Why didn't Porsche do the Plenum?
 

One common comment that I’ve seen lately (in dissing the plenum) is, “if it was that easy, Porsche would have made it standard”. I offer up two – admittedly imperfect – examples of manufacturers leaving easy improvements on the table for the aftermarket:

1) I’ve had an Evo Harley for about 13 years. Over the years I’ve tinkered with it (dynoing after each addition). I started with 46 bhp and I now have 80 bhp. I’ve added simple things (a torque-oriented cam, a carburetor, an air filter, and an exhaust). My stock bike came with all of those parts, but they were sub-optimized. My cost to upgrade, less than $1,000 (doing it myself). Does Harley want their bikes to be dogs in stock form? How could Harley leave a 74% power improvement on the table? Other than the exhaust, the bike is completely EPA compliant (and a EPA exhaust would only drop my power to about 70 bhp).

2) I put a B&M short shifter on my 996. The stock linkage looked like something out of a Kia. Does Porsche want their shifting to be more vague than it needs to be?

For those of you who think that factory stock parts are developed to the fullest, and there is no room aftermarket improvement, I think that your being naïve.

Lets look at your 2 examples.

1: The Harley....

There is NO direct competition....They are not competing with any other V twin cruiser. Except themselves. So if they bumped up the HP, they would lose things like driveability, yes a cam, carb, and exhaust will have some effect on the driveability, maybe not for an experienced rider, but for a beginner or weekend warrior (and there are ALOT of those) Harley Davidson would be limiting their product. They wanna make it as widely acceptable as possible. Also laws and regulations make engine mods on a large scale tough...it may still be EPA compliant, but maybe they dont wanna spend the money to test...and if they bumped up the HP, how many more would they sell? The answer is none....those that want an HD buy them, and if they wanna mod it, they mod it. Its not like a 1 liter sportbike, where there is competition from everywhere...Those bikes are looking to get the most out of the engine because of the competition.

2. B&M Shift kit....Its made from metal, rather than plastic...but the stock shifter doesnt just "break"....I have NEVER heard of a 996 stock shifter breaking. Then why not make the B&M standard....because SOME people, (me) dont like the stiff notchy feel. I had the B&M on my Boxster and purposely didnt do it on my 996. So they made the shifter perform flawlessly and they made it so a wide varielty of people will be ok with it....for teh hardcore, they can upgrade, and they sell the short shifter as a factory option.

I'll give you another example....

Suspension:

I have the PSS9, which I like better than stock....Its lower, and rides very good, if not better than stock...so why not make that the stock suspension...Well how many more 911s would they sell if they all came with adjustable coilovers....probably none. Also with height regulations and the bad adjusted dampening making some cars handle bad, they would rather give you a different option....I know my wife HATES the fact that it scrapes on every driveway. Me, I dont mind at all..I prefer the car lower....it handles better, and feels more planted....but its all a compromise. There will be some that prefer the stock car. Thats why companies dont do some things...now for the Plenum...It would be easy for Porsche to do so there is a reason they didnt...It could be that it reduced mileage by too much, maybe there is another downside....but you can bet they didnt do it for a reason. They are trying to get as much power from the M96 engines as they can.

One reason why porsche went with the longer stroke on the shifter is that it is smoother, less notchy and easier to shift from gear to gear. The B&M SSK is a shorter shaft hence a harder, notchier, less precise (relatively) than the stock. But, I find the stock to be to long of a stroke. Im sure there's more stock shifters than SSK kit out there.
Porsche went with the daily driver in mind with the 996, and their design philosophy has total change from a pure performance vehicle... the heritage is there, but has cut corners!

Newport996,

So I take it that you think the the $.29 plastic, right-angled, injection-molded, stock plenum is developed to the nth degree? That any improvement over that space-age design is impossible? Is that your point?

Nope...my point is that the overall design of the stock plenum is there for a reason. They could have, and do on the X51 kit....That entire kit gets 25 hp...if they could get that with a plenum alone, they would...unless there is a downside.

Much of the X51 kit is done for drivability and trackability not just HP. The X51 kit has additional radiator, Different Oil pan and many other parts that are "beefed Up" for reliability. These parts don't contribute to the HP, but make the engine more reliable under higher performance conditions that the demographic who would order a performance kit may put the car under. Porsche doesn't just want to bump up power but also not have a warranty nightmare.

As for the Plenum....

Maybe someone at porsche said, hey this point we need to link these two areas to the throttlebody and a designer in a cad machine just put together a T for the prototype engine and they used cheap injection molded piece that allowed them to make their HP, Mileage and emissions goals. If they didn't, evey potential piece that could be a problem would be looked at and based upon cost it would be modified to work..

BTW: I don't think porsche could have safely done anything in plastic for a better plenum. The piece RSS has is comes to a point in the middle. I don't think porsche would risk a thin plastic point in an area near the engine after all the filtering. Also a metal insert as someone has proposed would not do for a production vehicle.

