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The Radium King · 12-21-2011, 11:24 AM

ok, update.

caveat - analysis officially works only for 3.2 S, but only because i don’t know anything about 2.5/2.7/2.9 intake systems.

whereby, airflow is limited by the smallest constriction in the system,

whereby, the only diameter that is inviolate is the maf housing which is fixed at 3” (to make it bigger would confuse the computer).

whereby, the throttle body is sized at 2.67”, introducing an unnecessary constriction in the system.

let it be stated that a 3” throttle body would increase intake efficiency.

now, the cayman, 996 and 997 all have 3” throttle bodies and share the same Porsche part number, so are interchangeable.

997 throttle bodies are hard to find, but there are lots of 996 units around (one currently on ebay for $100) and lots of cayman units around as folks take them off to install the ipd product (i just found one for $100 over at planet 9).

now then, with a larger throttle body we need a larger intake plenum. given that the throttle bodies are interchangeable so should the plenums. therefore we have 5 choices:

cayman ($300) - this dog doesn’t hunt. it has that funky resonance flapper, which results in a different aos arrangement and throttle body positioned further upstream.

996 ($60) - this would work, but the 997 piece is better.

997 ($60) - this is the guy you want. similar to the 986 but improved - larger diameter, matching aos connection, comes straight out instead of at an angle, improved flow characteristics. improved flow characteristics? as per earlier in this thread, it was shown that you want the inside radii as the air turns the corner into the intake runners to be as rounded as possible. examining images of the 997 plenum on pedros site (here: TechnoPower2 Kit ) it is evident that the 997 plenum has as much radius as possible given space constraints. in fact, the radius is better than that of the ipd product (images and dyno here: 986 Boxster / S | IPD Plenums ).

technotorque 3 ($300) - this is just a modified 997 plenum, with the addition of a splitter. as shown in this thread, the splitter does not contribute to airflow efficiency. this is further evinced by a guy on planet 9 who put a larger throttle body on his car and got a dyno; gains were equivalent to ipd but without the splitter or the cost (here: 75mm TB and Cayman Plenum upgrade for 987 - Articles ).

ipd ($850) - as above, i can see no benefit to paying $850 when i can get equal or more gain from a $60 part.

so, $100 Cayman/996/997 throttle body, $60 997 plenum, a 3” duct to the maf housing, a pair of silicone adaptors to mate to the intake runners, and some hardware (the larger throttle bodies are actually thinner and require shorter bolts). in for under $200 and a 10 hp gain (if you believe the above dyno).

12-21-2011, 11:24 AM	#27
The Radium King Registered User Join Date: Apr 2010 Location: Canada Posts: 3,128	ok, update. caveat - analysis officially works only for 3.2 S, but only because i don’t know anything about 2.5/2.7/2.9 intake systems. whereby, airflow is limited by the smallest constriction in the system, whereby, the only diameter that is inviolate is the maf housing which is fixed at 3” (to make it bigger would confuse the computer). whereby, the throttle body is sized at 2.67”, introducing an unnecessary constriction in the system. let it be stated that a 3” throttle body would increase intake efficiency. now, the cayman, 996 and 997 all have 3” throttle bodies and share the same Porsche part number, so are interchangeable. 997 throttle bodies are hard to find, but there are lots of 996 units around (one currently on ebay for $100) and lots of cayman units around as folks take them off to install the ipd product (i just found one for $100 over at planet 9). now then, with a larger throttle body we need a larger intake plenum. given that the throttle bodies are interchangeable so should the plenums. therefore we have 5 choices: cayman ($300) - this dog doesn’t hunt. it has that funky resonance flapper, which results in a different aos arrangement and throttle body positioned further upstream. 996 ($60) - this would work, but the 997 piece is better. 997 ($60) - this is the guy you want. similar to the 986 but improved - larger diameter, matching aos connection, comes straight out instead of at an angle, improved flow characteristics. improved flow characteristics? as per earlier in this thread, it was shown that you want the inside radii as the air turns the corner into the intake runners to be as rounded as possible. examining images of the 997 plenum on pedros site (here: TechnoPower2 Kit ) it is evident that the 997 plenum has as much radius as possible given space constraints. in fact, the radius is better than that of the ipd product (images and dyno here: 986 Boxster / S \| IPD Plenums ). technotorque 3 ($300) - this is just a modified 997 plenum, with the addition of a splitter. as shown in this thread, the splitter does not contribute to airflow efficiency. this is further evinced by a guy on planet 9 who put a larger throttle body on his car and got a dyno; gains were equivalent to ipd but without the splitter or the cost (here: 75mm TB and Cayman Plenum upgrade for 987 - Articles ). ipd ($850) - as above, i can see no benefit to paying $850 when i can get equal or more gain from a $60 part. so, $100 Cayman/996/997 throttle body, $60 997 plenum, a 3” duct to the maf housing, a pair of silicone adaptors to mate to the intake runners, and some hardware (the larger throttle bodies are actually thinner and require shorter bolts). in for under $200 and a 10 hp gain (if you believe the above dyno).