scott is that your new motor? Is it EFi + slide valve ? very interesting looking induction stacks...

thanks. frank

Frank,

This engine will be controlled by a MoTec M130 ECU. The ITBs are a shaftless butterfly design by AT Power in the UK. It is an 8,000 RPM 3.6L engine for the PCA GT3 class in my 2232 lbs car (with me in it). William Knight is the engine architect and I bought almost all the part for it from him.

This week I tried a 997 GT3 titanium muffler. Same headers (William Knight). I take a whole day to do the job (such poor welding skills)!

Compared to the Dynomax it is noticeably quieter in the city. At WOT it's pretty much the same. Sound is better imo. Weight is lighter.

But I lost noticeable power in the high revs. At least 10hp.

Looks good though. http://forums.pelicanparts.com/uploa...1584803726.jpg
http://forums.pelicanparts.com/uploa...1584803726.jpg

Which ports did you use on the muffler?
The 2 inch 'quiet' ports or the 2.5 inch ports?

How much power are you running? My guess is you used the upper ports, or it was just a day to day variance of your car or the dyno. I experimented with the GT3 muffler on my 3.2, dare I say I may have started the trend back in 2010 it when I took the muffler off my GT3 to install a center muffler bypass, and a bell rang in my head. I fabricated diverter valves and used a 944/964 vacuum canister along with a MSD programmable rpm switch to activate a Pierburg vacuum solenoid. On the dyno there was no difference between the upper or lower ports at the approximate 250-260 hp level. At 400+ hp, there is a 20 hp difference. If you used the lower ports, it's completely straight through so there should be no power loss at all.


http://forums.pelicanparts.com/porsche-911-technical-forum/570968-quiet-muffler-doesnt-kill-power-does-one-exist.html#post5628339


http://forums.pelicanparts.com/uploa...1287700810.jpg


http://forums.pelicanparts.com/image...7381/19764.jpg

This would be the ultimate setup.. kinda wish someone made an 'off the shelf' conversion setup for early 911 owners to run the GT3 muffler.
Interesting that there is no power loss between quiet and loud ports up to 250 ish hp.

i suspect even in quiet mode the flow is massive for what we need for a 3.2 etc, given it's designed for 450-500hp!

I agree.
Only thing I don't understand (that's a lie, there are many things I don't understand) is about pipe diameter from the collector and to the muffler. If the collector is a 2 inch hole, then is there any point in expanding to 2.25 or 2.5 before reaching the muffler?
The quiet port is a 2 inch hole.. the loud port is a 2.5 inch hole.

I cannot afford to pay a shop to experiment with all these options, and my welding skills are pretty ugly.

Yes I did use the upper ports. This is my daily driver with a fresh 3.6 installed with your chip 🤓 (and headers from William Knight). I'm guessing 270-280isch crank HP

I did try the lower port as well, but that is way too loud for a street driven car IMO.

Maybe this could work

https://soulpp.com/product/porsche-991-gt3-911r-valved-side-muffler-bypass-pipes/


Crazy expensive though!

We have an active exhaust system the pretty much does the same thing as the 997 GT3 muffler but is built for the G body engines. They are quite a bit more expensive than our Sport or Street mufflers but nothing like the cost of the GT3 back box.

http://forums.pelicanparts.com/uploa...1584983617.jpg


Also working on a GT3 back box system for a Pelican member. System is also being designed for more modest engine outputs than the 450hp GT3. The headers and secondary system won't be too expensive, the titanium muffler is the big ticket item.

http://forums.pelicanparts.com/uploa...1584983749.JPG

http://forums.pelicanparts.com/uploa...1584983749.JPG

I sincerely wish we had a good dyno comparison with the same headers. I think the Dynomax design I made will make more HP than the GT3 muffler. It is in my opinion unbeatable for the price if power is what you want.. Good work in Denmark. Thanks for sharing your results with forum. William Knight

William, have you tried the Borla dual in/dual out? looking for something a bit higher quality than the dynomax.

https://www.borla.com/products/proxs_dual_indual_out.html

****, its got an internal x pipe

Many years ago, todays may be different. It had a deep sound and was not bad. If your running stock motors the muffler is not nearly as critical. Large cam higher HP is where it is more critical. I however like the look and sound of one of the last set ups Mike Desilva did. It had the two mufflers with horse shoes shape feeding them. The bola is probably pretty good. William Knight

I prefer the GT3 style center exit, but was looking at Mike's dual vibrant system.

I was thinking that perhaps 2 mufflers, one for each bank with a horseshoe connecting the 2 outlet pipes, similar to the Burns muffler for the Cayman.

http://forums.pelicanparts.com/uploa...1585083867.jpg

I'm not sure how powerful the motor will wind up being. 3.2SS, twin plug, carbs, ssi, 964 cams. Piston and barrels are the Mahle 10.4:1 RSR style for carbs. all built off a 79 SC.

That image is pretty much what a GT3 muffler does when connected to the loud ports.
Sort of..

The interesting thing about the GT3, is that even using the loud ports, it is not as loud as say the M&K muffler. When you see the image of the cutaway GT3, it looks like the loud ports are a direct to exit flow.. however the inlet pipes have a space between where they enter the can, and the internal tube. I think this allows the volume of the muffler to act as an expansion chamber.

When using just the quiet ports, I found some resonance at the lower rpm.. the 2 small port pipes are basically pointing directly at each other so the gasses collide head on. It's not obvious when looking at photos of the cutaway, but when you look at the muffler from the side, you can see how they 'head butt' each other.

Thanks Mike, I was going to add that it is similar in style as the exits for the oem 997 muffler.

The crossover seems to be about 50% of the diameter of the pipe it is connected to. Reminds me of the connectors between header tubes on some motorcycle race bikes

Hi Steve,
Did you notice a difference in peak torque between the upper and lower ports between 3k - 5.5k rpms?

Not on a 3.2 with 250-260 hp, but on a GT3 with over 400 it's across the board