cliftyhanger
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| posted on 20/1/16 at 04:13 PM |
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Zetec manifold for my spitfire
My spitfire is happily running its dunnel efi and std focus manifold. However, there are a few things that bug me.
1. It is a 1800 silvertop, with 2ltr cams. Its OK, but I am thinking of a 2 ltr blacktop at some stage.
2. The TB's have K+N's with vert short trumpets. Currently sorting an airbox so I can fit 50mm trumpets, thats all the space I have.
3. Exhaust. And this is what this post is about. Space is limited, I thought about an ST170 manifold, cutting it where it turns into a pair of pipes
and remaking them so the pair go in front of the sump and exit on the drivers side. However, having offered an ST170 up to the car, the front
suspension turret will foul badly.
As an act of desperation I resorted to evilbay and found this
Ford Focus Mondeo 2.0l Top Mount Turbo Exhaust Manifold | eBay
4-99 Toyota MR2 Black Lexus Rea
My thoughts. Is it sensible to chop the collector off, extend the 4 pipes to whatever length, and then re-attach the collector. The 4 pipes would need
to be touching each other, but I can't see that is an issue.
And then, is there an ideal length of primary for the zetec? And is a 4>1 better than a 4>2>1?
And my head hurts...
Ta
Clive
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Paul Turner
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| posted on 20/1/16 at 04:31 PM |
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I sold one of those brand new of my crate blacktop for £15, the seller is having a laugh at that price.
My manifold is 4 into 1 with 1.75 OD pipes 26" long all into a 2 1/4" silencer. Works perfectly from standard Silvertop, standard Blcktop
and 208 bhp Silvertop.
 
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cliftyhanger
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| posted on 20/1/16 at 04:43 PM |
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The manifold advertised is quite different to the std focus item. Seems to be larger diameter pipework, and the collector isn't the odd pressed
affair. Hence my thinking it would be a good place to start with all 4 pipes facing straight down.
It does indeed seem the primary length should be 36"+ long, but is a 4>2>1 preferable? Particularly for mid-range torque?
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coozer
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| posted on 20/1/16 at 04:47 PM |
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I've got one of them manifolds for my turbo. I've had two off that seller over the years, very quick delivery as well.
1972 V8 Jago
1980 Z750
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cliftyhanger
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| posted on 20/1/16 at 04:52 PM |
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Any chance of pics from different angles?
I take it the pipes are approx 1 3/4"? And would the idea of 4 downpipes look feasible?
For the money (£125 delivered) it would be cheaper than buying a pre-cut flange and the bends for the "tricky" bit, let alone getting it
welded.
(BTW this is a plan, along with the blacktop, for next winter, but I like to think ahead)
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snapper
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| posted on 21/1/16 at 06:42 PM |
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The tuning of exhaust manifolds is a complex matter.
It is unlikely with your packaging needs you will achieve any worthwhile extra scavenging.
The maths for manifolds takes in to account cam duration, peak torque and bhp.
To get the full benefit the inlet manifold track is also calculated.
The lengths can vary for the exhaust using 1st, 2nd, 3rd etc. Harmonics so you can chose less than optimum length but still get some results.
For the moment I would just make one that fits, if you have enough space then 4 into 1 for top end power, 4-2-1 for low down torque, for a road car
this is best
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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cliftyhanger
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| posted on 21/1/16 at 09:41 PM |
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I realise the design, or at least the lengths, are complex to work out. Hence the idea of copying the primaries of another, decent, manifold.
It seems the 26" length (just noticed I put 36 in my previous post, my typo) is regarded as a good length, which should be achievable. In fact,
anything longer than what is fitted would be an improvement.
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