I have a 2004 996 Turbo Cab X50 with just about all of the mods possible. I want to replace my stock Plenum and was wondering what you guys are using and recommend.

 

All the mods possible? So you have a fully built 3.8 stroker w/ Gt 35's and Mackenzie heads?

Most real world results on the plenum hasn't been that impressive is you are still running K 24's.

 

I believe changing the plenum is more popular among the lower power P cars, Cayman... Boxster... There are so many different things you can do to gain better power with the TT than the plenum.

 

For what it's worth I'm running a IPD Intake Plenum 70mm Porsche 996TT 01-05 can just as easily do the 75mm for the same price. Changed the plenum because the absurd little tinker-toy plastic piece of rubbish that the factory puts in ceased function. The IPD is billet and is supposed to have a less turbulent, restricted flow.

I have GT28s, most of the other details are in my signature. A few are left out--just had a new stage 3 clutch put in, the plenum is brand-spanking, all the turbo hoses are now silver silicone ( obviously avoid boost bleeding off with hose bulge). New "water pump" as Porsche choses to call it. Already had a 650 kit with other mods to go with it.

But if do have a stroked monster the plenum I'm pointing out may not suit your needs. I still have a 3.6 without Mackenzie heads. Sounds like your car is potentially at a different level of modification or is the Dr just being nasty. jj

 

Thanks for your feedback. Let me list my mods so you guys could have a better idea of what my car has. My 2004 996 Turbo X50 has the following mods,

Giac flash
AWE Headers
AWE Exhaust
EVO Intake
EVO Hoses
5 bar fuel regulator
Diverter valves
Short Shifter
Coil over suspension
Strust Bar
Sway Bars
Teckart spoiler, side skirt, rear skirt and wing

What plenum do you guys like best? I was looking at Turbo Mikes Plenum. Have any of you guys used this Plenum?

 

You are not going to get much out of a new plenum. If you really want a big power jump for a modest amount of money, have your K 24's converted to 24/18's.

 

There's a ton of research on this and let's look at (please try to visualize) the mechanics of the turbocharged motor....

Your car it TURBOCHARGED so the intake system is, by very definition, the intake side of the equation is already PRESSURIZED so a larger PLENUM won't make a material difference in HP/TQ. If you have a N/A car then INTAKE restriction is perhaps an issue because the "downstroke" on a motor (from top dead center to the bottom of the compression stroke) is all that there is to SUCK air into the engine. So in this case a BIGGER intake is helpful. Turbocharged engines (for more power) need MORE AIR VOLUME + copious quantities of additional fuel and this isn't created by a larger PLENUM it is created with LARGER TURBOS ~ PERIOD ~ to create MORE INTAKE PRESSURE and until you get well past 700 horsepower then (maybe) a completely larger intake system COULD give you more power (assuming) the intake side of the cylinder heads (plus the exhaust side) have already been ported out to the size of coffee-cans, etc....

Do as the good Doctor already instructed an get MASSIVE turbos done. You'll be happy with the results. Next is going to be BIG intercoolers and of course, more fuel (larger injectors), hollowed out exhaust system, headers, a much stronger clutch, and well, while you're at it, MASSIVE front brakes (at a minimum) since the PLENUM won't help you in stopping the car at this point. Seriously, the plenum is a waste of money. It's a CHEAP part with ridiculously high profit margins which is why everyone pushes it as the next-coming and etc.... and it's absolutely pointless to consider until the rest of the above examples are complete.

 

I think you can get lower intake temps with plenum. The stock one is T-Shaped and there is alot of turbulence/friction so the turbos have to work harder for the same pressure and so the temperature increases.

I would like to see back to back tests tho.

 

He has an EVO Intake on his list.

 

your runningstock k24s ? and are running waste gate actuators ? EBC ?

 

You get LOWER intake temperatures with MASSIVE intercoolers. To suggest "air friction" in a pressurized system (as a cause of increased intake temperature) in a system that REMAINS at a static pressure (as is the nature of turbocharged engines) is to misunderstand the nature of the beast entirely.

The higher intake temperature is because the Turbo's run off of EXHAUST gasses and spin at 300,000 rpm's. That's why we use intercoolers. We would like to keep intake temperatures below 300 degrees farenheight. Stubble in the intake system doesn't have a marginal impact this problem. You may have noted that in drag racing applications the guys are loading the intercoolers with COLD ICE between runs.

This argument is, again, relevant for NATURALLY ASPIRATED engines. For the turbocharged applications, sure it COULD help but by the time you finished sanding down and mirror-polishing the inside of the intake system the OTHER guy will have bolted on some MONSTER compressors and blown you away.

 

If you are adamant about adding a plenum, try the Jasper Motor Werks or IPD.

 

Yes, I totally missed the point, thank you for the explaination. Question, the engine takes the air from the IC thru the Plenum. I'm sure it also takes air from the intake too, but since there is no pressure from the intake. Usable air from the intake should be minimal, right? or the turbo just help sucking air from the intake and only use air from the take? This is very interesting. Thank you for the Turbo101.

 

It's all about flowing more air through the motor to burn more fuel. You just have to consider that the motor (in a turbocharged system) doesn't easily run out of air since it's the AIR that is being PRESSURIZED by the turbochargers so it's more a problem that these engines run out of FUEL because the turbochargers do such a great job of PRESSURIZING the intake system. When the intake system is pressurized by a couple of turbos spinning at around 250,000 rpm's you don't have a "lack of air" issue. At the BLEEDING edge of performance you have your cylinder heads ported out, you have your intake system redesigned and matched to the new MASSIVE intake-side porting on the cylinder heads, larger airbox installed because you've sucked a couple of V-Flow filters into the intake system and collapsed some intake hoses while running the hi-boost setting and etc so that system gets swapped out for larger hardware (for some truly incredible increase in flow) and you're running a dragster, not a sports car. There's too much to consider here for most people. I liken the intake plenum to some guy placing a 2-Foot high spoiler on the back of a Honda Civic. You can tell everyone you have it but the performance is the same. Better yet, since this is an intake-thread, it's like the same Honda Civic owner placing a RAM-AIR hood with a HUGE scoop on top of the hood that sticks up three feet ABOVE the roof of the car. Does it help airflow? Yes. It is of material benefit? No.

 

This is pretty much dead on and is the same explanation I got from Todd K.
Go read up about how my buddy pulled a whole length on me w/ the K24/18 hybrid turbos and a total of 14K in upgrades (I have over 30K). I am telling you, 24/18's a new tune bigger IC's (I like my Evos) and a retune and your car will put close to 600 at the wheels. Of course you will then need a stronger clutch. Don't wast your money on the plenum which isn't cheap to install.