tips, tricks and gothas of installing a 991 GT3 muffler in a 911

[Bill Verburg]

Title says it all, I have a Ti, 991 GT3 muffler coming and am looking for any and all info pertaining to adapting it to my '76 Carrera 3, mit 993 engine w/ B&B headers

[sc]

Hey Bill,
Check these out...
-https://rennlist.com/forums/964-forum/1056398-question-re-gt3-exhaust-installation-on-a-964-a.html
-https://rennlist.com/forums/964-forum/867388-gt3-exhaust-install.html?ispreloading=1
-http://forums.pelicanparts.com/porsche-911-technical-forum/725955-please-recommend-right-header-muffler.html
-http://forums.pelicanparts.com/porsche-911-technical-forum/1110035-gt3-muffler-mounting-75-964-motor.html
-http://forums.pelicanparts.com/porsche-911-technical-forum/1019903-thouths-997-gt3-muffler-smaller-displacent-air-cooled-motor.html

[Bill Verburg]

Originally Posted by sc

Hey Bill,
Check these out...
-https://rennlist.com/forums/964-forum/1056398-question-re-gt3-exhaust-installation-on-a-964-a.html
-https://rennlist.com/forums/964-forum/867388-gt3-exhaust-install.html?ispreloading=1
-http://forums.pelicanparts.com/porsche-911-technical-forum/725955-please-recommend-right-header-muffler.html
-http://forums.pelicanparts.com/porsche-911-technical-forum/1110035-gt3-muffler-mounting-75-964-motor.html
-http://forums.pelicanparts.com/porsche-911-technical-forum/1019903-thouths-997-gt3-muffler-smaller-displacent-air-cooled-motor.html

Thanks that helps a lot

at least 1 guy did the install w/ B&B headers like I have

I'll try and contact Butzi gear in New Milford Ct.too he seems to know his stuff

[Steve W]

Depending on how much power your motor puts out, and how you route the exhaust, the backside of the titanium muffler is delicate, and you can easily crack it and blow it out. If you route through the upper ports, and develop 400 hp, you'll blow it out in 5 seconds flat the first moment you go full throttle, but at 250 hp, probably no worries. If you port through the lower ports then should be no problem at 400+.

With 400+, the steel ones crack on the backside too, which is why we weld reinforcement braces on the backside.

This is because without the two side mufflers the system was originally designed to work with, the exhaust pulses on high hp motors create harder pressure impacts on the backside of the mufflers which break them.

[Steve W]

[Bill Verburg]

Originally Posted by Steve W

Depending on how much power your motor puts out, and how you route the exhaust, the backside of the titanium muffler is delicate, and you can easily crack it and blow it out. If you route through the upper ports, and develop 400 hp, you'll blow it out in 5 seconds flat the first moment you go full throttle, but at 250 hp, probably no worries. If you port through the lower ports then should be no problem at 400+.

With 400+, the steel ones crack on the backside too, which is why we weld reinforcement braces on the backside.

This is because without the two side mufflers the system was originally designed to work with, the exhaust pulses on high hp motors create harder pressure impacts on the backside of the mufflers which break them.

Good to know, engine is a slightly modded 993 nvr, w/ one of your chips, dyno says 263 rwhp a @6250

plan at first is to use the upper inlets only as they are the quite ones(please correct my if I am wrong) and cap the lower loud ports, A future project may be valved dual inlets but i don't want to get into that just now


Should I be thinking about reinforcing the back of the Ti one?

[Steve W]

So 263 rwhp around 300+ hp at the motor, using the upper ports, and blocking off the lower, I don't know if it will blow as is. The picture is a newish one I personally blew out the first drive out on my GT3. Where it I have circled in the blue sharpie marks is where I was thinking of having a titanium plate reinforcement welded across the back and underneath, after some discussion with the exhaust fabricators next to Burns mufflers. Obviously adding the titanium reinforcements comes to the point that you close the weight gap to using the steel muffler. If you can weld reinforcement that would be my suggestion. I have active diverter solenoids and run the titanium muffler on one of my 3.2s, and a reinforced steel one on my GT3. If it's at the track, I set the active valves to stay open to run straight out the lower ports to lessen the chance of blowout. No problem all these years.

Jeff Gamroth runs the titanium one on one of his personal race cars, but I don't know what motor he has or how he set it up.

[Bill Verburg]

Originally Posted by Steve W

So 263 rwhp around 300+ hp at the motor, using the upper ports, and blocking off the lower, I don't know if it will blow as is. The picture is a newish one I personally blew out the first drive out on my GT3. Where it I have circled in the blue sharpie marks is where I was thinking of having a titanium plate reinforcement welded across the back and underneath, after some discussion with the exhaust fabricators next to Burns mufflers. Obviously adding the titanium reinforcements comes to the point that you close the weight gap to using the steel muffler. If you can weld reinforcement that would be my suggestion. I have active diverter solenoids and run the titanium muffler on one of my 3.2s, and a reinforced steel one on my GT3. If it's at the track, I set the active valves to stay open to run straight out the lower ports to lessen the chance of blowout. No problem all these years.

Jeff Gamroth runs the titanium one on one of his personal race cars, but I don't know what motor he has or how he set it up.

yeah a buddy of mine has a Gamroth 4.0, over 400 hp, they use headers w/ a valved inlet, sounds great!!