Jeremy, Ralph - please educate me on 3.4/3.5 exhausts

[Jgordon]

I am nearing the end of the rebuild. My wrench says (and probably rightly so) that I should just get the correct tail end on the engine now, rather than do it later. I've been searching the archives, but can't seem to figure out the differences in the various systems. The car's still with Rick Deman - he feels that the stock headers are fine, but that I should go with a cat bypass and a muffler. He has a B&B single in, dual out muffler that he'd sell me, but I'm wondering what you guys have used. I know you've both done a lot of research, so please help me out here.

I've been searching the board, but can't see whether particular companies' components are typically compatible, whether a 3.4.3.5 would necessitate one company over another, etc. etc.

Is B&B a good muffler? would I then need a B&B cat bypass? what is the best combo you guys have found?

I know a couple other guys have done this too - Rdane, asphalt gambler, so please chime in.

Thanks a lot.

[Jgordon]

More questions - I read a thread from Souk in which it seems that a pre-muffler (with baffles?) would offer more hp than a cat bypass (straight pipe?) Is this what you guys have found?

Thanks.

[rdane]

74.4 crank and 98mm P&C right? That makes it a 3.365 or something close. Not a true 3.4 anyway.

I know Ralph went to headers and was thinking a Monty mufler at one point for better flow. His is a true 3.5. I'm sure he'll answer.

Not the cheapest answer but I thought the best to get the most out of my engine. If I didn't have to pass any harsh admissions (my CIS 3.4 passed WA emission tests with a 2/2 Dansk and SSIs) I would backdate to SSIs and a 2/2 Monty. ( I also have a new-unused 2/2 Monty for sale)

[Jgordon]

I noticed a 2/2 dansk on ebay. Is that used when you simply take off the cat altogether, or is it used when you take off that crossover pipe? would a 2-inlet hook directly to the exhaust headers?

my current plan (if I can put together the money) would be stock headers, cat test pipe and a sport muffler. Would that be worth it, or would I be coming back later to change the headers? Any configurations you can think of? and is a B&B muffler good, or are the stories true about poor welds and splitting?

Thanks again.

[Carrera3.5L]

Well, you certainly do have alot of different options available to you and they do get confusing! Alot depends on the motor configuration and extent of modifications as well as your intended usage. Don't forget another variable (and sometimes most important): cost.

Your stock heat exchangers and catalyst will certainly work, it just would not be ideal for a larger displacement "hot-rodded" motor. However, this is what Andial retains (and probably many other CA shops) for all of their cars because of stringent emissions laws in California (both visual and tailpipe test). You would either retain your stock muffler or replace with a single-in and either single-in or dual-out version based on your preferences. Are you leaving power on the table? Certainly, but you don't have any hassle.

A pre-muffler in place of the catalyst is the next step up and is fairly inexpensive. Using a factory euro-spec version or from one of the aftermarket manufacturers such as Dansk, Fabspeed, etc, etc. work great on 3.2L motors when combined with an aftermarket muffler. Again, IMO this is also not the ideal set-up for a larger displacement motor but it does give a pretty good "bang for the buck" and the pre-muffler is easy to swap out every other year for emissions testing. Muffler choice would be as the previous example.

IMO, you not only want to slightly increase the pipe diameter for a larger displacement motor, but also want to get rid of the restrictive exhaust routing that helped choke the 2.7/3.0/3.2 motors to begin with. Thus, SSI's would be the next logical step up. They are only 1 1/2" OD though, so they may be a tad small for a modified 3.4L but still better than either of the above options. They also look great compared to the stock system BUT you also have to pay for their premium quality. There are better options in your particular instance IMO. You would use a dual-in and either single-out or dual-out muffler depending on your preference.

Next question you have to ask yourself is do you want to retain heat? If no, running larger diameter headers w/o heater boxes wrapped around is an option. There are various header manufacturers out there crafting them in different diameters and grades of material, from mild steel to 321 stainless. These types of headers may also assist in cooling the motor as there is nothing underneath to hold the heat in. I would suggest 1 5/8" for your street driven application, as larger may hurt your low and mid-range and your mild cam selection will not make power anywhere near 7,000 rpm anyway so you would be able to take advantage of larger 1 3/4" or 1 7/8" diameter headers.

