Jump to content
SAU Community

Recommended Posts

i am buying a JJ dump/front pipe this week and am wondering what to do about the cat, i already have an aftermarket cat-back. I have been told to knock out the inside of my current cat-back to get most airfolw out of it (yes, i know it would then be illegal). Im wondering how much louder would it be (current loudness is sounds great but not loud enough to get unwanted attention)? And would doing this be the equivelent, if not better (air flow wise) than buying a hiflow cat?

Link to comment
https://www.sau.com.au/forums/topic/169788-knocking-out-cat-guts/
Share on other sites

  • Replies 43
  • Created
  • Last Reply

Top Posters In This Topic

f**k I hate threads like this.

A gutted cat is only going to get you maybe 5kw more.

- Is it worth the fine ?

- Is it worth the showoff attention it attracts (ie flames) ?

- Is it worth dump raw exhaust fumes directly into the atmosphere ?

Seriously, anyone who does this on a street car deserves a slap.

Panzy's.

PUNCH IT OUT! :)

However if u drive ur car daily & ur worried about police go for a hi flow..

Cos the comment above about it blowing flames only when u gun it and back off is incorrect..

They seriously blow flames at any time! im talking to the extent where a little blue flame will pop out

changing into second gear at 2500rpm.... :banana:

If yous are worried about punching a cat out cause of the effects to the atmosphere, do not modify your car and get an aftermarket computer which is illegal in NSW as it plays with the emissions, thus effecting the atmosphere.

I think a stock cat or hi -flow cat vs a hollow cat is a very free performance gain, especially at higher hp levels.

Im sure it could be easily a 5-10kw gain at anything over 220rwkw.

Its up to the individual and thier princibles.

MY2C

Ive seen 860RWKW with a pair of 4inch cats, this was a horsepower hero dyno beast, if there was any real gain to be had, it wouldn't have had cats

"If yous are worried about punching a cat out cause of the effects to the atmosphere, do not modify your car and get an aftermarket computer which is illegal in NSW as it plays with the emissions, thus effecting the atmosphere."

Plenty of aftermarket computers can be tuned to be more fuel efficient and better emmissions than the factory 9.5:1 AFR at full load, i remember reading that 60% stock cars 5 years old would fail the drive cycle.

Dont punch your cat guts out in the first place and you have solved your own problem with the cops. Simple... why make it complicated.

I'll tell you now, if you punch them out, you are a prick, and deserve a huge fine.

If you want to know what pollution is like, move to asia and live there 24/7, then come here and tell me that you still want to punch your guts out.

not taking it out on you, but be a little more considerate and forget the 13 year olds that you will please with flames coming out your pipe.

Edited by arbess

i want flames....burn my fully sick body kit....which is already scrapping the ground.....

seriously it will stuff up the rear end making it black....shoot flames, buy a lighter...and 5kw...learn how to drive better and u wont need those 5kw....

Thx for the input, you guys love your flames, i didnt know it would blow flames, was just asking in regards to having a bit more power and also coz i dont have and wont have a spare dollar any time soon to buy a cat. Might just leave the one i got as i have a kit fitted and car is getting resprayed next week, dont wanna burn that fresh paint.

id hate to go against the crowd but going from my own personal experience i belive it makes a huge difference. even if thats true and on paper it only makes u an extra 10kw but an extra 10kw at the wheels is still pretty good. And i didnt notice a difference in top end power but i thought the way the engine felt overall was a well worth improvement. Felt more agressive and i dont belive it makes much difference to the db reading but i think personally the note is alot better. Generally speaking most skylines sound the same but with the combination of having a straight through pipe and a titanium exhuast everyone who knows my car can tell its mine just by the note. And yes it does smell pretty bad if your behind the car but im never behind my own car and yes it does pop flames but ive been told it looks awesome not becuase you can see flames coming out the end of the car but because you can see it coming towards you in a blue flame down the pipe and then watch it turn yellow once its through. I think ill stick with my decision :/

Guest
This topic is now closed to further replies.



  • Similar Content

  • Latest Posts

    • No, you're wrong, and you've always been wrong about this. The Nismo has 2 sets of openings. One is a real 2-way, and the other is a 1-way. There is no 1.5-way possible with the ramps that they offer. A real 1.5-way does exist. That Cusco stuff I posted is a prime example. If the forward drive ramps are, say 55°, and the overrun ramps are, say, 30°, then you will get about half as much LSD effect on overrun than you do on drive. It is real, it realy works. OK, you're slightly right. The Nismo has 55° and 45° ramps on the 2-way, so it does offer less LSD effect on overrun. But, I think that just means that they've (probably) sensibly established that you do not want actually equal LSD effect on overrun. You just want "quite a lot, but not quite as much as the drive LSD effect".
    • Just wanted to unearth this and post my baby with the new front ❤️😝 Took her to my wedding rehearsal today. Next up is getting wide skirts (after wedding)
    • Yea, that is what I was getting at in my ramblings too. The nismo one actually is a 1.5 way and a 1 way. They don't do a *2* way because a true *2* way would have equal ramp angles. Or is that a true 1.5 way? Realistically I think a "1.5 way" does not actually exist. A diff can either lock in two directions or one. It also doesn't help that a LOT of people in Australia speak about 1.5 way diffs are referring to their 1 way diff.
    • Well, the trouble with that ^^ is: The configuration shown is absolutely a 1-way, not a 1.5-way. There is no way that a 1.5-way can be said to offer LSD action only on acceleration. If Nismo cannot get that right, then it is impossible to believe their documentation. That ^ is not a 1.5 way setup. That is a 1-way.   And so now I have allowed all doubts to flourish and have gone back to look at the MotoIQ video. I originally made the mistake of believing him when he said "this is a 1.5-way" at the ~6:10 mark. Because what he did was take the gear assembly out of the 2-way opening and just rotate it one place to the left to drop it into the 1-way opening. When he dropped it in there, the cam was "backwards" compared to the correct orientation shown in all other photos of that config. The flat shold have been facing the 1° ramp side of the opening, not the 55° ramp side. And I thought, "gee that's cute", but I was concerned at the time, when he put the other ring back on, that the gap between the rings looked like it was wider then in the 2-way config. And then I said a lot of things in my long post on Tuesday that could only make sense if the guy from MotoIQ was correct about what he'd done. BUT... I have now done my homework. I grabbed a frame of the video with the 2-way config, and then grabbed another with the "1.5-way" config, snipped out the cam and opening of that frame and just pasted it direct on top of the 2-way config. I scaled it so that the triangular opening was almost exactly the same height in both. AND.... the gap between the plates is wider with the cam installed in the triangualr opening backwards. That is.... it cannot go together that way. There would be massive force on the plates all the time, if you could even reassemble it.  So, My statement on the matter? The Nismo diff is actually only a 2-way and 1-way. There is no 1.5-way option in it, regardless of what they say. Here's a photo of a real 1.5-way ramp opening from Cusco (along with the 1 way option). And the full set of 1 through 2 way options from their racing diff, which is not same-same as what we'd typically be using, but...the cams work the same. A little blurry, but it comes from this Cusco doc, which is quite helpful. AND.... Cusco do in fact do what I suggested would be sensible, which is to have rings that do 1 and 1.5, and 1.5 and 2. Separately.  
×
×
  • Create New...