RSS Plenums?

The link below is from a 6-speed thread. If dyno is accurate, $1,000 for claimed HP & torque gains might be very cost effective compared to other options. Has anyone here replaced their "plenum?" http://www.6speedonline.com/forums/s...ad.php?t=75109

I coughed and out came some plenum...

Nice looking product but $1000 to get 15HP you won't even feel, I'll pass.

You'll definitely feel 15hp.

The dynograph posted showed 20+ hp and torque improvements to the wheels. Not too shabby.

And that's w/o reflash..just bolt-in? cool.

I contacted RSS about the cost and through out the idea of a group buy and they were interested in the prospect of that. If anyone is interested lets get a count and offer them a $. Better yet maybe we can get the $250 header dudes to make it for $125. Kidding, post interested parties on group buy. JW

guess its me. but where does it bolt on

I'm interested.. Please add me to the list.

I'd be interested in the group buy.

Every Day, I haven't had any luck in joining 6-speed. If you could help group those guys we might be able to get a better deal. JW

Great minds think alike - I already posted a group buy message there and on RennTech...

for $1K is it better to do a reflash instead? if a reflash will give you about 25hp isn't that a little cheaper....?

oh yeah...... i posed this question before on one of my post............ but GMG and also a couple of other places are also offering their version of a plenum....... r they all crated the same...? i think GMG is offering it for around $800............. anyways, anyone whose done this....please info

The HP gains are at the wheel. Check out the RRS link for the plenum page of their web site. I think they made a couple mistakes as they have MY01 listed as a 3.6 liter engine. I understand why HP/torque gains are so different between 3.4 & 3.6 liter but I don't get why the results would be different between a MY99 3.4 liter and a MY00 3.4 liter? Again, probably just a mistake. If I can get close to 25 & 25 with a full money back grantee (as stated by RRS on 6-speed) I'm in for a group buy. Porsche_smile - flash won't get you close to 25 HP alone. You'd need exhaust, CAI, and headers to get anywhere close. http://roadsportsupply.com/IPD_Plenums_Porsche.html

If they guaranteed 25hp for the 3.6L, that's good. If we don't get 25hp, they'll refund and pay for the installation/removal costs? Am I asking for too much?

i'm in on the group buy but for my turbo

what is a typical cost to dyno the car before and after (so as to verify any increase) ?

I am having a hard time believing those hp gains, that is a lot of power gain for an intake, the factory peice is huge for 300-320hp.

I'll try to get my dad into this GB too, he's not too willing, as $1000 ain't pocket change...but I'll see, so put as a maybe...thanks Chasen

i think if it's 25hp at the wheel that's huge.... and for only 1K.....? i need to see some dynos and consistency.....

Guys, deputydog95 from 6speed posted this dyno sheet for the 3.6L. It doesn't look as impressive as the 3.4L dyno, HOWEVER, it does smoothen out the torque/hp curve a little, especially around variocam activation. Regardless, for ~$1,000, I expected a +hp increase across the board, not just when variocam kicks in.

I might be interested. For my 997 if it's a decent discount. So many HP claims, I just have a skeptical opinion of 27 HP from a large T-plenum to a Y-plenum. If I added up all the easy HP gains claimed,ie. exhausts, chips, airbox, and now plenums etc. I could essentially bolt-on 100 HP

I emailed RRS and said we had app. 10 interested parties and quote us a $. I"m also going to contact GMG racing because someone mentioned they had a similar plenum they use that is cheaper. I'll keep you informed with new info. JW

Arnee - can you get the 3.4 sheet?

never mind, I found it

I smell snake oil (on a NA car) and God I hate the abuse of the "R" and "S" letter combination in Porsche circles but I guess it sells................................

That is what I say, the factory plenum is huge for just 300-320hp, I dont see how you could improve on it. Second thing, GMG said it has been out for over a year, where are the cars that have them?

+1

JW996, please add my name to the list. I have a damaged (partially melted) stock manifold sitting in my garage. I replaced when I rebuilt my car. If you look at the stock T shaped plenum, you can see that the incoming air is running onto a wall. With a Y shaped plenum, the flow of air into the heads is smoothed out. I'm not an engineer, but with all the intake & exhaust modifications that we do to improve performance, aren't we trying to increase air flow in and out of the engine? (ie. turbos, superchargers, cold air induction systems, ported heads, headers, etc.) The factory powerkits that I have seen for the different 996 & 997 models include an improved intake manifold. To me it makes perfect sense that this part will improve performance. I would be happy to post my before & after 0-60 and1/4 mile times after I get mine. If anybody wants to see a picture of the stock plenum for comparison, I will gladly take a picture of the spare one in my garage (it is undamaged). JW996 thanks for posting this thread...I'm anxious to try it.

Fletch - I'd like to see a picture of the stock piece. Does anyone know if this new unit needs a chip to maximize benefit or of it can be used with an aftermarket CAI (EVO or K&N)?

You guys diss the Turbonator but buy this, they are both snake oil! This plenum is nothing but a glorified vortex booster / fuel saver. Ciao, J.

I could be interested as well if the price is right.

A couple of points. The X51 kit uses a different intake manifold, heads, cams, headers and software to make 25 hp so you're being pretty optimistic thinking you're going to get 20 from just the plenum. Second, the dyno chart shows a reasonable (small) gain throughout the rpm range but not enough that it would be noticable in the car. The 19 hp gain when the cams shifted has more to do with the fact that they shifted a couple of hundred rpms later on the blue run. I don't think that had anything to do with the plenum. I'd be interested in seeing all 6 runs. Jim

has anyone done this mod before? and the issue with GMG having a car running around with this mod for the past year? yeah.... where is it?

