Nice work. Did you have a chance today? I know it before and after the work?

@@mikepetersen3 no, not today. Ha! My original comment was from over a year ago. I was referring to my experience with my 2001 Boxster S I was experimenting with in 2021. Mine was equipped with the sport design package. (bolstered seats and GT3 look wheels) It also had the standard Borla bolt on cat back exhaust for 986 actually bought it from the dealer that way. It's a real coincidence I made a dealer inquiry about a 99 5-speed base model in Black😅 today!!

The numbers don't lie :-)

Thank you!

Good luck! Fun car ;-)

Having one negate the other does not make engineering sense, but stranger things have happened. I too would like to dyno the intake with stock exhaust, but it’s time consuming and somewhat expensive to swap exhaust and retest. That is not likely on the to-do list.

Hi Mike, per my comment below... there is a deeper discussion on this specific topic here: 986forum.com/forums/performance-technical-chat/75484-ipd-plenum-best-performance-mod-3.html. Net net, we might pick up a 2-4 HP with a tune, at best. The car is already "tuned" and I do not expect much upside. Car is running ~ 11.8 A/F @ WOT, might be able to lean it out to 12:1 or 12:5:1 and pick up a few HP, but it will not change to overall results that the upgrade is not making the claimed performance gains.

The only downside of the 996 plenum is what inlet tube to use. Im sure there is a solution out there, but I have not looked for it.

Very helpful. Thanks for sharing!

Hi Paul, there is a deeper discussion on this specific topic here: 986forum.com/forums/performance-technical-chat/75484-ipd-plenum-best-performance-mod-3.html. Net net, we might pick up a 2-4 HP with a tune, at best. The car is already "tuned" and I do not expect much upside. Car is running ~ 11.8 A/F @ WOT, might be able to lean it out to 12:1 or 12:5:1 and pick up a few HP, but it will not change to overall results that the upgrade is not making the claimed performance gains.

@@mikepetersen3 There's more to it than just leaning out the mixture on a modern car. You'd get better power across the entire rev range as ignition timing can be tuned as well. I reckon you could see another 20hp out of a tune.

@rumpii. You are correct, it is theoretically possible to advance the timing and gain more horsepower, but that assumes the existing tune is poorly written. Most cars are tuned to advance the spark to deliver maximum torque and horsepower, this also delivers maximum efficiency. They will advance the spark to the point that it detects slight knock, and then pulls the spark back. This engine, like most modern engines, has several knock detectors, so one has to assume they are functioning properly and the car is advancing the spark to its most advanced realistic point. When I do the dyno test, I do run 93 octane to allow the program to deliver as much spark as possible. Furthermore, as this car has had both a stock tune and several aftermarket tools, none of which delivered more than 2 or 3 hp, I am confident that or horsepower could not be found simply by advancing the spark table.

@@mikepetersen3 I think you'd be surprised with the results if you went for a tune with the combination of spark+mixture, but if you're happy with your current results then I guess there's not really any need! Awesome car anyway, hope to mod my 986 similarly!

Hi @rumpii, take a look into the attached link and we have a deeper discussion on the topic in the blog. Net net, the car is tuned for both spark and A/F, in fact it was tuned twice. It is not a factory tune. 986forum.com/forums/performance-technical-chat/75484-ipd-plenum-best-performance-mod-3.html .

I agree but even better is getting an ECU tune. I don't know the exact number but I know I feel a difference..I also enclosed the intake system on the top to section off hot engine air. I have the original EVO intake with fabricated piping to the 74 TB and 997 plenum. The EVO intake cover is a perfect fit, with no gaps. Fabspeed is a copy of the EVO. This along with the Softronic ECU software, race headers, and by-pass pipes..This thing flys like a bat out of hell.

Your theory is correct, you need to have the correct air to fuel ratio for maximum torque/power. This car has been re-mapped, and during the dyno runs we always monitor the air fuel ratio through the wideband sensor in the exhaust pipe. You can see it on the chart at the bottom. For most engines the optimal air fuel ratio for performance is between 11-12:1. The chart shows the car is running at its optimal fuel ratio range for both dyno runs. BTW, The dyno runs were done 1year apart, the car had settled in with driving after the install and before the testing.

You are correct.

There is a longer discussion above, but I can assure you that the loss of horsepower down low is not a tune in issue. Is this car is designed for track use, I’m less concerned about low rpm performance. And the modest gains above 4000 RPM still make the solution livable.

I would agree with that sentiment... I do think a low restriction air clean and removing the snorkel helps.

If you look closely we actually added HP at the top end (albeit slightly) but lost in the mid range. I’m other words, slightly better for the track but a loss for the street.

There are still many ways to improve the engine, it's just the IPD is not one of them.