If you wish to retain heat, again there are a variety of header manufacturers out there who offer lightweight headers w/ heater boxes. You mention B&B, many people on this board have experience with them, both good and bad. Me personally, I believe it is silly for a manufacturer to build components that are only compatible within their own product line. This radically decreases their target selling market. Stainless headers do look nicer and will generally last longer than mild steel headers, but again you pay for the premium material. This is something that you have to weigh.

Reid Washbon makes the best headers for 911 based motors that I have ever seen. He made them for all of the IMSA 962's as well as other high-level motorsport programs and they are truly works of art. They are so esoteric that I could never even get close to affording a set.

There are so many different muffler options out there I wouldn't know where to start. Dansk, Monty, B&B, GHL, Fabspeed, Coast and the list goes on. IMO, muffler choices for people are just as much about power potential as they are aesthetics, sound quality, decibel level, materials and cost. I don't believe there is any right answer, a rear muffler is personal preference. I personally would rather have a muffler that maybe makes 1 hp on the dyno and doesn't drone than one that makes 10 hp on the dyno but drones and resonates so bad the car is undrivable. Other people may think the opposite, it's individual preference.

For race use (because they are too loud on the street), Coast Fabrication mufflers are also outstanding. One muffler for each bank that attaches out of the collector of each header. We use these muffler types as the basis for our VW 1.8T and VR6 exhausts, and we regularly win or place high in magazine exhaust "shoot-outs".

My choices for 3.4L DME street use?

$0 Budget - leave exhaust stock

<$1,000 - Premuffler with aftermarket single-in muffler of your choice

>$1,000 - 1 5/8" headers (w/ or w/o heat) with aftermarket dual-in muffler of your choice

I've typed furiously for the past 10 minutes, guys what have I missed?

Ralph

EDIT for LOTS of typos!

[rdane]

Worse case scenario is $900 for a muffler and $900 for SSIs or a bit less for headers. Most power gain. A 3.365L is a lot closer to maximising what what SSI supplies than a true 3.5 is. Depends on how much you want to take advantage of the rebuild which is where your mechanic is going I think.

Anything under $2K is peanuts compared to what you have done already I suspect. Look around and you can do it for $1500 with the best of both worlds and still have heat.

The Monty (not becasue I am selling one) is a better product for your use than the Dansk IMO and having had both. Athought I didn't get back to the dyno I would also expect to see the difference.

The 1 in 2 out works well with the stock exhaust and a cat bypass. The 2 in and 2 out work best with headers or SSI generally.

[Carrera3.5L]

Originally posted by rdane
The Monty (not becasue I am selling one) is a better product for your use than the Dansk IMO and having had both. Athought I didn't get back to the dyno I would also expect to see the difference.

We'll find out about any power differences (back-to-back on the same dyno on the same day) between the Dansk dual-in and Monty dual-in soon enough, whether I end up buying yours, or one from Steve Weiner or even getting one from Aase direct (they're out right now). I've got dyno time already scheduled at the end of the month.

The Monty does indeed appear to be higher quality in other areas, such as grade of materials and neatness of welds, internal design, actual weight, warranty, etc. Aesthetics, sound quality and decibel levels are up to individual preference and will be among the variables (power/torque outputs included) that I will use to determine what works in my particular instance.

Ralph

P.S. - I agree with Dane and others that state that you should be exhaust "optimized" at somewhere between $1,500-$2,000.

[Jeff Alton]

What about 993 HE with rotated flanges and a muffler like a Triad? 993 HE cand be had for around 200 and I think the Triad is in the 500 ball park.

Ralph, are the pipe sizes you listed ID or OD?

Jeff

[rdane]

Originally posted by catca
What about 993 HE with rotated flanges and a muffler like a Triad?

On a 3.4? Big step backward IMO. Not to mention the hassle to get it all right. Current 993 Triad is too constrictive for a 3.6. But it is very quiet.

My guess...and it is just that.. is a set of SSIs and a Monty would do much better on a 3.4.

