DIY Exhaust Mod – Gain of 10+ HP!!!

[JAAY]

The automatic would definitely make a difference and also I have hight flow cats, headers and a totally different motor. None the less great job documenting all of this!

[chipmunk]

Changing the manifolds does make a difference. I remember EDC saying that the drone decreased appreciably when he installed free flow manifolds.

Just curious - with that configuration, would a high end performance exhaust not be better than modifying the std muffler? Or do all performance exhausts suffer from the same drone problem?

[JAAY]

I have had many exhausts and they all had drone that was deafening. The stock muffler had made the most power in conjunction with some cheap headers and good high flow catalytic converters.

[chipmunk]

Interesting - I did wonder about that. I originally thought that the drone was related to the design of the exhaust system and the materials it's made from. I have now come to the conclusion that the car - location of the engine, seating compartment, etc are susceptible to reverberation from the exhaust sound i.e. it doesn't matter what system you use - when the exhaust noise reaches a certain level you get the drone. This seems to be in line with your experience as well. Maybe this is why the Boxster exhaust is so quiet in std form...

[JAAY]

My thoughts exactly. It is what it is and there is nothing we can do about it.

[JAAY]

I just put my long tube headers on and with the 1" holes yes there is tiny bit of drone, nothing like an aftermarket exhaust at all. I had no drone with my shorter headers.

[jdlmodelt]

Originally Posted by JAAY

Now someone needs to get the angle and get 2 1" holes (25mm) in that middle pipe. If my car wasn't behind 2 ft. of snow I would do it.

I just drilled 3/8 holes in my tail pipe and couldn't tell the difference. My factory exhaust has always sounded like a Honda Civic from the driver's seat. Are my CATs plugged?

[chipmunk]

3/8 will be fairly quiet, however you should hear it when you start and at idle. You need to go a bit bigger to get an overall increase in sound. Just be careful going too big. Read the previous reports that I have given regarding the drone you may get at 1".

[Slate 01]

JDLMODELT, comments like yours have made me stop considering drilling anything into my exhaust. The exhaust sound is important to me, but in reality just a ego/notice me kind of thing, at least for me. I actually don't need the ego stroke to love my Porsche. To each his own. However if I come across a real nice exhaust system that is going cheap, then I will be stroking my ego immediately.

[chipmunk]

My observations in all of this are that Porsche must have designed a quiet exhaust for a reason - as JAAY has pointed out, all his previous after market exhausts have droned. Also, randomly drilling holes in things is generally not a good idea and once done there is no turning back.

[jdlmodelt]

Originally Posted by chipmunk

Last stage of the test complete. I had 15mm holes and it sounded OK - quite raspy though. I increased the size to 20mm and then to 25mm. Big difference. At 15mm you could hear it at idle and a little over that. At 25mm you hear all the time. Much deeper sound and louder.

I have updated my video (apologies for the sound of rain in the background in the last 2 tests) but I think the camera toned the sound down so if you listen to all 5 x recordings they sound the same loudness. In fact, the last one is at least twice as loud as the first.

Porsche Boxster 986 Crios Mod 2 - YouTube

Excellent comparisons. I liked the throaty sound at 25mm. However, from some of your newer posts, you indicate 25mm is too much volume.

[chipmunk]

Originally Posted by jdlmodelt

Excellent comparisons. I liked the throaty sound at 25mm. However, from some of your newer posts, you indicate 25mm is too much volume.

No, the volume is fine - not loud, more like a background purr that you can hear through the rev range. When you open it up it's almost a little disappointing as you don't get the corresponding increase in exhaust note - primary because the higher the engine speed, the more exhaust gas passes along the original route, rather than out the drilled holes.

My only concern was the introduction of a little drone at 2800rpm - nothing like aftermarket exhaust however something to consider. On the flip side, the exhaust sounds like you would expect a sports car to sound.

I will put together a "driving video" when the weather warms up a little. It's a bit too cold at the moment to put the roof down!

[Niche]

So based on this thread I drilled my muffler. Sounds a little better, but will be returning to stock. There's a slight "hum/drone" that is a bit annoying. May be I drilled holes too big?

Here is stock:
https://www.youtube.com/watch?v=h03dShxx1Xk

Drilled:
https://www.youtube.com/watch?v=fah0Jx_BQ08

[chipmunk]

How big did you go?

[Ian c]

Originally Posted by particlewave

Here you can see the center chamber and baffle pipe more clearly. That pipe connects chambers 2 and 4 and diffuses into chamber 3.

I'll try to dig out a photo I took whilst cutting Into a 2003 .
They're different .
I modified mine into a "permanently open Pse" inside the muffler , then welded it closed again .

[chipmunk]

I have a 2003 so definitely interested in any photos you have. Drilled sounds so much better but you need to be prepared for a small amount of drone.

[Ian c]

I thinki Drilled mine as well in case it was needed later ....
I'll have a look later , but I think I remember drilling a pilot around 1/4" while it was easy and off the car with the tips removed
But basically on a 2003 the chamber layout and gas flow is different ...

My idea was to follow what porsche did with the Pse which to all intents was a modded stock muffler , as they all ready took care of engineering out the drone

[holtzy822]

yes yes i know this is an old thread but Im considering drilling the holes in my 97 base. I live in California so does anyone know if this would effect the smog at all? I'm thinking i want to go with 3/4" holes to avoid the drone but still have a noticeable difference. If its still too quiet ill drill it out some more. I'm sure it cant drone worse than my 87 944.

[chipmunk]

I'd go half inch and then increase from there. 1 inch provided a nice deep tone but there is a little drone (more noticeable on steep inclines). It is also noisy inside when driving at speed. I have just put a std box back on and it's nice to be able to hear my music again without turning it right up.

[holtzy822]

ill just leave this here https://www.youtube.com/watch?v=wHRZ6_C6VZw

But in all seriousness I plan to do the mod when I pick up my car (a week -_-) I just hope it wont effect the ability to pass smog