There is no reason to keep the secondary cats. Mandrel bent cat delete pipes can be had for under $250; the install should take about 2 hours. There is a lot of unrealized potential in the 3.2 that was deliberately left untapped by the factory. Porsche's marketing dept likely did not want the lowly roadster beating up on it's older more expensive brother.

Hp
 

PM Sent. Sorry I did not post here.

Have you ever tried going completely catless ? I have. There was a significant loss of low end power, not to mention CEL"s galore, along with the fact that the vehicle would not pass emissions/inspection testing.. I've spent considerable time (and money) over the years experimenting and testing various exhaust configurations for the 986 boxster. And, I can assure you that there is no easy or inexpensive way to improve upon and gain power over the oem system . I suggest that you gather some actual experience on the topic before making any more sweeping assumptions

Easy Danger, I made no sweeping assumptions other than the factory header/cat arrangement is sub-optimal. When you were running with out cats, did you have the ECU reflashed to match your new exhaust set up? Certainly opening the exhaust may cost some low end power, but that would depend on the diameter of the pipes, not the the cats.

Are you of the opinion that the back pressure from your cats is "enhancing" torque/power at lower RPM?

I think an easy way to gain a few pony's is to leave the stock headers in place and remove the secondaries. $250 buys a 2-3% hp increase on an S plus a loss of ~35lbs. If you then opened the intake with a better set up, reflashed the ECU and added an underdrive pulley. I think you'd get gains that you could feel for about $1200-1500. Earth shattering? No. However, if properly fettled, there is no reason why the 3.2 can not make around the same BHP/liter as the 3.4 996.

Has anyone here dyno'd any of their mods? If so please post some graphs as well as A/F's. I am not looking for the end number but the difference. Anyone?

JaaY,

Have you dyno'd your 3.4?

I'd like to see some dynos too. I guess it's not as popular among this crowd as it is in the tuner or muscle car world (I own an RX7 as well)

But I still love you guys :)

It all sounds good on paper Shad but in 7 years of looking I have seen very few examples of success with this. None were inexpensive. The best example was a few years ago when a guy had quality headers, racing exhaust, well thought-out custom one-off intake, larger TB, plenum, ported intake runners, and a custom dyno tune to make the most out of his changes. He did find about 25 hp at 6500rpm but it cost him $6k to get it done and the torque curve was significantly narrowed. Lap times after all this... no measurable improvement. He gained paper hp but sacrificed a broad torque curve and driveability in the process. The car was also no longer street legal.

Ultimately it is your car and your dough so if you think you can find the magic bullet here, have a go and let us all know how it turns out. A cool dyno slip doesn't really interest me. Until I actually see a car turning faster laps by making these changes, I'll be on the sidelines. Compare this to dropping in a 3.4L, the difference in performance is instant and measurable in significant improvement in lap times. :)

I have dyno'd my car more times than I can remember. I'd like to not re visit the BS I had to deal with when posting my graphs. HP numbers are subjective. I used my dyno time to tune and compare products.

My signature states the best result combination with no loss of hp or torque.

This guy tells it like it is with proof. in his case the ebay headers were not a good choice. I run turbowerx only because I got a great deal on them.


Porsche 996 by OZ951

Sorry for taking such a hard line. However, before dissecting and removing parts from the oem exhaust system with hopes of improving power and performance, one needs to first have a methodical plan in mind. For example, the removal of the oem headers/precats requires either an improved custom version of the original design, wherein headers/precats are fabricated in such a way that they incorporate longer, equal length primaries with larger diameter specs followed by a high flow merge collector and high quality low cell cats. Or, a single header design based on similar specs along with relocation of the cats further "down stream" . In my experience, these are the only two ways that one can gain "real" performance as it relates to street applications without the concern for triggering CEL's and the need for re-mapping the ECU . Neither of these two approaches are inexpensive undertakings. Having said that, if one has a limited budget, my recommendation would be to leave the oem headers/precats in place and simply delete the secondary cats for the purposes of weight reduction and elimination of some unnecessary back pressure, along with a good quality cat back that will further eliminate unnecessary back pressure and weight, and perhaps result in better sound .

see what you've done?!?!? you've got 'em all arguing about exhaust again. if there's a takehome from all this it's that the boxster engine has quite a bit of intake/exhaut tuning going on, what with cams that change profile as rpms increase, and resonance flappers on the intake that open and close to optimise airflow. things to beware of in the hp chase are:

a) there is often a compromise between high rpm hp and low- to mid-rim torque. exhaust mods that facilitate better airflow (more hp at high rpm) can rob mid-range torque due to loss of back pressure. even the oem porshe x51 power kit used on the 911's has lower torque numbers than stock engines at lower rpms. so, ask youself - what kinda driving do you do?

