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R32: Gtst To Gtr Cat Converter Upgrade


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Hi Guys,

Just starting a thread for those interested, on the weekend I did an upgrade of my R32 GTST from a standard cat to a GTR one.

So, reason why is that the GTR is made for alot more HP so in theory should be higher flowing than GTST.

I have looked at both items off the car, and the body of the GTR one is much larger. Also, this is a very good option vs an aftrermarket high flow cat because it has the thread for the EGT (Exhaust Gas Tempreature) sensor, and if its not plugged in, you will get an ECU fault code coming up you cant get rid of.

Tools needed:

13 & 14 mm spanners, 9/16" socket & spanner and Exhuast sealant.

Difference: Not sure yet as it was double demerits this weekend, wasnt really willing to open it up with only enough points left to wipe my butt once. No noticeable noise increase.

So, Steps involved:

1. Source GTR Cat.

2. Make sure you get the bolts with it. The GTST Cat is not threaded, and uses the threads from the bolts themselves to bolt on. The GTR cat is threaded and therefore, you need correct nuts and bolts for it to work (I didnt have them so I needed to rummage through my old mans collection to find some).

3. Unbolt EGT Probe. This is tricky as you need an open ended 13mm spanner, they are uncommon.

4. Unbolt 4 nuts holding in the old cat. Requires 9/16" spanner and socket for nut and bolt. Make sure you look after the gaskets unless you want to go out and buy new ones as you will have to re-use them.

5. ok, and then you need to clean up the joins and use some exhaust sealant, and then bolt the GTR cat back in. Requires 14mm Spanner only.

6. Screw EGT sensor back in.

7. Check for Leaks. Done.

Some notes. This is much much easier with a hoist. Photos to come soon.

Ok, Photos are now here to be viewed, please note the difference in size of openings and the EGT sensor hole present.

Conclusion. Although in theory it seemed like a really good conversion, I have driven it around fairly hard now and it seems like there is very little difference in power. I suggest perhaps a 3% increase or maybe less (but still noticeable at times).

What I might say though is due to the ease of doing it, its still worth it because, once the rest of the system is upgraded, I will know its not the weakest link, and at the moment, it seems the cat back section is whats causing me restriction not the cat itself. Also, it should allow the install of Large, high flow cat back sections for GTR's, providing it follows the same route and hangs on to the body the same way.

Any comments fire away.

  • 3 weeks later...

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