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TR5/Early 6 DCOE Cold Air Box


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Hi,

 

I've been mulling this over some more and after making a few cardboard mockups, have persuaded a friend to draw the finished one up in a CAD program, we're cutting it on Monday and I'll TIG it up and fit it. To get around fixing issues I've removed the studs and will use bolts. I'll fit the lower (inaccessible) bolts first, slide in the trumpets (they're the ones that go into the throttle body locating the chokes) and then fix them in place with the top fixing and tab washer, I figure that'll hold them because it's a sung fit into the carb body.

 

Another friend has a metal spinning business and just happens to have a part that will do as a 75mm inlet trumpet with a nicely radiused end.

 

All that'll be left to do then is make up a carbon fibre lid with a cross section of a segment of a circle of the same diameter of the PI airbox, following the taper of the airbox rearwards, should be easy :unsure:

 

To make things even more challenging I'm planning a MK2... :wacko:

 

Stu

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Hi,

 

Great that they're still people out there thinking about this.

 

Must say I go with the guys that like Simon's homemade creation, seems to pretty much fill the available space and looks professional too.

 

The only issue I have with the open-front/open-top box design is, as Jean says, what a pain they are to fit.

 

I haven't got to the cardboard fabrication phase yet, but I had it in mind to try a three piece form of construction, similar to K&N filters. An open box section being sandwiched between front and back plates.

Hope that makes sense!

 

Peter

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Hi

 

Another way to do it may be to use some 3mm Ali sheet for a backing plate attached with countersunk screws to the carbs, this could have rivnuts placed so as to be easily accessible for mounting a box like jeans onto ...

 

Stu

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  • 1 month later...

Thanks for the comments guys.

 

Neil, I was thinking about that, I had read that a taper towards the rear helps maintain velocity, fingers crossed. The airbox is up pretty tight against the servo (about 1/4"), although I suppose I could increase the clearance around 5 & 6 by curving the box around the servo.

 

I came across a firm that produces curved ally tubes so I was considering a 90 degree bend coming out of the carb (which will just fit inside the box) then arranging each curved trumpet in a herring bone pattern (looking at the carbs), this would give the benefit of a longer inlet length. A lot of messing for probably not much gain, but it would be 'project' for when I finish.

 

My other thought, after reading an interesting article on tuning Lotus engines, is unequal length trumpets. It seems that by having two short and two long trumpets they get a wider, but slightly lower torque curve (the 'amount' of torque under the curve stays the same you're just altering the shape). By alternating the short and long inlets on the firing order you end up with longs on 1, 2 and 3, and shorts on 4, 5 and 6, which happily follows the shape of my air box.

 

Any thoughts, I'd be really interested to hear what people think.

 

Thanks Stu

 

Ps looking forward to Stoneleigh tomorrow, I'll be there armed with tape measure and camera hoping to get some idea of how the front screen should sit and where the various rubbers and seals go around the doors, backlight, etc, if I can persuade someone to let me loose on their car!????

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