Exhaust choices for a six?

SummerSledSix · 01-23-2002, 09:22 AM

Guys,
Recently finished shoe-horning a 3.2L six in my teener. When the question came to exhaust system, my local guru's suggested headers with 1 5/8 diameter, which I bought from B&B. By the way, their welds are beautiful, but their alignment sucks.

Anyhow, question 1: why 1 5/8 and not some other diameter? I suspect it's part of the "tune" part of tuned exhaust, but how do you figure it?

Question 2: Got one of those dual in-dual out stock muffler hacks for the track (and when I'm p/o'd at the neighbors), but I like the sleeper effect; any recommendations on a good flowing quiet muffler setup for the 3.2, or is that an oxymoron???

Jim Smolka · 01-23-2002, 10:23 AM

John,

Congrats on the 3.2 project.

You can use an early OEM 911 muffler with 2 in 1 out. This should be somewhat quite with reasonable flow rates.

AFAIK, the size tubing results in the 'best' results (HP&Torque).

David McLaughlin · David McLaughlin's Garage

Or you can have the best of both worlds and have a two in three out with the possability of capping two for "stealth" mode like my /6. Look at my sites for pics, email me for more if interested. Mine was done by AJUSA, but I'm sure anyone could do it.

Mike914six · 01-23-2002, 01:17 PM

I like Dave's idea.

I have a 2 in 3 out set up and it is quite load, and very drone like at highway speeds (puts me to sleep if I don't vary the RPM's). I have not tried capping the middle two, but I bet it would work well, and it woud be much easier than changing the whole muffler for track outings. I did the muffler mod myself (search the 911 board for instructions). You will need a welder. I noticed a large performance gain when I added the middle two outlets.

356&914&912E · 01-23-2002, 02:16 PM

Try calling Dave at Triad.

http://www.olywa.net/triad/

I've seen the product, owners love it, and I ordered them for my 914/6 2.7.

Ron

356&914&912E · 01-23-2002, 02:17 PM

Try calling Dave at Triad.

http://www.olywa.net/triad/

I've seen the product, owners love it, and I ordered them for my 914/6 2.7.

Ron

SummerSledSix · 01-23-2002, 03:56 PM

Hey, I like the idea of a cap-able 2 in, 3 out. That might just be the ticket, got a welder and a hole saw, just need to find some tubing...

SummerSledSix · 01-23-2002, 04:24 PM

Went looking on the 911 'board for instructions on the muffler mod, couldn't find actual how-to, can anyone point me in the right direction?

The muffler I'm running now is a modified stock to 2 in / 2 out with the original port welded shut. Question is, is this just punching 2 holes in the banana, or is there some baffle modification too?

Saw a couple of posts talking about just adding one additional port on the opposite side, ie, "mirroring" the stock outlet. Any opinions on flow and sound?

jabb · 01-23-2002, 06:12 PM

Here is a recent post and some Muffler options that people are using from the 911 board... good pictures and some sound clips...
lots of good information

http://www.pelicanparts.com/cgi-bin/vb/showthread.php?s=&threadid=55444&highlight=flowmaster

Mike914six · 01-24-2002, 04:21 PM

Here are the instructions I used:

http://www.911t.org/WklyReprint/modified_muffler.htm

JmuRiz · JmuRiz's Garage

How do you cut those inside holes out? Or if you go w/ a 3 outlet do you need those internal cuts? Thanks.

Nathan
...now I only need the 6 to put the exhaust on

SummerSledSix · 01-24-2002, 06:40 PM

Mike, thanks for the link, direct hit! My local expert said "ya have ta open up the muffler to do it right (like your article says), but the half a**ed way would be just to cut the outlets". Thank the gods for cutoff wheels. If I'm reading that diagram right, the new outlets are in the same chamber as the inlets, hard to believe those other chambers do much, but hey, that's the "tuning" part, I guess.

Also intrigued by some of the dual Flowmaster posts on the 911 boards (see jabb's reply above). Those guys really seem to like the sound. A PAIR of Flowmasters cost half of a new oem 911 banana, but you have to mess with some tubing and welding (just like hacking the banana). Hey, it ain't "correct", but neither is the 3.2 lurking in my engine well...

