I was going to give you all my wiring information... but since you poo-poo'd all over my project, I'm instead reporting you to the moderator(s) as an unregistered sex offender!

:P

Joking aside,

There were 6 or 7 wires that from the factory harness that I tapped into.

The cooling fans (high and low speed) were pretty obvious. Both the Porsche and GM architecture use low side switching relays. This means that one side of the activation coil in the relay always has 12V applied while the other side of the coil is controlled by the ECU. When the ECU wants to activate this relay, it "sinks" the current on the pin... or in less fancy terms, it simply pulls the terminal to ground.

The fuel pump was a little tricky. The Porsche engine controller uses a low side side to power the fuel pump relay, but the Chevy ECU uses a high side switch. I had to swap the wiring around in the fuse box, but I got it to work with the factory Porsche relay.

Both the fuel pump and cooling fan relays pull power from a master power relay called T87. This relay is controlled by the engine controller and is designed as a safety function. If the engine controller ever goes dead, it will cut power to potential fire sources such as the fuel pump and fuel injectors (Chrysler calls this the ASD / 'Automatic Shut Down') The Chevy ECU has provision for it's own T87 relay, but the Chevy uses high side switching while the Porsche expects a low side switch. I fixed this issue by adding a poor-man's logic inverter with a simple 12V relay.

The ignition signal was a straight forward switched 12V signal, but the starter solenoid used a second redundant relay (for safety? Dunno...) The secondary relay for the starter circuit was bypassed.

Check engine engine light was a simple one-to-one connection.

I still need to hoop up the wires for the cruise control, but those too look like a simple one-to-one connection.

Like I previously mentioned, I'm a bit of a masochist when it comes to wiring stuff. :)

As for the structural integrity, you really need to poke around down there without an engine in place. The pieces that are removed are only used for the factory engine mount. There isn't any torsional rigidity that is lost. I didn't believe this either when I first started investigating this project, but once I had the engine completely out and the car on a lift that, I saw how this section of body wasn't important anymore.

Intredasting!

As I mentioned I'm hoping to do something cool this winter. I currently have an Audi 2.7tt sitting in my buddies garage, but I'm not sure that I want to deal with intercooler piping for two turbos. That same buddy also has a belt-drive 4.2L V8, so we'll see.

I recently did a 2.7tt swap into a B6 chassis A4 (the body style which came with the horrendous timing chain eating engine), so I've successfully pulled off a Motronic based swap and some of the wires you mentioned sound familiar. My Box is a 2003 so it's DBW which throws some confusion into the mix. But your wiring is a good help! Thank you!

Did you wire the OBDII/K-line connections to the GM ECU? I'm interested to see whether or not you can perform OBDII readings using the factory Porsche connection. Emissions testing around here is based on that function essentially.

Audi 2.7tt swap sounds like a horrible idea...

I LOVE IT!!!

For the OBD connector, the plan is to run the GM Class-2 (J1850) wire to the Porsche OBD connector in the driver foot well. I currently have a completely independent and separate OBD connector in the trunk for the the GM ECU. I'm pretty sure the J1850 wire is on a different pin that what the Porsche uses. If I can't pop an additional pin in the Porsche connector, I'll just re-wire a entire new connector that I have laying around at work.

Once this is complete, any diagnostic scanner would work the same as it would in any other car. They'll even be able to toggle the engine light to verify you didn't just yank the bulb.

IMO, the only advantage of the 2.7tt is the turbo noises. But the additional work required to install the engine that is attributed to the turbochargers of the 2.7tt seems like almost the same amount of work as would be require to simply turbocharge the 4.2L... so... there's that to consider...

Oh wow I didn't know they could do that with the lights. Definitely good to know!

The nice thing about the motronic ecu into motronic body was that the CAN bus was compatible. My car was actually emission tested with the 2.7tt in it and passed without issue. As far as pin-outs with your car goes... I'd imagine that Porsche follows the same protocols that VW/Audi/BMW does in this link, considering they are all Motronic based.
https://en.wikipedia.org/wiki/On-board_diagnostics#OBD-II_diagnostic_connector


It would be interesting to see what happens if you wired the GM CAN wires into the Porsche CAN circuit. I'm not an automotive controls engineer... I just work in the plants and figure out how to assemble them and keep the lines running... so you'd probably be better versed to figure that one out. Are the communication protocols consistent across all makes, whether it be a Motronic or Delphi based ECU...

Hello Andy,

well the centre of Stuttgart at the rail station area is still a very big building site now. But it's getting better. Worst was over the last year or so. Only one lane, where normally are 2 or 3 lanes. So always big traffic jams everywhere not only at rush hours. But as you might know this not only a project that concerns Stuttgart centre, it tries to change the whole infrastructure in the Stuttgart area. So railways, airport connections and also the complete old railway station area is now a building site.

http://bilder1.n-tv.de/img/incoming/origs17859416/3932732395-w1000-h960/Stuttgart-21.jpg

And they again run out of money. They wanted to finish the project in 2021, now they say 2023. We will see.

