Opinons on OEM Euro Pre Muffler

[JB36]

I just had a new M&K and and the factory pre muffler installed on my '87. My mechanic told me the Euro pre muffler makes less power than a stock cat due to turbulence created by the baffles. Would a Fab Speed have been a better choice or would this have the same effect? I wanted something that looked more like a cat and didn't produce a raw sound so I went went for the pre-muffler. The butt dyno is inconclusive.

[RarlyL8]

A Fabspeed cat bipass tube coupled with an M&K muffler is a GREAT sound! I helped out one of Ben's local customers with that setup on his '87 and was very impressed with the results.

[cdrik915]

I just hope for you there'll not be a problem on your Fabspeed , i know what i'm talking about....

- bad quality
- No efficient after-sale ( new parts with the same issue....)
- Big problems of elements welded at the opposite of that they should....

Ohhhh , that shine !!!, splendid !!! , but not fits fine in my case.

[CharlesJones]

Hi,

I'm no expert, but everything I have read or heard about the subject has said that the oem euro pre-muffler gives the best power if you're keeping the original heat exchangers - better than a cat and better than the cat bypass (i.e. a straight tube). I have heard of many people with US cars swapping their cat for a pre-muffler or a bypass to release more horsepower, but I have never heard of anyone with a euro car changing their pre-muffler for a cat to get more power. I honestly expect that your mechanic is mistaken.

[Wavey]

Your mechanic has it backwards. The OEM premuffler, and the Dansk version of the same, are a straight-through design, with an open tube through the middle and muffling material around the outside. Fabspeed is basically the same, but they have had fit and customer service issues (do a search). Any of these make more power than the straight cat replacement pipes, per Bruce Anderson's testing. They sound better too.

[deshetlr]

I understand M&K is working on their version of a pre-muffler. Maybe you should check with Ben.

[Maxhouse97]

Yeah just went onto Ben's website and they are taking pre-orders for his pre-muffler/cat bypass. No mention of price or characteristics though. Wonder how it compares to the Fabspeed that our sponsor sells. I'm in the market for one myself...

[Porsche-O-Phile]

Dumb question, but why use a premuffler at all? I was considering pitching these altogether on my '74 and running directly into my regular exhaust.

Do they REALLY matter? What would be the problem with just having a shop weld up a straight pipe of the proper length with mating flanges for the exchanger/muffler on it? The pre-mufflers look heavy as hell.

[CharlesJones]

I think a straight pipe would work just fine - as far as I am aware that is all a cat bypass is - just a straight pipe where the cat or pre-muffler would go. However, I've heard a pre-muffler makes a shade more power than a straight pipe due to it's slightly higher back pressure.

[Wavey]

My Anderson book is loaned out, but I believe it's more significant than "a shade" - like 4? or 7? hp.

[alf]

I have run a

Euro pre muff with Dansk 1 in 2 out. Sounds great, stable idle.
Straight pipe with 1 in 2 out. Too lound, some droning and sketchy idle.
Straight pipe with stock muffler. Sounds great, stable idle.
Power? No idea, did not run dyno.

[Porsche-O-Phile]

Interesting about the power implications. . . Has anyone confirmed this with dyno testing?

[rnln]

problem is sound. The straight through with muffling material surround such as premuffler, cherry bomb, etc will reduce your noise a little bit.

Originally Posted by Porsche-O-Phile

Dumb question, but why use a premuffler at all? I was considering pitching these altogether on my '74 and running directly into my regular exhaust.

Do they REALLY matter? What would be the problem with just having a shop weld up a straight pipe of the proper length with mating flanges for the exchanger/muffler on it? The pre-mufflers look heavy as hell.

[JB36]

Originally Posted by Wavey

Your mechanic has it backwards. The OEM premuffler, and the Dansk version of the same, are a straight-through design, with an open tube through the middle and muffling material around the outside. Fabspeed is basically the same, but they have had fit and customer service issues (do a search). Any of these make more power than the straight cat replacement pipes, per Bruce Anderson's testing. They sound better too.

This is why I went with a pre muffler. I also couldn't imagine Porsche putting something on the euro cars that decreased horse power.

Thanks for the responses.

[JeremyD]

Originally Posted by Porsche-O-Phile

Interesting about the power implications. . . Has anyone confirmed this with dyno testing?

I know Bruce Anderson did - pretty sure he did it with Jerry Woods - and if my memory serves me correctly - it's documented in his book. apparently the 3.2 likes to have just a wee bit of backpressure as opposed to a straight pipe in place of the cat. I know when I had my stock heat exchanges - I had a dansk premuffler and a dual out dansk sport muffler - one of the better sounding exhausts I have had on the car. (this was before Ben and MK)