Compared to the 991 Turbo and S models the 991.2 Carreras have smaller 3.0 liter flat-6 motors that are moving less air. However, as they are all now turbocharged the plenum potentially poses a similar restriction.
I contacted IPD and told them I intended to test their product. In return for using the BoostAddict.com Project 991.2 and arranging the dyno time I received a discount on the product. IPD also provided the install to make sure it was done properly.
VF-Engineering generously provided use of their facility and it was chosen because they have a Dynojet and a Mustang dyno in-house. Now, the test car is RWD and a base C2 but in order to dyno the car the front wheels need to be moving due to the wheel speed sensors. That meant the Dynojet was disqualified. Note, if you have a 991.2 Carrera, S, or GTS and intend to get a Dynojet graph make sure you find an all wheel drive linked Dynojet.
As you read in the Mustang vs. Dynojet article the Mustang is a more conservative load bearing dyno. That being said, the baseline numbers are very strong:
345 horsepower and 327 lb-ft of torque to the wheels on the Mustang completely stock at 1000 miles on 91 octane pump gas. Considering the 370 crank horsepower rating this is a very healthy example. The car also clearly is underrated.
You will notice a bit of a dip in certain areas on pull three. The car is quite consistent but heat soak starts to become a factor.
IPD changed out the factory plenum for their plenum with the car still strapped on the dyno. This is not easy to do. It is recommended that one do the plenum install on a lift. The good news though is that the engine does not need to be dropped to do it.
The bad news is you have to remove the taillights, bumper, spoiler, fans, etc. Almost everything needs to come off the back. Make sure someone with experience installs the part.
So what are the plenum testing results? There is an average hp gain, average torque gain, and max gain of 21 horsepower and 21 lb-ft of torque. There is even a modest increase in the peak figures but the area to focus on is from 3700 to 5200 rpm:
Let's compare pull number 2 from the baseline to the plenum to give a clear picture:
The shape and area of the gains in the curve is reminiscent of the 991 Turbo. Basically, there is more meat in the middle of the powerband. An area that gets a lot of use.
Average horsepower goes from 266 to 270. Average torque goes from 290 to 294. Peak horsepower increases by three wheel horsepower and peak torque by 6 lb-ft. The max gain though is 21 horsepower and 21 lb-ft of torque at the wheels at 4700 rpm.
Now, this is with no tuning changes and no fueling changes later in the day when the car was warm and air temps increased. The plenum is showing gains in less favorable conditions which is a good thing.
Now, do I feel it seat of the pants? Not exactly. I do not feel a spool gain or a throttle response gain but there is a sense of added urgency when revving out past 4000 rpm. This is difficult to quantify which is why we have the dyno to measure and not our butts.
Is the part worth $950? Yes. It's free horsepower and torque in the mid-range. It is coming from removing a restriction and not from increasing boost or messing with octane. Some people speculate boost pressure increases but the factory gauges are not showing me any different numbers in this regard.
Personally, I'm sold. If I didn't like it or feel it was not doing what was advertised I would take it off the car.
Hopefully more people test it and see for themselves. IPD mentioned that some of their gains on the other turbo Porsche models are so large they even dial back the graphs to show the worst runs as people do not believe them.
The proof is right in front you. The plenum is a great place to start when modifying your turbocharged 911.
A huge thank you to the crew from IPD along with VF-Engineering for being so generous with their time and making this a successful test. Thank you!
The original factory piece for those that are curious: