Cat bypass with resonator

[Cunningr]

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

[edc]

Originally Posted by Dave80GTSi

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

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.

[Dave80GTSi]

Originally Posted by edc

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

[edc]

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.

[Dave80GTSi]

Originally Posted by edc

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 normally deters people. The labor cost to remove them is often more than the manifolds themselves.

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

[gsy4771]

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

[ike84]

Originally Posted by gsy4771

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

[elgyqc]

Originally Posted by BrokenLinkage

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.

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.

[Dave80GTSi]

Originally Posted by gsy4771

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

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:



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

[edc]

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.

[gsy4771]

Originally Posted by Dave80GTSi

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:



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

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?

[Dave80GTSi]

Originally Posted by gsy4771

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!

[flmont]

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

[Dave80GTSi]

Originally Posted by flmont

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

[flmont]

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

[Dave80GTSi]

Originally Posted by flmont

would the softtronics tune be the same as the ROW tune.

No idea, I'm not familiar with that.

Likely others here who are can chime in.

[flmont]

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

[Dave80GTSi]

Originally Posted by flmont

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

https://www.ecudoctors.com/

[flmont]

Cool...Thank You sir..!!

[edc]

Originally Posted by Dave80GTSi

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

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.