Exhaust Material

[D3bb4]

Hey guys,

Just wondering if anybody has ever seen an exhaust made out of 4130 chromoly steel before?

Looking to use it for headers and an exhaust, but concerned about if it goes brittle and such, if it needs to be braced, etc.

Is not for a road car, is basically only being chosen as it's the only material avaliable with a 0.9mm wall thickness. Stainless and mild have been ruled out. Titanium is too expensive and too difficult to work with.

Any help appreciated

 

[rob323]

Far too brittle, especially at that thickness, and requires special welding techniques so that it doesn't crack around the welds.
Why do you want to use material that thin?

 

[D3bb4]

thin = light. Can't seem to find stainless or mild in anything smaller than 1.2mm wall, and even then it's scarce.

Is pretty much for a kart, so weight is a huge factor. A 1.6mm wall exhaust will be about 6kg, 0.9 would be under 3 I think, roughly.

 

[evopwr]

Assuming s.s. weighs 8000kg/m (which is conservative), per meter length of 1.5'' pipe:

1.2mm thick weighs 1.24kg
0.9mm thick weighs 0.93kg

IE fuk all difference.

 

[trippy]

steam pipe you will never have a problem

 

[D3bb4]

Headers + primaries + secondaries alone at 8000kg/m^3 which is pretty much density of all steel = >6kg in 1.6. Already done the calcs. Only needs to be 0.7-1.0mm.

1.2mm wall isn't all too easy to come by either, so may as well try and find better/lighter. 1.2 will be used if is no alternatives.

Stuff all difference means something in this application, hence why am putting effort into trying to find something every little bit counts.

 

[rob323]

So this is for a 4 cylinder, 4 stroke go cart????

 

[evopwr]

wouldn't your exhaust length be kept to a bear minimum for a gokart? hence not much material to start off with?

Most of the weight will be in the flanges, which need to be 10mm thk, so no matter what material you use you will have that weight.

Not really sure how you get 6kg, that sounds way too much IMO(edit: if you use 1.6mm thk, that sounds OK).

Also its pretty standard issue for most S.S. manifolds to be made using 1.3mm nominal thickness material. There is a reason why that thickness is nominated (thermal stress resistance, mechanical strength, etc).

-Alex

 

[D3bb4]

Go kart, R6 engine. Only flanges will be on the headers, the pipe work will try to be flared tubes with clamps. Length has been chosen for good power band.

 

[EVO-00X]

Have you looked at carbon fibre? It's another alternative and wont get hot either = big plus!

 

[D3bb4]

thought about it. haven't seen it done as a whole system though, so dicey about it

Has it been done for anything other than mufflers?

 

[D3bb4]

seems that carbon fibre is only good for up to 320 deg c, so is no good for a system.

 

[evopwr]

I'm sure you're not the first to design a 'super lightweight' exhaust manifold without using exotic materials.

What's everyone else done?

I honestly don't think shaving a kilo off the exhaust manifold is the most critical part of the go-kart. The driver could probably go on a diet for a week and loose 2kg before the race!! haha

 

[D3bb4]

haha, true. but is also a design thing. so yeah, lighter is better. was way overweight last time, so cutting everywhere.

Titanium, Cept that's expensive, hard to aquire and nobody wants to bend it. One shop in sydney's done an exhaust with it before, cept they wont have material for 2 months and they dont wanna tell me where they get it from can get it from melbourne, but yeah. lobster cutting it for bends doesn't look like fun.

Even 1.2mm wall steel, NOBODY wants to bend it. other than the custom places. Not 1 exhaust shop in NSW wants to touch it.

 

[evopwr]

You need to get donuts/prebent sections in S.S. tube

afew places sell it.