RPM pickup for Dynojet?

B6/7 S4/RS4
#1

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?

#2

Oh c’mon. I know someone on this forum has a good idea on the best rpm pickup point!

I actually asked a major shop (NOT JHM) and was told they don’t give out that sort of information. Like it’s proprietary to them. Really disappointing as we support them but they can’t seem to support us with a very small ask. I’d go dyno there but it’s a 1500 mile drive.

#3

Well my car is a bit older and the only other car I needed to do this was the same year as mine and thats about 10 years older than your car probably is.

From what I remember its green from the coil packs and purple off of the ECU.

You can do speed as thats what a lot of euro based companies do.You can actually pull open your vag com and log 003 and then block 006? whatever one is speed. Log those in each gear and you will be able to track rpm and speed quite accurately. 5th gear pull would be the closest to 1:! but thats crazy speeds on a dyno. If you feel comfortable then go for it but man…

Thanks for posting this. Let us know how things turn out.,

#4

We tried everything and we also ended up splitting the wiring covers just below the coils and going for wires coming right off said coils. No luck. Really strange.

I may have to seek out a different type of dyno. Anyone know how Dynapacks read engine rpm?

#5

we did all testing on dynojet. we just moved the plastic protective cover from the cables going to the coil and connected the little crocodile thingy to the cable. there are only 3 or 4 cant remember exactly but works every time. we used the port side fwd coil (1st coil on drivers side , the one closest to the bumper)

#6

We were never able to get a signal. I did pop the top half of the coil wiring cover and no matter what we tried, I could not get an rpm signal. We’re actually going to test on a different dyno (Mustang) where we know we’ll be able to get an rpm signal using their software.