I've called GMG and waiting for them to return call, will post after I hear. JW

good job jw.....see if they can provide some dyno and if there's a group buy discount

Talked to GMG and they are working on $ also. I asked if it is snake oil and he said that with the Y design you are createing more velocity entering the engine. The more modified the car(exhaust,flash,etc.) the more effect you will have. It will not throw you back in the seat like a turbo or super but you will probably notice the difference. I also asked why dyno run shows more improvement on 3.4 and it is due to the design incorporated in the engine banks from factory. 3.6 has different design which doesn't respond as well. Will update with $. I bet it will probably be around$800, if $ is $950 + -. JW

http://www.6speedonline.com/forums/s...t=75109&page=4 FYI - if interested check out the most recent response from RRS and a drawing of design.

I love it when RSS uses the word "should" over at 6speedonline in the thread about the same product. QUOTE "3. All plenums "should" provide improved performance with any and all other mods. We haven't tested the plenum with any after market super chargers but the plenum allows for greater air flow so fundamentally it should enhance any forced induction system." UNQUOTE Come on everybody get your snake oil while it's hot! Ciao, J.

If the air was being blown into the system this design and the diagram would make sense but remember the air is being sucked in. In other words, it's being sucked around the corner, not blown into the T and forced around the corner. I just checked my cars and, while I didn't take them apart, it looks like they all have the T design. That makes me a little skeptical. Porsche put a lot of development into the X51 and the cup car. Jim

Exactly! On a turbo car, maybe but on a NA car, no way!

Kolshack, I just spent the last hour searching through my garage for my old intake manifold assembly. I thought so highly of it that I tossed it in the garbage once I got my car assembled. The quality of the stock manifold is terrible. I will attach some pictures of my engine while I was assembling it. You should be able to see the plenum from different angles. To the sceptics: I'm always surprised when performance parts for the Porsche are being discussed. A well designed header will add performance to a Mustang a Corvette, a Mercedes, or any other car....but people doubt the performance gains claimed by manufacturers of aftermarket Porsche parts. Take a look under your Porsche at the stock header, then look at a quality aftermarket header. It's not difficult to see that it can be improved upon.

Sorry guys, one more rant while I'm on a roll. I don't understand the analogy of being sucked versus being blown....either one sounds fine Seriously, if you put a better intake manifold on a naturally aspirated engine, you will get more power.....if you do the same to a supercharged or turbocharged engine you will also get more power. In the post on the six speed forum, the representative from RSS states to Deputy Dog, "If you do not make the power that is stated, we will give you a full refund". That does not sound like snake oil to me.

What is he supposed to say?! He has to stand by his product or he is fcucked! You are really the perfect customer that I'm sure breed Sea Monkeys as well. Never mind, run along now and get yourelf a very expensive piece of aluminium that will look nice as a paper weight.

Mr. C4, I really appreciate JW taking the time to post this information for those of us that would like to squeeze a couple of extra ponies out of our cars. I can appreciate and respect the opinions of others who are sceptical of performance gains claimed by manufacturers of aftermarket parts. The beauty of a forum like this is everybody is entitled to their own opinion. What I don't appreciate or respect, is someone who is arrogant and condescending in the manner in which they express those opinions. I don't recall resorting to personal insults because I had a different opinion than you. I'm going to exercise restraint and not tell you what I think of you at the moment.

If it would make you feel better, please go ahead.

It really wouldn't. I'm going to spend a few minutes on e-bay and see if I can find some nice sea monkeys.

Mark, First I'm not one of the guys that thinks that the factory parts can't be improved on. I'm pretty sure I've spent more on 996 mods than just about anyone. Check out the mods to my 996 racecar on www.jimbreakey.com . On the other hand, I'm very very skeptical about any simple bolt on modification that the vendor claims will add 20 hp. It's not going to happen. I'm not saying you shouldn't do it but I'm telling you if you expect anything more than a very small improvement you are in for a big disappointment. BTW, you can't tell a good header by looking at it. Jim

Hey guys this is all in fun and the appreciation of the cars. I do believe that there is the ability to make improvements on stock cars. Sometimes the claims seem hard to digest but if improvements were all snake oil then all the cars that were raced would be completely bone stock. JMHO. Let's be cool with all our opionions. Thanks. JW

I could not tell, is the group buy on?

