A couple of odd exhaust questions

[ubersonic]

Hi all,

As per title I have a couple of odd ISF exhaust questions I've been searching for the answers too to no avail

Firstly, it's been well attested to that the ISF can still pass MOT emissions testing without the secondary cats as long as the exhaust is warmed up, my question is though can it pass with only the secondary cats if warmed up.  I.E running aftermarket headers (with tune to clear the CEL) but with either the factory midpipe or an aftermarket midpipe with sports cats?

Second question, is there any noticeable performance difference between the exhaust options out there? Or is it just a case of everything is better than stock, maybe a 1-2hp diff, just pick what you like the sound/look of?

Thank you,

[hockeyedwards]

Prepare for spiel.... 😛

Yes IS F can pass MOT test without secondary cats on the emissions side. Here lies the problem, officially the car SHOULD NOT pass an MOT without its secondary cats. The guidance was updated some years back that if 'factory emissions equipment' had been modified in any way, it was deemed a failure, regardless of emission result.

So your questions surrounding the primary cats, would yield the same answer 'technically' speaking, should be a failure. Whether an MOT tester however is up to scratch on whether your car should have primary/ secondary cats, is your grey area and where most would just rely on the emissions test result and call it a day. The only other point would be the secondary cats are much more obvious at a quick glance under the car, so would primary cats be less likely to be spotted as 'missing' - who knows?!

I don't want to open a can of worms regarding exhaust option, as everyone and their dog has an opinion. Some would tune with OEM equipment until that is the limit, then if you want more you start modifying. Some will modify equipment and then tune to 'maximise' results from the offset. Less cats = more noise and less restriction and I'll cut my comments there 🤣

[mr2lad]

Armytrix system claim an extra 18.8 bhp and 22.3 nm torque and 2.3kg less weight, 

[BillNick]

Whereas Invidia do not publish any gains.

[EP80]

i think the OP is precisely asking if anybody out there has removed primary cats and run the OEM secondary cats only, then installing a single aftermarket sports cat downstream of OEM secondaries. If I understand that correctly, I have never seen this on any forums, generally its the US guys and they just pull them all off. 

I would think this would all come down to your sports cat being up to the job of making up for removing the manifold/primary cats either side. If you feel a bit splattercash though, I know of one aftermarket sports manifold with inbuilt cats. 

https://www.novel-japan.jp/en/exhaust/exhaust-system-for-is-f/

Assuming these will pass the Shaken in Japan, note how tiny the cats are......

They come up second hand from time to time on Yahoo Japan.

[Jgtcracer]

10 hours ago, EP80 said:

i think the OP is precisely asking if anybody out there has removed primary cats and run the OEM secondary cats only, then installing a single aftermarket sports cat downstream of OEM secondaries. If I understand that correctly, I have never seen this on any forums, generally its the US guys and they just pull them all off. 

I would think this would all come down to your sports cat being up to the job of making up for removing the manifold/primary cats either side. If you feel a bit splattercash though, I know of one aftermarket sports manifold with inbuilt cats. 

https://www.novel-japan.jp/en/exhaust/exhaust-system-for-is-f/

Assuming these will pass the Shaken in Japan, note how tiny the cats are......

They come up second hand from time to time on Yahoo Japan.

Novel manifolds……..got to be my dream mod for the RCF.  
 

If only they weren’t so expensive

[EP80]

3 hours ago, Jgtcracer said:

Novel manifolds……..got to be my dream mod for the RCF.  
 

If only they weren’t so expensive

Lovely looking kit alright, I like how the ISF sounds stock personally but I wouldn't mind the extra power.

I forgot Icode when I said one option, their's is also titanium and has inbuilt cats which are a little larger than Novel. Saw a couple ISF's covered in Novel and Icode parts go for cheap which I seriously considered but I wanted a stock one.