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      07-25-2013, 04:52 AM   #1
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High Flow Cats. The Deal?

What are the facts with these things? I hear lots of differing opinions which state that...

- They don't flow much more than stock cats
- Performance gains vs stock are minimal
- Catless nets much more performance gains than high flow cats
- They will not pass exhaust probe (not OBD) emissions inspections
- After 1yr or 2yrs they start to deteriorate and will no longer control emissions
- They do/do not control rasp
- They do/do not control noise

Basically as I live in a country that demands a yearly vehicle inspection which involves an exhaust probe emissions test I need to make sure that whatever cats I have at the time will do the job and for mimimal hassle I was considering installing high flow catted midpipes (DPs are catless) so that I didn't have to swap exhausts each year (I definitely DO NOT want to swap DP's in/out each year). Of course I want max performance gains (hence the DP's are catless) but I am trying to figure out if it is worth paying a lot of money for high flow catted mids or if I should just leave the N54 catted mid pipes in place OR, just make the effort to lay on the floor once a year to swap out/in catless mids & N54 mids. The best performance gains will be had fully catless, I understand that but how big is the difference between high flow cat and catless?

At present I have non-resonated N55 mids and BMW PE which sounded amazing with the stock DP's but it is just too much fully catless. I haven't reinstalled the N55 resonator so I don't know if that'll do anything at all but from the video's I have heard of catless DP's, N55 mids and PE or aftermarket axle-back it still sould like shht with ultra-loud cold-start and mega rasp. I am hoping that N54 mids, catless resonated mids or high flow catted mids will cure it and bring me down to where I was pre-DPs, if not a touch louder.

Does anyone have a similar yearly inspection who has catless downpipes and N54 mids? Does your car pass?
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      07-25-2013, 07:11 AM   #2
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i pass emissions fine with only 100 cell race cats in the midpipe
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      07-25-2013, 07:27 AM   #3
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      07-25-2013, 09:24 AM   #4
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Quote:
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Basically as I live in a country that demands a yearly vehicle inspection
I would consider moving
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      07-25-2013, 09:54 AM   #5
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I would consider moving
Will you accept a British migrant in Florida? Tell your department of immigration will you, I'd be there in a heartbeat !
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      07-25-2013, 10:57 AM   #6
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i pass emissions fine with only 100 cell race cats in the midpipe
I heard those HJS race cats are the real deal. I know at one time AR offered them in their catted DP's, but the cost was pretty high. Is the sniffer test in Sweden similar to the one done in the UK?
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      07-25-2013, 11:02 AM   #7
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Quote:
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Will you accept a British migrant in Florida? Tell your department of immigration will you, I'd be there in a heartbeat !
Inspection/Emissions are for your protection and that of the environment as well, most states here require some form or another annually. Florida, on the other hand, might be a whole diff story.
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      07-25-2013, 12:22 PM   #8
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Inspection/Emissions are for your protection and that of the environment as well
That's B.S. becasue modern cars (cat or not) produce WAYYYYY less emissions then cars made even 10 years ago.

I remember back a couple decades ago when Florida still had inspections my 2.0L turbo car made 10 times more emissions than my dads 8.0L Viper. And at the time that was stock for stock.
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      07-25-2013, 01:53 PM   #9
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Quote:
Originally Posted by aquajon View Post
That's B.S. becasue modern cars (cat or not) produce WAYYYYY less emissions then cars made even 10 years ago.

I remember back a couple decades ago when Florida still had inspections my 2.0L turbo car made 10 times more emissions than my dads 8.0L Viper. And at the time that was stock for stock.
I wouldn't say it's BS. There are plenty of unburnt hydrocabons and other things even from todays SULEV and PZEV vehicles if you were to remove the catalyst.

I do agree compared to 10 years ago they are a lot better but without a catalyst there is still harm to people and the environment.

I do find, however, most catted downpipes pointless, IMO. Either go catless or stay stock.
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      07-25-2013, 09:21 PM   #10
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Enrita has 100 cell and I have 200 cell race cats....working very well so far! I did go completely catless and the smell was horrible and I could not roll my windows down. With the race cats smell is almost completely gone, after warm up you cannot smell anything. I believe they flow way more than stock. I have looked at both cats and with the race cats you can see plenty of daylight through them and oem you cannot. I couldn't tell you as far passing emission as I don't have emissions to worry about.
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      07-25-2013, 10:45 PM   #11
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      07-26-2013, 02:42 AM   #12
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cells

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Who wants to help me count cells ?

I think you can mange
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      07-26-2013, 06:59 AM   #13
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Quote:
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I heard those HJS race cats are the real deal. I know at one time AR offered them in their catted DP's, but the cost was pretty high. Is the sniffer test in Sweden similar to the one done in the UK?
dont know but they insert a probe and rev it till 2500-3000 rpm for a couple of seconds till the reading is done. i pass REALLY JUST . i have to beat the car hard before so they are really hot.
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      07-26-2013, 07:34 AM   #14
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dont know but they insert a probe and rev it till 2500-3000 rpm for a couple of seconds till the reading is done. i pass REALLY JUST . i have to beat the car hard before so they are really hot.
Yup, it's the same test here and therefore I have decided to take a chance on 200cell High Flow Catted mids. It doesn't appear that the Cats will flow significatly less than Catless pipe, maybe 3hp worth but I consider that worth it to beat laying in the snow/rain covered street to change them. From what I've read a Catless pipe will have 10% more flow area than a 200cell HFC.

