph and upshift to 3rd using the steering wheel buttons. You should feel it shift. Slowly accelerate more to about 3000 rpm in 3rd. Shift to 4th, you should feel it shift and the decrease in RPM. Now that we are confirmed in 4th gear, slowly accelerate to 3200 rpm. The dyno operator should hit the start run button at this point. Floor it. RPM will climb – be ready though, at 4000 rpm, you will want to turn off snow mode. This is when the fun really starts. Obviously, let off when you reach the maximum RPM you wish to achieve.
Why does this work, and why snow mode? Simple – snow mode prevents downshifts except at very low RPM. Even as low as 3000 RPM. The downside to snow mode, and the reason we have to turn it off at 4000 RPM is that is also limits throttle open percentage to approximately 60%. Won’t make much power that way.
So, now you know the best way to dyno your automatic IS300.
This also works on the road when using software to interpolate horsepower and torque, such as Virtual Dyno.