Weight Vs Back Presure

I just cant make up my mind. Our mufflers are Heavy. Very heavy I would guess around 50kg. But what's best? Lose 50kg or lose a bit of back pressure by only having bypass pipes. I reckon lose the weight. But can it throw a fault Help Guys.

I just did the bypass and love it. If you're ok with the sound levels, I think the general consensus is that you lose low end torque, but gain a bit on the higher end. I can definitely feel the loss of torque, but the car feels better without that extra weight out back. I didn't get any ecu fault. I did get a psm and abs failure the first time I started it with the bypass pipes, but since then everything's been fine.

Thanks for your reply I really cant make up my mind.

It's difficult for me to understand this preoccupation with weight shaving...Unless you track your car and need to shave a few seconds. Heck our roads and their speed limits barely allow us to redline the engine in 2nd gear. So please explain what the point is. I want to learn.

I track my car, and being a C4S, it isn't the lightest thing out there. So far with the spare tire, interior insulation/rear seat removal & muffler bypass I have saved around 150 pounds. I'll save another 75 or so by going to racing seats, so this is a nontrivial reduction. If I didn't track the car, you're right, I wouldn't bother(unless I'm doing the muffler bypass for the sound!)

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It's fun. Following your logic, there isn't much case for owning a Porsche at all.

Weight loss in a Porsche is just another way to 'modify' your ride even if the track isn't your life.

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I have considered buying bypass pipes for at least part time use but the loss of low end torque has kept me from purchasing them. The relatively weak low end torque(below 3500 RPM) on my 2000 C2 is one of the VERY FEW things that I don't love about this car. Lowering the low end torque even more, even if it is accompanied by a more aggressive sound and the loss of about 50 lbs. from the rear, is very unappealing to me. Let�s face it, on the street in these cars we spend most of our time at relatively low RPMs. On the track, however, it is a totally different story.

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It's true, I wouldn't do this for weight savings on the street. Also, the removal for me was NOT easy, and I'm ok with mechanical stuff. I would definitely not consider putting it back unless I had to. That said, the sound is unbelievably sweet. This is how all Porsches should sound, it's just out of this world. I hope this helps with your decision!

Well, please tell me where my logic is flawed. I assume that car manufacturers, especially high end ones, of which Porsche is a prominent member, take all accessories into account when they set up a car for day to day use even the occasional romp. Thus Porsche presumably calibrates its suspension, fits special N tires etc... Am I alone in thinking that they must know something about their products? If they do, are we presumptuous in wanting to alter the "perfect" balance built in by the manufacturer? Unless the mechanical modification, be it weight paring or so-called enhancements, serves a special purpose, are we tampering with the dialed-in balance? Example: People replace their factory 18" wheel and tire combo with the now fashionable 19" not knowing what the effect will be on handling, without modifying camber, dampers etc. Is that a correct approach?

I come across this argument a lot. The thing you have to ask yourself is "What was porsche's intended purpose in designing this part/system"? You said it yourself, they design it for day-to-day use. They designed the 996 for the masses(albeit car enthusiasts), not race car drivers. Have you seen a gt3 cup car's interior? It's completely stripped. They don't run mufflers. For racing applications, these things are a hindrance. For the average consumer, they're essential for drive-ability. So yeah, Porsche does a great job engineering their cars, but they engineer the exhaust not to **** off your neighbors and meet emissions. Given this constraint, I'm sure the muffler that's in there is well-engineered, but it's still engineering according to a constraint. You can definitely screw up the weight balance by taking stuff out. Reducing weight off the front of the car for example, isn't always a good thing as it shifts the weight to the rear & therefore less traction for the fronts. That said, our 4wd cars have much more weight on the fronts than the C2, and the weight is already enough on the C2 to counter most understeer. This is why I wasn't overly concerned removing the spare tire. Taking weight off the rear however is a very good thing, since the rears already have way more traction than what's necessary(being rear engined). Also, by removing weight from the extremities, you are reducing the polar moment of inertia of the car, which is very desirable(think formula cars) As for 19 inch wheels, I would never run them, due to the extra rotational mass. Replacing with 19's isn't going to upset the weight balance though, as you're increasing weight evenly on all 4 sides of the car. Most serious track guys run 18's, and lightweight 18's at that.(Btw 19's are a factory option on the 997's) Certainly camber should be adjusted after any suspension/wheel change, in order to take into account the modification. It's certainly possible to get better performance from the car if you know how to do it, but many-a-times someone will slap on a big ol supercharger without adjusting the suspension/tire size/reinforcing the drivetrain, and then performance is compromised. Edited with afterthoughts!