For a 3.6, a big Monty and a set of tweaked 993 OEM H/E might well be another story.

[Carrera3.5L]

Originally posted by catca
Ralph, are the pipe sizes you listed ID or OD?

Jeff

Header diameters are usually quoted in OD by manufacturers and thus I did the same. Here is a general inches to mm conversion off the top of my head:

1" = 25.4mm

1 3/8" = 35mm

1 1/2" = 38mm

1 5/8" = 41mm

1 3/4" = 45mm

1 7/8" = 48mm

Jgordon, I think we've certainly filled your head with various scenarios and tried to spend your money, let us know what you decide on!

Ralph

[Jgordon]

Guys, this is an amazing amount of qualified information. I'm thinking that I have to keep heat - I drive the car year-round, and women need heat (they already think it's loud and rough, at least I need them to be warm). So that means that I'll be keeping some kind of header with heat, as opposed to just a set of naked pipes. You're right, that 2k would be peanuts at this point. On the other hand, that's the problem - I'm at the edge of my budget as is.

Do you think it's worth trying to track down a B&B cat test-pipe and taking the B&B muffler with the stock headers, or should I wait until I can afford to do it all and go with SSIs and a top of the line cat bypass with a perfectly matched muffler? How much hp do you think I'd forgo with that kind of a setup?

Could I use the stock headers with no cat or bypass at all? Would they mate to Rdane's monty, or to another 2 inlet muffler?

Thanks.

[rdane]

It is worth keeping what you have for the moment if your budget is tight.

With SSIs and a 2/2 you don't have a cat or a cat bypass. You do have to back date an oil line or two. But for a 3.4 with heat that is what I would do (did) in the long run, SSIs and a good 2/2 muffler. All of the better 2/2 will be fairly loud btw. Want less noise? Do a 2 in and 1 out. But it is a compromise.

You will want to back date the heat as well with this set up. So the bonus is a weigh drop. You'll still have plenty of heat with the SSIs.

Have fun with the 3.4 it is an awesome motor.

[Jgordon]

I think I agree with you. Plus, if I were to do this, I'd take the time do do it right - make sure I'm getting the right components and find a good deal on them.

Just out of curiosity, how much hp do you think the three setups would restrict?

1 - stock frmo the headers back
2 - stock headers, B&B cat bypass, B&B muffler
3 - full system - SSIs, dual in dual out

I know there's no precision, but if you could hazard a guess I'd appreciate it, just to know which paths are available and what they offer.

[rdane]

some 1 - stock from the headers back
more 2 - stock headers, B&B cat bypass, B&B muffler
most 3 - full system - SSIs, dual in dual out

Depending on the engine and how it was built you might well find 15/20 hp here. Maybe only 10 total. No way to tell off a dyno. Take a look at what the factory did on their race cars of the period and duplicate it if you can stand the noise. Headers (SSIs) and a sport muffler are pretty much it. Factory was picking up something like 30hp (IIRC) from Rally exhast to megaphones.

I'd do a search on BB....not sure that is something you want. Dansk and Monty seem to best for durability and HP.
3 liters are only getting a reliable 10hp from the SSIs or early style HEs. A 3.356 won't better that. A good muffler should add to that number.

[Carrera3.5L]

Here are a couple of visuals that show the exhaust routing differences:

Below is the stock heat exchangers with a Dansk pre-muffler and Dansk single-in, dual-out muffler. Notice how the right bank exhaust joins the left bank via crossover pipe and than down into the catalyst/pre-muffler/bypass pipe and into the muffler? Not the ideal exhaust routing for power. In this stock configuration, you can remove the catalyst in favor of a pre-muffler or bypass pipe (if your state allows). The pre-mufflers are usually in the $100-$300 range and an aftermarket muffler can be up to $900 depending on brand.



The next image is that of the same car equipped with 1 5/8" headers w/o heat mated into a dual-inlet, dual-out Dansk muffler. Here you could substitute these headers for SSI's or larger diameter headers w/ heater boxes wrapped around. These would run into a dual-inlet muffler of your choosing. This configuration is generally louder but is how the early 911 exhausts were engineered until the mid-70's. Notice in this configuration there is no provision for a catalyst, so if you do have emissions testing you may have to pull this exhaust completely off and reinstall the stock exhaust. Not that big of a deal, but set aside an afternoon to R&R.



