Another Newbie Exhaust Question

[bobbyboy]

I've gone through loads of exhaust topics, and it's fried my brain a bit!

My GT4 has standard downpipes, cats and Y piece. From there on it has a Main Factory Fujitsubo Giken system.

It's a very quiet system, no louder than standard.

I don't want a noisy system, just a little more life to it.

As I understand it, fitting cats, such as Torqens own brand HFC's, can increase volume but not excessively so. Is this correct?

Other issues that seem to crop up in posts that I've read are some MOT failures and fault lights on the dash after fitting HFC's. I don't want to have to deal with stuff like this, so are these normal'ish type issues?

Another thing I'd maybe look to change is the Y piece. I guess swapping that for an aftermarket section also increases its sound , but I've not really seen any feedback on that. Anyone have experience of this too?

[Jack94]

If you're happy with the sound you've got and just want a bit more volume then HFCs are a great shout, they'll free up a few extra bhp too. 

 

Sports cats of any brand seem to be a bit hit and miss with emissions, but if you get them hot before test and have a fairly "friendly" tester you should be fine. 

 

The only fault they'll throw up is the CEL due to more pollutants getting through the system. Again it can be hit and miss whether this happens but you're better off getting the car remapped and the rear O2 sensors turned off. It makes absolutely no difference to how the car runs and eliminates this problem. 

 

Changing to a regular aftermarket Y pipe probably won't make any difference in terms of sound/volume but might help the system flow a little better. 

 

[bobbyboy]

Cheers for the confirmation.

Was hoping the fault code thing would be a bit of a myth or rarity to be honest, so will have a think about it. 

[msitpro]

Changing to either de-cat or 200 cell cats will be the biggest increase in volume you can make, but on a standard-ish sounding current system should be good.

 

Personally what I'd like to see on the market would be 200 cell cats with dual honeycomb cat 'bricks' per side, as per standard, but of course more free-flowing. (standard cats have a honeycomb 'brick' before and after their bend)

 

I have single 200 cell cat per side and with extensions it comes on occasionally. I may add some steel wool inside the extensions to try eradicate it.

[Andy_Muxlow]

Tarmacsportz also do some HFC which iirc have been tested and pass mot regs. 

I have HFC on my 370z she passed her mot the other weekend. 

[bobbyboy]

Thanks for the feedback. I may take the plunge in the New Year and try a pair of HFC cats, possibly with a new Y piece too.

If the EML lights up, I'll then have to look into the remap option.

[Andy_Muxlow]

Mine has never had eml come on. Some HFC come with extended sensor connectors. 

[bobbyboy]

One of the reasons I started this thread was to see how often the eml light came on with HFC's.

Definitely seems to be very random.

And what is an extended sensor connector? 

[msitpro]

the biggest factor in my experience in how frequent or how likely the EML will come on is the length of tube the sensors are attached to.

 

You can see here that the Torqen decats have a tube sprouting off the middle of the tube that the sensors screw into. It is also against the flow of the gases so it has to go 'uphill' to get to the sensors.

 

When I had my full exhaust built, contrary to my request, the exhaust company did not add a length of tube to take the O2 sensors out of the flow of exhaust gas post-HFC. The EML came on ALLLLL the time, it would return within minutes of driving after clearing it with a OBDII tool.

 

I added (at their cost) something like these: https://www.ebay.co.uk/itm/O2-Oxygen-Spacer-Sensor-Angled-Extension-90-Degree-m18x-1-5mm-Universal-Exhaust/383286866100?epid=21020085015&hash=item593dad70b4:g:-qkAAOSwYjVadBLo

 

EML still occasionally comes on, so I might stuff some stainless wool down them.