Amazing! Thanks.

I will be waiting for the data!!!!


TT, please post the pictures or send them to Woosh and to me. One of us will post.



JB

 

I dug around and around.

Here is the data for all to see (colors in top picture get flipped in bottom picture...oops):




Another way to see it:



1. One can really do this and not violate my state's law if the outer shell of the muffler is not violated. The orange is the drilled hole. It is INSIDE the muffler. This is a tiny mod compared to the RUF muffler, etc. BMWdemon's muffler is way more hacked than this one, for example. It has not blown his car up.... This should be "do-able"

2. Tom's mechanic is part lucky dog and part genius. Tom is brave.

3. The stock muffler, as Tom feels, likely is converted into a cat with a muffler bypass. Why it avoids resonance is just plain dumb luck. I suspect the shape and size of the muffler by Porsche is about 1/4 wavelenght of something....to cancel out the drone, that may be the "physics" of why they (EP and PSI, a copy of EP per some posts here) keep the Porsche joiner.

4. I hypothesize that the hole size simply alters the ratio of air going "bypast" the muffler and to the muffler. In theory, one could optimize this via a dyno .....Woosh is in a position to do this.

5. Woosh, please try to video tape with each hole size. Then, perhaps, people can pick their noice level.....sounds silly, but imagine if you could do a 100 dollar or less mod and select your noise level....baseline noise on your video camera with stock exhaust will be key for people to judge.


6. This picture expains my hypothesis. In fact, this then drives the question of the cat....changing that would give, perhaps, maximal performance....200 cell cats may be the sweet spot in terms of cost....anyone know?...or just leaving stock alone. Stock is durable.

7. This answers the hot air and rust idea/issue....no holes outside happen, neither is an issue.


8. If this works, I promised Tom a beer. One for his mechanic too.


Woosh, I await your data. Will be offline for a bit, but will be back. I suspect the turbos spool faster, etc. Tom, I defer to you to post the video, but the cat is out of the bag.


Tom, I think you figured out something pretty big...

Sound
power
spool up faster
no drone
CHEAP

Makes sense to me pending the dyno data....


JCB

 

Damn, and all I wanted is my Porsche to sound like a Porsche.

tw

 

Here is the video for the car after the holes were made. It is very nice IMHO:


http://youtube.com/watch?v=ZngXA7ibKN8


Please comment. TT Tommy says there is NO drone. I fully believe that.



JCB

 

Tough to campare sounds over the internet, but would appear to be deeper and more "Growly" than stock.

 

that is ghetto.....

 

drilling holes? hmmmmm...I'll stay on the fence but that seems a little...well, for lack of words...and being nice...not good? I'll wait and see/hear the results after your testing.

good luck

 

I love this thread. Yes, I'm a cheap bastard.

 

Sounds good to me!

- KJ

 

Dyno? More info? More comments?
I also wonder how much louder my GT2 stock exhaust is over a standard tt and how much hp difference they make?

I like the concept here. It is totally possible for DIYers to make up great stuff that works, and there isn't too much like this that one can do with these newer Porsches. Keep it up!

I also wonder why no one seems to swap their stock tt exhaust for a GT2-X50 unit? I know they are louder and make more hp but how much of each and is it worth bothering with? You can get these exhausts shockingly cheap. [No desire to hijack this great link. Just a question that I think also relates.]

I would really like to see the dyno results. I recently bought another GT2 exhaust to play with, so if I screw mine up, I can always put my stock unit back on.
John Rice

 

Thanks. Woosh is doing the mod this weekend and doing testing next weekend on a dyno afaik. I defer to him to post his opinions prior to the dyno run. He has built exhausts, etc., so he is on the high end of experience relative to the average person (at least he has a lot more than I). I used to be Reynolds 753 certified for those that know ....and a machinist, but that was a long time ago. Lot's of people used to open up the stock exhaust and get more power and earlier spool of the turbos. Sharky01 ran one, per his posts, for about 9mo before moving to another system (I think Fabspeed). He told me it was super. I don't see much reason to think that this could not achieve the same thing, yet be a lot less work. BMWDemon's exhaust is a lot like that too....funny how no one cut the exhaust tube before afaik.

On the GT2/X50's:

.... I wondered the same thing and found out that the GT2-x50 exhaust and the stock, of the same year, are the same thing.


Not sure if here or rennlist.....but that is what I heard. Part number on them is supposedly the same. Year to year suppliers changed. Not sure if that is the biggest issue. I think in general the exhausts all are about the same. x50 "may" have been tuned or sound...or it may just be a year thing......
Anyone know for sure?

FYI.


(K24's must make more noise/air movement...so that could really change things).

If I am wrong, please correct me anyone. Just my take on things...change was late in 02 and I suspect due to the same European sound laws. That being said, this mod if it frees up air will likely dwarf any difference if there is one anyway.

My 2c only.

JB

 

I am more curious than ever. I have the 911 GT2 Service Training book [Service Information Technik 2002, 911 GT2, PNA 495 220]. They have extensive details about the GT2 vs tt engine [and the X50 is not exactly the same spec]. They state "Modifications to the supercharging system and EXHAUST SYSTEM as well as adjustments to the Motronic have increased the engine's power...".

I don't have access to part numbers but I am curious. My brother told me my exhaust was notabley louder than the 996tt cars he was familiar with. I haven't been around any tts when I am in the car to compare noise level. Definite curious tho.

BTW, those of you interested in your cars would serve yourselves well by getting copies of these while they are still available. I have these for Porsches back from the 60s. Technical info that you will never see anywhere else.
John Rice

 

duh! I haven't studied this manual in a while. It further states "In order to reduce exhaust back pressure, teh exhaust system at the rear silencer of the 911 GT2 has been modified compared to that of teh 911 Turbo [996]. The applicable parts numbers can be found in the parts catalogue.
That's all for now, folks.
John Rice

 

Sorry for the wait on results, I was tied up with family business this last weekend and had limited time. I was originally going to drill the mod holes in the exhaust during the little time I had allocated on the weekend then dyno this week, but decided for consistency in reading output on the dyno that I wanted to have the car strapped down and do the mod after I dynoed a few runs on the same day, with the car strapped, then multiple runs back to back.

Just knowing the Dynojet there are small variances from strapping, SAE correction, fan placement, cool down time, etc that I am going to do my best to minimize, especially since we are most likely dealing with a few HP, and not something that is so obvious.

I am looking forward to testing it, and I am trying to make time to do it properly, I will post all conditions results and pics...
Vince

 

News News !! Please