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The Radium King · 08-22-2012, 07:12 AM

see what you've done?!?!? you've got 'em all arguing about exhaust again. if there's a takehome from all this it's that the boxster engine has quite a bit of intake/exhaut tuning going on, what with cams that change profile as rpms increase, and resonance flappers on the intake that open and close to optimise airflow. things to beware of in the hp chase are:

a) there is often a compromise between high rpm hp and low- to mid-rim torque. exhaust mods that facilitate better airflow (more hp at high rpm) can rob mid-range torque due to loss of back pressure. even the oem porshe x51 power kit used on the 911's has lower torque numbers than stock engines at lower rpms. so, ask youself - what kinda driving do you do?

b) false/misleading claims. you'll often see cold air intakes designed for the 2.5 engine but also sold for the 3.2 engine claiming 10 hp gain. perhaps on a 2.5, but mebbe not for the 3.2; make sure you check. or, vendors will sell a 'package' of various mods, where one mod hides the deficiencies of another (i.e., the ipd plenum that is sold for the cayman deletes one of the resonance flappers and actually robs the engine of low-rpm torque; vendors hide this by only showing dynos of the plenum with an associated chip flash).

c) dynos. these can be misleading. mods that rob low-end torque are often presented by the vendors with dynos that don't have any data under 3500 rpm. another trick is one used by the tuners "my tune will add 10 hp" but all they do is increase the rpm limiter to 7400 or 7600 rpm; of course you'll see more hp as you proceed up the curve, but is it good for your engine?

so, there are seveal mods you can look at:

1) exhaust - headers/mid pipes/muffer. headers area the cheapest as there is a lot of good chinese stuff on ebay, but toughest to install and, if without cats, note that the engine cumputer has a sensor that checks for these cats; delete them and you get a code. there are cats on the midpipes too, but deleting these won't get a code. you will see many threads on this board with people typing in bold capitial letters about the hp and tone benefits of the various configurations.
2) intake - you can modify the plenum, throttle body, intake tube and/or airbox. again lots of argument on these, but in my opinion the aftermarket cold air intake units are pos; they do a worse job than oem at sealing out hot engine air, and they tend to use the same air sensor housing for 2.5/2.7/2.9 and 3.2 engines which is wrong, as the diameter varies between engine type and affects how the computer works. there is a current trend on this board to modify the airbox from a cayman or 987 and this seems to add hp, is cheap for parts, but labour intensive unless you diy. regarding plenums and throttle bodies there are products from ipd and pedro, but expensive ($1k) for mebbe 5 hp gain. again, there is talk on this board about using 911 plenums and throttle bodies to achieve the same thing for cheaper.
3) tune. several vendors out there, but again you are looking at $600 to $1k for mebbe 10 hp and, as noted above, a lot of this is achieved by moving the rpm limiter up. to understand, the comuter has the ability to manage a 25% change in airflow from anticipated; once this is exceeded it can no loger adapt. changes to exhaust and intake start pushing this limit, so consider the flash as the last thing you do after a lot of mods.
4) underdrive pulley (udp). this is just a smaller main accessory drive pulley. reduces load on the engine, increases torque and power by perhaps 5 hp throughout the rpm range. cheap, relatively easy to install. given all this, the udp is often stated as the best bank for buck mod out there. you can get 4" and 5" sizes, and they do affect alternator performance, so if you have a big amp in your car perhaps stay away.
5) low temp thermostat. good for the engine, keeps it cooler (160 vs 180 degrees) and is touted to add 5 hp on a hot engine. for real? i dunno, but a good move nonetheless.
6) weight loss. 10 lbs = 1 hp. lighter wheels (the oz alleggeritta are light and cheapish, also note rotating mass is more of a bad thing than non-rotating). lighter seats. ditch the person in the passenger seat. aftermarket exhaust tends to be lighter, so perhaps the weight reduction offsets any hp losses. lw battery.

so there.

