GaryM
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| posted on 23/1/08 at 08:16 PM |
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Xflow bike carb inlet mainfold length
Hi
I'm trying to design an inlet manifold to use with my xflow FZR600 bike carb conversion.
It would be nice to try and make it as short as possible so I stand a better chance of the air filter sock remaining inside the bonnet but i'm
sure the length will affect the performance of the engine in some respect.
I noticed that you can buy DCOE manifolds for 1600 xflows in two lengths 3.1" and 4.25".
Any advise would be greatly appreciated.
Cheers
Gary
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jacko
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| posted on 23/1/08 at 08:19 PM |
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Hi have a look at my photos under zx9r + manifold
my manifold is about 70mm
Jacko
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02GF74
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| posted on 24/1/08 at 09:50 AM |
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what is wrong with hole in bonnet - easy access to cold air.
unless you fit in some cunning ducting, underbonnet air will have passed through the radiator so be warmer.
cold air = more power = faster
hole in bonnet = less weight = faster.
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Jenko
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| posted on 24/1/08 at 12:00 PM |
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It's not just the manifold length - you need to look at the length of the entire inlet system from ports to Trumpet ends.
As previously mentioned, an exhaust cut is not such a bad thing, nice cold air - that said, an x flow is quite thin, and if you can fit 40's
under the bonnett, you should not have any issues.
Do some measuring, and figure out if the longer manifold will fit...if not, think about using the smaller one, but possibly using longer
Trumpets........there is some useful info below - From the Jenvey site:
What is the correct overall system length?
Induction length is one of the most important aspects of fuelling performance engines.
In our experience an under-length system is the greatest cause of disapointment, with loss of up to 1/3 of power potential. There are a number of good
books on the subject and the serious developer is referred to these and, in particular, dyno trials. A guide figure, from the face of the trumpet to
the centre of the valve head is 350mm for a 9,000 RPM engine. Other RPM are proportional, i.e. for 18,000 RPM the figure is ca 175mm.
Any air feed system to an airbox or filter can have a large effect on the power curve and must be considered carefully - particularly if the airbox is
small.
The induction system is part of a resonant whole - from air inlet or trumpet to exhaust outlet - and the ideal length is heavily influenced by the
other components.
So, assume the xflow to rev to 6000rpm - Then an ideal length from valve head to butterfly would be approx 466mm
PJ.
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