I think I want to weigh in on this, but in the interest of full disclosure, I have in the past bred sea monkeys, and may yet do so in the future, so Mr. C4 may simply want to skip this post. In any case, I used to believe what appears to be the conventional wisdom on porsche forums, namely, that if it were so easy to extract a couple more horesepower, Porsche, mighty Porsche, would have done so. Now, don't get me wrong, this is not a Porsche-bashing post. I would be willing to wager that I have more loyalty to the marque than just about anyone...my engine could grenade tomorrow due to the presence of a shop rag in the cylinder bearing a porsche crest and the word "Heinz" monogrammed in the corner, and I would not hesitate to go out and get a replacement engine as fast as I could (and no, I'm not rich). I'm 30, on my third p-car, and will never be without one. However, it is very well documented that Porsche, as of late and especially during the development of the 996, has been extremely senstive to cost issues and has made numerous compromises in the performance category to save costs. A particularly striking example is an account given by the designer of the 996 (Pinky Lai) in a book I have (can't remember the title at the moment), who explains that he was forbidden to incorporate a retractable spoiler, despite its obvious aerodynamic and design advantages, because of costs issues. He described his dealings with management on this issue as a knock-down, drag out, battle, and indicated that the board felt strongly that it would simply be too expensive. Of course, he finally prevailed, but if memory serves, not until after numerous direct appeals to the board of directors. In other words, I don't believe the "porsche doesn't compromise" mantra we so often see from so many Porsche afficianados. I love Porsche, but they are in business of turning a profit, and you just can't do that as well if every part on your car is R & D'd to death or incorporates the latest and greatest manufacturing techniques or materials (think polishing the inside of a header...or plenum). Another good example was Porsche's change to the early 3.4 exhaust cans, which I believe Porsche admitted netted a few more horsepower over the old version. This was undoubtedly an "easy" change, but one that was not, after all, incorporated on the 99 3.4's. When people with new 1999 911's swapped their exahust for an aftermarket exhaust in 1999 in a bid to increase performance, people like Mr. C4 undoubtedly would have cried out that the stock exahust is already super effecient and that if it were that easy to improve Porsche would have done so, but he would have been wrong. Thus, I can definately see how, especially after knowing Porsche's mentality during the development of the 996, many performance parts could be improved upon. If every part on a Porsche was engineered to the hilt for max performance, our cars would cost 5 times the amount they do. Besides, modding these cars is fun. Even if the gains aren't miraculous, and even if they are hard to justify on a dollar-per-horsepower measure, the bottom line is that many people find it enjoyable to attempt to extract as much performance as possible without having to crack open the engine or install a supercharger. I know I do, and I know headers, for example, would be on my car right now if cost were not such a big consideration for me (o.k., for my wife). I think this is one thing that makes these cars fun for many people, obviously not everyone, but some.

/\ good post........

Scott I agree great post but I still do not believe.

Ironically enough, based on what I've seen thus far, I don't believe either, but I'm certainly not saying its not possible. I'm very curious to see what the consensus is after these things get installed!

OT jw996 , still happy with your new headers? /Rob

Good post Scott and good luck with the headers. FWIW, here's what I think. There are many ways to make your 996 a better sports car. Personally I think the most valuable are suspension changes but engine performance can be enhanced. What bothers me are HP claims that make no sense and people buying into them that have no idea what the part even does. "add me to the group buy, what is it anyway?" There was some guy on this thread judging headers on how they looked. I think owners should either 1) work with a good race shop that can tell them the likely outcome of different mods and measure the results or 2) educate themselves on how their engine works so they can make their own evaluations. Headers are a great example. How many have taken the time to learn how they work? The Phelum is interesting in concept but if you look at what Porsche did with the X51 you quickly figure out that you probably need a more radical cam to take advantage of more air coming in. Will it help some. Maybe. 20 hp. Not a chance. Anyway, it's your money, spend it however you want. Jim

NO WAY this will give 20hp. I'll bet it WILL improve performance slightly, though. 20hp? NOPE - but I'll bet somewhere between 5-10 MIGHT be possible. Maybe. People need to take dyno tests with a grain of salt. People look at graphs and think it is the TRUTH, when in fact it is just a measurement on that car, at that time, in those atmospheric conditions. They will run the dyno over and over until they get a result that looks marketable. They aren't lying- they are just showing you the best possible graph they were able to achieve. Put a car on a dyno and run it several times in one day and you'll see different result every single time!

It is BS, make sure you guys write back when your car doesnt feel any different and you just dropped $800-1000 on a pretty piece of aluminum. Why would Porsche sell there 25hp for like $10-12k when all you need is a simple intake PIECE, not the whole intake like porsche sells.

Good input ElTorrente! I'd say this is valid for the after dyno and the before dyno in opposite directions. As everyone knows what HP the car should have at the crank, the to the wheel HP is ususally unclear, so missing 5-15HP on the before test, makes the dyno result after the mod even more impressive. I guess all of us would be skeptical if they'd test the HP at the crank of a 996 3.4 at 287 before and the dyno after the mod at 304; however, this would still show an impressive gain of 17HP!

Well, if people are so sure that all performance gains in a Porsche cost mega $$$, then.......because they can!

What I want to know is why this thing costs $1,000.00!?!? It should be ~$200 max!

Just take a look at the factory piece your are replacing, it is humongus for the airflow needed to support the 296/300/320hp these engines put out. For Porsche to get the same gain, it took a bunch of parts (sorry I dont have the list off the top of my head). This may sound stupid but I am looking out for people not to be taken. Where is the car(s) that have the intake installed for a year now, why now are we hearing about them, why not a year ago. Just some things to think about.

I agree, I continually see, exhaust systems w/30 HP gains, ECU programming w/35HP gains, cold air intakes, 12-15 HP, Y-plenums 27 HP in the 997S! the list goes on. The engine output is the sum of a carefully controlled and tested input/output flow, not to mention internals and testing after changes are made to reprogram the ECU for the particular engine system.. From the illustration they present it seems like the splitter actually reduces they airflow diameter. Plenum Comparison Sorry for the skepticism, but there ain't no free lunch, or in this case $1000 real bolt on intake large HP gains

I don't need more power, my car is faster than I am......................................................