b) false/misleading claims. you'll often see cold air intakes designed for the 2.5 engine but also sold for the 3.2 engine claiming 10 hp gain. perhaps on a 2.5, but mebbe not for the 3.2; make sure you check. or, vendors will sell a 'package' of various mods, where one mod hides the deficiencies of another (i.e., the ipd plenum that is sold for the cayman deletes one of the resonance flappers and actually robs the engine of low-rpm torque; vendors hide this by only showing dynos of the plenum with an associated chip flash).

c) dynos. these can be misleading. mods that rob low-end torque are often presented by the vendors with dynos that don't have any data under 3500 rpm. another trick is one used by the tuners "my tune will add 10 hp" but all they do is increase the rpm limiter to 7400 or 7600 rpm; of course you'll see more hp as you proceed up the curve, but is it good for your engine?

so, there are seveal mods you can look at:

1) exhaust - headers/mid pipes/muffer. headers area the cheapest as there is a lot of good chinese stuff on ebay, but toughest to install and, if without cats, note that the engine cumputer has a sensor that checks for these cats; delete them and you get a code. there are cats on the midpipes too, but deleting these won't get a code. you will see many threads on this board with people typing in bold capitial letters about the hp and tone benefits of the various configurations.
2) intake - you can modify the plenum, throttle body, intake tube and/or airbox. again lots of argument on these, but in my opinion the aftermarket cold air intake units are pos; they do a worse job than oem at sealing out hot engine air, and they tend to use the same air sensor housing for 2.5/2.7/2.9 and 3.2 engines which is wrong, as the diameter varies between engine type and affects how the computer works. there is a current trend on this board to modify the airbox from a cayman or 987 and this seems to add hp, is cheap for parts, but labour intensive unless you diy. regarding plenums and throttle bodies there are products from ipd and pedro, but expensive ($1k) for mebbe 5 hp gain. again, there is talk on this board about using 911 plenums and throttle bodies to achieve the same thing for cheaper.
3) tune. several vendors out there, but again you are looking at $600 to $1k for mebbe 10 hp and, as noted above, a lot of this is achieved by moving the rpm limiter up. to understand, the comuter has the ability to manage a 25% change in airflow from anticipated; once this is exceeded it can no loger adapt. changes to exhaust and intake start pushing this limit, so consider the flash as the last thing you do after a lot of mods.
4) underdrive pulley (udp). this is just a smaller main accessory drive pulley. reduces load on the engine, increases torque and power by perhaps 5 hp throughout the rpm range. cheap, relatively easy to install. given all this, the udp is often stated as the best bank for buck mod out there. you can get 4" and 5" sizes, and they do affect alternator performance, so if you have a big amp in your car perhaps stay away.
5) low temp thermostat. good for the engine, keeps it cooler (160 vs 180 degrees) and is touted to add 5 hp on a hot engine. for real? i dunno, but a good move nonetheless.
6) weight loss. 10 lbs = 1 hp. lighter wheels (the oz alleggeritta are light and cheapish, also note rotating mass is more of a bad thing than non-rotating). lighter seats. ditch the person in the passenger seat. aftermarket exhaust tends to be lighter, so perhaps the weight reduction offsets any hp losses. lw battery.

so there.

I hear you, improperly done mods typically decrease performance. I'm not saying there is a magic bullet. What I'm saying is there must be a reason that that the 996 make 10 more HP per liter, or 20% more HP for 6.25% more displacement. IIRC, the heads are the same and the cams are the same. The CR is almost the same 11.3 to 11.1. That leaves the engine management, exhaust and intake as possible choke points. It's not magic, it's physics. what one can do the other ought to be able to closely match in scale. IF Porsche had built the 3.2 to the same level as the 3.4, we'd be complaining that the 3.2 only has 275-280HP.

6K for 25hp? OK, a 3.4 buys you 50HP over an S, what's that cost? It would likely make 6K easily palatable.

So much for sweeping assumptions. Great minds think alike...;)

As long as we're not talking about using cheap eBay headers, or going catless I guess so. :)

p.s. By the way, if you have a source for high quality mandrel bent cat delete pipes for only $250, by all means let the forum know where they can get them ! Most aftermarket companies charge $500 plus for them .

Wow boys, I never knew you were so passionate about exhaust lol.

Well, for $6-8K a guy who is handy with tools could install a good used 3.4L and his car would actually be measurably faster. Ask JAAY. :)

JAAY, thanks for the link to that guys build. A very honest and thorough appraisal of his findings without all the hype, bravado, and confirmation bias so often found on other websites like suxspeed. He clearly "gets it". :cheers:

TOP SPEED AUTO ACCESSORIES, INC.

