Lefty's Deceiver

Folks,

Anyone done this on a 911? I have a 3.2 Carrera and want to hook up the RPM signal. The manual says it requires a 5-18 V, 50% duty cycle, square wave output signal.

Is that type of signal available on the rear of the Tachometer? What kind of signal drives the tach? I don't have an oscilloscope so cannot check.

Thanks
Tristan

bobt993

[QUOTE=Lefty's Deceiver]Folks,

Anyone done this on a 911? I have a 3.2 Carrera and want to hook up the RPM signal. The manual says it requires a 5-18 V, 50% duty cycle, square wave output signal.

Tristan,

Works directly off the tach on my 993. I probed the wires with an oscilloscope to find the proper pulse/duty cycle. I passed this onto to another Rennlister and it worked just fine for him. I am not sure if there are any diffs in the harness for my 96 993. If you want the picts of what to look for a can send them directly to you. The whole effort takes 30mins and calibration takes another 5 mins or so.

kary993

I sell these G2X units and you should be able ot hook directly to tach as mentioned.

TheOtherEric

As an alternative to tapping into the tach on a 993, I'd recommend tapping into the thick pack of wires that connects to the ECU under the drivers seat. RPMs is pin 6, Black/Violet. While you're at it, you can easily grab the throttle position sensor signal, which is pin 53, White/Green. That might not help tristan but I'd thought I'd throw that out for any 993 owners.

Matt Marks

Ditto this. All of the 911's that I've heard of with this unit also tap at the DME. I tapped pin 6 as well on my 968 - took all of about 15 minutes to do.

May want to PM APKHaos (Tony) from Trackvision as he's helped a bunch of guys with all sorts of dataloggers on how to do installs and he always has them tap the DME.

APKhaos

Eric is absolutely right. This is the best solution, by far. Adding the TPS signal is a real plus. There are no standard analog inputs with the G2X, so there are a few extra pieces to buy to input the TPS signal. Tim at Racepak can give you details. You need a 680-CA-AUX-084 Aux to Vnet cable and a 230-VM-AN-5V 5V analog Vnet.

TPS is a VERY valuable signal to log. Brake pressure is another. In both cases, most people are surprised at how much they are off full throttle when they would have sworn that were at full throttle. Same for brake pressure, which will show you more about your braking habits than you ever wanted to know :-)

kary993

While you can hook up to the DME here is a picture of the wires on the tach for your reference.

Lefty's Deceiver

OK. Thanks guys. I have found the black and purple wire on my tach...will also look on the DME. Incidentally, this color wire was the same on my 74 Carrera!

Tristan

Cris Brady

Tony, do you know if anybody has pulled the TPS signal from a later 944na? I don't want to go diving into the electrical diagrams if somebody else has already done this. I don't even know if the n/a's even have that signal.

APKhaos

Cris,
The 89 944 does not have a throttle position signal. Its a simple switch for idle position, which is not useful. DME Pin 7 is the output of the air flow meter. I suspect that this would give a useful reading of throttle state, even though its slightly delayed from the acutal gas pedal action.

cstreit

Do you just tee off the tach signal wire then?

When I tried this trick on my 70 to hook up the DL-90 Aquisition system not only didn't it read enough signla for the unit, my tach stopped working! I finally had to rig up an inductive pickup...

APKhaos

Chris,
The DL-90 has two separate RPM inputs - a high level input for an inductive picku, and a low level input which works nicely with tach or DME signal. Did you try the low level input?

I've used the inductive pickup with varying success. Most annoying feature was that the RPM would fall to near zero when the throttle was off - during braking. Drove me crazy trying to fix that!

Lefty's Deceiver

I got it working - thanks everyone. I just spliced into the black and purple wire. Easy.

However, I did notice that the tach reads higher than the G2X so I have no idea which is correct. My idle is about 660 rpm - Tach shows around 900 or so.

Thanks very much for the information.

Tristan

bobt993

You need to calibrate the rpm's by following the setup on the unit. I know, boring, but read the manual and it will walk you thru.

kary993

Just use the in car display to set the number of cylinders, this will get your RPM's to read correctly. You are likely not set to the correct numberof cylinders, 4,6,8?