How optional is the exhaust system a car? Every single part of

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yes, that's why race cars plug the exhaust and tractors have the little flapper thing

So what are my options here?
Will a rattling inside, caused by rust on the mufflers and expansion chamber, imply that rust is being sucked in to the cylinders?
Would I be better off removing them and using cloth as a makeshift filter?

>>15275445
Cut it off after you fabricate the straight pipe.

>>15275539
But a straight pipe won't offer any resistance to particles traveling upwards, will it?

bump?

>>15275533
nothing will be sucked into the cylinders. The manifolds will provide enough protection against dirt etc. defying gravity and entering the engine.

The biggest danger to the engine is cold air coming in the manifold immediately after engine shutoff. A cold breeze can cool a hot exhaust valve fast enough to warp/crack it. But I've only ever heard of that happening with cracked or very loose manifolds/headers. Big fucking hole, real close to the port. Doubt it would happen with the entire manifold still intact, unless it's a real short manifold.

The biggest danger to you is fumes at low speeds / stop & go traffic. That and hearing damage.

If your car has an oxygen sensor, you want to retain at least a foot of pipe beyond it to keep the outside air from screwing up the reading and thus your A/F mixture.

>>15275559
>resistance to particles traveling upwards
Who told you that particles travel up an exhaust system?

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>>15275890
>hearing damage.
My car has no o2 sensor, I'm thinking of separating from where I've marked.

I'm worried about extracting the part marked A, the expansion chamber, since it seems to send air back into the valve from what I've seen by googling.

>>15275922
Well, currents of air flow in many directions, and take into account this car won't always be running

>>15275466
The flapper is mainly to keep water out. Dirt is secondary

>>15275890
>The biggest danger to the engine is cold air coming in the manifold immediately after engine shutoff. A cold breeze can cool a hot exhaust valve fast enough to warp/crack it.

Makz cecedees

>>15275949
Just buy a cheap muffler and clamp it on after the cat. You have $30, right?
Also straight exhausts are illegal. Not only for excessive noise, but also the lack of a cat if it was originally equipped.

My friend's Focus ZX3 had the bolts holding the exhaust to the manifold snap and so he was running just headers for like a month before he decided he was sick of driving with the windows down due to fumes. Car hasn't had any issues related to it come up so far, and it sounded pretty cool too.

>>15275949

The expansion chamber will make a difference - there's a whole math with regards to the total volume of the exhaust system and how echos with just the right resonance can suck more exhaust out of the cylinders at certain RPM's.

This does not mean that there will be airflow literally carrying rust up the exhaust pipe in reverse direction, if that's what you're worrying about. There are waves of pressure felt upstream but the net flow is always downstream.

But back to the effects of removing it... any change to the total length of the system screws up the resonance math anyway, so if you're doing any cutting at all, it can potentially come out with no performance losee. In best case conditions a perfectly tuned exhaust is only good for a couple hp over an arbitrary-length straight pipe anyway.

Most OEM resonators/expansion chambers etc. are mainly sized/shaped to change the tone/sound of the exhaust, not to improve performance.

>>15275995
It has no cat as I can tell by the image posted, I'll probably end a straight pipe in a muffler when I make it, but since the whole piping is fucked I'm not going to have much luck replacing the rusted muffler alone

>>15276031
any change to the total length of the system screws up the resonance math anyway, so if you're doing any cutting at all, it can potentially come out with no performance losee

So cutting fucks up resonance but that's mostly sound and not performance related?

>>15276018
Maybe he was lucky?

>>15276047
What year is it? Anything past the mid 80s is sure to have a cat

>>15276051
1990, I'm from spain so european production was always a step back.
It's a citroen BX 14 TGE and I'm practically sure it has no cat.