Capt. Obvious

I'm looking into retrofitting a 997 front differential into my 996 Turbo. I understand the basics of how PTM makes decisions about torque split and the sensors involved. But what I haven't been able to find any information about is the specifics of HOW the center differential is controlled by PTM. Is it a scaled 0-5v (or 0-12v) signal, or is the solenoid pulsed rapidly to create the desired torque split? The 997 Turbo forum was not very helpful, so hopefully there is someone in here who might have more technical knowledge about the .2 all wheel drive system.

For those who will undoubted ask "why?" the answer is "because I can." The viscous AWD in the 996 is primarily designed for high speed stability, not traction. Also, the viscous coupling is known to wear out and leave the AWD essentially useless. I like the idea of having all wheel drive so I figure I might as well see if I can make this work. I'm hoping it's controlled via a scaled signal because then I can just have an on/off switch and **** to control the split. Otherwise, I might have to get extra nerdy with G sensors and an Arduino or something.

Thanks for any help.

A picture to keep you interested.

BucketList

Pretty car. I was told the AWD controller was the same between the turbo and the .2 C4S but I can't help you on the diff. I am assuming you checked the ratio's.. Don't want front/rear speed differences. No idea on the electronics.

Capt. Obvious

Final drive ratios are the same on 996, 997.1, and 997.2; and the front diff is the same for 997.2 Turbo and non-Turbo cars. All that information has been readily available and relatively easy to find, which is helpful. I just haven't been able to find any technical documents that outline how the torque transfer is modulated, or even a way to test the operation of the center diff (you'd think there would be a procedure doc for techs to test it with PIWIS or something). I guess I'm just going to have to buy a diff and start experimenting.

997ajk

Coming from Subaru world, there were few options that allowed for improved control or manual setting on DCCD equipped cars. Take a look at the link below, they might be your best bet.

https://www.dccdpro.com/shop/

Capt. Obvious

I'll update this thread with additional info as I come across should anyone in the future be looking for similar data.

After some more research on how electromagnetic clutches work, I believe the clutch is controlled via pulse width modulation (PWM) rather than a simple 0-12v regulated current. Thanks to 997ajk, I did find out Subaru uses a similar clutch system on the WRX STi and I'm betting it's also how Porsche accomplished it. I think a DCCD controller might work on the 997 diff too.

Capt. Obvious

Okay, I've figured out some useful info. It IS controlled via pulse-width modulation and the clutch is at 100% lock-up at 12v. I'm most likely going to purchase a DCCDPro unit for this, thanks again @997ajk for bringing that to my attention.

My next question for the class is: does anyone know at what temperature the "PTM Inactive. Too hot." warning message is triggered? There is a temp sensor for the diff controller oil. Since it's basically a lightweight differential oil in there, I'm assuming it's somewhere around 200-220 degrees? If Porsche found it important enough to put a temp sensor in the front diff, I'm guessing I should install a warning light on the dash for it.

My 997.2 diff arrived today:

997ajk

Great to hear ! Car looks amazing, keep us updated on the progress.

Cheers!

NoogaSparrow

@Captain Obvious any update? curious on progress...

Capt. Obvious

This thread was linked to in a another thread and it made me realize I never updated this one.

My 996 has a 997.2 front differential in it for almost a year now and it works fantastic. If you want to know more, the swap starts here in my build thread: https://rennlist.com/forums/996-turb...-rough-34.html