08-22-2012, 07:12 AM	#52
The Radium King Registered User Join Date: Apr 2010 Location: Canada Posts: 3,128	see what you've done?!?!? you've got 'em all arguing about exhaust again. if there's a takehome from all this it's that the boxster engine has quite a bit of intake/exhaut tuning going on, what with cams that change profile as rpms increase, and resonance flappers on the intake that open and close to optimise airflow. things to beware of in the hp chase are: a) there is often a compromise between high rpm hp and low- to mid-rim torque. exhaust mods that facilitate better airflow (more hp at high rpm) can rob mid-range torque due to loss of back pressure. even the oem porshe x51 power kit used on the 911's has lower torque numbers than stock engines at lower rpms. so, ask youself - what kinda driving do you do? b) false/misleading claims. you'll often see cold air intakes designed for the 2.5 engine but also sold for the 3.2 engine claiming 10 hp gain. perhaps on a 2.5, but mebbe not for the 3.2; make sure you check. or, vendors will sell a 'package' of various mods, where one mod hides the deficiencies of another (i.e., the ipd plenum that is sold for the cayman deletes one of the resonance flappers and actually robs the engine of low-rpm torque; vendors hide this by only showing dynos of the plenum with an associated chip flash). c) dynos. these can be misleading. mods that rob low-end torque are often presented by the vendors with dynos that don't have any data under 3500 rpm. another trick is one used by the tuners "my tune will add 10 hp" but all they do is increase the rpm limiter to 7400 or 7600 rpm; of course you'll see more hp as you proceed up the curve, but is it good for your engine? so, there are seveal mods you can look at: 1) exhaust - headers/mid pipes/muffer. headers area the cheapest as there is a lot of good chinese stuff on ebay, but toughest to install and, if without cats, note that the engine cumputer has a sensor that checks for these cats; delete them and you get a code. there are cats on the midpipes too, but deleting these won't get a code. you will see many threads on this board with people typing in bold capitial letters about the hp and tone benefits of the various configurations. 2) intake - you can modify the plenum, throttle body, intake tube and/or airbox. again lots of argument on these, but in my opinion the aftermarket cold air intake units are pos; they do a worse job than oem at sealing out hot engine air, and they tend to use the same air sensor housing for 2.5/2.7/2.9 and 3.2 engines which is wrong, as the diameter varies between engine type and affects how the computer works. there is a current trend on this board to modify the airbox from a cayman or 987 and this seems to add hp, is cheap for parts, but labour intensive unless you diy. regarding plenums and throttle bodies there are products from ipd and pedro, but expensive ($1k) for mebbe 5 hp gain. again, there is talk on this board about using 911 plenums and throttle bodies to achieve the same thing for cheaper. 3) tune. several vendors out there, but again you are looking at $600 to $1k for mebbe 10 hp and, as noted above, a lot of this is achieved by moving the rpm limiter up. to understand, the comuter has the ability to manage a 25% change in airflow from anticipated; once this is exceeded it can no loger adapt. changes to exhaust and intake start pushing this limit, so consider the flash as the last thing you do after a lot of mods. 4) underdrive pulley (udp). this is just a smaller main accessory drive pulley. reduces load on the engine, increases torque and power by perhaps 5 hp throughout the rpm range. cheap, relatively easy to install. given all this, the udp is often stated as the best bank for buck mod out there. you can get 4" and 5" sizes, and they do affect alternator performance, so if you have a big amp in your car perhaps stay away. 5) low temp thermostat. good for the engine, keeps it cooler (160 vs 180 degrees) and is touted to add 5 hp on a hot engine. for real? i dunno, but a good move nonetheless. 6) weight loss. 10 lbs = 1 hp. lighter wheels (the oz alleggeritta are light and cheapish, also note rotating mass is more of a bad thing than non-rotating). lighter seats. ditch the person in the passenger seat. aftermarket exhaust tends to be lighter, so perhaps the weight reduction offsets any hp losses. lw battery. so there.