Anyone know a reliable way to get an RPM signal to a dynojet other than the OBDII bluetooth dongle that Dynojet has? My local AWD dyno does not have the dongle and we can’t find a good source to get an ignition signal from.
I’m testing an RS5 but I figure the RS4 is probably similar in terms of where to look.
I did take a bit of the sheathing off from the wiring harness leading to the coils near the throttle body. Not sure which one would provide a good signal though.
https://s20.postimg.cc/5307w6uod/72_E52084-936_E-40_B4-9895-_DBDBB41_B7187.jpg
The other option is “math” and the dyno does have software that’ll allow us to interpolate the rpm.
"The last option is gear ratio. This is a RPM option in the software which allows you to specify the gear ratio of the gear being tested as RPM divided by MPH, so that the software will calculate what RPM is based on drum speed at that point in time.
To calculate the gear ratio value, put the vehicle in the gear you will be making the run in, and then hold it steady at roughly 2/3 of the max RPM for the engine (or peak torque RPM if you know this). Take the RPM from the vehicle’s tach and divide by the speed you are reading on the dyno software speedometer. This is your calculated gear ratio. You enter it into the RPM configuration box below the drop down menu in the RPM Configuration. This works best on manual transmission vehicles and can provide RPM data when it is otherwise difficult to get."
I know the peak torque and the actual gear ratio of the S-Tronic in the RS5 too.
Second question…4th gear is 1.175 and 5th is .915. I’m assuming 5th would be better as it’s closer to 1:1 but at the expense of higher dyno speed and loading the car up for a longer period of time. Thoughts?