GT3 m/c swap on C2.2, no PSM

So, I recently undertook the job of swapping out what I'm pretty sure were the original rubber brake lines with braided stainless units from Goodridge, the old fluid with Motul RBF 600 and, most notably, the 997 GT3 master cylinder. Being that my car is a non-PSM example, this was a direct bolt-in with no error lights, etc. It took like 20 minutes and now that everything is back together, the results are fairly staggering. The pedal used to feel somewhat long under normal use, despite being fully bled and with new pads and rotors. The fluid was just below the 3% moisture threshold, too, so I think the feel at the pedal was down to master cylinder bore and old rubber lines. After the swap, the pedal is extremely firm but with plenty of ability to modulate pressure to avoid ABS intervention, even when driving hard. The lack of pedal travel also makes heel/toe shifting a lot easier too. I can't recommend this mod highly enough, particularly for the cost. The master cylinder was a little over $200 and I also like that I'm not blasting around canyons on a 20-year-old, 140k mile m/c. https://www.fcpeuro.com/products/por...er-99735591030 I'll do a write-up on the process for my ongoing series of 996 stories on Jalopnik, and will update this post with that link when it goes live.

Now finish the job with the GT3 brake ducts on the front and you’ll be golden. About the least expensive performance upgrade out there.

Yep, spent the $10 on a set of those and installed them as well.

Or even gt3 upright (or rsr uprights ) and calipers ti finish it off. Btw its a great upgrade.

I've been at looking at doing this as well. Is there any significant difference to be aware of with a car that does have PSM? Is any coding required to ensure the PSM error doesn't stay on?

I put the 997 Turbo M/C in my 996 Turbo (same part as the GT3 at 1/2 the price - TRW PMN 166 is the manufacturer's part#). This will cause PSM errors 100%. The fix is to add a brake proportioning valve set for minimum change between the M/C front output and the ABS module front input. The prop valve seems to delay the pressure rise just enough to keep PSM happy. Works 100% for me. I used a Tilton 10mm bubble flare input/output prop valve to avoid all the adapters some people find necessary and I bent up new brake lines to go between the M/C and prop valve and then from the prop valve to the ABS. The setup gives a VERY HARD pedal feel and required some adjustment from the driver under very heavy threshold braking as it WILL easily lock up R-comp tires at 130+ MPH. It also seems to go into "ice mode" once in a while, which never happened with the stock M/C. Some threads: https://rennlist.com/forums/996-turb...psm-fix-2.html https://rennlist.com/forums/996-gt2-...r-psm-fix.html

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There is a long thread on this. The issue is the psm tests the system and it doesnt like the gt3 mc. I think there is a fix but didnt pay much attention to the issue becuase it was irrelivent to me.

Anybody know if the 996 Turbo master cylinder is compatible with a 996.2 C2 with PSM? I just installed new slotted rotors and DS2500 pads which has improved the pedal feel over the old stock brakes but the pedal is still too soft for my liking. Brake fluid is 6 month old RBF600 and I have a set of Goodridge SS lines to go on next. If that doesn't do it I'll be looking at the M/C but don't want to deal with PSM/ABS issues. I think the 996 Turbo M/C sits in between the 996 C2 and 997 GT3 in terms of piston size. Maybe it would help some?

Nope its the same. The gt3 swap is actually a 997 part. All 996 cars have the same mc. The 997 gt3/cup is 2mm larger bore.

All that I have read says: 996 C2 uses a 23.8mm piston 996 C4S/Turbo/GT3 uses a 25.4mm piston 997 GT3 uses a 27mm piston Is this incorrect?

Yeah, because my car is non-PSM there was no light and no adapters necessary for the fitting closest to the firewall. Direct bolt in.

@khyatt Didn't mean to take away from your success, you are lucky to not have PSM. Did you swap in the SS lines at the same time as the master cylinder or were they installed prior? Also, what are you running for pads? Thanks and congrats!

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Who knows i got my info from threads and did not do any real research. I thought they were all 25mm? Never really checked part numbers either. I just went straight for the 7-3 mc for the firmer pedal.

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You may be correct. The parts catalog shows one part for all C2/C4 cars: 996-355-910-00 without PSM, 996-355-910-40 with PSM. For C4S/Turbo/Gt2/Gt3 all use the same part: 996-355-910-50. 997 C2/C2S/Targa/GT3: 997-355-910-10 997 C4/Turbo/GT2: 997-355-910-30 I don't have the dimensions for any of these. Interestingly the TRW PMN 166 part is listed for all 997 GT2/Gt3/Turbo and all other 997 with ceramic brakes.

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I did swap in Goodridge stainless lines at the same time and I'm currently running Hawk HPS on stock rotors.

About to put in a 996 GT3 master cylinder along with 996 GT3.2 front calipers / GT3 front uprights and GT3 rear calipers etc. What have people done for the larger connection on the master cylinder? Adaptor? Or replace the line? 04' 996 C2 non PSM* I have both a 996 GT3/GT2 master cylinder. The 996 GT3 has an M10 (I think) and M12? At the front. The 997 GT3 has two M12 connections. So if my car has an M10 and M12 I'll use the 996 GT3 if it has two M12 I'll use the 997 GT3. ​​​​​

U can order the line from the gt3 mc and it will fit right into your abs unit. Or they make adaptor fittings

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Thanks I think (hopefully) I'll be covered for both scenarios. If my 996 has an M10 & M12 I'll use the GT3 MC and if it has 2 M12 (which I'm fairly sure it has) I'll use the 997 GT3 MC. What about removing the pressure regulator?