Should I Replace My Compliance Cat? And With Which Cat?

[some_cs_student]

Hi,

I've been told that getting a higher flowing cat may assist in getting more power out of my R33 GTR.

It currently has a largish exhaust system I think its 3inch all the way through, and standard turbo's and air intake.

I've noticed that there are a few different cats around there is the X-Force Stainless steel high flow cats from Just Jap for $160

Apparently it can flow 570CFM and it comes with flanges.

There is also a group buy on X-force cats and exhausts

They are 2.5, 3 and 3.5 inch for the "racing" cat I'm not sure if the racing cat is a marketing name or if its race-use only and doesn't comply to the EPA regulations.

And then there is the

Batmbl selling catco cats

There website says:

The prices were:

* 3" large body BOLT ON Catco cat (ceramic inside) - $230 including delivery

* 3" Catco cat BOLT ON (metal inside, 5" round body **not 4" like Magic cat & Metal cat**, 200csi cell - 706.2 CFM!

Which cat should I be using? Will it make much difference to performance?

I'm considering the X-force from JustJap at the moment, it seems to be reasonably priced but I'd like some opinions.

Also, if I get a larger cat will it make any difference to the exhaust volume at all? I assume its very little but....

Regards,

Gareth

[some_cs_student]

Or would it be smarter to save some $$$ and not buy a new cat?

Compliance cats today are usually 3 inch, does it make a difference if I go for a larger cat?

[siddr20]

is the complicance cat hi-flowed already?

I got my self a magnaflow hi-flow cat.. Made a fair bit of difference, before i chucked on the rest of the exhaust!!

Otherwise just check which cat is the most flowing..

Edited February 4, 2008 by siddr20

[some_cs_student]

is the complicance cat hi-flowed already?

I got my self a magnaflow hi-flow cat.. Made a fair bit of difference, before i chucked on the rest of the exhaust!!

Otherwise just check which cat is the most flowing..

Hey,

I don't think the compliance cat is high-flowed. If it does make a fair bit of difference I'd change the cat, how much difference are we talking about?

And the larger the cat the more the flow, but will there be any noticeable difference between a cat that flows 570CFM and 706CFM?

I mean I'm not changing the turbo's anytime soon, just aiming to get cat + powerfc + tune.

Regards,

Gareth

[zertek]

steel pin and hammer

[DLOOOK]

hey,

I ended up going for the just jap highflow cat on my 33 GTR. For the power im chasing ~240-260awkw this cat will suffice. Although too be honest, i didnt feel a noticeable difference between my compliance cat, and the highflow. Side by side, there was a noticeable difference in size and restriction, so im sure it made some difference.

Next mod im goin for is front pipes.

[some_cs_student]

I ended up going for the just jap highflow cat on my 33 GTR. For the power im chasing ~240-260awkw this cat will suffice. Although too be honest, i didnt feel a noticeable difference between my compliance cat, and the highflow. Side by side, there was a noticeable difference in size and restriction, so im sure it made some difference.

Next mod im goin for is front pipes.

Hmm, interesting, I'm not sure if my front pipes are standard or not.

I wonder if anyone has done a before and after run after changing the cat...

[some_cs_student]

So no more comments about the cat's?

Is it worth the extra $$$ for the Catco cats compared to the Just Jap X-force cat?

[justin911]

how big is the stock 33 gtr cat ? I was thinking i could just gut that ? or would it be to small still ?

[WYTSKY]

hey guys, I got a thread going about going from a gutted cat to a highflow... I really notice a loss of power going from basiclly a straight pipe to an xforce highflow.

Then again, I also noticed a big increase in power from when the cat was normal to gutted.

if you don't have a white car then gutting ur current cat is best for performance. If you do, you will start to notice a yellow tinge to ur rear bar because the cat is not filtering the carbon monoxide.(you have to degs or buff it off each week) bit of a pain really.

[Dose Pipe Sutututu]

those $160 SAU special X-Force cats from JustJaps are shit. I have one in my car and when the exhaust/engine gets hot... I lose 2 PSI of boost.

I use to run a CATCO cat that was welded directly onto my old cat back, noticed heaps more power and no boost drop, since I changed my catback and fitted a new cat I noticed less power and boost drop once the car gets to optimal running temps.

[Jmaac]

If youve already got a 3" system just keep it, the amount of restriction on it will be neglible unless your running massive hp. Better yet gut it out and bolt it back into place

[some_cs_student]

Then again, I also noticed a big increase in power from when the cat was normal to gutted.

if you don't have a white car then gutting ur current cat is best for performance.

Great for performance but bad for the environment and a huge fine if you get busted with it in Vic!

And I mean huge...

If youve already got a 3" system just keep it, the amount of restriction on it will be neglible unless your running massive hp. Better yet gut it out and bolt it back into place

Then why does a gutted cat allow less restriction and therefore more HP? (either that or a lot of people lie about the HP increase )

I'm sure people have advised me that it can increase HP even on cars that are not running massive HP.

[delljit]

i have the same problem, except i drive a gtst witha catback exhaust. My next mod upgrade is the front pipe and cat, i was probably going to go with a http://bosimporting.com.au/index.php?page=...t&Itemid=27 and the batmbl split dump. Should i go with that cat or get soemthing more expensive? Street use only.

[GeeTR]

Step 1: Don't buy beer for 2 weeks.

Step 2: Use afore mentioned money ~500, and use to buy the best metal cat you can. I'd suggest maybe a 4-5 inch depending on your power goals, from S M B

Step 3: Never worry about ur cat again...

[some_cs_student]

Step 1: Don't buy beer for 2 weeks.

Step 2: Use afore mentioned money ~500, and use to buy the best metal cat you can. I'd suggest maybe a 4-5 inch depending on your power goals, from S M B

Step 3: Never worry about ur cat again...

Haha, ok, no beer until the cat is in

I'm going to try to get a 3inch high-flow (probably the x-force racing cat, not the $160 one) that does not have a ceramic inside as its not good for the skylines to have ceramic inside (apparently)

Regards,

Gareth

[CEF11E]

I have a 3" metalcat that has been in service for 12 months. the innards have desintegrated atfer a few track days with a near perfect 12:1 afr. and i am not the only one. i need to buy another cat but may not buy another metal innard cat. once bitten twice shy.

spending $300 on a cat every 12 months is rediculous. going to their website they claim to be the best and say the xforce items are not street legal. I think i am going to go a magnaflow.

[Bliksem]

5" Catco Round body here... I noticed a difference changing from stock

[yc89]

i'm big JDM parts fans the only part on my BNR34 not from japan is X force 3.5" High flow cat nothing wrong with it. =)

[GeeTR]

I'm going to try to get a 3inch high-flow (probably the x-force racing cat, not the $160 one) that does not have a ceramic inside as its not good for the skylines to have ceramic inside (apparently)

Interesting, id like to hear more on this theory