Plenum design idea

[TurboRA28]

Hi all, I need to make a plenum for the 1mzfe engine.

It needs to be super duper flat. Not much bonnet clearance.

I am talking like 6 cm in height, but have plenty of width..

So I am thinking a very flat oval kinda shape.. Height 6 cm, width 20cm and 32cm long.

Is this acceptable having no height in it and hence not much air space above the runners? All the volume is in the width of it really..

Suggestions?

Thanks
Joel

[JustenGT8]

6cm is cutting it fine but assuming your bellmouths are machined into the baseplate it should be OK....you want at least 2 inches so you make it What would the total vol be though?

[TurboRA28]

Ahh I remember that rule of thumb now.. Been too long since designing manifolds..

I am struggling to work out the volume of an oval cylinder shape?

[JustenGT8]

Just break it down to a rectangle and 2 semi circles...near enough. Remember to include the runners down to the back of the valve too as all counts as 'plenum' vol You should make 4-6 litres easy which will be enough.

[SillyCarS]

assuming the angle of the runners to the plenum isnt too great i cant see any reason why it wont work well, also with a lower angle u'll have more room to place ur stacks inwards. are they offset or will they sit opposite?

[TurboRA28]

I want to retain the lower half of the manifold so the runners are in a straightish line ..

The big challenge I see now is being able to get to the bolts to join the 2 halves together once this top section is made.. As the oval shape would cover access to the bolts..

Whats the current thoughts on internal raised bellmouths vs flush?

[SillyCarS]

its the radius of the bellmouth that makes the flow laminar, if anything having it flush will elimante the areas at the base of the runner (that protrudes into the plenum) at 90 degrees that will cause stagnation

on the other hand i dunno if you would get an eddy formation due to the flow along the wall

give me a min and ill do a quick paint on what im talking about

[SillyCarS]

ok, i hope this makes sense. and show in one is why i ask about the offset

[JustenGT8]

Flush is better for you in this case no question....easy way to do it is with a router bit believe it or not

[TurboRA28]

wood router bit?

[JustenGT8]

wood router bit?

Yup but a tungsten carbide one - 13mm radius wood bit

[Norbie]

A friend of mine made a custom plenum for his VG30, and for clearance reasons it had to be wide and flat. He had all sorts of problems making it strong enough though, as the pressure changes inside the plenum made the "roof" flex in and out until cracks formed on the edges. This is something to keep in mind when you design your plenum, make it out of thick material and/or build in plenty of internal supports. Even a relatively small pressure differential can have a big effect on a large surface area.

[jezz]

Joel,

Have you looked into the Honda accord V6 manifold ?

[TurboRA28]

You dont happen to know what year that is do you?

[WHITCHY]

Hey dude, if my google skills don't let me down, its 1998-2002
this style
http://cgi.ebay.com.au/1999-Honda-Ac...item518fb3efd2