mattjhunt
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| posted on 20/11/08 at 07:38 AM |
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Shorter inlet manifold?
Got a set of webers on my crossflow that wont fit under the bonnet, rather than cut the bonnet people have suggested getting a shorter inlet manifold.
Anyone know of any downsides to this?
Anyone know of a source of a cheap second hand one? (Ebay have none).
Cheers.
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Mr Whippy
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| posted on 20/11/08 at 07:43 AM |
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shorter ones produce slightly lower torque, apparently but if that is really an issue on a light weight 7 is doubtful
will still be several times more than what comes out of a BEC 
[Edited on 20/11/08 by Mr Whippy]
Fame is when your old car is plastered all over the internet
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dubstar_04
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| posted on 20/11/08 at 08:39 AM |
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The torque isn't less its just lower in the rev range.
The length of the manifold runner from the atmosphere or plenum to the back of the valve affects at what point the peak power is realised in the
engine speed range.
The reason for this (If anyone is interested) is because when the valve closes the flow pressure in the manifold is bounced off the back of the valve
and returns to the entrance of the carb or the air plenum. Once the pressure wave reaches the atmosphere or plenum where the pressure is less than in
the tract the the pressure in the tract turns negative causing ambient air to be drawn in. this then sends a pressure wave back towards the valve.
The point at which the optimum power is achieved corresponds with the engine speed when the inward pressure wave is synchronized with the opening of
the valve and the wave continues into the cylinder.
I have all the calcs to make relevant callculations somewhere if you need them.
cheers,
Dan
[Edited on 20/11/08 by dubstar_04]
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Mr Whippy
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| posted on 20/11/08 at 09:08 AM |
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Thanks for the clarification 
Fame is when your old car is plastered all over the internet
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PaulBuz
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| posted on 20/11/08 at 04:55 PM |
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Nothing to do with inlet manifolds.
Just had to say, LOVE the avatar whippy!
ATB
Paul
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dubstar_04
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| posted on 20/11/08 at 05:25 PM |
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Thats me on the left!!
I don't have a BEC, i'm just a nancy!!
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blakep82
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| posted on 20/11/08 at 07:30 PM |
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i'd be interested in calculators to design manifolds please
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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PerS
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| posted on 21/11/08 at 09:32 AM |
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http://www.rbracing-rsr.com/runnertorquecalc.html
//Per
Per
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martyn_16v
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| posted on 21/11/08 at 09:46 AM |
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quote:
Originally posted by dubstar_04
The torque isn't less its just lower in the rev range.
Higher, a shorter intake will push the resonant frequencies up.
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