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Andy Gside

High Flow Cat question!!

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So next year i will be going for the TD NA package ( UEL DECAT w/ Overpipe & Tune)

Is it worth swapping the frontpipe cat out at the same time as getting this done with either a BERK HFC or COBRA HFC frontpipe....... 

Has anyone done this yet? If so whats it been like for MOT's i know some people with the OEM front pipe & the TD KIT struggle with MOT's wondering if with a HFC to replace the front pipe cat would make it worse / same / better ?

Also reguarding BERK & COBRA frontpipes, which is better as BERK = £250 and COBRA = £465 seems weird if they are both the same why theres £200 diffrence! 

Any comments are appreciated!! Many thanks, Andy!

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I use the OEM front pipe with my catless Rogue manifold and Harrop supercharger. I don't have any trouble with the MoT but I, too, have wondered about a Cobra or Berk hi-flow cat.

Sent from my Oppo X3 using Tapatalk

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41 minutes ago, Varelco said:

You will struggle to get through an MOT with the Berk HFC. Can't comment on the Cobra.

Is that will the decat manifold or stock manifold ?

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Back in 2017 I had my car modified at Abbey, I had an ACE CS400 manifold installed, alongside a Cobra HFC. Performance is great, torque dip eliminated. However I was never that happy with the sound. It was okay-ish with the rest of the exhaust stock but I kept looking for options to make it sound better.

Last year during lockdown I purchased a Q300 catback, which is meant to be one of the quieter systems, but I still found it a bit loud and droney at about 2.5K RPM. I got rid after three months. I then went to just a Remus backbox, still with the ACE and the Cobra HFC. Much more bearable than the Q300. But was still getting a little bit of annoying rasp sometimes at low revs.

So last month, I decided to see if removing the HFC made a difference. I swapped it out and went back to the OEM front pipe, which has a resonator. That has got rid of the rasp, and I haven't really noticed any loss of performance or efficiency. That said, I'm not a track driver, and probably don't drive as hard as most, so I might have lost a tad of top end power but not noticed. But I am at least happy with the sound now. So the exhaust system now goes ACE manifold > OEM front pipe > OEM midpipe > Remus backbox.

All that is a long way of saying that in my experience, I've found that the system sounds better with the OEM front pipe, and I've haven't really noticed if going back to it reduced power. If you're getting a decat manifold, just be aware that a high flow cat might make the system noisy if you have anything other than an OEM catback. Whether that bothers you or not is up to you. 

As for MOT compliance....I think the general consensus is that with a decatted manifold, and the second cat in the front pipe replaced with a HFC, you might be at risk of not passing emissions - at the very least you will have to make sure it's tested with the exhaust piping hot to make sure it passes. Mine has never failed the MOT since it's been running with just the Cobra HFC as the only cat...however that's because I've made sure to always take it back to Abbey for the MOT, who will make sure to test it when it's thoroughly warmed up. 

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Thanks, that's useful to know.  I really don't want more noise and if the power is hard to tell a difference with then there's no point.

I'm using Rogue manifold > OEM front pipe > TD super resonator > TD exhaust (Harrop supercharger).

The Rogue is very similar to the Ace and it has the twin overpipe for true 4-2-1 flow.

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4 minutes ago, Conscript said:

Back in 2017 I had my car modified at Abbey, I had an ACE CS400 manifold installed, alongside a Cobra HFC. Performance is great, torque dip eliminated. However I was never that happy with the sound. It was okay-ish with the rest of the exhaust stock but I kept looking for options to make it sound better.

Last year during lockdown I purchased a Q300 catback, which is meant to be one of the quieter systems, but I still found it a bit loud and droney at about 2.5K RPM. I got rid after three months. I then went to just a Remus backbox, still with the ACE and the Cobra HFC. Much more bearable than the Q300. But was still getting a little bit of annoying rasp sometimes at low revs.

So last month, I decided to see if removing the HFC made a difference. I swapped it out and went back to the OEM front pipe, which has a resonator. That has got rid of the rasp, and I haven't really noticed any loss of performance or efficiency. That said, I'm not a track driver, and probably don't drive as hard as most, so I might have lost a tad of top end power but not noticed. But I am at least happy with the sound now. So the exhaust system now goes ACE manifold > OEM front pipe > OEM midpipe > Remus backbox.

All that is a long way of saying that in my experience, I've found that the system sounds better with the OEM front pipe, and I've haven't really noticed if going back to it reduced power. If you're getting a decat manifold, just be aware that a high flow cat might make the system noisy if you have anything other than an OEM catback. Whether that bothers you or not is up to you. 

As for MOT compliance....I think the general consensus is that with a decatted manifold, and the second cat in the front pipe replaced with a HFC, you might be at risk of not passing emissions - at the very least you will have to make sure it's tested with the exhaust piping hot to make sure it passes. Mine has never failed the MOT since it's been running with just the Cobra HFC as the only cat...however that's because I've made sure to always take it back to Abbey for the MOT, who will make sure to test it when it's thoroughly warmed up. 

Thankyou for taking the time for the detailed reply!! Really appraciated!! 

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11 hours ago, Andy Gside said:

Is that will the decat manifold or stock manifold ?

That would be with the a decat manifold. It would be mega loud too.

Definitely need resonators in your front pipe as Conscript has mentioned. In my experience with exhaust setups:

Stock Manifold - Stock Front Pipe - Perrin 2.5" Resonated Catback - OEM+ , nice sporty sound but fades out and quietens down above 5k rpm

Stock Manifold - Berk HFC front pipe - Perrin 2.5" Resonated Catback - BOOM fest, exhaust was loud and became binary, acceptable at steady cruise, but very loud on any application of throttle or overrun

Stock Manifold - Fujitsubo Decatted dual resonated front pipe - Perrin 2.5" Resonated Catback - Bit louder than just the catback, good modulation of sound relative to how much you bury your foot all the way to redline, odd burble off throttle.

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22 minutes ago, Varelco said:

Stock Manifold - Berk HFC front pipe - Perrin 2.5" Resonated Catback - BOOM fest, exhaust was loud and became binary, acceptable at steady cruise, but very loud on any application of throttle or overrun

Is the Berk HFC so-named because that's exactly what everyone thinks of you every time you pull out of a junction? :D

I gather they can be verging on antisocial. 

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I’ve heard that Rogue do make a really good sports cat, you have to ask them nicely though. 
TBH if you’re staying NA the best gain for price is the TD NA package. If you don’t want a noisy car then leave the middle cat and cat back exhaust as OEM. Whilst can gain some more power changing these bits you will definitely get a lot more noise and cabin drone doing so. 

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