Just a quick one.. does a turbo inlet plenum need to have internal trumpets ?? or can the plenum just attatch to the carbs trumpets ??

cheers Alan

The plenum on my Rotrex blackbird is basically an alloy box which sits on the tb's.

I think you would ideally have smooth airflow into the ITB.

I was only looking t this myself last night as I was wondering whether it would be possible (albeit modified and sealed) to use the orginal airbox as a plenum?
I think that they should stay on, but that there proabably not that much differenc being under pressure

Is the fireblade airbox not just plastic tho ??

The idea of fabricating a plenum isn't bothering me I would just like to know the best design for it before I start chopping

quote:

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Originally posted by tompat3463
Is the fireblade airbox not just plastic tho ??

The idea of fabricating a plenum isn't bothering me I would just like to know the best design for it before I start chopping

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Mine is ally and split so I had to pin at 6psi !!!

I doubt the standard plastic one will hold together at 10psi, thats a lot of pressure at 6psi I am pushing 200bhp which must be near the limit of the gearbox.

I made trumpets for inside mine, do not know if it made any difference but the do slot into the front of the TB's. I welded into the plenum, leaving 3/8" proud which slots into the TB's then glued in with silicon

[Edited on 21/3/12 by mark chandler]

I have read somewhere that trumpets inside the plenum make for a smoother boost delivery

On the same note a cylindrical plenum with entry at one end is also unsuitable as the first cylinder that the boost comes to gets all the brunt. That's why u see conical plenums rather than straight tubes. I do like the idea of the plenum being the shape of the oem box but as mentioned doubt that the abs would be up to the job !!

Al

Trumpets are better than no trumpets, and if you're designing from scratch you may as well incorporate them.