Cat by-pass or Euro pre-muffler w/M&K

[Lyle O]

Good day all. I upgraded my '87 Carrera with M&K Euro pre-muffler, M&K exhaust (street 1/1) and SW chip (93 octane). Really great, however, I was expecting a more aggressive sound from the exhaust. Brian at M&K has suggested a switch to straight by-pass pipe instead of the pre-muffler. Anyone out there done this or know how this will change the sound? Any other ideas? Thanks in advance.

[9dreizig]

First post and no pic? WTF???

[jackb911]

Lyle, I have a M&K 1 in/2 out sport muffler with a GHL stainless cat bypass pipe on my '87 Carrera. It's VERY aggressive sound-wise.

The pre-muffler does noticeably reduce the aggressiveness as you can tell from this YouTube video which compares the sound of a test pipe vs the M&K pre-muffler:

M&K Pre-Muffler - YouTube

My car is louder than I'd like and I'll be replacing my test pipe with a M&K pre-muffler. If you are interested in a trade + some cash on my end for yours, PM me. The GHL pipe is a very nice piece, not a cheapo like a some others (Bursch, etc.) and fits the M&K perfectly.

[Lyle O]

So, for 930 (9dreizig), I don't have a great pic, but here goes anyway. Sorry, I am new at this.
Jackb911, I appreciate your offer. I am going to run it on the weekend without the muffler (pre-muffler only) to see how that sounds. For special occasions I may keep the pre- and stick a tail pipe on it. If that's the case, I am interested in your test pipe. If that's too much I will let you know, and we can work a swap.
Thanks a lot.

[JAR0023]

No direct experience with M&K but what you are saying echos my limited experience. I've run factory Cat, gutted Cat, and now a pre-muffler on my '86. My main muffler is the OEM Bischoff(sp?) that has been modded. Can't speak to the mods other than I have the PO's shop reciepts for $300 to perform the mods. Best description I can give is the muffler on my car sounds a bit more like a baffled muffler than one with packing. I'm assuming the shop shortened the flow path and removed said packing for the mods.

Back to your question. With the Cat the car really wasn't that loud at all until high in the rev range. I then swapped out to a gutted Cat. The car was piss off the neighbors loud. Louder than the M&K in the video. Again very mechanical like a two chamber Flowmaster. Really was too much for a daily driver. So, then I switched over to a pre-muffler and that took the edge right off. Car sounds healthy at idol but it's much smoother and then gets plenty loud at high revs.

I think you are on the right track with the straight through bypass.

J

[Arne2]

Jack, that is the best video I've seen to show the difference. If that was yours, well done!

[mb911]

Cat bypasses are way to loud IMHO and I have a fair amount of experience. we always sell waaay more premufflers over cat bypasses .

[tcar]

Originally Posted by Lyle O

Good day all. I upgraded my '87 Carrera with M&K Euro pre-muffler, M&K exhaust (street 1/1) and SW chip (93 octane). Really great, however, I was expecting a more aggressive sound from the exhaust. Brian at M&K has suggested a switch to straight by-pass pipe instead of the pre-muffler. Anyone out there done this or know how this will change the sound? Any other ideas? Thanks in advance.

You have a 1/1...

'9dreizig' has a 1/2.

A 2-out is always a lot louder than a 1-out. That's why so many people plug the R outlet part of the time (long trip, mother-in-law's ride to church, etc.).

Straight by-pass pipe will help maybe 20% at the most.


Remember. Your car sounds a LOT louder to people outside or in another car than it does to you the driver. A LOT louder.

Get someone else to drive your car while you watch, or follow to get a better idea.

[jackb911]

Originally Posted by Arne2

Jack, that is the best video I've seen to show the difference. If that was yours, well done!

Nope, not mine...another Pelican posted it on here several months back and I've been wanting a pre-muffler ever since. The 2-out M&K sounds great but it is a little too loud for me with the cat bypass in place.

[mclmk8d]

Lyle, 13 seconds of idle: M&K pre-muffler, Steve Wong Chip(93 octane), and M&K 1-in 2-out GT3 muffler
IMG_0274.MOV - YouTube

[wes_r]

I just put on an M&K 1/1 with a straight pipe and it's too loud. Don't get me wrong, it sounds mean and nasty but a bit much for daily driving.