I'm on the wait list now...

As for the cheap eBay, that would be on a case by case basis. I've heard some are pretty good, others are complete crap. All other mechanical things being equal, going catless will make more power.

HaHa "suxspeed" the official bling site of Porschedom! :barf:

My oem exhaust manifolds had a minimum of 1/4" extra weld thickness at the entrance & exit pipes pre & post warmup cat. Grinding this away to minimum weld thickness minimizes the flow restriction while maintaining emmisions compliance. This should enhance high rpm power & possibly low rpm torque. Replacing the oem exhaust manifold gasket with a quality, thick header gasket MAYBE will reduce engine temp, although this is the one area of the engine you want hot since hot air moves faster than cold.

Have you used their test pipes? Were not talking about a complex piece here, pretty much an 90 degree L pipe with a few minor angles.

Shadrach74,

Here's the answer to all of your header/cat exhaust woes . A set of custom fabricated headers and precats from M&M Exhaust in Germany. They feature longer, equal length primaries with 2.25 diameter piping, along with an F1 style merge collector and HJS 200 cell trimetal cats - beautifully made from T316 stainless steel . Net hp increase - probably somewhere in the range of 8 to 10 hp at the wheel . Cost - approximately $3800 . Aggregate cost- about $300 or so per hp . :)



http://www.fvd.us/us/en/Porsche-0/Boxster_986-13-41/-/-/item/item_details/VID_57324217-VCD_35203588-gid_28-sort_4-display_50-item_BES98601200S/EXHAUST_-_Tuning_-_Headers-BES98601200S-Sport_Headers_`Brombacher`__986_S_-04_with_200_cell_sport_catalytics.html

I'm starting to think you just have a Woodrow Wilson for Chinese goods, my pipes were equal length, metal was T304 stainless, merge collectors were the same, pre cats? Not a problem for the 2.5 people. The only thing I see is a higher price.

Look at them again . They probably seemed like they were longer, equal length primaries with a real merge collector. And, worse they were probably less than 1 5/8 in diameter .

I can't look at them, they ain't mine anymore, whatever Johnny, they improved the performance dramatically.

No, I have Fabspeeds. I assume Topspeed was refering to 6speedonline in his post, thats the go to place for bling mods!

Almost anything is better than that 3 hole flute they shipped it with

This thread is exhausting ! :cool:

Absolutely accurate prodriver. I go there when I need a good laugh. :)

Ya think? What a work of art...

My freudian slip is showing! I meant to say Topless. :cheers:

Shadrach74 They call that the "anti 911 cannibalism of sales" exhaust system.

Recall that you ears are only good for so many vibrations before you begin to ask people to repeat themselves. You get to choose what you spend those vibrations on and how long to extend your natural hearing.

Every time I pull up next to a car whose vibrations I can feel in mine with the windows closed I wonder at the choices people make. Same goes for loud motorcycles. Think those drivers will look cool with hearing aids?

And pollution controls are good for all of us, every time I hear of someone bypassing them, again I wonder. For a seldom used race car...sure. Can't be a fanatic or not have some fun. But for a car that is just going to the store? And I sure can't feel 6 HP difference in HP or whatever it is. Maybe its just the 'my pipe is bigger than yours' thing, da ya think?

Mike, I don't think anyone was advocating running catless on the street. It was a technical discussion based on my perception that some folks believe that the back pressure from catalytic converters actually broadens the power band. A properly designed exhaust system without cats will always produce more power than one with cats.

As for the noise, I share your disdain for overly loud pipes regardless of the vehicle. My town is plagued with Harley D-Bag wannabes on bikes so loud they will startle other drivers. While I find these riders terribly annoying, in the case of motorcycles, a certain amount of noise increases the awareness of other driver's to a cyclist's presence. As someone whose been street riding for 20 years, I'd prefer some noise over over quiet when riding a bike in traffic.

I think you're reaching, if my hearing goes it will be from draining the massive air compressor nightly at my dads for 20 years, that was the loudest thing I ever heard in my life. The headers on the 986 only really made it scream on the top end anyway.

PS You seen people with their Ipods at all? I can hear that $%^ ten feet away, what do you think that does to the tympanic membrane? Oh and lest us not forget that my neighbors have subwoofers louder than any exhaust I've ever heard. Considering their concert hall is a car cabin, I'll take my "risks" with the sport exhaust button. One more thing, if you're going to lose sleep over someone bypassing the cats, just lay your head down knowing that the EPA request to lower emission from coal plants was just kyboshed.

Will not add more horsepower, but stripping all the heavy stuff out will make it faster. Pull the not necessary parts of the interior, and install lighter racing seats.

And plenty of time at the track, autocrosses, and driving schools.