Anyone know about the "red cap" mod for the S model 997.1?

 

Yes, it basically disables the function of the Helmholtz resonator in the air box, increasing the intake sound somewhat. I cannot possibly envision how this $225 device could ever add power, despite the claims of manufacturers, but I've never been very imaginative .

 

Why not get a 1.5" cap and just block off the resonator and leave the stock intake in place? What am I missing?

 

Exactly. This very thing can be accomplished with the inverted cap from a quart of Castrol synthetic motor oil. $7 versus $225. Manufacturers claim that the "smoothness" of the replacement intake tube measurably improves airflow and adds power. I checked with Bigfoot (who, coincidentally, was riding a unicorn) and he agreed with the manufacturers' claims. He then charged me $225 for his advice.

 

I installed a 1.25" pvc plug, fit perfect and sounds great. Total cost $1.35

 

That's the way to go! Although I would pay $225 to meet Bigfoot or a unicorn for that matter

I also tend to go with the original airbox as the best unless you are going with a full 2 air intake system. The others look nice and add some sound but add little (and some say they take away from) performance.

 

 

It plugs the Heimholz resonator under that offshoot tube of the intake hose that connects back to the airbox. I'd show you on a photo but don't have a stock airbox in either of my 997s anymore.

 

Petza914, thanks for the explanation! What airboxes are you using now and how do they compare to the stock airbox mod?

 

Both my 997s have active aero rear spoiler upgrades - a RUF CF decklid & wing on my silver car with E-ram upgrade and a OEM TT retrofit on the pink car so both had to be converted as the electrics and hydraulics don't allow for the OEM airbox to remain. The silver car has a Fabspeed J-Pipe and the pink car an Evoms intake. The silver car also has a complete Fabspeed exhaust - headers, mufflers, 200 cell X-cats so with the RUF forced induction and exhaust mods, the intake probably had greater results on this car than it would on a less modified one. The pink car has a stock exhaust except for a Gundo hack on the mufflers and an ipd plenum.

In both cases, throttle response is better, there is a little gain in top end at high RPMs where flow is increased, and the additional intake noise adds to the overall sensations, without any real downsides. On both filters I'm running a K&N Hydrophobic pre-filter to prevent the oiled filters from becoming water saturated when driving in the rain, compromising the filtering effectiveness. I do a UOA on all oil change samples I take and Silicon levels are not any higher than they were with the OEM airboxes so there is not additional dirt getting past these wire/gauze/oiled filters.

I like the design of the Evoms intake the best once full width decklid vents exist (TT decklid) or the second cutout is opened up in the non-turbo decklid as both intake locations are located at the fresh air openings and the rest of the airbox is closed to not allow warmer ambient engine air to be sucked in. The best aftermarket airbox is the Champion F77 CF one, but it's crazy expensive. I test fit one for my silver car but it wouldn't fit with the supercharger pulley setup or wing rams.

Hope that info is helpful.




Prefilter not shown in this photo

 

Yes, Petza914, this is, indeed, helpful; thank you. I've installed the Fabspeed SS headers and while it improved the top end, the bottom end/3000 rpm hump was made worse and I'm hoping that by improving air intake, it'll smooth out the torque curve.

I didn't realize the EVOM's draw cold air from both sides of the deck; this must, indeed, be an advantage? I assume this setup bests the stock airbox mod?

Lastly, have you retuned to compensate for your mods?

 

Yes, just blocking the Heimholz resonator port isn't much of an intake mod, though it does seem to assist with eliminating a slight dead-spot in the RPM range.

The newer style Fabpseed Y-Pipe design also draws from both sides and has a taller heat shield than the early J-Pipe design as well, but it's still a more open design.

I didn't do any tuning to compensate for the small changes on my wife's pink car. The silver car was tuned by RUF as part of the supercharger setup and that was an extensive tune that including replacing the standard DME with one from a TT in order to be able to have access to all the parameters that needed adjusting for forced induction.

 

 

Thank you , and yes, the stock decklid actually has a punch out or template on the decklid where you can make a hole on the right side that looks just like the hole on the left side and purchase the trim pieces to make it look nice.

There was a used Evoms decklid for sale in the marketplace either here or on Rennlist recently too. Might still be available if you search for it.