Project: 997/991 GT3 exhaust on 911 3.2

[winders]

Where are your headers made? In your shop in Huntsville? By a job shop elsewhere in the U.S.A.? Overseas?

[RarlyL8]

Do these wail like a modern GT3? I get that our engines do not have the rpm range to really get that scream. Just wondering if the firing pulse order, engine capacity, and flow rates give the same general sound. I Have heard a few 997 mufflers (not GT3) and I like an early car sport muffler tone better.

The R&D car that is used to build and test these systems is a 911SC. Yes the sound is different on the SC vs an actual 997GT3. The M&K M27 single out sounds better on the 3.0L engine. These GT3 systems typically go on large modified engines 3.4L-4.0L that need to breath well. Big overkill for a 3.0L CIS engine, ha!

Where are your headers made? In your shop in Huntsville? By a job shop elsewhere in the U.S.A.? Overseas?

I have many recourses and master welders at my disposal to have things built. Who I choose to do what depends on what needs done and when. Nothing is produced overseas and no components are purchased from overseas as that is not practical and would be difficult to control. Huntsville is heavy in machine shop contracting, lots of skill here. R&D, special projects, final assemblies and QC are done in my shop.

[stephen1070]

Brian,

Thank you for designing and producing these awesome heat exchangers. At one point I recall there was discussion of a ‘flat bottom’ evolution of the heat boxes. Is that a possible option on these?

Regards
Steve

[RarlyL8]

Yes the 1.63" flat bottom exchangers are finished and I just completed installation on several sets of headers that went out yesterday. 1.75" is next and will be done shortly. These will have a service panel same as the RSR version.

[BLACK3.2]

Originally Posted by RarlyL8

Yes the 1.63" flat bottom exchangers are finished and I just completed installation on several sets of headers that went out yesterday. 1.75" is next and will be done shortly. These will have a service panel same as the RSR version.

I hope those flat bottom heat exchangers are going on the set you’re sending me for my 964 RS build with Al in Seattle! I could use the clearance on the hills around here.

[skinnerd]

Does switching between the quiet and loud modes change the engine tune at all?
I'd be worried about that.
I'm exploring using a GT3 RS muffler with my engine build and we'll need to have two separate engine maps in the MOTEC engine management system to optimize both sides of the muffler.

[faapgar]

You do not need two setups with your Motec.With the new system with adaptive it will not matter.That is why you pay the money.Ciao Fred

[skinnerd]

Originally Posted by faapgar

You do not need two setups with your Motec.With the new system with adaptive it will not matter.That is why you pay the money.Ciao Fred

Adaptive and active are two different things as far as I know. The shop I'm working with is "the best" when it comes to MOTEC, modifying big bore Porsche motors, etc. Their dyno expert tells me for sure MOTEC needs 2 different programs....one for the quiet restrictive side, another for the loud free flowing side. This only makes sense to me.

[RarlyL8]

Yes the revised exchanger design rolled out quickly to take advantage of increased ground clearance for the 1.63" headers. I'm finishing up the patterns now for the 1.75" units to drop them off at the sheet metal shop this week.

The valves open when the engine is under load. I wouldn't think different programs would be needed if the parameters include engine load. The closed route is not restrictive as it meets the needs of the engine under the conditions required to keep the valves closed.

[BLACK3.2]

Originally Posted by skinnerd

Adaptive and active are two different things as far as I know. The shop I'm working with is "the best" when it comes to MOTEC, modifying big bore Porsche motors, etc. Their dyno expert tells me for sure MOTEC needs 2 different programs....one for the quiet restrictive side, another for the loud free flowing side. This only makes sense to me.

Rothsport?

My tuner tells me that without heavy load, the exhaust needs will be moderate and can be handled by the quiet pipes. The engine will not notice. More flow will be wasted at low load. Under heavier load, the valves will activate, opening the exhaust flow just at the time the engine needs it.

[skinnerd]

Originally Posted by BLACK3.2

Rothsport?

Yep.

I'll be over at their shop next month with my car and will talk further with them at that time.
That said, I've already pretty much decided to only have the quiet side hooked up...blanking over the sport side of the muffler.
Even the quiet side is loud enough for daily driving and will flow more than enough for my engine.

[Shahrams]

Subs

[BLACK3.2]

Originally Posted by skinnerd

Yep.

I'll be over at their shop next month with my car and will talk further with them at that time.
That said, I've already pretty much decided to only have the quiet side hooked up...blanking over the sport side of the muffler.
Even the quiet side is loud enough for daily driving and will flow more than enough for my engine.

Then why not instead go with a lighter, cheaper, less complicated muffler?