Hi GTsilber,

well, next time i can ship you a Radnabenabdeckung. Will be for a much cheaper than flying to Germany just to buy one. :D ;) Though it maybe was worth it, because you could see the Porsche plant and the Porsche museum in Stuttgart person. Hope you had the option for a factory tour too. And don't forget to visit Weissach and Leipzig. ;)

If you go to my Garage here on the forums, you see my other car in front of the Museum. Rare shot because today it's no longer allowed to park cars there. Especially if it's not a Porsche. ;)

Regards, Markus

There are many, many, many facets to the CAN bus that make them difficult, if not impossible, to play nicely with each other. In addition to (sometimes) different baud rates, manufacturers also use different message IDs on a platform-by-platform basis. Even if the message IDs match, each 8 byte (max) message is often broken up into multiple signals. Even when you're dealing with the same manufacturer, the CAN database descriptions are often modified for each platform and updated every couple of years with new information. Chrysler, surprise-surprise, is the only major OEM that updates their CAN definitions the least.

GM CAN bus is a whole unique beast unto itself. A "normal" CAN bus uses two wires; CAN_HIGH and CAN_LOW. The signal is a differential measurement between the HIGH and LOW wires. The two wires are used as a redundancy. If one of the two wires fail (shorts / disconnects) the CAN bus will still be operational albeit in fault mode. Good ole' GM decided to save a nickel on every vehicle and eliminate the CAN_LOW wire and force the CAN bus to operate in error mode at all times. This wonderful "invention" was named GM-LAN.

So yeah... wiring the GM and Porsche CAN nodes together will do nothing. :(



I haven't been to Stuttgart since spring of 2011, would be interesting to see the progress. Looks like I'll be in Munich and Regensburg the first week of August. I might have to pay the extended family in Esslingen a visit.

Whelp, had my first drive-line failure:

http://986forum.com/forums/uploads02...1469130410.jpg

To be fair, it was my own stupid accord that caused it.

I added some axle spacers to put the CV engagement back to stock geometry. These spacers required 15mm longer axle bolts. I scavenged the parts bin at work and found some M8 x 1.25 x 65 mm recessed hex head screws. I checked the grade and saw 8.8 and figured "Grade-8, these will be fine!"

Yeah, not so much. My dumb@ss forgot that these were METRIC bolts and 8.8 is more like a grade 5 bolt. I needed to find a 12.9 bolt.

Anyway, the threads of the 8.8 metric bolts ripped cleanly off the bolts and separated my axle from the transmission.

The good news is that the transmission flange and housing are both undamaged. Thankfully I was only going ~2 mph when the axle bolts gave up the ghost. Even the axle itself is rebuildable.

I ordered up a set of el'cheapo replacement axles and another spacer to get me back on the road. The long term plan is to buy a custom set of 23" long chromoly axles for 930 CV joints from a dune buggy shop. They cost $230 for the pair and will eliminate the need to run the spacer that (kinda) caused this problem in the first place.

DOH! Welcome to the club brother! :p

Yeah that sucks, i've been there and done that. Sounds like you know the problem though :)

FYI I'm dealing with a water pump gone bad right now. Meziere pump provided by Renegade took a ****************. Hopefully no damage done to the motor cause I don't think I can handle pulling that thing back out. What water pump are you running? You get the one from Renegade too?

Ops :eek: Metric 8.8 bolts is nono on a High Power machine .

Can you remember what you did?

Job well done
 

nice work it has the factory look A+.

Midwest LS Boxster meet!!! :cheers:

I doubled up on the 996 axle spacers on each side to compensate for the axle geometry

https://i.imgur.com/z6M7sLF.jpg

It seems like it won't fit or that they will bind but they dont at all, when the car is in the air the wheels/axle drop and push themselves towards the trans side and it seems like there's only room for one. If you jack the wheel up as if it were on the ground you'll see the axle pull away from the trans side, you get it high enough and you can fit two spacers in there once it's all bolted up and it's on the ground, there's play you got in there while its sitting (keyword SITTING, once you hit bumps the wheel is going up therefore, pulling the axle away from the trans not causing anything to bind all while keeping a good amount of cv joint on the wheel side cup.), no binding going on what so ever or any weird noises. I got the correct strength longer bolts for it. I've been driving on them for over 2000 miles now and no issues what so ever. I've launched it on sticky competition track tires and I haven't sheared any bolts off or damaged my axles so it's working so far :cool:

Edit:
Here's a similar spacer setup on a R32 Skyline. (I googled a bunch of drift vehicles suspension setups to get to my double/bigger spacer idea I figured that they get so low that their axle geometry has to get out of whack too and lo and behold theirs did!)

https://i.imgur.com/5xq4qe7.jpg