If anyone is still interested in group buy, PM me and I will give you cost for your application. I need year & engine size. JW

With regard to airflow. I cannot imagine a worse shape for the plenum than the Porsche "T". I have no idea weather they really get the HP gains they claim, but it wouldn't surprise me if they get some gain. A non-technical explanation is that you loose a huge slug of air in the porsche design. When the air hits that back of the "T" it stops, and then has to go either left or right. Well in doing so it has lost all that precious cylinder filling velocity which gives us our power as well as creating turbulence in a place where turbulence is not helpful . In the RSS design, the air is smoothly redirected to either the left or right cylinder bank. If these two designs have exactly the same diameter in and out, the smooth flowing design will flow more air. Please don't flame me, I am not standing up for their performance claims. Just applying basic fluid dynamics to the question.

Those Porsche engineers are so inept... Amazing they're still in business

Guys these NA engines HAVE NO ROOM IN THEM to produce these numbers. We have gone over this time and time again. The 3.4 L I think is better to squezze some hp and trq out of them than 3.6 L. IMO its a waste of 1k. So until someone buys this thing and puts it in their car and says WOW this piece is a MUST HAVE forget it. If these things produce 27 hp like some of these Dynos ive seen... Ill personally give away my car to The Salvation Army

You are so right!

For those who want a visual of this thing go to 6-speed site and RSS has photo comparison of stock and the new model. JW

Mr.C4, if I had your mkIGT3 (which is my dream car...I can't even buy one in the US...at least to drive on the street), I would not be trying to squeeze a couple of extra ponies (or sea monkies) out of my car. JimB, I never said that I could tell the performance of a header just by looking at it. I can tell that my Billy Boat header is an improvement over the stock header. The last engine that I put together prior to rebuilding my 996 was a N/A engine(Ford). I managed to increase it from 225 hp to 420hp. I used a lot of bolt on parts (mass air meter, throttle body, intake manifold, heads, headers, etc.). I also learned that sometimes the better quality part does not necessarily make more power (my Holly Systemax Mainfold had to have a casting flaw repaired right out of the box...the quality of Edlebrock manifolds was much better; however, the Holley made more power). I do believe that we can get more power out of our N/A engines without resorting to forced induction. I'm sure that a bottle of nitrous would do wonders. I do not believe that a simple bolt-on part, other that nitrous, is going to add 25hp! I do expect that I can realize a small gain from this part. Ife, I couldn't agree more.

Exactly a SMALL GAIN prob 5 hp which it will rob from the low end and there goes the throttle response when you go to MASH IT in 2nd gear. Lets all get in with a SC Group Buy now we are talking

How 'bout we just setup a 996TT group buy to solve our power-problems?

cobra06 Nowhere in my post did I call porsche engineers inept !!! The 996 is a first generation engine. In any first generation engineering design you never get all the performance possible out of any product. It is evolution of the design that leads to it. This engine is a masterpiece for a first generation, getting better in each new version.

With 4 posts here you have probably not heard of the thing called RMS. So much for masterpiece............................

I been hearing more PMS.

An internal combustion engine is a positive displacement pump and as such will take in as much air as displaced by the pistons at any given pressure. The air does not stop at any point, T or not. I compaired the diameter of the plenum to the size of a 8 cyl. 5.7 L Corvette MAF and it is comparable in diameter. I'm thinking the Porsche design is more than large enough to accomodate any demands placed on it. As to 25 HP gain, I have serious doubts. I've been wrong before but I don't think so this time. Has anyone seen the size of the restrictors placed on some racing series cup cars, I'm thinking the inlets are the size of a large thumb and they still make over 400 HP.

Thx jw996. I posted an engineer's opinion why in theory this might enhance airflow, and I got flamed. Only 4 posts recently, I don't remember what handle I used to post under back when I had a 996. Been a couple of years since lease was up, I am really missing the sweetest car I ever owned, ready for another.

can I jump in here?????? OK....this is my 2nd Porsche and I QUICKLY learned that almost all mods LOSE HP....why? The car is designed so efficiently. Thats all it is. The 3.4L has more room for improvement, but there is AT MOST another 20-25 hp TOTAL available in the motor. You will have to spend a good $3-5K to get it. This makes it cost prohibitive for most. Every 6 months or so there is a product that claims 25HP...simple bolt on....Wasnt it the K&N intake last? Before that such and such exhaust...then before that so and so chip, then the ebay headers...etc....Some of these products do indeed make positive HP SOMEWHERE in the power band...usually the high end...but at the expense of low end torque....For race cars and track cars, this is perfectly fine...for street cars, not so much as you feel the loss all the time. So what good is an extra 10 hp at 6000 rpm when you lose it at 2000? Headers SOMETIMES work for the same reasons. Just throwing headers on a car doesnt mean it will be more efficient. When building a 1976 BMW 2002 car with the stock engine putting out a whopping 95 HP...I thought about exhaust, dual carb, etc...I found out the driveability of that car would be severely compromised because it would gain a ton of HP on the top end, but lose alot on the low end...The muffler that was the most efficient and geve the best performance? STOCK. The hot carb setup wasnt an expensive Dual Sidedraft, although it looked mean...but a single weber 2 barrel gave the best overall performance...Similar thing here...the efficiency of the M96 engine is about 95%...getting the last 5% is costly and 5% on 300hp is 15hp....Also the HP of any engine from the factory can vary +/- 5%....so if your particular engine was strong, it will put out 315 hp....I say engine the car....all this talk about 15-20hp is almost useless....especially when you may get what, a .1 second advantage to 60?...ok rant over...if someone gets it....then report back.

I asked about this last year and thought Sharkwerks said these provide no gains? These have been on sale in Performance Products Catalog for years.

