It definitely wakes things up bit..

 

200-cell cats are very definitely a lot louder! The difference between stock cats and 200-cell is about the same as turning a PSE on/off

If you're going to use AWE cats however, I'd recommend you also use their headers, not X-51. Why? What rarely (if ever) gets mentioned on here is that the outlet pipe of AWE's headers and the corresponding inlet pipe of their cats (see where I've marked them on the attached pics) are a bigger diameter than stock / X-51 / just about all other aftermarket headers and cats. To avoid a power sapping step in the pipe, either use AWE's headers with their cats (a great combination that gives excellent top end oomph) or use FVD (or Fabspeed or whatever) cats that have the same inlet pipe diameter as the X-51 headers.

 

Ian I don't think AWE increased the tubing size of the cat piping. They looked identical to me when I installed the parts and I thought it matched up perfectly. For the sake of debate though let's say that it is true there is a slight difference in size. You would be going from smaller to larger..I actually would rather have it that way for the cat pipe to be larger than the collector flange of the header. If it was the other way around it would be a different story. Even AWE claims only 7rwhp with the header with the cats and mufflers already installed.


Dave

 

Hi Dave

The pipe size is just slightly bigger - we measured it in my local shop when I first put the AWE cats (with stock headers) on my car. You can see the pipe size for the whole cat section is bigger than stock as they have to step it down where the sleeves connect to the muffler inlets. The stock cat sections have no step-down.

I agree the effects are likely to be marginal but the full AWE header/cat combo does work well. Using AWE's headers with stock (or other aftermarket) cats wouldn't be good however....

 

Has anyone independently dyno tested a stock 997 (or stock with aftermarket muffers only) and then afterwards with the header / cat upgrade to see the actual improvement? I'm always interested in finding the best performing combo, and always looking to see if there is room for improvement over what I have now.

 

Ian I agree with you absolutely..not getting the AWE headers were more of a "money" issue for me. I like to mod the car and get the best bang for the buck. I bought the mufflers used from Raffi, the X51 headers for $550 and the only part that was expensive was the AWE cats. My total exhaust was had for $2400 US. I did the wrenching myself

 

AWE did this..but they are not an independent dyno. However, I always felt AWE was truthful in their finding. The fact that their dyno only showed 7rwhp for the headers bought a lot of credibility for me. In fact when I talked to Todd at AWE a few years back he even confessed it was the cats that had the true potential to unlocking power out of these cars. Header really just fatten up the midrange and a little more topend.

 

If the true potential to unlocking the power is in swapping the stock cats with less restrictive cats , why don't you go for big 100 cell cats and forget about these 200 cells cats ?
I believe the reason that the X51 headers work so well is that they have 48mm primary tubes. Most all aftermarket headers have only 44mm primary tubes.

 

Cat swapping provides the biggest benefit? I'd like to see numbers to support that- Sounds too good to be true, but if the numbers support it I'm game- Although I doubt I have much HP/TQ gains left to realize...

 

You can get more HP with an ECU Flash. Looking at your signature, which lists your mods, I see that's not on your list.

ECU, Cats, LWFW (improves hp to the wheels, doesn't change crank hp) would all add something. How much is rather hard to say. You can also get more zip by lightening your load- the TechArt's are beautiful, but heavy. A set of Fiske or HRE will reduce unsprung weight. Again, how much of a difference that'll make, or if you'll feel it, I can't say.

The LWFW, Cats, and ECU you will feel.
CATTMAN

 

Yeah I know- been slacking on getting the ECU flash. I want the flash to also remap the egas for more sensitivity input off idle. I think REVO can do that for me I just have to call / talk with them. I would be happier with a more sensitive input than more HP, I'm wondering how much more HP I can really gain? Already at +26 HP/TQ over stock.

 

There appears to have been issues with Check Engine Lights when using 100-cell cats and the BHP gains over using 200-cell are reported as marginal at best. Europipe seems to have made them work effectively however, but their approach is slightly different to most other manufacturers

 

Yes the Europipe 100 cell cats are very big and that's why they will never trow a cell,some manufacturors use cheap small 100 cell cats and these will trow a cell after a while...

 

NorthVan997C2S,

Glad to hear the O2 extensions worked for you!! That was certainly a cheap fix. Hope your spring and summer track season will be a blast!!

Thanks,
Rhonda

 

This is primarily because the catalysers are the most restrictive part of the system. The 400/600-cell cats required to pass emissions don't flow too well, but manufacturers are legally constrained to fit them. 200-cell probably wouldn't pass cold-start emissions tests and are even marginal in day to day use. But they flow very much better; hence the potential for noticeable increases.

My 2005 997S is currently stock except for a full AWE system. I've tried various combinations of exhaust on this car and the AWE is the best I've found. There is a very noticeable increase in torque between 3500 and 5200 rpm (then the engine goes flat like all 997S's do at 5500rpm) and a much stronger charge to the redline from 6000rpms upwards. The differences aren't subtle. At low rpms it does sound rather flat but pulls like stock. From 3200rpm it starts to sound good and from 4000rpm on sounds sensational. The higher the octane of the fuel you use, the better the sound and the performance - both VERY noticeable.

Previous combos I tried were 1) Stock with Tubi mufflers - fantastic sound, absolutely zero power increase. 2) Stock headers / mufflers with AWE cat sections - noticeably more torque through the mid range but sounded too raspy. 3) Stock headers, AWE cat sections, AWE mufflers - better than 2) but sounded dreadfully 'boomy' at low rpms. Adding AWEs headers gave a noticeable performance bump above 5500 rpm and sorted out the sound quality - the even pulses generated by the equal length headers make the exhaust sound a lot more crisp.