Jump to content
SAU Community

Recommended Posts

My arse it doesnt make more power. I had my car dynoed and it made 126 at the wheels. There was a massive power drop in the power band originally, thought it might have been timing or something. Guttered the cat and went back a few days later and my car is now making 140rwkw. I've got two dyno charts to prove it does work. No scanner though. its an r32 gtst by the way.

  • Replies 45
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

if gutting the cat makes no difference, then why do people claim to 'fell the difference' when they go to a 'high flow' cat which (from what i have interpreted) is just a normal cat flanges but with a greater volume inside?

it ain't any bigger in diameter it must be less restrictive..!

conclusion drawn by me: if high-flow cats make a difference then so does gutting the cat.  

bring on the disagreements!

I'd suggest that people want to feel an improvement when they have spent some cash :rofl:

I'm willing to bet if you did a blind test between cat and no cat no-one could pick the difference. Even if there is a kw or 2 on the dyno it makes bugger all difference in real life

/Disagreement

i bought my car with a gutted cat (didnt know)

went to replace it with a new catco 3" highflow and discovered it was gutted.

felt NO difference before/after, could tell a slight noise diff

very slight whistling/sucking sound sort of a thing instead of raw grunt noise, definately not worth the fine.

with mesh in the cat i could run a minium boost setting of 12psi, with out mesh no less than 14psi. it flows a s##t load more with the mesh knocked out. I could tell if my cat was in or not without a dout. Also cars that run anti lag can not have cats as they will just blow out and get very hot. Race car's will not have a cat because they restrict flow, FACT.

RBVS,

Race cars also don't use a hollow cyclinder (knocked out cat) in the middle of their exhaust, they use a straight through pipe as they know the hollow cyclinder increases back pressure.

What boost setup have you got to be able to run a minimum of 14psi?

Obviously a 14psi wastegate? or a stocker RB20 type wastegate with a gated bleeder?

There is no doubt there is power to be had if the cat is replaced with a straight through pipe.

Providing the cat you are using supports the kind of exhaust flow levels you are after then a cat is not going to restrict power hardly over a cat converter that has had its guts knocked out. Thats providing the cat is in good working order to begin with. A typical symptom of a stuffed cat is the lack of boost.

i heard of a guy who gutted his cat at the car now shoots 5 foot long flames...

'he' said 'he' cant notice any difference other than a louder exhaust noise and a large orange glow when changing gears off the rev limiter...

'he' is also an absolute champion of a bloke lol

haha fair enough

any restriction at all in an exhaust system especially for turbo vehicles reduces power

If i had it my way the dump would come off the turbo turn right and come out the front of the sideskirt :headspin: but u cant have everything i guess

A cat with the guts smacked out of it doesn't go meow any more... oh hang on, sorry, wrong type of cat.

A hollowed out cat is worse for performance than a new decent quality high flow one. A straight through pipe, in the same size diameter as the rest if the system, WILL out perform a high flow cat. The honeycomb is a restriction and regardless of how high flow it is it will still rob power. The rwkw difference between a straight through 3” pipe vs. a 3” high flow cat is more than 1 or 2kw. The difference between a 3” straight through pipe vs. a 2.5” cat is bloody massive!

Ok But getting back to Legalities though,

If you ever get pulled over and the cop is what most are (a c#%t). And he decides to defect you left, right and centre.

Hes not going to get under the car and undo your cat to see if its hollow or not.

Dont you get a defective notice where you've got like x number of hours to get it all clear.

And if that includes getting an emissions check, you would still have time to go to your local exhaust place and buy a new cat, fitting it and avoiding the $10000 fine???

Matt,

 

Exhaust Technology now have 3.5" cats that are supposed to flow in words "Anything you throw at it".

 

They are pricey but.. Some where up around the $400 mark.

 

I've got it written down some where.

I'll bet a $40 3.5" pipe still flows more than a $400 3.5" cat. But yes a 3.5" cat would be the go for everyday use and maximum horsepower potential.

I'll bet a $40 3.5" pipe still flows more than a $400 3.5" cat. But yes a 3.5" cat would be the go for everyday use and maximum horsepower potential.

Oh yer no doubt it does BUT its probably the highest flowing cat we have available in AUS, they have only just become available. :)

As I've said all along, Cats do rob power but so do hollow cats. Its only the straight through pipes that don't. ;)

For track days etc slap in one of those cheap JMS cat replacement straight through pipes. Not sure how it would affect the powerfc's tuning, Microtec would have no issues as you could have another map setup for it. :rant:

...Race car's will not have a cat because they restrict flow, FACT.

Funy how cetain race categories in Europe actually have to run them... and have for a good number of years now.

My car is getting dynod next week with 2 x mufflers and cat, then with centre muffler and cat removed, see if it makes more power or brings on boost quicker, if it does then ill drop it for Sprints etc

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • Hi guys . Can someone help me  I bought an Android screen for my Nissan fuga but it won't turn on   
    • My guesstimate, with no real numbers to back it up, is it won't effect it greatly at all.its not a huge change in position, and I can't see the air flow changing from in turbulence that much based on distance, and what's in front of it. Johnny and Brad may have some more numbers to share from experience though.
    • Which solenoid? Why was it changed? Again, why was this done? ...well, these wear..but ultimately, why was it changed? Did you reset the idle voltage level after fitment? I'm just a tad confused ~ the flash code doesn't allude to these items being faulty, so in my mind the only reason to change these things, would be some drive-ability issue....and if that's the case, what was the problem? Those questions aside, check if the dropping resistor is OK ...should be 11~14 ohms (TCU doesn't throw a flash code for this) ~ also, these TCU designs have full time power (to keep fault code RAM alive), and I think that'll throw a logic code (as opposed to the 10 hardware codes), if that power is missing (or the ram has gone bad in the TCU, which you can check..but that's another story here perhaps).
    • Question for people who "know stuff" I am looking at doing the new intake like the one in the picture (the pictured is designed for the OEM TB and intake plenum), this design has the filter behind the front bar, but, the filter sits where the OEM duct heads into the front bar, and the standard aperture when the OEM ducting is removed allows the filter to pulled back out of the front bar into the engine bay for servicing, a simple blanking plate is used to seal the aperture behind the filter This will require a 45° silicone hose from the TB, like the alloy pipe that is currently there, to another 45° silicone hose to get a straight run to the aperture in the front bar Question: how will it effect the tune if I move the MAF about 100-150mm forward, the red is around where my MAF is currently, and the green would be where it would end up Like this This is the hole the filter goes through  Ends up like this LOL..Cheers    
    • Despite the level up question, actually I do know what that is....it is a pressure sender wire.  So check out around the oil filter for an oil pressure sender, or maybe fuel pressure near the filter or on the engine. Possibly but less likely coolant pressure sensor because they tend to be combined temp/pressure senders if you have one. Could also be brake pressure (in a brake line somewhere pre ABS) but maybe I'm the only one that has that on a skyline.
×
×
  • Create New...