I'm already running aftermarket headers, mufflers, GIAC chip, and EVOM CAI....and I'm not sure I can get much more out of the car with a bolt-on approach to HP gains. Just those modifications have run me about $3900...so I don't think I'm going to put in another $1,000 to see if I can pick up (doubtful) another couple of horses. There are only so many horses you can realistically pick up with bolt ons...and with what I've already got, I'm not sure there's much room for improvement. I'm certainly not willing to blow another grand to find out. You folks who make the jump can tell the rest of us how it works out. I hope someone does an independent dyno. I'd be interested in hearing from anyone who plans to do this and who has done the same mods I have. Chuck

Chuck, your car felt great when I drove it on Monday...I think your mods were money well spent. I'll be the dummy that wastes his hard earned money on this new part, then you can take mine for a drive and let me know if you can tell the difference from when you drove it on Monday. If EVO would get the supercharger CARB certified, I would buy it. I want TT power without 4 wheel drive...I drove my buddies, I loved the power. The problem is, I'm still a juvenile delinquint. I like to be able to light up the back tires when I want. My wifies car has 420 ft/lb of torque and can roast them at will. She shouldn't be the only one that gets to have fun!

Chuck, I'm looking forward to hearing about your adventures with the G-tech. See you Saturday.

Mfletch here is a question what is the difference between the old and new evo intake? Woth the money or just more intake noise? Sorry to go off topic, so back on topic did they actually test this part with an evo intake or with a stock.

rountreed, I just had mine parked next to Chuck Jones (fellow Rennlist member) 996 on Monday. His has the new intake. It appears to be designed so that it does not take in as much hot air from the engine compartment. I'll see Chuck on Saturday at a PCA event. If you like, I can take a picture of both and post them. I think it was worth the money both for the sound and performance. If you look at my post within the last couple days regarding 0-60 and 1/4 mile times, it appears that I improved the performance of my car with the cold air intake, headers, and mufflers. I know that there are others who will disagree with me about the gains, so please judge for yourself. If you ever come to California, I'll gladly offer you my car for an afternoon in exchange for a ride in your jet.

Thanks, I think I will be in Iraq well before I make it to Calif. but the offer is very nice. I have read reviews on the older evo intake before but just have never been told what exactly they improved. Thanks Derek

Derek, please be careful. My family and I appreciate what you do.

Mark/Derek: To be truthful, I really don't think there's that much difference between the old and new EVO CAI's. From a logical point of view, I'm sure that EVO has some engineering and design considerations into the new intake...and in looking back and forth between Mark's and my car, the newer intake does seal off the air filter from the rest of the engine compartment, and channels air thru a plenum from the intake scoop on the left side of the trunk lid. But just exactly how much more efficient the newer design is, I really can't say that I see there'd be that much of a HP gain....maybe runs a bit cooler?? Mark: Did you think that the GIAC chip did that much more for the car as compared to yours? Granted, we're running tip vs manual...but I don't know if the butt dyno was that conclusive...We need to do another comparison drive. I'll bring my camera too this weekend Mark and we can take the pics for the forum if they want to see the differences in the CAI's. See you there.......Chuck

Chuck, I thought the chip felt like a noticeable improvement. I'm going to stick my neck out and get the plenum first. Are you having fun with the G-tech? See you Saturday.

Because they can?

I'm not sure this mod will add any horsepower, but why do you guys say there is no room to gain power? Our engines are efficient, but definately not the most efficient out there! Honda B18C (intergra type R) makes more than 100 hp per liter. Our engines' efficiency doesn't even match a Integra GSR's. Yet, the Honda community had come up with bolt on mods that make power on those engines. My friend Loi who builds Honda motor squzzes out 250 whp from a 2.0 liter. I can prove that he does make that much power, because we raced on the highway, and he was neck to neck with my 99 3.4. I think there must be room to squeeze out more power, it's just that the mods for our cars are so damn expensive and fewer and fewer people want to buy those mods now. As a result, it greatly slows down the development of new mods that makes real power.

What kind of torque is your friend getting? Curious.

I don't know the exact spec. of his motor, you can call him up to find out if you're really curious. I wonder how he can do it too. And now he has a stroked out K26 motor (from TSX) making 300 hp NA -_-. I wish he can do the same magic to my car too, but we're seriously lack of parts for our engine... sighz~ I couldn't imagine a little NA honda motor can match my 3.4 on the straight (and with his new 300 hp motor, he will rape me). O yah, it's not BS, Loi is the top Honda tuner in So Cal, and a spoon distributor in USA. http://www.sportcarmotion.com/index.htm

Here is a link to a 996 owner on the 6-speedonline site. He shows the before and after dyno results for the RSS plenum on his EVO SC'd car. The results look pretty impressive. He recommends it over a chip as a better bang for the buck. http://www.6speedonline.com/forums/s...ad.php?t=78328

Nice article but would have to agree would like to see results for us non SC 996 cars. If it holds true I may skip the GIACC for this.

