Cat bypass with resonator
 

I was seraching ebay for the cicuit werks bypass pipes, and found they also offer a bypass pipe with resonators. Looks like a cat but is a fesonator, was curious what that supposed to do? Does it change the sound, or is it more affective?

In Europe these sections are the cats. I guess it's easy to make from the same tooling but simply not put the cat core inside. Stick some snazzy marketing words in the advert and hey presto a new product line.

Resonator changes the frequency of the sound - Less drone sound. Mufflers makes the car quiet.

I just have resonators on my autox Boxster after the precats and no mufflers at all. My complete exhaust weights just 17lbs including the test pipe section and resonators. It is loud, but not super loud like an uncorked car. I could not daily drive the Boxster due to the heavy drone. Driving the car to the track or autox is bearable since I only do it once or twice a month.

Before my current setup, I had the eBay bypass pipes with no resonators and the eBay muffler. No drone what so ever. I was quite surprised. The only bad thing about the Chinese ebay exhaust stuff is the fit. I had to fab mine a little and make a custom mount to make it fit perfectly. I might be a little picky too....

I don’t think these cut down on sound as much as they ‘look’ like cats so you can pass the visual emissions check in states that inspect the exhaust.

Thanks for the replies. Theses are cat bypass with resonator, so I think they are intended to be used with the muffer in place. Just have not seen these before in this way.

If you are running a muffler that is known to drone, you might consider the test pipes with resonators. I ran the the cheap eBay test pipes (no resonators) and eBay muffler, and I had no droning what do ever. If you running a stock muf, skip the resonators. If you are running something like a GLH muffler that is known to drone, I would consider the test pipes with the resonators.

I live in California and just bought the Top Speed "test" pipes. Called the well respected exhaust shop in the area and he said he cant install them, its illegal to remove even the secondary cats.

There is no way I can burn the existing rusted bolts off without professional help (in more ways than one, ha!)

Any tricks you all could share?

Yeah illegal in cali for sure. Probably wont work but you could try soaking them with wd40 or some type of penetration lube let it sit for a couple of hours, see if that would work.

Look for a not so respectable shop, to cut the bolts for you.

Tell them you need you are installing because you will be tracking the car, so you will be switching in and out. I am sure thats belevable. :D

Myself have not had them installed, so good luck.

Seems I recall the bolts at the triangular plate are splined at the base and pressed in, so inspect yours and if this applies, turn the nut not the bolt.
Pretty sure I replaced with normal non-splined bolts. Was a while back.

Try a welding shop. They can cut off the old bolts in about 2 mins and they usually could care less about what you're doing to your car or why.

Everything after that is a fairly easy DIY.

Thanks all, good advice!

You also should be able to cut them off with a Dremel...

You could just pay them to remove and replace the bolts with fresh ones. Then carry on DIY replacement of the secondary cats.

That is a damn good idea, simple and to the point. Lol

Success, used Gilles Dremel idea for the bottom two bolts and used brute force to break the top bolt with a 13mm socket and a breaker bar. After that, the job was easy. After reading several post on the subject, I got the 2" Easy Clamps and they worked great.

Thanks again to all for the help!

I cut my rusty bolts off with a metal blade in a sawsall.

I have a set of these Circuit Werks secondary resonator pipes on order and incoming to me, arriving probably early next week.

I can take some pictures and post here then, if you wish.

Thanks - DM

Thanks I saw pictures, just curious of what the resonator id for and does to the tone.

I just installed the non-resonator Circuit Werks pipes, and the passenger side stock pipe was a nightmare to get out. I too ended up cutting the clamps to get it apart. However the 2" Easy Clamp was too large and didn't work. How did you get yours to fit? I ended up getting the stock clamp from Pelican.

The driver's side was a breeze, only taking me about half an hour to replace. The clamps and pipes weren't rusted like the passenger side.

It does sound better, but it's pretty subtle. Hardly louder than stock, but the tone is better. I'm not sure why you would need the resonated secondary pipe.

Picture looking up the exhaust end of the resonator. As you can see, it is a straight thru design with no obstructions.

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Looks nice, only thing I can think is they suppose to look like a cat installed in case of a visual inspection.

Is there a reason you stuck with the standard manifolds? You can get a freer revving engine and a shade more power with some cheap but better flowing ones.

That’s a fair question.

I considered the use of aftermarket headers, but I selected the non-cat OEM manifolds out of my interest in keeping the system as laterally compact as possible, avoiding the “splaying out” of the header tubes beyond the valve covers.

