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.

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]

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]

Thanks for the clarification

Nothing to do with inlet manifolds.
Just had to say, LOVE the avatar whippy!

Thats me on the left!!

I don't have a BEC, i'm just a nancy!!

i'd be interested in calculators to design manifolds please

http://www.rbracing-rsr.com/runnertorquecalc.html

//Per

quote:

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Originally posted by dubstar_04
The torque isn't less its just lower in the rev range.

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