Making a custom exhaust

Question

I drive a 1990's Citroen BX TGE16 with no o2 sensors or anyhing fancy on the exhaust as far as I can tell.

My exhaust is all rattly most surely from rust and age so I'm planning on changing soon. Thing is, with such a simple exhaust... Could I comission a local metal working buissness to make a 'tube' that would fit my exhaust system? I'm basically looking for a build that will let my engine breathe better and will sound nice.

What should I take into account when doing so? The law in my country doesn't take emissions or noise into account on cars classified as classics.

Edit:

Another aproach to this would be removing the exhaust and taking it in to the buisness, would driving without an exhaust be sensible in any way?

Answer 1

Possibilities

Yes! Absolutely you can have this done. The quality of work may vary depending on the level of experience of the shop you commission to do the work but you could end up with something like this, if you want.

I would not remove the entire exhaust and take it to a shop.

• How are they going to know where the exhaust should run without having the engine bay and frame available to measure everything up to ensure it fits into the engine bay correctly?

• Running the engine with no exhaust is not good for your exhaust valves.

• Exhaust fumes from your engine bay will get into the cabin and you will be breathing in some very noxious fumes that kill living organisms, that being you and whomever else get's in.

Keep the header/manifold

If you can use your current exhaust manifold that comes off your cylinder head, that's the most cost effective and reliable way. You don't want anyone fabricating that piece. You would then cut off the beginning of your exhaust pipe that bolts up to the manifold to use that. Your fabricator can then weld tubing that is the same as the current diameter of your exhaust pipe to that connector piece so it can bolt up to your manifold with the right connection.

Add in a muffler

You can then weld a muffler into the system. It's level of restriction may force you to tune your carburetor to match the restriction in the muffler. More backpressure will richen your system. Less will lean it out. You don't want to run rich or lean.

Rich wastes fuel

Lean runs hot, more oxygen, and can damage your exhaust valves and 'burn' them.

Here's a QA on burnt valves

• What exactly is a "burnt valve" and what causes it?

Conclusion

Yes. You can do it.

Put a muffler in it too, you need the restriction and the back pressure.

If you love the planet, put a catalytic converter in it.

You will probably have to tune your air fuel ratio to get things proper after you install your exhaust.

Take the whole car in when you do it so they can fabricate it properly and run the exhaust to match the current fitment.

Answer 2

I would not advise running with open headers or decatted exhausts.

NOx and CO emissions are not a nice thing to breathe in. Plus the stench will make for an uncomfortable driving experience.

Answer 3

I personally wouldn't drive around for very long without an exhaust.

In the UK, we have a number of exhaust fabrication specialists who are able to build exhaust on the car for you. Typically these utilize stainless steel and come with a lifetime warranty.

As an alternative, Bosul exhausts do manufacture a replacement system for your vehicle but it might take some effort to track one down that's for sale and at a reasonable price.

Answer 4

You could easily commission someone to make a "tube" to replace your exhaust, baring in mind if you replace the whole thing you will need to take various things into consideration such as exhaust hangers, flexi-pipe to handle engine flex (when the engine moves it will pull the exhaust away), etc

Ignore what Zaid said about decatted exhausts, If you make an almost airtight exhaust system you won't run into any issues with CO or "stench" + probably gain a few BHP

Answer 5

You need to check whether there actually is a cat in there or not, and exactly what the rules are. Most countries by the 90s had started enforcing emissions rules, and most countries' rules for classics are that they must meet emissions regs at the time the car was built. Clearly for an E-type Jag, the world wants them around as a moving work of art, and emissions are an accepted cost for their beauty. For a boring rustbucket Citroen, not so much. ;)

The engine will still run without a working cat, but it will probably run more rich than it should, which won't do your fuel consumption any good. You'll also get a big red light on your dash to tell you it's not working.

As far as cost goes, the main cost on anything is manpower. A mass-produced off-the-shelf exhaust will certainly be cheaper than a custom job. If you want to save money, why even consider custom?