Hothonda

I get the straps holding it in place part.

Just wondering....

Here's some humor - this was only a Honda:

reidry

^ It'll buff out, right?

Mike in CA

Money is correct, and I didn't mean to suggest otherwise. What I said was, "when the flappers open they do allow a shorter, more direct path through the cats to the center muffler although the side mufflers aren't closed off and completely bypassed when this happens ".

Poor syntax perhaps, but I was trying to say that the flappers DON'T affect flow through the cats and that the side mufflers are NOT closed off and bypassed. Just as Money described.

My original reply was in response to the question as to whether the results Money came up with would have been the same with the exhaust completely stock instead of with the Sharky. When tuning the exhaust and engine mapping, Porsche had to take into account changes in back pressure as well as changes in the overall length of the exhaust tract when the flappers open. Substituting the SW bypass for the center muffler makes a significant change in backpressure, so that also changes one of the important variables.

I agree, the results would likely be the same with the stock center muffler, but it's possible they wouldn't be. I've had some experience with testing small changes in a complex system and the results aren't always predictable. In this case we don't KNOW because the stock system wasn't tested so we're making an assumption. Sorry, it's just the way I think....

RFGGT3

Matt, thank you for sharing. It is very interesting and I love the video.
Really like your new plate.

Gravs

Thanks for clarifying. My assumption that the valves were between the side mufflers and the centre one is obviously wrong! Both you and money say they're before the side mufflers.

I need to get my head right under the car or find a diagram to satisfy my curiosity because the valves do actually sit physically between the mufflers but there must be some doubling back pipe work I hadn't noticed correctly!

ZZinger

I am running the sharkwerks bypass and I plugged the valves this afternoon. I like the sound more and the car feels very similar to stock. I myself do not hear much drone at all in the lower rpms if at all and I prefer the burbles and pops the car makes throughout the rpm range. I did the same thing to my F430, 458 and Vantage V8 (pulled fuse 22) to bypass the valves. I guess I just like my cars louder than stock. The mod took me about 20 minutes and I used galvanized wire to secure the vac line, small stainless screws to plug the vac line rubber connect tube, and installed a rubber cap I got from JEGS to seal the valves up. I just drove the car 40 miles at all speeds including auto mode and sport mode etc and I am planning to keep the valves plugged.

gt2urbo

Thanks for being the guinea pig money. I have a gmg center exhaust and feels amazing with the valves disconnected. Sounds the way it should have came from porsche

Bruno Giacomelli

To be clear on what the Rusnak service department told me: 1) "We don't reccomend the mod - we had an instance where a 997 GT3 had some oil leaks from a gasket that was probably caused by an exhaust mod that reduced back pressure; these systems also cause drone"; 2) I asked if it was a Sharkwerks bypass: "Not sure"; 3) I asked if it was just a bypass or a more extensive cat-back exhaust modification: "Not sure".

Money2536

1.) Bypass alone doesn't drone.
2.) Again, how is a GT3 any different than any other car? Ferrarri, Mustang, Honda, cars don't blow up by putting an exhaust on it.

Bruno Giacomelli

Agree, no drone.
As for SW being the cause for issue referenced, I think you can see by the responses it's far from conclusive.

rockitman

I think a full exhaust change out would be more likely to cause a rms leak. I had the issue with my 996-3 using a europipe exhaust with 100 cell cats. Hopefully just the 3rd muffler bypass is not an issue for this car.

Mike in CA

Paul, there are two inlets into the center muffler on each side. Path one is routed from the cat via a rather complex series of bends and chambers through the side mufflers to the center muffler. Path two is a straight shot from the cat to the center muffler with the valve stationed right before the muffler.

When the valve in path two opens, path one is still available, although the exhaust is now free to bypass it following the straight shot in path two. Some exhaust no doubt still flows through path one but backpressure is reduced significantly. It takes a little while staring at the whole configuration to figure out what is going on!

I won't speculate further on any issues one way or the other with this mod. Even if I was 100% convinced that there was no possibility of problems of any kind from doing the mod I wouldn't do it again because I decided that the additional sound produced by the mod was not pleasing and I preferred the stock exhaust note. Old fart perspective.....

Totally subjective, though, and if someone wants louder, go for it.

hfm

Thanks for clarifying.

By the way, it was nice meeting you at the get together and run. You had that amazing whitish Steve McQueen signed leather jacket and driving shoes, no?

Dan (should dress better)

Gravs

Did the valve mod today. Video was extremely useful thanks Money. Did a proper job too with screws in the hoses, caps on the valve nipples and all tied back.

BUT... I think I found out the real reason Porsche closes the valves up to 4krpm. It drones like crazy. It's definitely louder and I desperately want to like it but it's basically a loud drone, which completelŷ eclipses everything else. I found myself trying to keep over 4k as that's when it stops. Of course from then it sounds same as stock so there's no point!

As an aside I agree with Mike's theory that it being louder but not faster (significantly) actually makes it feel slower, almost a bit like it's lugging.

So I'll be reverting back soon .

It is a bit surprising that Porsche couldn't develop a system that wouldn't drone with the valves open all the time. Unless there is another reason they close the valves under 4k and therefore they didn't care about the drone. E.g. noise regs somewhere?

Forgot to say I am with stock centre muffler. Bypass guys say there is no drone with the valve mod.

UAEGT3

Thanks alot for ur input.