Pre Silencer bypass pipe

Amo · 08-03-2005, 10:12 AM

Hi,

Has anyone removed their pre-silencer and installed a bypass pipe.

If so what are the benefits?

thanks

Amo
87 911 Carrera

Bill Verburg · Bill Verburg's Garage

none, the ROW pre-muffler has been shown on the dyno to be superior to a straight pipe.

Amo · 08-03-2005, 10:28 AM

I've seen some pre-silencers that are cone shaped and others are cylinderical.
Which are better?
tx
Amo

Rot 911 · 08-03-2005, 10:30 AM

Which is on your car?

Amo · 08-03-2005, 10:33 AM

Cone, but I've seen a cyinderical one in stainless steel going cheap.

Also what is this all about:
911 SILENCER BYPASS PIPES 74-89
http://www.*****************/index.htm?Region=UK
(under exhausts section )
(EXHAUST 911 65-74)

Seems like u can do away with the rear box for £50!!

tx
Amo

Rot 911 · 08-03-2005, 10:51 AM

The cone is the ROW silencer and is the one to have!

Amo · 08-03-2005, 11:03 AM

What is ROW?
tx
Amo

gost · gost's Garage

Rest Of World.....ROW.... Where are you located?

Amo · 08-03-2005, 11:28 AM

England

gost · gost's Garage

Then you should have an Row 911, as you confirmed, has the cone pre-silencer and per Kurt's post is the one to have. I don't know which one is best to have but I would believe Kurt as he has loads more experience with the 911. Perhaps you should leave yours on and just remove your box and put a muffler-bypass on like the one Fabspeed makes and I have.
Good luck

S785Carrera · 08-04-2005, 08:37 AM

OK, I have heard this before. But I have never seen the question answered :Why / how would a pre-silencer dyno better than a straight bypass pipe? (technical reason) If it does, what is the difference in HP?
Any threads or links of the dyno data?

Mike

SpeedracerIndy · 08-04-2005, 09:03 AM

The expansion chamber from the euro pre-muffler probably produces a scavenging effect helping the engine breathe better. Just a guess. I have always heard the pre-muffler makes more HP also than a straight pipe or a cat. When I replaced my cat with a euro pre-muffler, I didn’t notice a difference, except the pre-muffler sounded much better. I keep telling myself that I feel the difference though to justify the money I spent on it!