V225, you're not that far from my viewpoint and yours is more detailed and makes good points. But, don't you think that removing the spare would make the front end even more "floaty" at high speed?

Hmm, I've tracked the 4S many times after removing the spare, and I've never found it to be floaty at speed. There seems to be enough weight on the front of the car. Of course, that's the best test for any modification. Do the mod, go out on track and time yourself. If you're faster, something must have gone right!

I would never remove the mufflers on a street driven car, be courteous to your neighbors and passers by. As for the weight balance, I like a strong rearward weight bias just fine. As for saving weight, a couple of racing seats, + spare pulled out and maybe a lightweight battery does wonders. PS: If Porsche was that concerned with the dynamics of the car, sunroofs would not be a standard option.

Weight loss is good for better gas mileage Go green...........light Anyway recalling the funny stats broadcast on tv when they plug something mentioning after a year that means a savings of blah blah I imagine for a generic driver savings and greenishness would show. Otherwise for some of us the foot could care less about anything except for go go go.

V225 There are some very good points there!. thank you.

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" But a manufacture adding mufflers is not a choice its a regulation"

The amount of noise suppression is at their discretion to a large degree. A GT3 at WOT is an order of magnitude louder than practically any other car in Porsche's line up, for example. I can live with that sound level. An unmuffled engine is something different, and is very, very loud. If you want to talk about "race cars", many tracks have noise regulations also, not to mention drivers wear hearing protection, not to mention the helmet. I certainly do if I'm going to be in anything that doesn't have a reasonable exhaust, but maybe I just enjoy having sensitive hearing...

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I agree with you on this subject, which is why my cars stay completely stock for the most part. I'm very **** when it comes to mods to a great car because I believe that in the case of high end cars, such as P cars, the manufacturers spent a lot on R&D to dial these cars in perfectly. I certainly am not an automotive engineer and I do not want to compromise the performance and feel of the car if I am already fond of the car. For instance, when you add the bypass pipes to a 911 you greatly reduce the back pressure on the engine which undoubtedly throws off this "perfect balance". In order to really do this mod correctly, IMHO, you must also adjust the engines intake system and ECU to compensate for the reduced back pressure, otherwise the engine will no longer be tuned to perform optimally. This possible imbalance, whether actually perceived or not, would bother me. This applies to most mods for me such as suspension, engine, etc. Did I mention that I am a bit **** when it comes to modding great cars?

So, not defending any particular mod here, but I want to make a point: No car manufacturer, including Porsche, designs a part or an entire car with one single objective in mind. That's a luxury no engineer on earth has, not even at NASA. When a Porsche engineer has to design an exhaust system, say, he doesn't get to think only about weight. Or even about performance. He has to think about component cost, serviceability, durability. He has to think about fuel economy and drivability (the reason these cars are slightly detuned to produce more low end torque rather than to maximize horsepower). He has to think about noise laws and emissions (Europe's noise laws, Switzerland's most radically, are dominant factors in the design of Porsche intakes and exhaust systems, and the reason the PSE exists). He also has to think about how much time was budgeted in the development process for that particular component, and how much help he could afford and how much testing time on the bench or the track. Every single part of every car is an artful bundle of compromises. A great car does it brilliantly, and I think that describes a lot of Porsches. But all the same, it leaves a tremendous number of variables that a tuner or an owner can mess with to make the car 'better' in one specific way regardless of cost, or to change its personality (which is how I picked my mods), or to screw it up completely (which I hope I didn't do). Cars aren't simple arithmetic; they're algorithms. Anyone can legitimately claim that the manufacturer's decisions were smart, for sure. But nobody can claim that any car is absolutely, objectively right for every person and every use. That's where the fun is.