I remember, some years ago, reading at length an article by a reputable German tuner (sorry, but can't find it now) that explained the reason that most bolt-on mods have little effect on the Carrera motor. The crux of the argument was that they don't address the most restrictive parts of the engine. From memory, the tuner stated that the valve and port sizes on this engine had been kept relatively small for an even torque output and this is where the biggest restrictions to increased top end power lie - they're simply too small to flow a lot more gas in naturally aspirated mode. This argument is supported by the fact that Porsche addresses just this area with its X-51 power kit. It gas flows the heads and valve seats and uses different cams to keep the inlet valves open longer (thus making the most of the small ports and valves). Porsche also uses an alloy inlet manifold to squeeze the very last ounce of efficiency out of the manifold to port interface (i.e. no lip or imperfections to impede gas flow). This is all in keeping with the argument the tuner put forward. The key to getting power from these engines would therefore appear be bigger valves and ports but I'm not sure if the heads have enough meat on them to be able to do this. Even if it was possible, it would completely change the engine characteristics and not necessarily in a way that would be any good for road use. In the absence of removing the main 'bottleneck' from this engine, changing parts that are not tthe limiting factor in the system will only lead to very small incremental improvements and this is borne out by all the (largely ineffective) bolt-on bits available for this engine.

Define "Little effect".

hmmmmm.,...... that's pushing out some impressive numbers for under $1K.......... i would like to see it on an NA car as well........... i've been following that site for a little bit............ i guess the numbers did come out right.......

'A small gain in percentage terms for the quantity, complexity and cost of the modifications undertaken'?! To put the definition in the form of an example: +20bhp on a 320bhp motor (the most anyone ever really seems to get from all manner of bolt-on 'goodies' despite comedy claims to the contrary) is 6.25%. The cost of this 20bhp is horrendous! Intake, headers, cats, mufflers, plenums, remap etc. etc. for 6.25%. And 6% is barely noticeable in reality! That's what I call 'Little Effect' and frankly a waste of money. Even X-51 at +25BHP = under 8% for how many thousand $$$? Years ago, we used to get +25bhp on 100bhp carburetted Ford motors with a cam and carb change. That's +25% for a few hundred $$$. That's what I call 'Big Effect' and worthwhile!

i agree....but to some of us, even the small effect is noticeable....... is it worth the price......? HELL NO.... but it's noticeable.......

ArneeA wrote: "How 'bout we just setup a 996TT group buy to solve our power-problems?" THAT is the best suggestion I've seen so far. All you need is about $65K for a "bolt on" car...then it's a done deal. I'm in.

I'm in!

i'll take two.........

i'll take two......... isn't it twin turbo????

Anybody tried this mod yet on a regular 996?

if it worked on a SC why wouldnt it work for an NA car... they didnt designed the plennum based a on an SC so why wouldnt it work... Im a believer in performance mod... granted they dont give that much noticeable power, but they do give better values, and that is the whole point. If the mod is reliable and doesnt blow your engine and increases performance then its a good mod. I just hate when people say porsche engineers know more...but in reality, its more than just engineers who have input on building an engine.

well said.... but i think it's a question more of a value to power ratio question.... if it only adds around 2-3% more power for $1K, is it worth the value.... i think here on rennlist, it's not whether or not something adds quality to the engine, but rather does it add quality with value.... i feel that our cars are NOT cheap so if it's possible to save here and there and have the sense that we got something well worth the money it JUST MAKES US FEEL BETTER.....

I understand what your saying, but if you look here: http://roadsportsupply.com/IPD_Plenums_Porsche.html the 3.4 996 increase 25hp/22lb for $1k... if the mod comes close to that, which I think it will, (the SC guy who did before/after dyno had 24hp increase, RSS stated 14hp for the 3.6. HP increase due to the SC, assuming). What other mod out there has these performance numbers for $1k. Not, any exhaust, headers, intake or flash by itself. Maybe together and your looking at $2.5K at least. Forget Porsche they want $17k for 25HP. I would rather have 120HP/80lb for $10k and get the SC. Yeah Porsche know how to get 25hp by doing internal mod, but someone did it cheaper, nothing wrong with that. I think the plennum is the best mod for the money.

i would have to agree... if the plenum does produce as stated... what we need now is an NA car with before and after and a couple of us to verify this... if so, this is a deal........im still waiting until my car can fly..........

On 6speed I asked the same question, RSS stated that they wanted to release the whole line of plennums rather than trickle the finshed product. Tunners have been doing this mod for years, they even put them on cup cars...theres room for improvement on these cars.

IMHO, I think there is snake oil involved. As Jim mentioned and a few of us have dished out $15k to prove, the X51 took MAJOR work to make 25hp. The first thing to notice on the dyno sheet is that the difference in only where the vario cam has kicked on one but not on the other. The "max" HP is actually LOWER on the Y Plenum. My suspicion is that the dyno runs were in different gears and the loading was enough to move the point at which the computer kicks in the vario cam. I believe K&N has the same deal with their claims. Is the plenum worth something... quite possible 1 or 2 hp. Is that worth a $1000.00????? Want to make your car go faster in a straight line, put on a supercharger or bolt in nitrous or buy a TT or GT3.

redridge, I agree with you 100%. I will put my money where my mouth is as soon as I can scrape together a few extra dollars. I won't do a before and after dyno, but I will do a before and after 0-60 and 1/4 mile run with my G-Tech. I've already done B&B headers and mufflers plus the EVO cold air intake. I plan on doing the plenum and GIAC chip (or flash). I would love to add a SC; however, I don't want to deal with trying to smog an illegal car every two years. If I only make my tiptronic as fast as a 6-speed car, I will be a happy camper.

Of course x51 is major work...your cracking the motor. Your saying the plennum might possibly get 1-2hp, can you tell us how you got these numbers? Porsche gets to me sometimes... does the x51 kit have any exotic materials that is different than the stock? I dont think so, the only difference is the design of the x51...more aggressive design, so why didnt they just give us the x51 design instead...marketing, its all about money. Why does a $65K car jumps to $97K because of options, x51 is just one of those options to rape customers who wants a little more power.... Ill stick with aftermarket, expensive as they are, compared to Porsche, Im glad the tunner guys are around.

is it flying yet?

