Hi Flow Cat recommendations

[HCR32 type M]

Hi Guys,

I have a Just Jap 3" dump pipe and the Kakimoto REGU 06&R 3.5" cat back exhaust. I was wondering what to do about a hi flow cat.

The three options are 100 cell 3" hi-flow cat, 100 cell 3.5" hi-flow cat or a transition from 3" to 3.5" (no cat).

It is going in a R32 GTST with the RB20 and will be running a Hypergear ball bearing hi-flow turbo (G2 or G3 trim, not sure yet) on the standard exhaust manifold.

It will be mostly driven on the street.

Let me know what you think...

Cheers Ange

Edited March 1, 2019 by HCR32 type M

[Silverhks]

I'm confused. Where are you thinking of putting the cat? The Kakimoto bolts to the dump pipe right?

If the last is true, I would put a 3" cat in the dump pipe.

How are you going to transition from 3" dump to 3.5" Kakimoto?

Edited March 1, 2019 by Silverhks

[HCR32 type M]

28 minutes ago, Silverhks said:

I'm confused. Where are you thinking of putting the cat? The Kakimoto bolts to the dump pipe right?

If the last is true, I would put a 3" cat in the dump pipe.

How are you going to transition from 3" dump to 3.5" Kakimoto?

I thought the cat goes in between the dump and the Kakimoto?

I have both parts on the way, so I haven't physically seen them yet...

Edited March 1, 2019 by HCR32 type M

[Silverhks]

I'm still new to this platform. However, aftermarket dump pipes like that are usually designed to mount to the existing cat-back eliminating factory cats. If you want a hi-flow cat you then have it fabbed in as far down the dump as possible. This hurts emssions on cold starts but works just fine once warmed up while allowing the best flow for your turbo.

 

The specifics of this platform I could have very wrong though. I hope someone more knowledgeable will chime in soon.

[GTSBoy]

Almost all dump pipes and cat backs assume the retention of a factory sized cat.

Thought 1.  100 cell cats are useless as cats.  Also not legal.  You might as well have a punched out fake cat as waste money on a 100.

Thought 2.  200 cell cats actually work.  Not as well as a proper cat, but they actually do something.  They are also not much more restrictive than a 100 cell cat.

Thought 3.  As you're only putting it on an RB20, you won't need to consider massive flow potential, so a 4" cat (rather than the more extreme 5" that people squeeze into RB25+ exhausts) will do the job.  That's a 4" cat matrix with 3" or 3.5" flanges to suit your other exhaust parts.

Thought 4.  It is very common to have to buy a cat with no flanges and get them put on to make all this shit fit together.

[HCR32 type M]

7 minutes ago, GTSBoy said:

Almost all dump pipes and cat backs assume the retention of a factory sized cat.

Thought 1.  100 cell cats are useless as cats.  Also not legal.  You might as well have a punched out fake cat as waste money on a 100.

Thought 2.  200 cell cats actually work.  Not as well as a proper cat, but they actually do something.  They are also not much more restrictive than a 100 cell cat.

Thought 3.  As you're only putting it on an RB20, you won't need to consider massive flow potential, so a 4" cat (rather than the more extreme 5" that people squeeze into RB25+ exhausts) will do the job.  That's a 4" cat matrix with 3" or 3.5" flanges to suit your other exhaust parts.

Thought 4.  It is very common to have to buy a cat with no flanges and get them put on to make all this shit fit together.

I will be fabricating what ever option I end up with.

So use a 200 cell 4" hi-flow cat and fab up the correct flanges to suit each end?

[GTSBoy]

15 minutes ago, HCR32 type M said:

So use a 200 cell 4" hi-flow cat and fab up the correct flanges to suit each end?

Essentially, yes.

As to exactly which make&model of cat to use.....I'm not sure what the cool kids are running these days.  MetalCat was cool for a while.  I think it has been Venom more lately, but that could have changed.

[Silverhks]

See, I knew I was to new here to open my mouth. Apparently I never learn ?

 

At least I know better than to give legality advice...

[rakka]

Our 100cpi venoms on its way from george. originally received the 5" but our GTT sits fairly low and before even trying it on it seemed like it was gonna scrape on every speed bump. so sent that back and went with the 4" instead.

quality seemed great and priced bloody well. customer service was on point too. so yeah i reckon venoms where its at these days lol

and if anyone thinks it was a mistake sending the 5" back for the 4", please lemme know haha. i've read it shouldn't be a restriction til about 250-300kw, and ours is only about 200 right now

 

[K_arlstrom]

9 hours ago, GTSBoy said:

Thought 1.  100 cell cats are useless as cats.  Also not legal.  You might as well have a punched out fake cat as waste money on a 100.

Just a note on that, my 100 cell cat is working, and my car passed emissions with it (to the standards set by Nissan, that can be seen in the engine bay). I believe that there are bogus catalytic converters, and those that are truly working...

[HCR32 type M]

7 hours ago, rakka said:

Our 100cpi venoms on its way from george. originally received the 5" but our GTT sits fairly low and before even trying it on it seemed like it was gonna scrape on every speed bump. so sent that back and went with the 4" instead.

quality seemed great and priced bloody well. customer service was on point too. so yeah i reckon venoms where its at these days lol

and if anyone thinks it was a mistake sending the 5" back for the 4", please lemme know haha. i've read it shouldn't be a restriction til about 250-300kw, and ours is only about 200 right now

 

Cheers, is George on the forum or do you buy them online?

[Dose Pipe Sutututu]

14 hours ago, Silverhks said:

See, I knew I was to new here to open my mouth. Apparently I never learn ?

 

At least I know better than to give legality advice...

Haha, yeah they're not like VAG or BMW.

[rakka]

18 hours ago, HCR32 type M said:

Cheers, is George on the forum or do you buy them online?

He might be on the forums dunno. I do know he’s on eBay Australia, is on FB, has a website just google venom exhausts Australia, and also +61 402 753 146 (publicly advertised mob). He has iMessage so you should be able to text him for free if u have iOS. Dunno if he’d ship overseas but worth a shot I guess. 

Tbh if we’re talking cats ur probably gonna spend a lot less just getting it done locally.

Edited March 2, 2019 by rakka