custom air box - feed bore diameter and 1 or 2 feeds

Competition engines and ancillaries - general discussion
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smckeown
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custom air box - feed bore diameter and 1 or 2 feeds

Post by smckeown »

I have a questions regarding the size of hole for air feed on an air box.

I'm assuming, and it is an assumption, that there same theory applies to this feed hole diameter as the theory regarding inlet port diameter. i.e. too large a diameter will kill air speed. I have tried and tested port diameter and have a good compromise currently.

Now turning to my new airbox design, i'm after some advice regarding should I have 1 or 2 air feed holes (1 either side) and what their size should be.

If anyone has any good links or sources of information, or even better practical experience I would be most grateful

thank you
sean
205 8v Track car
Guy Croft
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Post by Guy Croft »

No, it's a different regime.

The airbox is the 'open volume' that the negative waves in the inlet tract will see and from where they will be reflected back to the cylinder as positive - giving good cylinder filling.

The duct to the airbox should be as big as you can make it - 3- 4 inches diameter. It's important to give the airbox a large capacity feed to keep it at atmospheric pressure.

GC
smckeown
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Post by smckeown »

Thanks very much for the reply Guy.

Would there be any advantage to running a feed from both sides as I have the room. All the airboxes i've seen only have one, so i would have assumed this would be for good reason.

Lastly, is there a benefit of the air feed coming directly from the front of the car, via cut out lights?

thanks
sean
205 8v Track car
smckeown
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Post by smckeown »

I managed to research more, once I found out the correct terminology in this area. I have since discounted trying to benefit from any ram air effect, via the front lights. I will be running a filter that is boxed off to prevent heat soak attached to the side of the airbox.
205 8v Track car
Guy Croft
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Post by Guy Croft »

Hang on.

You should definitely try and capture air from the forward motion of the car, proven ram effect over 70mph or so (trust me) via a well-shaped convergent intake duct on the front region, say spoiler, run that air via large pipe to a sealed airbox with large (say K&N slab) filter then to the plenum..

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smckeown
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Post by smckeown »

thanks for the advice. The main issue i'm concerned with with a feed from say the light is water getting sucked into the system. Specifically getting the filter wet and therefore reducing it's performance or restricting the system.

I havent seen any filter company mentioning performance when wet etc, I may have to make some calls.

Here is the airbox that has just been made for me, to house 8 injectors.

All images compressed so wont hurt the 56k peeps :D

Image

Image

Image

I'm expecting to habe a cone filter on the end for when I need the light (not very often). And then have a cold air feed from a cut out offside light most of the time, with an inline air filter along the lines of a bmc cda or K&N Apollo Universal Cold Air Intake System:

Image
205 8v Track car
Yugo_Turbo

Re: custom air box - feed bore diameter and 1 or 2 feeds

Post by Yugo_Turbo »

I think the best solution would be to take air from the front grill, just above the radiator ;)...of course if there is place above it.
That's the way the factory prepared SuperTurismo cars feed air to engine.
The panel filter can be used in that case.
smckeown
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Re: custom air box - feed bore diameter and 1 or 2 feeds

Post by smckeown »

like my old one you mean ?

Image

that one didnt allow to be mounted closer to the grill to facilitate inlet tract tuning (lengthening)
205 8v Track car
Yugo_Turbo

Re: custom air box - feed bore diameter and 1 or 2 feeds

Post by Yugo_Turbo »

Yes, use that as a base, and add a section which will conect it to the grill.
It should look something like this:
Image

Here are some more pictures od works race cars which have plenums lake that:

Image
Image

I hope it helped :)
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