The OEM non-cat manifolds might not flow as well as would a set of proper headers, noted. But for a street car I figure that they will serve me well enough, and they are most certainly a big forward improvement over the OEM cat versions which are a flow horrorshow.

Plus, you then know right from the start that the OEM parts will fit properly, without the need to monkey around with the often times imperfect configurations and alignment problems that one can many times see with aftermarket exhaust components. ( ... but having said that, the Circuit Werks resonator pipes, not shown in these new pictures below, turned out to be a perfect fit!)

Thanks - DM

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http://986forum.com/forums/uploads02...1525092977.jpg

If it helps my car is only road use and I've fitted the cheapy aftermarket manifolds to both my Boxsters with no issues and a slight improvement both times. I saw your pics and saw that you had already removed them. That is the one part that nornally deters people. The lbojr cost to remove them is often more than the manifolds themself.

I assume that the comment above refers to the often encountered difficulty in getting the 6 steel manifold bolts out of the aluminum cylinder heads without snapping them off?

If so, having the bolts out thus offers the perfect occasion to replace the lot of them with M8 x 42 mm long studs and matching SS flanged nuts

Years from now, whoever might have any need to remove these manifolds will thank you for your efforts to "stud" them today!

Cheers - DM


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Do you still like the setup? I'm thinking about the circuit werks pipes you installed and wondered how they worked for you?

Just so you know, those"resonators" are just glass packs. I've not heard them in person but if you're keeping your stock muffler I'd be shocked if they did anything at all in terms of sound.

Sent from my SM-G970U1 using Tapatalk

You are right about the splined bolts. They can be cut off with a Sawzall or hacksaw if you have lots of time. When I do muffler work I only take the saw under the car with me... I replaced with stainless steel bolts and nuts.

I'll assume that this is directed to me, since I posted the pictures?

If so, then yes, I've been very pleased with the stock non-cat manifolds and the Circuit Werks "resonators". Aside from the fact that all of the white insulation which was a part of the "resonator" portion of the Circuit Werks pipes was blown out after about the first 10 minutes of use, ending up in the muffler!

Fortunately I was able to fish out most of this insulation after removing the muffler - what I could not remove eventually blew out of the muffler's tips.

One difference between the older pictures that I posted and the car as it sits today is that I ceramic coated the manifolds, as you can see below:

http://986forum.com/forums/uploads02...1649633634.jpg

The use of the non-cat OEM manifolds resulted in a notable performance boost as compared to the cat manifolds as shown in the second picture in Post no. 23, so I am well pleased.

DM

I know most of the users here are in the US but what you post above as the non cat manifolds are just the standard ones in Europe. For 986 we have the cats in what you guys cal the midpipes. With the 'sports' manifolds there is a noticeable freeing up at the top of the rev range and the engine much more willing to rev more with more urgency.

Thank you for the response. How you had issues with the car passing inspection? You do not have any cats with your setup? Also any warning lights?

No inspections required in my county, no warning lights, no worries whatsoever!

Hmm , So for those of us who have to do emissions testing Via the plug under the dash,.and the 2002 manifolds have the 02 sensor B4 the cat, could you backdate to 1999 manifolds or header's and still pass emissions ,if you welded a bung into the Exhaust header,..?? for the 02 sensor..? Thanks frank

Take a look at my second picture in Post no. 20 of this thread.

You can see that these manifolds do not contain an O2 bung, but there is one at the front of the Circuit Werks resonators.

You need to fab up a pair of cable extensions for the FRONT O2 sensor so that it can reach the shown CW bung. A 'Search' of this forum will bring forth discussions about how to make these extensions.

Finally, you need to do a ROW tune which ignores the presence of the REAR O2 sensor since this system does not require the use of these second sensors. Thus, no dashboard warning lights.

DM

Ah ok..great I have the mid pipes installed and I do have those bung's..so just extend the harness and find some header's ! would the softtronics tune be the same as the ROW tune.? Thanks again,.. Frank

No idea, I'm not familiar with that.

Likely others here who are can chime in.

Thanks Dave...what did you do for your ROW tune.??

https://www.ecudoctors.com/

Cool...Thank You sir..!!

For what it's worth the ROW tube does monitor the rear lambdas. I know because when you add sports cats you often get the cat efficiency CEL code. You can right angle space the rear lambda or have it coded out.