[famoroso]

Anyone have a line on one of these mufflers? If so, I'm interested.

Also, anyone have the part numbers handy? I assume there are at least four...

997 GT3
997 GT3 RS
991 GT3
991 GT3 RS

However, there's probably a ton more part numbers given .1 vs .2 for both series and the part number supercession game.

[skinnerd]

Originally Posted by BLACK3.2

Then why not instead go with a lighter, cheaper, less complicated muffler?

For a couple of reasons.
The GT3 muffler makes great power for the larger (3.6, 3.8) air-cooled engines.
And more importantly more me is the sound.
I just really like how a GT3 muffler sounds when hooked up to a large displacement air-cooled engine.

They look great on an early car also.

[Nux]

Originally Posted by jpnovak

Do these wail like a modern GT3? I get that our engines do not have the rpm range to really get that scream. Just wondering if the firing pulse order, engine capacity, and flow rates give the same general sound.

I Have heard a few 997 mufflers (not GT3) and I like an early car sport muffler tone better.

Just curious about sound clips. I have not seen (heard) any.

just fell over this thread as I'm doing another GT3 install

IMO it's the best sounding muffler for air cooled 911's I've ever tried. However, for bigger motors like the 3.6 - it's not the most effective.

Sound clip here:

https://www.instagram.com/p/B-FDFtVlVtZ/

[famoroso]

Originally Posted by Nux

just fell over this thread as I'm doing another GT3 install

IMO it's the best sounding muffler for air cooled 911's I've ever tried. However, for bigger motors like the 3.6 - it's not the most effective.

Sound clip here:

https://www.instagram.com/p/B-FDFtVlVtZ/

Amazing! Thanks for sharing. How deep, or not, is the tone? I know our cars aren't six liter V8s, but I tend to prefer basso profundo to screamers, when it comes to exhaust tone.

I am in Brian's queue for a set of headers and his Active Exhaust, Split Secondary System for a GT3 box. Unfortunately, I still haven't found the GT3 box. I am going to run his 2 in / 1 out muffler in the interim, but the search is on for a GT3 box!

Anyone have a line on a 997 titanium unit? If so, please let me know.

Why do you say it isn't as effective on bigger motors? GT3s have bigger motors and the rear box is one of three mufflers in that system?

[Nux]

Originally Posted by famoroso

Amazing! Thanks for sharing. How deep, or not, is the tone? I know our cars aren't six liter V8s, but I tend to prefer basso profundo to screamers, when it comes to exhaust tone.

I am in Brian's queue for a set of headers and his Active Exhaust, Split Secondary System for a GT3 box. Unfortunately, I still haven't found the GT3 box. I am going to run his 2 in / 1 out muffler in the interim, but the search is on fire a GT3 box!

Anyone have a line on a 997 titanium unit? If so, please let me know.

Why do you say it isn't as effective on bigger motors? GT3s have bigger motors and the rear box is one of three mufflers in that system?

Idle is deep, city driving is surprisingly quiet and at WOT its just a glorious howl.

It's very effective on the big motors, but just not THE most effective. We did back-to-back tests with GT3 and Dynomax 17231 on a 3.6, and the Dynomax has better top end flow.

[mikedsilva]

Originally Posted by famoroso

Amazing! Thanks for sharing. How deep, or not, is the tone? I know our cars aren't six liter V8s, but I tend to prefer basso profundo to screamers, when it comes to exhaust tone.

I am in Brian's queue for a set of headers and his Active Exhaust, Split Secondary System for a GT3 box. Unfortunately, I still haven't found the GT3 box. I am going to run his 2 in / 1 out muffler in the interim, but the search is on fire a GT3 box!

Anyone have a line on a 997 titanium unit? If so, please let me know.

Why do you say it isn't as effective on bigger motors? GT3s have bigger motors and the rear box is one of three mufflers in that system?

Here ya go.
https://rennlist.com/forums/market/1228561

[mikedsilva]

Originally Posted by Nux

Idle is deep, city driving is surprisingly quiet and at WOT its just a glorious howl.

It's very effective on the big motors, but just not THE most effective. We did back-to-back tests with GT3 and Dynomax 17231 on a 3.6, and the Dynomax has better top end flow.

Hi Martin
which pipes are you using on the GT3 muffler with the 3.6? Here is how we had the muffler plumbed on one we did late December. No valves but wish we did. The sound is actually pretty glorious, but we had a bit of drone between 2000 and 3000... above 3k it was magic, but loud.

On my 3.0 with a GT3 muff, I only use the smaller ports.. and use a 2.25inch diameter pipe.. it's perfect. At higher rpm, it fricking screams!