Mfletch: If you buy the plenum...I think I can arrange for a before and after dyno. Since you have a NA car...maybe we can put some of the mystique to rest here....however since you have a Tip...will that affect anything? Logic says HP is still HP regardless of transmission. (Yes/No??)

You don't want to lose too much torque for the torque converter.

Salvation Army is gonna love you!!!

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996CABOVA: What city do you live in so I can contact the Salvation Army there and see where their storage yard is? I just want to be helpful here....anything for a fellow Rennlister.

BTW, You can tell a good plennum, by just looking at it.

LOL! You're cracking me up, dude.

[QUOTE=RayGT3]An internal combustion engine is a positive displacement pump and as such will take in as much air as displaced by the pistons at any given pressure. The air does not stop at any point, T or not. I compaired the diameter of the plenum to the size of a 8 cyl. 5.7 L Corvette MAF and it is comparable in diameter. I'm thinking the Porsche design is more than large enough to accomodate any demands placed on it. As to 25 HP gain, I have serious doubts. I've been wrong before but I don't think so this time. guess what... wrong again

It is kind of fun to read this post after Eric's dyno results...28hp! 996CABOVA the Salvation Army is going to love you. Be sure to save the receipt....it should really help on your taxes next year.

I replaced the plenum and had them do the REVO flash, and holy crrraaaapppp! I noticed a huge huge difference. My car feels amazing now. I'm from inland empire area but saw teh AD for Stutgartt Performance in Costa Mesa,CA and tried out the sample revo flash, loved it and sw teh owners car had the plenum, what a difference. Very muchworth the money. Jeremy

OT: Jeremy... I've in the Corona/Riverside border. I'm surprised I haven't seen your car around town. I drive a Guards Red C4S.. you won't miss it. EDIT: I'm going to RSS tomorow afternoon to get the plenum and check out their shop (Stutgartt Performance). can't wait.

Hey, I wonder, if Ive seen your car around town. I live off Limonite, we should get together sometime soon and exchange notes, Let me know how it goes at stutgartt I really liked those guys. And I love the plenum and the REVO.

Check out the response Joel Reiser of PCA gave to the same question. The old adage comes to mind; if it sounds too good to be true it usually is. Even at half the hp gain $1000 would be good price. My only concern would be; what is the down side. There usually is one. A CAI lets in more air so the engine breaths better but it also lets in more contaminates. http://www.pca.org/tech/tech_qa_question.asp?id={6CFA8B0D-0D04-4B49-9360-B60C43938235}

Reviving an old thread here. Spent the evening on the dyno. Some positive results... Making things simple... my X51 made 285 peak avg hp stock (evo intake). With the RSS plenum, peak hp jumped to 303 and with the plenum and Revo Stage 2 at 9-9-9, it made 308, thats 23 hp for $2500. From 6600 to the limiter at 7400, it was putting down over 300hp The area under the curve (important stuff) has a huge change in the 6000-6800 rpm range. Car also has fabspeed cat-bypass and mufflers. Over the winter I plan to do some more testing with an underdrive pulley and a custom exhaust.

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What kind of dyno were you on ? With a 3.6 NON x51 I have seeen over 300 hp. Lots of potential differences but with an X51 you should be well over 300 hp easy to start with.

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Were the exhaust mods already done when you got your baseline number? If not, I'd say that they are far more likely responsible for jump in peak HP.

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Nice gains Ed....

Ed, thanks for sharing your impressive gains. Kudos to you for reviving an old thread in which you were previously doubtful of the benefit of this part. Please keep us posted on the other mods...I'm anxious to see if the underdrive pulley proves worthwhile. I see that I was hoping this part would make my tiptronic car as fast as a manual transmission car. I sold the tiptronic car and bought a 6-speed...I guess that fixed the problem. I have always hoped all the mods that I have done to my car, might be good for a combined 25-30 hp gain (or 10%). You realized a very nice gain from your modifications.

Exhaust mods were throughout. I don't think the exhaust really adds anything. Yes, you can always post higher numbers. I had cold pulls with over 320 hp, but those should not be counted. There is a right way and a wrong way to do dyno testing. The right way is running SAE corrected and you keep making pulls till the hp is steady. If you start with a cold motor, you will get a few higher HP pulls, but they will keep declining. You want to have the engine up to full operating temp and the runs showing consistant, within +/- 1 hp in consecutive pulls. Then you have real numbers.

On the contrary, exhaust is the easiest way to increase peak horsepower on any engine. The result is obviously not necessarily a more powerful engine in any usable way, and torque is usually what you give up, but a less restrictive exhaust does raise your peak. To me, it's hard to parse out what the plenum does if it was added at the same time as exhaust mods. I'm very interested in this mod, which is why I asked.

[QUOTE=BruceP;7023293]On the contrary, exhaust is the easiest way to increase peak horsepower on any engine. The result is obviously not necessarily a more powerful engine in any usable way, and torque is usually what you give up, but a less restrictive exhaust does raise your peak. To me, it's hard to parse out what the plenum does if it was added at the same time as exhaust mods. [QUOTE] The exhaust has been on for a while and was in the baseline. Comparing the baseline to an estimate for "stock" I don't see much gain there. I'm hearing from more people on the newer cars that there is not much lost in the exhaust anymore. The fabspeed, and most systems for this car, still use a lot of turns and a same side in/out muffler as is the stock. Over the winter, I plan to put on a different exhaust design with new mufflers kinds of where the stock cats were and a center exit exhaust. Less turns, maybe more HP? Definitely less weight. I will do dyno's before and after when we do it.