Mike914six · 01-25-2002, 05:36 AM

Yes, you need to open the muffler to make the internal holes. I cut a big ‘door' in the top and then welded it shut again. It didn't look that great, but nobody can see the top when it is installed. A couple of those baffles go all the way around (it is not clear in the picture), so I think you would need to do the internal holes to get even flow side to side.

I already had the OEM muffler laying around so I used it. If I didn’t have a donor muffler I would probably go with something like the Flowmasters, or more likely Supertraps. Supertraps are also ‘tunable’ for sound by adding and removing plates, so you don’t have to swap the exhaust when you want to get loud (or need to get softer).

Jim made this post awhile back, he might have some advice?

http://www.pelicanparts.com/cgi-bin/vb/showthread.php?threadid=3053

gruntie · 01-25-2002, 06:15 AM

Anyhow, question 1: why 1 5/8 and not some other diameter? I suspect it's part of the "tune" part of tuned exhaust, but how do you figure it?

Beware, I had a LOT of problems a few years ago when I fitted a set of these to the 3.2 in my 914. They were also 41mm ID (1 5/8") from BB, and replaced a set of 38mm ID mild steel headers. Power dropped from 244bhp @ 5894rpm to 215bhp @ 5076rpm. After much expensive rolling road time it was proved to be the B&B system at fault, they replaced them with another set of smaller bore and that finally cured the problem.

SummerSledSix · 01-25-2002, 08:10 AM

My paranoia exactly. With the fitment issues I've had, I've become a little suspicious in general. Of course, I went from 88 HP to 200+/- so I've no idea if I left some horsepower on the garage floor so to speak.

How did you narrow it down to the B&B? How did you get them to replace the headers? Was it the tube size or the plumbing? The mentors I've relied on haven't steered me wrong yet, and I trust their experience over mine, but I'm curious to know the theory behind the diameter and length tuning. Is there theory behind it or just years worth of fabricators and dyno's? Anybody have any leads?

gruntie · 01-25-2002, 09:10 AM

The rolling road process was done by Autofarm, so I was able to back up my complaint with dynoplots from a well known source. Isolating the problem was simply a long drawn out process of changing one thing at a time & then re-testing (including several different tuned mufflers, a pair of original 914/6 heat exchangers, and a set of "anti-reversionary exhaust cones", no less).

Whether or not the problem was due to the ID or the plumbing we couldn't say: we assumed ID as the headers used previously were smaller, but they were also a different shape, so it actually could have been either. Interestingly the replacement set from BB were not only smaller ID but of a different pattern as well, so maybe there's a clue. We haven't put it on a rolling road since but I can tell the power's back again purely by seat of the pants.

At the time I enquired about the science of exhaust tuning, but was told that it's a "black art" based on much trial & error. 914's of any sort aren't exactly common over here so we only had a vast amount of 911 experience to draw on. Incidentally the engine is a European 3.2 running 911E cams & 46IDA's, so that probably factored in somewhere too.

SummerSledSix · 01-25-2002, 09:47 AM

A European 3.2 w/cams? Yee-Hah! Where is "over here"? Do they have speed limits where you come from?

gruntie · 01-25-2002, 10:10 AM

Old England, and it's max 70, at least when someone's looking. But now they've dug a tunnel, the German autobahns are even easier to reach............

David McLaughlin · David McLaughlin's Garage

With the caps on, I swear the "music" level is 1/2 the open mode. For in town use, I will run the caps (boys in blue have told me they like it better), but on the runways and tracks (and highways), I'll run wide open.

'YMMV'

Here's a couple more pics of my set up...

DonNewton · DonNewton's Garage

I have the twin baby FlowMasters on my built 2.7 conversion. Let me tell you, you'll get very addicted to the sound. Admittedly, my car only plays on the track, and would probably get me thrown under the jail here in Fairfax, VA (home of the wild PC monsters). The good thing about the FMs is that you don't have the high pitched, gravel in a tin can sound that many of the larger displacement flat 6s have. Personally, I feel that's a good thing. Don't have a clip I can attach here, e-mail me, I'll send you a short video so you can hear it in anger.