Remember for a production vehicle the cost to produce the plastic piece is much less than a cast piece. Porsche talks about the cost of reducing the number of casted pieces as a major cost savings in the new facelift cayenne because direct injection allows them to change castings for the cylinder head to a single piece casting instead of a two piece because of cooling properties.

Unless I'm missing something here......... "I/we" have yet to see a bone stock 3.6 996 with a before/after dyno chart. (And I'll be the first one to say I-was-wrong should a bunch come in with the numbers that should be showing), but, I'd still like to see a few dyno's come back (3-5 different cars) with some hard facts on the increases. And I say a few different cars just knowing all aint the same car-2-car.

Whats my point......... Point here is that there is alot of speculation against what Porsche may-or-may-not do, but purley based on this plenum being advertised to give XXhp. I've got no doubt that this plenum is a true piece of art compared to whats on the car now........but im' a numbers guy and wanna really see some.

lets remember that porsche "dumbed down" the cayman for purely marketing reasons!

The downside might not be as apparent as some would think, take the short shift kits, the factory did in fact test a significantly shorter shifter on the 996 before release (I have seen the piece), after a bit of track testing they found no decrease in lap time but did find a significant increase in miss shifts which was a war. issue that they did not want on their hands.


I am sure there is a noise regulation of a no peice less then 2 mm width restriction after the filter from enginering

KaamaCat, not trying to HJ the topic but would love to see a pix of that 351 Cleveland you have or is it? Please post some pix of that CAT.

Dumbed down? In what way? That engine in the Cayman is operating (as almost all NA porsche engines) at about 95% efficiency....If you are saying they should have put in a 3.6L or 3.8L engine, then ok....but the engine in the Cayman is not "Dumbed Down".

Why did they put a plast "T" instead of a cast aluminum piece similar to this aftermarket Plenum? Economics.

The plastic injection piece probably took $5k-10k in employee time, probably $30k in rapid protoypes, and $10k for the mold(s). The cost per piece, probably $10-$20.

For Porsche to do the plenum similar to aftermarket one would cost well over $100k in design, flow, full engine testing (done in a way that would make porsche comfortable (warranty, driveability etc). A "T" will always work but when you get creative you may find holes. The testing would be the same as they do now. High heat (death valley), severe cold (sweden), high humidity, high speed, fluid/flow tests etc etc. They then have higher mold costs, and the prototype is more expensive. Now, one could argue that they could possibly have done this in plastic instead of aluminum which would negate some factors. I think it is possible.

There are other factors
*The carrera has 312-320hp at 2950lb (approx).
Why would you want to sell a carrera at (allegedly) 350hp, wouldn't that be too close to the Turbo? Notice when they up the HP on the carrera the Turbo generally goes up. So now you have more R/D cost because they would need to boost the Turbo (no pun intended).

Why would you spend so much on one part? What would happen if they did that for most parts? It would be a Saleen S7.

At a certain point they will get to where BMW was with the M3 motor and have no room to increase HP. Then the only choice is to add more liters and possibly heavier motors. Leave themselves some room.

Weight increase is minimal but still, if they did this to 30 pieces you could have a 20-40lb increase. (alumuinum)

Porsche is a car builder not a component builder. The simple answer is economics. They probably have 20-50 parts they would like to modify when they get a chance to get to them but highly engineering every part is not cost effective. The Carrera would almost certainly cost $200k or more for a car they went through and made all these parts perfect.

Asking why they didn't do the plenum... Why not ask why they come with sunroofs (roof) - people want them (plenum) - most owners are happy with 320hp and a stable/reliable car. Why do they not come with CF/Kevlar hoods, fenders, and trunklids? Or CF rims (cost/value)? or 51lb seats (carrera est.) When they could easily drop 10lbs by using aluminum/alloy instead of steel (cost/value). Or back seats? (this is easy... Insurance.) What about a lightweight flywheel (not much design in that (more warranty risk)? What about... a carbon fiber chasis!

"dumbed down" in that they managed to keep the cayman artificially lower than the 911 because the cayman has, according to all the magazines i've read, the chassis to probably out-pace a 911 on any roadcourse, if the power were equal.

therefore, with the cayman, you're not getting the best car porsche could've made at that price point.

the tepid reception the cayman has recieved is partially due to this, IMO. here in sofla, where porsches are a-dime-a-dozen, the cayman is seldom seen.

...but the 3.2L boxster S engine IS dumbed down/de-tuned so it wouldn't compete with the 3.4L 996. porsche purposefully put in 4 catalysts and lowered the compression ratio.

Hey this isn't new for porsche... They did the same to the 924S. It would have been a faster car top and 0-60 than the 944 because of the more aerodynamic body and less weight, so they lowered the compression ratio slightly and detuned the engine.