Will follow with interest! I'm keen on mods that release a little more power from the engine, but having a lowly 3.4, I can't risk losing torque in the process. It's great to have somebody experimenting with this and willing to spend the money on measurement.

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There has been alot of people doing dyno runs and the same number of people shooting down those with dyno numbers. It will still be a split. Ed was a skeptic and now seems to realize that it does "work." I've had the plenum since RSS released it in day 1 and since day 1, I've felt an improvement with motor response and smoothness. And no, I don't have dyno numbers, trap speed, lap times, exit speeds, certificate of hp increases, whatever.

I thought this was debunked as a chocolate teapot by an unimpeachable source using unimpeachable methodology? But it seems the people willing to keep posting "butt" dyno and "real" dyno (both sets of quotes represent equivalent credibility) gains keep coming. Very impressive display of cognitive dissonance. You guys should go debate the Subaru owners on cold air intakes, and how much stiffer a chassis is when you bolt on enough blue anodized aluminum trim. The more you think things are different, the more you realize they're the same.

Cold air intake... 0 hp, chassis brace... 0 seconds faster, lots of cool blue stuff on your WRX... priceless.

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It's always puzzled me about car forums. Engine mods are the one thing you don't dare discuss because folks will either say a) you spent more than the car is worth, or b) the gains are imaginary. You'd think it would be the most fun topic to talk about. But I wouldn't post dyno numbers at the point of a gun, and I keep my feelings about my own mods about as private as I do my politics.

Now, when we've gotten talking business, could someone with a RSS plenum measure the inlet side and answer with that diameter. Please? TIA, Pete

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ID or OD? Didn't even think about it but inlet OD is same as stock since it mates to stock pieces. Didn't measure ID before installing; shoot RSS a note and ask them. Link to my pics.

ID. How your pictures look like both the plenum and TB are milled slightly bigger?

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Stock TB

This is so interesting issue that I have to test it myself. So I just bought one ( used ) from evilbay... Results from testing will be issued later. Of course I will also use a K&N filter and Mobil oil during that dyno test...

FYI, you can download the WinPep 7 software from DynoJet's website and overlay runs. If you(we) run on a DynoJet, we should be able to email each other the .DRF files and compare them with even correction factors.

Nice posts, Ed. In the past, I've contacted several of the s/w companies about flash upgrades for my X-51 and never gotten a definitive answer (i.e., they have set up the s/w for the standard engine but not the X-51). My interest in, and questions about, the RSS plenum have been similar, so you have answered a goodly portion for me. Please do post the exhaust info when you do the mod; I have a full Fabspeed exhaust, too and have wondered about improvements for the track, especially weight reduction. And if anyone else has definitive before/after dyno info about X-51 flash upgrades, please post. Cheers.

because the Revo SPS system lets you change back and forth between stock and race program, you can clearly see the difference. The problem is, for the 5-10hp you gain, you have to spend $1500 and run race gas. I would go with the plenum first, then maybe an underdrive pulley. The X51 flash is really only to maximize performance on 100 octane and I don't think you will be able to get anything more than the stock X51 map on pump gas. I know, I was tripping CEL's with the stock map on my X51 once the fuel changed to 10% ethanol. I was fine on Ultra 94, but got hi-speed misfires on the 93 octane after the change.

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We have over here only mere Bosch/TAT dynos, I guess that's it about comparisons.

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Thanks for that info. It confirms my thoughts. X-51 is a well-tuned engine. Your data indicate that it accomodates higher air flow by producing more power (say, 6% increase). Further optimization of the combustion process + higher octane yields only ~2% power gain.

The X51 kit does not include any electronic parts whatsoever, BTW. This leads to the question that Motronic itself must be able to control injection and A/FR to gain this 25 hp, mustn't it? And flashing it -atleast together with other mods- could gain something.

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Ed, Just curious why your X-51 did 285hp stock. Most stock X-51 dynos I have seen seem to be around 300hp. THe dyno below was my stock X-51 showing 302hp. This was done on a dynojet in December 2008. Not trying to stir the pot but I looked at most of the X-51 dynos I could find just to confirm my car was "normal" and in general my graph seems to be representative of most X-51s....or so I thought.

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Just to add my $0.02 to this thread: an underdrive pully is great for the track, but you need power tools to install it - i.e., cutting off part of the engine. It should help to keep your accessories from parasitic HP loss - perhaps up to 3HP. And it does wonders for keeping your power steering fluid from overheating. But if you use your car on the street, you will suffer from low voltage, and poor accessory performance - think AC in the summer lol. -td

My dyno runs, with the motor at full temp, with the fabspeed exhaust were 288-290hp. I would venture a guess you would lose a few hp moving the smoothing up to 4 or 5. Do you have the .drf files? Even at that, does not make up the difference. What year is your car? I had the 2nd X51 in the US, not sure if anything changed, but again, I would not expect much. Not sure, maybe just mine is a bit weaker, more hours on it, or some compabination of other variables. Drivetrain loss, etc.

I should really do a run on the dyno. My car had the RSS plenum + intake + exhaust installed when I bought it. I love the sound and responsiveness, but I don't have a baseline for comparison.