Fabricating an exhaust

[jim]

I'm making an exhaust but I'm struggling to figure out bend angles and making brackets

Does anyone have any advice?

[drake1994]

i make my exhausts from straight tube and preformed mandrel bends and just work my way from the manifold back. i use pre formed bends so that i can cut them in half or go past 90 degrees, and use a marker pen to put two lines over the joint, then tack it and check it, get it all tacked and checked, make sure it clears everything and does hit anything then weld it

[ianperry3112]

I made the exhaust for my old Suzuki Swift (Mk 1 GTi) rally car, including a long 2-into-1 downpipe. All relatively straightforward if you start at the front and work backwards as drake1994 suggests. Keep the pipe runs simple and don't introduce bends you don't need, and the old principle of mark and measure twice and cut once is wise. If you use pairs of 45- or 90-deg pipe bends you can align the pipe to just about any angle you want.

I used pre-formed pipe sections on the Suzi, too, the whole exhaust cost under £100 and a day of measuring, offering up, marking, tacking, refitting, welding and offering up for the next step. Even the GF looked impressed. And it sounded good!

If you use preformed pipe sections you might be lucky and get lengths with one end splayed slightly to make a socket for the other pipe to fit into. If you do, remember to use the wider section at the engine end of each section, so that the narrower pipe (i.e. male) is the outlet carrying the gas into the wider "socket" pipe (i.e. female). If that makes sense?

Don't forget as you are putting it together to make at least two bolted or clamped joints to make it easier to take off and put on :-) (i.e. don't get carried away and weld every joint!)

Hangers - you can get strap type hangers that you can attach using a U bolt round the pipe, or weld old bolts (M8 is about right) to the exhaust pipe and use standard figure-8 rubbers. To work out where to put the bolts, the easiest way is to hang the exhaust temporarily using old welding wire or wire coat-hanger wire to hold the exhaust in place (you can tie it to suspension or openings in body pressings for this, as you aren't going to drive around like that) and then use a marker pen to locate where you want to weld the bolts on. I assume the car has its original hangers still in place, so you can attach the new hangers to them?

Good luck!

[ianperry3112]

Forgot to ask last night (I blame the combination of beef and red wine, cheese and port).

What is the vehicle, do you have a design for the exhaust or are you kinda working it out as you go along? Why are you scratch-building rather than getting it off the peg, is it a bit of a one-off or are you just feeling adventurous?

[jim]

Thanks for the ad I've Ian, I'd fortunately put the flared ends the way you'd suggested which is lucky!

I'm making it for my mk1 cortina, there was a manifold and system available but they were 5-600 but they're not being made anymore.

My other option was an Ashley system but they aren't great and have twin box plus they're mild steel so for about £100 I've got the bits to make a single box stainless system.

Plus I like the challenge!

[ianperry3112]

Hi Jim,

Sounds like an excellent project ;-) My experience of Ashley systems mirrors yours - cheap-ish and loud, not expected to last a long time.

I hope it goes well, good luck. Some photos would be good, I'd be interested to see how you get on.