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Well said!

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The flaws in your argument are liability, comfort, and what Bruce said. Porsche makes severe compromises on performance for other things. Take, for example, the Porsche Boxster. A mid-engine roadster, near 50/50 weight distribution, and you might think "wow, I bet that car is well balanced!" but you'd be wrong; they went to all this trouble to give it near-supercar handling, but then specified wheels, tires, alignment and pressures that make it understeer like a front-wheel-drive/front-engine car. Porsche is simply terrified of its owners doing stupid things on public roads and focuses an insane amount of effort into keeping trophy wives out of ditches! Performance drivers have to make a number of changes to dial out the understeer and get the oversteer needed to actually go fast. Same is true for the 911, but even moreso due to the weight distribution. Even little things, like increasing the pressure in your 996's front tires to that of the rear tires will make a huge difference in handling. You ultimately need larger tires, camber plates, control arms, etc, to dial out all the understeer that Porsche designed into the 911 for liability's sake. There are a myriad of other compromises made, too. PASM for one. Sure, it gives nice firm suspension in sport mode, but why waste all that extra weight on soft suspension when it's not necessary? A straight-up firm suspension would be lighter and just as good. The active engine mounts, too. Things like carpet in the interior- comfort. Radio, A/C, etc. Mufflers are horrible for performance- they just make it quieter. And all the useless engine bits to meet emissions laws- air oil separator, secondary air injection pump, catalytic converters (all 4 of them, really) - all adding weight and robbing power, and causing many very expensive repairs. Porsche did design a great car - perhaps the best daily drivable race car ever, but there are a few things that can be done to make them even better as a race car at the expense of daily driveability N ratings are just marketing, btw. There are a lot of WAY better tires out there that didn't pay Porsche to rate them that you should buy instead. They cost a whole lot less than N-rated tires, too.

Ok, thanks to everyone who piped in. I get your point(s) that nothing is perfect and that tinkering in search of that perfection is perfectly (pun intended) legitimate a pursuit. I am unfortunately one of those who is loathe to mess around with what I perceive as being as close to perfect in its class and at its price as is possible without compromising the driveability factor. I have limited myself so far to cosmetic mods but admit to being intrigued by the Fister exhaust. Maybe I'll do it but would hate to affect any other part of that famed balance...I suppose that I am in DreamCarrera's camp.

Just put it in perspective. Something so small as changing the exhaust to an aftermarket model, even if it does detract from this perfection, will be such a small change that you wouldn't notice it. There is definitely a point at which attention to detail becomes paranoia! Just be careful: Modifying is addictive....

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With no malicious intensions I am going to say one word!. A word you can hear a lot on Porsche forums. "IMS Bearing". Bit more R&D would have been aprcitated. LOL.

Doing my eyeball calculations I don't think a bypass is going to change the back pressure much since the can is so large in the first place. Header tubes are a primary source of back pressure. Going big reduces over smaller tubes. Like I always try to tell guys a tappered tube give the best of both worlds but nobody does much for porsche. Going overboard like too big of a tube might endanger the exhaust valves but thats not happening with the mods talked about. Again its the header tubes that is the main back pressure item. On the note of lighter, heck yah its good for the car to take a body sized weight out of the rear. Thats not even thinking of fuel consumption or easier on tire wear. You'ld get better cornering. er uh um I take that back. No matter what the rear would still be getting taken to the max for cornering so its still going to get tires as often. Maybe the shocks would live longer though Anybody getting their wife one of these make sure you make a video when she see's the stick shift option you get her. http://www.youtube.com/watch?v=18iclflph1A

Many thanks Guys some real good feedback for me to digest. This is the best Porsche forum there is. The UK forum is so stiff upper lip.