Making new exhaust?

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Not-a-Number
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Making new exhaust?

Post by Not-a-Number » Mon May 12, 2014 1:56 pm

What size tubing should I use for my exhaust and hows the best way of going about it?

2L engine and want to go 4 into 1 before it comes out the body.

Ive had a manifold flange lasered.

Should I buy donuts or get mandrel bends done?

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Re: Making new exhaust?

Post by 7ish » Mon May 12, 2014 2:06 pm

You can but 90 and 180 degree mandrel bends of different radius from people like autobend.... they have an on-line catalogue so you can figure out what you need. Only rule for cutting tube... always cut square to the tube (or you will have some nice ovals that won't match up...)!
7ish

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Re: Making new exhaust?

Post by Rookie » Mon May 12, 2014 2:28 pm

Use pipemax to make sure you get it right.
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Re: Making new exhaust?

Post by Not-a-Number » Mon May 12, 2014 6:35 pm

Whats a good method of figuring out bends? Or do you just take a guess and then make it up as you go? Cos thats my method for moet things.

What size tubing for a 2L?

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Re: Making new exhaust?

Post by bzrse7en » Mon May 12, 2014 6:52 pm

Cross sectional area of port = cross sectional area of tube would be a good start. However I think the headers can be slightly larger than the port, a step to stop reversion (or whatever it is called) is a good thing.
I'd just do a bit of research on the net, look at layouts, pipe sizes etc, most will be designed for packaging, a few will have a scientific approach to design while others will be designed with bullshit, or copied off something that works. "What works" is pretty variable.
There will be a sweet-spot length for the primaries, as long as you have them all the same length and close to the length of others, you'll be right.
I have a book somewhere that has a table of primary lengths based on (I think) valve timing written by A Graham Bell.

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toppo
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Re: Making new exhaust?

Post by toppo » Mon May 12, 2014 6:54 pm

Not-a-Number wrote:Whats a good method of figuring out bends? Or do you just take a guess and then make it up as you go? Cos thats my method for moet things.

What size tubing for a 2L?
I used 41mm tube for my primary's up from the 38mm that was there and kept all four the same length as much as I could given the space I have, then into a 4 into 1 collector with a 50mm outlet onto a flange, will go out the side of the body in 50mm tube

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Re: Making new exhaust?

Post by 7dreamer » Mon May 12, 2014 7:40 pm

Im sure Ive seen some one use foam pipe lagging or those pool noodle sort of things with a bit of number 8 wire up the middle so you can bend it and package your primary's just so then replicate it in cold hard steel.
A guy I worked with once also back purged his exhaust headers so that the inside was super smooth , and like Patrick said any joints were overlapped so that any back flow had some where to go.

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Re: Making new exhaust?

Post by Rookie » Tue May 13, 2014 11:03 am

Like I said, use pipemax, why guess?

It is single handedly the best program for this.

http://www.maxracesoftware.com/PIPE395.htm
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Not-a-Number
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Re: Making new exhaust?

Post by Not-a-Number » Tue May 13, 2014 12:00 pm

Yeah but it costs $75 unless you have a free one you can give me. Also whats the volumetric efficiency of a zetec on bike throttle bodies with custom intake runners, custom intake plenum and mazda 626 airbox?

I will look for a dodgy copy of it.

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Re: Making new exhaust?

Post by Rookie » Tue May 13, 2014 12:16 pm

I think it is worth paying for personally.

You will pay that for a flange, and if you are going to do it you might as well do it right.
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