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Question about cats before tuning

Pumba83

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Hi there

I'm getting a mafless tune done on my vt super 6 in a few weeks. Whilst I was fixing an exhaust gasket on the weekend I realised the previous owner has bashed the centre of the cats out. Now fully knowing this is um well illegal wil it reduce my tuning results at all or will it be ok to replace the cats after the tune is done?

Cheers
 

PIR4TE

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Everything else kept the same, there's not a huge difference in performance terms between a gutted cat and a high flow cat.
While the change is truly marginal to hp, economy and torque, it may be enough to throw an O2 sensor out of range and trip the CEL, so best to do the cats first or at the time of tune to save $ and hassle down the track.
If current budget priorities preclude that as an option then you are really only dealing with the guilt of the gutted cat. Which isn't an issue as you are going mafless, I would have thought?
If the paranoia of being caught and fined for keeping a gutless cat or the spectre of polluting the world keeps you awake at night take solace in the fact that cats wear out like that anyway. It's not your fault, forget what you saw, you are fine.
 
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DrZ

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Yep, exactly as PIR4TE says.. Its up to your budget man if you want to get it done (plus morals) [or if you can handle the smell, but since you only just realised its gutted, I am sure you will be fine]

In terms of results, yes, you will get a better hp with out cats altogether, marginal improvements over a set of 200cell hiflows (yeah I am pretty sure 100 cell balistics are illegal emisions wise, but then technically your running a cat and cant be fined for having no cat, just emisions and noise depending what state your in) [oh and in most cases after a tune, your car doesnt really meet emissions anyway, so... Either way I guess there is no reason to be feeling guilty]

imo, if budget permits get a 200cell cat, now or later so you cant be done for running no cat, but thats an uncommon pick up, usually just emissions and at that point you fit a cat to get it over pits.. But in terms of tuning, its not an issue man.
 

Not_An_Abba_Fan

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The O2 sensors are before the cats on a VT so it won't make any difference to the tune whether they are there or not. The only difference it will make is a few kW's on the dyno.

At the moment I don't think there are roadside emissions testing in WA, and certainly not in Bunbury. If you had a copper that knows cars, he will pick no cats straight away from the smell of the exhaust and order an EPA test.

You didn't get the VT from Luke did you?
 

PIR4TE

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Thanks for that, I didn't know changing anything after the bung in the headers will not affect the tune at all.
 

DrZ

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Pretty much won't, yes. You start restricting it and it'll lower you peak HP, make it flow to much and then you will loose low down torque..

But anything about zorst, ask Not An Abba Fan (aka NAAF [aka godfather of exhausts]). He knows his ****.
 

Pumba83

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No naaf I picked the car up in mandurah and it was an absolute dud, sent the engine off to get rebuilt to find the bottom end had been replaced with a stock ecotec block which had a manual crank with some studs just snapped off for clearance two cracked heads with no semi forged internals 1st mistake was sending the wife and her mum to view the car while I was away working. Wow it has 20 inch rims and a s/charger must buy it.

But she's all rebuilt now and ready for tune soon just wanted to know about the cats and if there are any other things I need to do before tune as its still being run in only done 700kms since rebuild
 

Pumba83

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And how much is a few less kw's (roughly)
 

Pumba83

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So considering I've spent 8k I might as well get the cats eh
 
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