I'll go out on a limb and deviate from Dane's opinion. If you're willing to spend the money on SSI's for your 3.4L, I would go one step further and use larger 1 5/8" OD headers with heat from a header/exhaust manufacturer that makes them in this size. I believe that you will be ultimately happier going this route. I personally am not a fan of B&B but many people on this board seem to have good luck with them. YRMV.

Ralph

[asphaltgambler]

To me it would seem as you have already made the $$ commitment to do the 3.4 - Seems a shame not 'finish' it off with headers and a muffler.

If you want heat...........B&B makes the best headers............ and the worst mufflers.

If you don't need heat there are a couple of other manufacturers listed above that have a good rep.

[rdane]

Originally posted by asphaltgambler
To me it would seem as you have already made the $$ commitment to do the 3.4 - Seems a shame not 'finish' it off with headers and a muffler.

Lots of choices and good opinions. But I think all of us who have built 3.4/3.5s would agree on the comment by AG, "finish the engine." It will be money well spent.

[Jgordon]

I'd love to finish the engine, but there are two constraints - I want to get it back on the road, and money. I plan to complete it asap, but the summer's almost gone and I want to actually drive around. I didn't think I would enlarge it when I put it in the shop, so I didn't do any research or buying of parts. So I guess I'll drive it as is, while researching and buying the parts. Then I'll install as time allows.

Thanks for the help - you guys are an amazing resource.

[JeremyD]

Walking in - in the middle of the movie... I can't tell you how many hours I've spent researching this or - emailing known experts on this very topic...

Like many subjects on the matter - there is much speculation on different configurations.

To me - it comes to performance vs cost. What's the biggest bang for the buck.

When it came time to talk exhausts for my 3.4 project - and yes - 3.5 would have been nice - but I didn't want or need to split my case - again - there were lots of different opinions.

#1 - Ralph is the godfather of the 3.2 upgrade... He's been there, done that - has the t-shirt and the dyno to prove it.

That said - Ralph had his own set of constraints to deal with. First and foremost would be emissions and a system where he would have to swap back and forward between exhausts.

The feedback that I received regarding exhausts - and I will not name names, but I can assure you these are respected porsche community folks told me that your exhaust and cams should be matched as well as possible. 3.4 takes you up a notch in size - and the SSI's and Dansk (heat exchangers) really don't have sufficienct diameter/flow. From there and with a milder cam (964 or similiar) the 1 5/8's are more that sufficient. Any wilder cam and you should be looking for a little more diameter and better collector to get the most out of the top end, especially if you do the extrude hone, TB increase, etc.

I was told again by some of these same "experts" - that the GHL headers are not even equal length - that the mufflers are prone to splitting. I've also been told that B & B makes the best headers - but their mufflers are garbage - this is pretty common dialogue.

So, long story - I am going with a set of B & B headers to compliment my 993 supersport cams, that compliment extrude hone intake, that compliment my bored out throttle body. I'm also getting ben mcfarland to make me a muffler that will fit my B & B exhaust. (I sent him the B & B boat anchor that I had with my system) The muffler is where I am taking the biggest risk with the unknown. I have to hand it to Ben - he is professional - he's been very open to my requests and I really hope that this works well - for me - and for him - because it will give a great upgrade to those that go down the B & B path...

I plan on dynoing the engine with the help of the fabulous Steve Wong and been assured that if there are issues, this will become evident when dyno tuning.

One thing I want to mention is that we all tend to get wrapped up in our little pelican community... that's good - but it can also be bad... There are lots of folks that are pushing the Porsche envelope that are not dialed into the day to day activities of Pelican Parts Forum. Over the past six months I have talked to several folks that are running 3.4s. Some pretty mild - some along the same lines as what I am doing with my car. Some have dyno'd in the 210 rwhp and some have been close to 250 rwhp. The proof for me will be in the pudding...

[JeremyD]

Good god that's long - sorry...