Home Built Exhaust?

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Home Built Exhaust?

Postby Garreth on Mon Jul 22, 2013 5:42 pm

Hi guys,

So I have asked around concerning the purchasing of a made up exhaust for my locost. These prices range in the R3500.00 region and as a student I cant really do that right now :| .
I am currently toying with the idea of making my own exhaust system from pre mandrel bent sections of mild steel or stainless and TIG welding them together in the correct arrangement.

I have looked at the LocostUSA site and there are some neat looking systems. Hopefully this post will encourage others or if you have built your own, post it here.

I want to know the feasibility of doing this. Yes it involves time (what doesnt) and I can TIG weld pretty well these days (see my blog on tumblr).

1) Has anyone attempted this and to what success?
2) Does anyone have a DXF file or CAD drawing of the flange for the exhaust side of the 20V Silvertop I can send for laser cutting? (what thickness would you make this flange 5mm?)
3) What size tubing would be ideal for the 1.6l normally aspirated engine, research says 2 1/4 inch?
4) If I use mild steel what is the process to coat, paint, electroplate, passivate etc the will work?

The muffler I will make by inserting a perforated tube into a larger diameter tube and fill it with heat resistant packing. This wont reduce air velocity by very much but will silence in relation to the density of the packing.

Or am I misguided and rather save up and get one made? ( I think making your own exhaust and making sound great is an awesome challenge :D )

Any ideas, advice or past efforts successful or bad post them up lets see whats out there.

Cheers
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Re: Home Built Exhaust?

Postby ross on Sun Jul 28, 2013 11:11 am

I've never built an exhaust system, but I fabricated the top coolant pipe for my Cobra using pre-bent sections and that worked very well. The shape of the pipe was at least as complex as a single header on an exhaust system; I'd say it can definitely be done, I also have a set of 20 valve S/T headers complete with the flange.
Locost chassis with Toyota 20 valve blacktop and T50 box.
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Re: Home Built Exhaust?

Postby Garreth on Sun Jul 28, 2013 9:20 pm

Hi Ross,

I have the original manifold which obviously doesn't fit due to the pipes and flange, was thinking that I just cut off the old pipes from the flange, clean it up and use it as the base for the new manifold? Wouls save having to make up a new flange...

Im looking to make the exhaust go out over the top chassis member and down, like a water fall, and then link them up to the single pipe. Does your spare one do this?

I have heard of manifolds cracking so would it be best to make the final pipe a slip on with an extension spring or will a bolt on flange be ok?

Cheers
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Re: Home Built Exhaust?

Postby ross on Mon Jul 29, 2013 9:26 am

Hi Garreth,
I'd use the original flange, sounds like you're intending to go the typical locost route by bringing the pipes out over the top of the chassis. The important thing is that as far as possible the primaries should be the same length, then I'd go 4 into 2 into 1. My system (built by viper) has a flange to connect the single pipe that runs to the silencer, I've seen the spring arrangements but I couldn't comment on the pros or cons. Good luck.
Cheers,
Ross
Locost chassis with Toyota 20 valve blacktop and T50 box.
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Re: Home Built Exhaust?

Postby andersonhdj on Mon Jul 29, 2013 11:48 pm

Maybe some useless info:-
Higher grade stainless-316/L- tends to work harden and crack on exhaust systems. You could probably successfully use 308/304. 304 tends to rust if a hands not kept on it.
If you're using mig/tig, use a purge line to get perfect welds inside as well as out, it's an irritation to have to seal n peal but the end result is always worth the effort!
If you go the stainless route, when you come to polish always use a virgin wire brush or scotchbrite wheel,
if it's had contact with mild steel, rust is guaranteed and pickle/passivate will be required to restore.
Generally, longer runners produce more torque, short runners more power, higher in the rpm range. there are some complex calcs out there for this, but generally, runners should be kept below 30" long and then as Ross say's, should all be equal length.
Will have a look and see if i've still got the theory on this, if i have i'll post it.
A slip on would probably be a better plot than bolt on.
Hamish.
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Re: Home Built Exhaust?

Postby Garreth on Tue Jul 30, 2013 11:16 am

Hi Hamish,

Thanks very much for the info :D :D much appreciated :)
Have you got anything on doing it out of mild steel? Why do or dont do it?

And yeah would be grateful if you could post that stuff up :)
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Re: Home Built Exhaust?

Postby andersonhdj on Tue Jul 30, 2013 6:19 pm

Hey Garreth,
No, no info really on mild steel and it would'nt be my first choice.
Despite my previous statement re stainless, i would still do it that way for a number of reasons,

Stainless bends are available off the shelf in Dairy quality and in all shapes and sizes, point being no bending required.
Last edited by andersonhdj on Tue Jul 30, 2013 11:18 pm, edited 1 time in total.
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Re: Home Built Exhaust?

Postby Garreth on Tue Jul 30, 2013 7:17 pm

Hamish you are a champ !! :mrgreen: :mrgreen:

This info is fantastic!! Makes the planning of this build much easier.
I would love that info on bluing the flange partly for my own knowledge bank and maybe if its simple enough to carry it out instead of paying for passivation.

Once again thanks for the info :D
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Re: Home Built Exhaust?

Postby bad ass bob on Tue Jul 30, 2013 8:28 pm

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Re: Home Built Exhaust?

Postby andersonhdj on Tue Jul 30, 2013 11:23 pm

Hey Garreth, I'll pm the calc sheet to you when i open my laptop again, prob later in the week, if you still want it.
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Re: Home Built Exhaust?

Postby Garreth on Wed Jul 31, 2013 8:20 am

Hey Hamish that would be great!!

Thanks in advance :D
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Re: Home Built Exhaust?

Postby Garreth on Wed Jul 31, 2013 10:14 am

Found this if anyone wants to take a look, the video series is at the bottom of the page

http://www.stainlessheaders.com/index.aspx
Completed 1.6L 20V ST
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Re: Home Built Exhaust?

Postby Garreth on Thu Aug 01, 2013 7:41 pm

Anyone that has a made up exhaust by whichever company, and willing to measure...

Could you please tell me what length your primary and secondary tubes are? obviously a 4-2-1 system.
Looking to see if what I have found is a good estimate.

Right now looking at 600 mm long primary and 300 mm secondary...(want good mid-range power this is a street car)
Also my system will be going with 38,1 mm OD header to 50,1 mm OD tubing with wall thickness of 1,5 mm. That sound right?


Cheers for now
Completed 1.6L 20V ST
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Garreth
 
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Re: Home Built Exhaust?

Postby ross on Fri Aug 02, 2013 11:07 am

Measure the length of the factory exhaust you have, that'll have been designed to give optimum street performance.
Locost chassis with Toyota 20 valve blacktop and T50 box.
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Re: Home Built Exhaust?

Postby Garreth on Sat Aug 03, 2013 2:56 pm

Hi Ross,

The problem with the factory lengths is that they don't fit well in the body. They are an awkward length meeting just on the chassis top member.
The other problem is getting equal lengths. I have measured up that 500 mm long will give me good positioning and weldability as well as body work clearance for heat etc.

I am just trying to find out if this length would make the engine under perform? The secondaries would be 250 mm long then.

I could just say stuff if and make it with the 500 mm primaries 250 mm secondaries as I really wouldn't know the difference never having driven it. But I would like the peace of mind and decent performance out of her.

Cheers
Completed 1.6L 20V ST
Designing Ariel Atom Clone
http://www.garrethslotus.tumblr.com
Garreth
 
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