Going to put my cat back on to smooth out the exhaust note and kill the fumes. Do not want to part with the M&K!

[Cherry Bomb]

Hi Jack!

How much noise difference from US catylitic to M&K/Dansk premuffler? Better yet, how performance difference from the same? I will have B&B 1in > 2out x 4.5" tips.

[jackb911]

Cherry Bomb,

I don't have the M&K pre-muffler yet (but I will at some point). With the GHL cat bypass and the M&K 1-2 and a stock chip, the performance difference is negligible. I also have Ben's outlet baffles in place which toned down the sound somewhat, but not much.

Performance-wise, the car seems to have lost a bit of low-end torque without the back pressure of the cat but it seems a little stronger at higher RPM's. This combination is very loud except at cruising speeds, where it is nearly as quiet as a stock muffler.

Because of the loudness, even moderately aggressive driving on the street is out of the question because of the overzealous, revenue-driven law enforcement in my community. I'm not a track guy anymore but there is no way this system as is would pass a db check at a track with sound limits. Ben's dual outlet system is considerably louder than his single outlet.

It sounds AWESOME tone wise, it's just a little too much for the street unless you drive like a grandma which is pointless with a car like this. Hopefully the pre-muffler will calm it down a bit.

[9dreizig]

Originally Posted by tcar

You have a 1/1...

'9dreizig' has a 1/2.

A 2-out is always a lot louder than a 1-out. That's why so many people plug the R outlet part of the time (long trip, mother-in-law's ride to church, etc.).

Straight by-pass pipe will help maybe 20% at the most.


Remember. Your car sounds a LOT louder to people outside or in another car than it does to you the driver. A LOT louder.

Get someone else to drive your car while you watch, or follow to get a better idea.

9 Dreizig has a zork tube (is this thread about loud !!)
Lyle doesn't let anyone else drive his car ( especially his wife!)

[sbrown.nw]

Thanks for posting this. Have a cat bypass with a magnaflow 1 in - 1 out and it is too loud with resonance at 3K. I hope to get a 76 factory pre-muffler today if it is in good shape and will fit my 85 euro 3.2. My car sounds quite close to the first part of the video right now...

Scott

Originally Posted by jackb911

Lyle, I have a M&K 1 in/2 out sport muffler with a GHL stainless cat bypass pipe on my '87 Carrera. It's VERY aggressive sound-wise.

The pre-muffler does noticeably reduce the aggressiveness as you can tell from this YouTube video which compares the sound of a test pipe vs the M&K pre-muffler:

M&K Pre-Muffler - YouTube

My car is louder than I'd like and I'll be replacing my test pipe with a M&K pre-muffler. If you are interested in a trade + some cash on my end for yours, PM me. The GHL pipe is a very nice piece, not a cheapo like a some others (Bursch, etc.) and fits the M&K perfectly.

[sbrown.nw]

Still looking for a pre-muffler that fits a 3.2.

[Tincanguy]

I have a Fabspeed cat bypass, SW chip, and a Monty 1in, 1out muffler on my 88 Targa. Love the sound! Throaty but mellow. Dynos out at 206 RWHP

[Pstallo]

I have a MK premuffler, standard muffler, and Steve Wong chip. At idle, the sound has a much 'bassier' sound than without the premuffler. Interestingly, it is louder at idle than it is at speed (at least from the driver's seat). Steve Wong told me I would be happier with a premuffler than a cat bypass because the cat bypass produces a harsher, raspier tone. Listening to youtube videos comparing the two, I'm glad I chose the premuffler. I've considered an M&K dual-out, but Brian warned me that it was LOUD for my neighborhood. I am still waiting to hear an actual live example before I shell out the money.

In a nutshell, I trust Brian and Steve in their recommendations. They are both honest and realistic.

[Lyle O]

Great to see this thread again. FWIW, I ended up converting to SSI with M&K 2/2 sport. The sound, for me, is sweeter than sweet. I wanted an aggressive sound and I've got it. But I agree that the pre-muffler with M&K 1/1 was great.

[shaunmbenson]

Pstallo -- how do you find the performance difference with the MK and chip? That's the set up I'm thinking of going to