Last edited by Cozy; 07-26-2013 at 07:45 AM.
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      07-26-2013, 11:03 AM   #15
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Yup, it's the same test here and therefore I have decided to take a chance on 200cell High Flow Catted mids. It doesn't appear that the Cats will flow significatly less than Catless pipe, maybe 3hp worth but I consider that worth it to beat laying in the snow/rain covered street to change them. From what I've read a Catless pipe will have 10% more flow area than a 200cell HFC.
When is your car due for the test? I'd definitely like to know the out come, I'm heading over to the other side of the pond in Dec and would love to run catless DP's with race cat midpipes.
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      07-26-2013, 12:03 PM   #16
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It's not due until April next year so I have months of fun FBO to before I see what's what but theory is thst it should pass with HFCs. Ive run HFCs on cars before with no issue but it's dependant on the engine really if it passes as if its overly unenvironmental the HFCs won't cut it. People here do run Catless, lots of people but it's totally illegal and an MOT fail. To get around this most people swap in their original Cat for the test but there are quite a few test centres that will overlook the fact your Cats went missing for a cash in hand fee. That again is totally illegal and it's a sort of back alley word of mouth thing to find them as they can be charged legally and stripped of their testers license.

For less headache for me I chose catted mids but when you are here and if your anywhere in my area I'll be happy to show you how to play the system if you want to go that way. The penalties for you if caught by the police would be that you'd get given a warning with 7days to rectify/reinstate the Cat with proof provided to the police of this work. Next up you'd get a fine which can be pretty big and finally they may chose to withdraw your plates which means the car is no longer registerable. Worst case? Car gets crushed or impounded and auctioned off. If you get caught with no Cat during your MOT (the test) then you cannot use your car other than if you are driving to a shop to repair the fault and then back again to the test centre where it must pass.
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      07-26-2013, 01:03 PM   #17
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Perfect.
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      07-26-2013, 02:07 PM   #18
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To the OP. You may also want to take a look at the Vibrant GESI HO series catalytic converters. We helped with some of the initial testing on these cats prior to their release. They are a very efficient and high flowing alternative to going catless and feature a full metal catalyzer that has held up well on turbocharged vehicles. Our beta test set is showing no signs of failing after two years of abuse on a 996 turbo. The 996 turbo is a perfect vehicle to test catalytic converters on as they are placed directly after the turbo and will have significant stress placed on them.

PM Me if you need some more in depth information or photos.

http://vibrantperformance.com/catalo...1022_1063_1326
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      07-27-2013, 04:46 AM   #19
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Hi Mike. Thanks for taking the time to reply and offer help. Before I saw your post I purchased two HJS Cats as they were available locally but in future if I need I'll definitely take a look at Vibrant.

Last edited by Cozy; 07-29-2013 at 03:17 AM. Reason: Damn auto-correct!
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      07-28-2013, 11:55 AM   #20
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No problem. I hope that works out well.
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      07-28-2013, 12:55 PM   #21
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I know I might get flamed for this but here it goes. Other platforms ie; EVO and STI running way more boost, anywhere from 19 to 30 PSI need kittyless. Have you ever seen the factory downpipe on an STI running factory 14.7 PSI? It's basically a flat plate with a 2.5 inch pipe welded into it mounted to the back of the turbo (and the waste dumps into this also). You want to talk restrictive and Subaru is ok with that at 14.7 PSI factory! In my opinion, up to about 350 WHP plus or minus @ (15-17 PSI) and only three cylinders blowing through each cat should be fine. Obviously there is a point where the cats will produce to much backpressure and heat and will become a problem but I don't believe that point is at 15-17 PSI. I think most DD would be ok at this boost with factory cats and secondary delete running 15-17 PSI. At higher boost levels kittyless would be necessary. I also would think that a nice 200 cell would be a nice compromise.

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      07-28-2013, 02:07 PM   #22
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I know I might get flamed for this but here it goes. Other platforms ie; EVO and STI running way more boost, anywhere from 19 to 30 PSI need kittyless. Has you ever seen the factory downpipe on an STI running factory 14.7 PSI? It's basically a flat plate with a 2.5 inch pipe welded into it mounted to the back of the turbo (and the waste dumps into this also). You want to talk restrictive and Subaru is ok with that at 14.7 PSI factory! In my opinion, up to about 350 WHP plus or minus @ (15-17 PSI) and only three cylinders blowing through each cat should be fine. Obviously there is a point where the cats will produce to much backpressure and heat and will become a problem but I don't believe that point is at 15-17 PSI. I think most DD would be ok at this boost with factory cats and secondary delete running 15-17 PSI. At higher boost levels kittyless would be necessary. I also would think that a nice 200 cell would be a nice compromise.
I am running 15-17 PSI on cP-e downpipes with HighFlow cats, stock mid cats, mid muffler, and Dinan's axle Back Free Flow exhaust.

Will be removing the mid cats, and muffler to free up more flow
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