I have a question regarding the size of the holes.
Now i have around ½", if i go up to 1" does it affect the rpm range where i can hear it?

Did the crios muffler mod to my '02 2.7 today. I used a long 3/8" drill bit for initial hole and then used a carbide die grinder bit welded to an 8" piece of 1/4"dia bar stock that would fit my air die grinder. Made an oval about 1/2" X 3/4". I really like the mild sound difference plus I do think it added just a touch to the bottom end to mid range. thanks crios....

Another happy camper! Thanks crios!!

I did the drill mod on my 2003 Boxster and ended up using a 7/8" drill bit as final hole size. I did not have a 1/2" for my heavy drill. Worked as desired with a nice low growl at low RPM"s but no noticeable droning or noise increase at cruise RPM with the top up. I did have to use a cold chisel to start the hole for the drilling and had to step up drill size to make the final hole.

Changed exhaust tips to the two round S type to go with the new sound.

Great Mod!! :cheers:

I know this is an older thread, but I just picked up a 98 2.5L and immediately removed the snorkel and put two ovalized 9/16" holes in the internal muffler pipes as described here. So glad I did. The muffler modification is subtle, mainly deeper and louder right off idle. The snorkel removal is a must. 5000rpm and up is spine tingling now.

I will probably be doing the Pedro's/PSE partial muffler bypass in the near future to give a little more exhaust noise.

Another Happy User!! Thanks Crios!

It just took me 5 min to make the holes in a '99 2.5 Boxster, and the change is great! I made two holes of 1/2 and the sound is great at idle, a lot better than stock! Did have a chance to try it on the road but it doesn't seem to be any ressonance.

I'm glad i did it! :)

I did 1" holes. :)

1 inch is quite a big hole. How does it sound?

Also very interested. There is a hint of raspy or hiss with mine when cold, with smaller holes. You have to lean down by the exhaust pipe to hear it. Any nasty sounds with the 1" holes?

I took my Toyo Sports exhaust off and put the std exhaust back on - resonance took the pleasure out of driving the car. It's a tiptronic and the box generally keeps the revs in the 2000rpm range until you are over 60mph, or you keep it in manual mode. Pity really as there was a noticeable increase in performance with the sports exhaust and it sounded good, when it wasn't resonating!

I've now drilled 2 x 10mm Crios holes in the pipes (thought I would start small). Definite increase in sound when idling but nothing really at higher revs - as you would expect. Think I'll take it up to 1/2 inch (13mm) and see how that changes things. I'll also record the sound and post it in case anyone wants to see the difference - unfortunately don't have a recording of how it was originally.

I have a 2001 base and have been apprehensive about just drilling holes in the stock exhaust. Concerned with resonance and such. Would love to hear your impression of not only the sound but the general resonance issues or any positives and/or negatives. I am looking for a little meaner sound but really don't want to make the car an annoyance to drive at particular rpms. Yeah I guess I am wanting to have it all.

Slate - I put this off for the same reason. I finally wound up doing 9/16" holes about 10 months ago. The sound at idle is much deeper and throatier, and a general increase in roar over the RPM range with zero noticeable resonance. Overall, I'm very happy with the sound. I'm even considering enlarging the holes to 1" to get just a little more growl out of it.

I don't think there's much chance of getting a lot of resonance or that annoying "coffee can muffler" racket since you're only bypassing one chamber ;)

1" sounds glorious. No drone or resonance at all. I may take the car out tomorrow. I'll try and post a video. Stay tuned.

OK - here is the sound of the exhaust with 10mm, 13mm, and 15mm holes. Subtle difference in sound - the 10mm is a little more raspy and the 15mm a slightly deeper note. If you go larger I would image it will get even deeper.

Porsche Boxster 986 Crios Mod - YouTube

Based on the great results I had when I installed the 2nd cat delete pipes on my top speed muffler, im thinking that doing the 2nd cat delete pipes with the stock muffler may also produce the great improvement in exhaust tone and throttle responsiveness.

Has anyone tried that?

chipmunk, looks like your AOS is going bad.

Thanks for doing the controlled test. It's great to have direct comparison data like that!

:) That's steam - it was less than 2 degrees outside. Although that said, it did smoke when I started it up for a run earlier in the day and I have started to wonder about the AOS - from what I can see it's an easy enough job to do so may give it a go myself.

Here ya go 1" holes. The password is 986 to watch the video.

Private Video on Vimeo

That sounds pretty good - I am sure that you can hear it when you open up on the road too.

Yea, you hear it, but no drone at all.

I'm a little confused as to why the holes need to be at such a steep angle where lots of people are having trouble getting the hole started. Isn't any place you can reach on that pipe still in the same chamber and would produce essentially the same results? Why not shoot for deeper in the pipe where the angle is much shallower and easier for the drill to start?
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