Modify your Pre-CAT

[Elanlover]

So in your experience the stock hollowed out precat is better than a PCE? (Or am I misunderstanding what you wrote?) Did you buy a PCE and not use it?

The PCe is a better solution for a couple of reasons (at least the one nitroman designed). It allows for much smoother exhaust flow out of the turbo exhaust manifold. The precat is not exactly smooth on the interior when the catalyst material is removed. Also, the PCE allows you to keep your precat intact in the event you ever want to re-install it or if you just like to keep all your stock components n a box in the garage like me.

In terms of performance, I don't think there's much of a perceivable difference either way though.

[superbad]

Yeah, that's all exactly what I would have thought. But I read the post as if he had originally put in a PCE, then swapped it out for a hollowed out precat and found that it worked better than the PCE.

[kmckmc]

I purchased a hollowed out precat. I had it installed 2 months ago. My S2 ran without problem; however, the sound was more than my ears can handle. I decided to swap back the original precat (this S2 is already main cat-less and has s/s 2.25 exhaust pipe).

[nitroman]

If you are maintaining the complete stock 2" exhaust there is probably no advantage in using a PCE vs a hollowed-out precat. I would use this general rule: the portion of the exhaust occupying the precat position should equal (ideally) or exceed* the size of your exhaust system.

*(ie: 2.25" exhaust, 2.5" PCE... whilst not ideal, makes more sense than a 2.5" exhaust with a 2" hollowed-precat)

[DeanG]

I had my first longish ride of about 50 miles since putting on the hollowed out precat. Generally the car feels much smoother although there is one odd thing. When I first push on the gas hard the power builds then there is an abrupt hesitation before the power comes back. I am thinking it may be the blow off valve but I don't hear it operating. Stock Federal car with a mountain chip, blow off valve and hollowed out precat.

[nitroman]

When I first push on the gas hard the power builds then there is an abrupt hesitation before the power comes back.

Can you correlate these events to what is happening on the boost gauge, please?

[GeoffSmith]

An Elanscan run would be good.

[Doug]

Dean, you could also disconnect the battery and make the ECU reset and relearn and that could smooth things out.

[texaselite]

Where did the pictures go from this post?

I am seeing some loose pieces of metal in my muffler...thinking main-cat or pre-cat disintegration?

Would like to see how to access the pre-cat and potentially clean/gut it out.

[HJ2]

Eat your hart out!
viewtopic.php?f=79&t=16507&p=218277&hilit=ypres+to+do#p218277

Here's how i emptied mine:

1. Car on bridge
2. unbolt exhaust from pre-cat
3. Hammer and chisel, hammer away till empty

[steve matthews]

Texas, check the Fed. down Pipe or UK down pipe threads.
This is the better road to travel in the long run.
I do have a PCE for sale but this is only a temporary fix because the
down pipes deliver so much more.
Steve

[Doug]

the stock main cat can break loose and rattle under the car -- mine did years ago and I remember a few others having the same issue.
I have never heard of the precat core breaking on its own so this is unlikely to happen and if it did I doubt it would give any metallic noise or pieces.
Yes, if you find the pictures they show the honeycomb material inside the precat which is pretty distinctive. But could pre-cat pieces make it thru an intact main cat to the muffler area? I doubt it.

[texaselite]

This is what I was able to fish out of my muffler (other pieces I can see in there)...very corroded piece of metal:

[steve matthews]

Texas, go for it, replace the exhaust. 2.25 or 2.5 piper or peco.
Steve

[Doug]