Airbox dimensions/volume

[anonymous-user]

Following on from this thread, it got me thinking. I'm going to be fitting Jenvey ITBs to a K series and I assume (hope) that the trumpets will be the right length.

However, if I'm planning on enclosing these within an airbox with a cold air feed (it's mid engined so is going to need some sort of ducting for this), the fact that trumpet length is important leads me to believe that the volume / dimensions / resonance or something of the airbox will be important.

Other than having seen some commercial cold air systems using a smooth expansion from the ducting into the air box to keep air flow laminar and use the venturi effect to increase air speed, are there any other constraints and how do I calculate these for a specific engine / rpm / power output, etc.?

[chuntington101]

i think size is also a factor. i read on an forum about forced induction that the sizer of the plenum needs to be about the same saize as the engine. so for the K it would need to hold about 1.8ltr! now i maybe way off here but it would be worth looking into or if anyone can tell me im talking total C**P.

Chris.

[GavinPearson]

To give you a guide the Jag S-Type 3.0 that came out in 1999 had an inlet manifold of 9 litres to give it maximum power. It would be fair to say it wasn't the most responsive at low speed and it was reduced in volume for 2002, which improved matters.

For a K 1.8 you will need about 5 to 6 litres of volume if you want it to breathe.

I'd have an air box of at least that size, maybe 20% bigger to get air in, slow it to take out the turbulence and not lose power.