Catted Headers - Cat relocation experience?

[Chsi]

Hello everyone, recently pretty much every welding point of my exhaust is starting to rust apart, and the middle muffler already fell of completely (although ridiculously loud it was fun to see what sound that little d15z8 could eventually produce, even with its catted headers). Now i'm looking into aftermarket exhaust systems, but - at least here in germany - pretty much every system thats not just the rear muffler bolt-on is optimized for the models that have the cat under the car, not in the headers. Now I'm considering moving my cat underneath the car instead and switch over to an exhaust setup of the sportier models.

Besides still having to clear up the legalities of that in germany, what are the technical problems i might run into? Could i reuse the little cat piece, is it universal or would i need a different one? Could my Ecu even handle having to relocate the 02 sensor, and will it still be able to adjust the air/fuel ratio correctly? Will it bork the way the car runs on cold starts or in closed loop? I dont have any experiences making serious modifications to cars yet, and not alot of contacts in my vicinity. If anyone has any experiences or insights please let me know, it would be greatly appreciated!

 

Chsi

[dr_broon]

If the reason for moving the cat is to fit an aftermarket exhaust, it might be best looking into an adjustable cat replacement (test) pipe - something like this

https://share.google/n1r8yBj8vDQZ475Xs

Then you'd be able to keep your current setup, but use this to make up for the difference in length

You'd have to check that the fittings are right for your exhaust. Other than that, a custom exhaust place would be able to either make a section to fill the gap or even a full system back from your headers

[Chsi]

2 hours ago, dr_broon said:

If the reason for moving the cat is to fit an aftermarket exhaust, it might be best looking into an adjustable cat replacement (test) pipe - something like this

https://share.google/n1r8yBj8vDQZ475Xs

Then you'd be able to keep your current setup, but use this to make up for the difference in length

You'd have to check that the fittings are right for your exhaust. Other than that, a custom exhaust place would be able to either make a section to fill the gap or even a full system back from your headers

Alright, thanks, those are ideas I havent even fully considered. I'll have to talk to the german TÜV legalities people, because most of the time fitting anything that doesnt have extensive proper german papers is incredibly hard (and/or expensive). Might be different with just an extension pipe though! And if i were to get a custom exhaust from a workshop it might require additional emissions testing, which could be a bit of a hassle as well, and i might be able to doge that by using stock parts of other models. All of that i'll have to clear up, but tha sk for the Idea!

Do you think if I got my hands on a castless D-series header and downpipe without cat, that the cat itself would be universal? Because at least from the looks of it the cat-piece itself is straight, and only the immediate short headers and pipes afterwards seem bent. 

[Fenny]

Oh yeah these exhaust LOVE rust, my mb2's mid pipe fell to the ground while driving and it sounded like a kanjo racer, my ears still hate me. The one on the Rover coupe, which is the same basically apart from maybe different hanger location, had insane blowing so i changed that too, still blows pre cat...

I didn't know they made models with an upstream cat like yours, I guess the VTEC E engines were the d series efficiency flagship so they had to do that. Good luck with it

[Chsi]

1 hour ago, Fenny said:

Oh yeah these exhaust LOVE rust, my mb2's mid pipe fell to the ground while driving and it sounded like a kanjo racer, my ears still hate me. The one on the Rover coupe, which is the same basically apart from maybe different hanger location, had insane blowing so i changed that too, still blows pre cat...

I didn't know they made models with an upstream cat like yours, I guess the VTEC E engines were the d series efficiency flagship so they had to do that. Good luck with it

Yeah, it's the second time that happened too... last time it was the end muffler. Cant lie though, even though it was ridiculously loud i cant say i didnt enjoy it... had to record a few videos of it, for memories sake...

 

 

 

Now its crudely welded together and still blowing underneath the middle console (the handbrake handle becomes slightly toasty on long drives), but at least the police hopefully wont stop me for it. Its just temporary until i find a way to resolve my upgraded exhaust issue...

 

Yeah, it took me a while as well until i realised my cat situation, but i'm glad i did before planning ahead too far. I'd have loved to try and do some improvements performance-wise, but with the ECU being non-chippable due to the economy stuff being hard-coded in it, there isnt really alot to do. But at least they do the efficiency thing pretty good, without hypermiling but still driving a little conservative i managed to hit a max of 42.8 mpg. 

 

[Fenny]

14 minutes ago, Chsi said:

Yeah, it's the second time that happened too... last time it was the end muffler. Cant lie though, even though it was ridiculously loud i cant say i didnt enjoy it... had to record a few videos of it, for memories sake...

 

 

 

 

Now its crudely welded together and still blowing underneath the middle console (the handbrake handle becomes slightly toasty on long drives), but at least the police hopefully wont stop me for it. Its just temporary until i find a way to resolve my upgraded exhaust issue...

 

Yeah, it took me a while as well until i realised my cat situation, but i'm glad i did before planning ahead too far. I'd have loved to try and do some improvements performance-wise, but with the ECU being non-chippable due to the economy stuff being hard-coded in it, there isnt really alot to do. But at least they do the efficiency thing pretty good, without hypermiling but still driving a little conservative i managed to hit a max of 42.8 mpg. 

 

Didn't know I could add videos ahaha, here's what mine sounded like (cut off right after the cat)

[Chsi]

46 minutes ago, Fenny said:

Didn't know I could add videos ahaha, here's what mine sounded like (cut off right after the cat)

That sure sounds wild, truly supporting all the straightpipe civic stereotypes haha