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Are 2 CAT's better than 1
russbost - 20/4/17 at 01:12 PM

Just thinking out loud here.

Car I'm currently building for a customer has the latest 2016 ZZR1400 engine which already has a small CAT built into the first section of the exhaust where it goes 4 into 1, I normally keep the headers & this first section of exhaust & then add to it as required,

My question is this, if I simply add my normal IVA exhaust system which has a CAT built into it & use a power commander in the usual way, is there any reason why 2 CAT's in series would actually produce a worse result in terms of the right balance of gases for IVA than just having my normal single CAT?

SPYDER - 20/4/17 at 01:26 PM

Hi Russ. Will the second CAT get hot enough to operate properly?

Stevie_P - 20/4/17 at 03:05 PM

A few cars have precats as well as the main cat.
My old TVR Chimaera and Toyota MR2 being a couple.
I assumed it was to get the emissions down ASAP as the precats will heat up really quickly being in the manifold.

Don't think this helps the OP question mind.

Steve

Dick - 20/4/17 at 03:58 PM

I hate the pre cat that they fit into the headers have seen to many engines go bang due to them breaking up up and being drawn in via egr's systems or back firing engines. Take them out and bin them

Stevie_P - 20/4/17 at 04:02 PM

This is a bit of a problem with the Toyota engine for sure.
Plenty stories of them being ruined by dragging bit of wayward cat ceramic into the chamber..

russbost - 20/4/17 at 04:21 PM

quote:
Originally posted by SPYDER
Hi Russ. Will the second CAT get hot enough to operate properly?


Well, I guess that's my question, or at least a part of it, I'm not sure that the first CAT being only a small bike CAT is enough to do the job on its own, the gases should be good & hot coming out of that CAT (not that bike headers ever run exactly cool!!), but I guess the Q is whether they still have enough CO & HC's to make the 2nd CAT start working, I don't think temp itself would be a problem, looking at the lack of any paint left on the first exhaust box of any of my cars, but will a CAT still work if there is only a limited amount of the gas to work with?

Dick - 20/4/17 at 05:39 PM

quote:
Originally posted by Stevie_P
This is a bit of a problem with the Toyota engine for sure.
Plenty stories of them being ruined by dragging bit of wayward cat ceramic into the chamber..


Yep these and the merc v engine had a few of these in bits in the workshop

indykid - 21/4/17 at 05:25 PM

Does the bike have another cat in series?

If not, it's no more engine so shouldn't need any more cat...

Ugg10 - 21/4/17 at 06:42 PM

quote:
Originally posted by Stevie_P
This is a bit of a problem with the Toyota engine for sure.
Plenty stories of them being ruined by dragging bit of wayward cat ceramic into the chamber..


Also a Maserati problem, had a friend with a quattroporte that had this issue, bit more expensive to change the engine than a Toyota.

russbost - 22/4/17 at 11:52 AM

quote:
Originally posted by indykid
Does the bike have another cat in series?

If not, it's no more engine so shouldn't need any more cat...
,

not unless there is anything within the actual rear pipes, which I don't think there was, but I strongly suspect that the bike probably doesn't have such strict emissions criteria to adhere to, I guess it's going to be a case of suck it & see