cat efficiency codes, cats and spacers

[sambb]

Agonising over which way to go with a dump pipe/front section - To build it around the stock cat (and avoid a CEL altogether) or build it around a 100 cell or the like and rely on a second o2 sensor spacer/standoff to avoid the CEL. Whichever way I go it'll flow into the stock 2.25'' system half way along.

I'd really like to hear from people who did a high flow cat/dump and used only a second o2 sensor spacer to avoid the CEL. Sucess or not? eg do the spacers work reliably say on 2.5'' front pipes but not on 3''? Are spacers more effective if only a front sysytem is done versus a full system? Are 100 cell cats way more prone to CEL with spacers than 200 cell cats are?

And out of curiosity, the second o2 sensor seems to be looking at only the flow after the first cat in the cat assembly- the sum of the two cats isn't looked at. Anyone know if its possible to eliminate the second cat housing (with a bit of welding etc) and still be guaranteed to avoid the CEL?

thanks

[rgvlee]

If you doing the downpipe wouldn't you have your tune updated to deal with this? And at the same time deal with any potential cat CEL issues as a result? I wouldn't think you'd take out the stock restriction without updating the tune to allow for this.

I was told for street that a 100 cell cat wouldn't pass emissions. 200 cell is fine which is what I went with.

[sambb]

Phase 2 will follow later. simply cannot afford dump + cat + tune all at once - not without getting divorced that is! If I can get away with hardware only then that'll atleast get the ball rolling. I'll just run an MBC in parrallel with the N75 to cap max boost if there turns out to be any nasty spikes and see how it goes on phase 1 like that for a while- happy to be a guinea pig on that one.

what got me thinking that the standard cat with enlarged in's and out's might still be good bang for buck was talking to Plautos. His exhaust was initially 3in into the standard cat and 2.5'' out and he experienced a boost rise from 1.3 bar up to 1.6bar so the standard cat has to be capable of good flow especially at phase 1 levels of tune - added bonus to doing it that way is no cat code.
But having said that a 100 or 200 cell with a spacer would likely be even better, but on a dollar per HP gain compared to the standard cat, who knows?

[noone]

From previous results with the Polo on stock turbos, the dump is where a lot of the power comes from in an exhaust upgrade. The rear muffler and rear section flow pretty well for the volume of output from a chipped Polo.

Bought a magnaflow Cat and exhaust spacer, never got around to getting it installed. yours cheap if you want it.

[brad]

Stock Cat is 800 cell IIRC. You should be able to be error free with a 200 cell cat. 100 will cause lights.

[Paazuzu]

Stock Cat is 800 cell IIRC. You should be able to be error free with a 200 cell cat. 100 will cause lights.

The dump pipe combined with the 200 cell cat will cause a CEL. Happened to me after laps at Lakeside about 4 days after installation.

[sambb]

Paazuzu,

Were you running a spacer on the second o2 sensor when the CEL happened? Is your XForce a 100 cell or 200 cell?

[Paazuzu]

Paazuzu,

Were you running a spacer on the second o2 sensor when the CEL happened? Is your XForce a 100 cell or 200 cell?

I was running no spacer with the Xforce 200 cell (euro 4 compliant for emissions). I was expecting a code eventually but knew I'd be getting the stage 2 tune which would eliminate it. If I was you I wouldn't bother with the spacer as your tune is going to remove the code. The exhaust by itself delivers a slight performance improvement, but you won't really benefit from it until you have the tune too. My two cents anyhow

[rgvlee]

The only improvement I noticed with the exhaust on stock tune was less lag. Performance same same.

[sambb]

sorry maybe I didn't make it clear. I already have a phase 1 tune and will be staying on that tune for a while after the dump pipe is installed. I'll phase 2 it down the track when it suits. Thats why in the mean time on phase 1 I want to be damn sure that I will not throw a code if I run say a 200 cell with a sensor spacer.
So yeah I'm wondering what experience front piped stage1/phase1 people had as far as avoiding CEL's with the use of sensor spacers.