Wiring up Gauges Subaru = Porsche

OK, this is really going to test the brains trust out there.

I'm building a speedster with a Subaru 2.5 twin cam motor, and have aquired a set of Porsche 911 instruments.

Any clews on wiring up the instruments, in particular... the Tacho.. gulp.... any help out there ??

Bill

Provided the tachometer is designed for a 4 cylinder, you shouldn't have any problems. First thing is to find out which ECU or FI computer is being used to manage the engine. All of them have a tach output (Even the OEM). Locate that wire and use it to drive your Porsche Tach. The tach does nothing more than count ingition pulses so there shouldn't be any problems. I have a Subaru engine in my sandrail and I've had 2 different computers driving the Fuel injection. An Electromotive and currently a Redline. Both units had a Tach output wire or terminal.

An adjustable rheostat or correct impedence resistor can be used to adjust the impulse to the tach for a 4 cylinder engine or you could swap the tach (or innerds) for one from a 912/914 or have the tach modified by place like Hollywood speedometer.

If you have a 911 Tach, its already for a six cylinder so you will be miscalibrated right at the start. Vendors can fix that. The year of 911 tach you have also may make a difference. The 3.0 tachometers from 1978-1982 are triggered by a square wave signal, not the standard pulse of the other 911 (older and newer). Those tachs, OFTEN, will not read a standard signal. For whatever reason, some of them do work regardless. You'll know pretty quick.

Regarding the other guages, if it is possible, just use 911 sending units if they fit. If not, use the subaru and call Palo Alto speedometer and give them the info. They can sort it out rather nicely.

The 911 tach needs 12volts switched power, ground, signal and of course instrument lighting.
angela

Damn Angela, I wish my girlfriend would talk to me that way. You got any sisters into Porsches. Jk

Hahaha! Not only did God break the mold when he made me, He screamed with horror threw the mold against the wall as hard as he could! ;-)

The 3.0 tach caught us by surprise. We dumped a stock 3.0 into the spyder with the original 3.0 ignition. It wouldn't fire the tach (the brazilian knock-off VDO's). So I did a little research and came up with the square wave thing. Of course, this fellow is doing it the other way around, an unknown 911 tach with the subie (which I assume is standard pulse). So it should work but if he has aquired a 3.0 tach, it may not. Thought I'd save him the aggravation it caused me...

Worst case, he ships it off for change-over which he would have to do anyway to get it calibrated.
angela

G'day gang, thanks for your help, I really didnt expect to get an answer, I try the things suggested and report back at a later date.

One more question... I've seen a electronic devise that screws onto the speedo cable to convert to electronic,,, any idea where to get them

Thanks

bill from Down Under

I second Angela's thumbs-up on Palo Alto Speedometer; they VDO'd my crappy Chinese 356 style tachometer and they did an incredibly professional job; these guys/gals have a surgeon's touch with these things.