Inlet Plenums

[allanallen 528 2 Cars]

i'm making an inlet manifold for my supercharged mi, am i right in thinking that the plenum needs to get smaller as the cylinders get further away??? haven't been able to find much info on this subject so any help is appreciated.

 

I've seen a couple of different designs, one which has a steady taper down the full length of the plenum and another which has a shorter,sharper taper between the last 2 inlet ports and some with no taper at all.

 

I'm leanin towards the design with the taper down the full length as i'm led to believe as the taper gets smaller the air velocity increases so the inlet ports recieve the same amount/volume/pressure of air (???). Is this a load of bollocks?

 

Is the amount of taper critical??

 

any input appreciated as i haven't got a clue (as you can probably tell)

[brianthemagical 1]

you should probably be able to calculate it, if you know how. as the pressure drops towards the end of the plenum then the taper should idealy compensate for this but no doubt that the drawing in of air from the cylinders will have an effect. as of yet i don't have a degree in motorsport tech so i can't help.

[niklas 1]

I imagine you want less volume (= short runners & small plenum chamber) for a faster response. Anyone agrees/disagrees?

[allanallen 528 2 Cars]

I imagine you want less volume (= short runners & small plenum chamber) for a faster response. Anyone agrees/disagrees?

 

the runners are fairly short anyway, mainly due to lack of space.

 

As for calculating a taper, i wouldn't know where to start. Anyone else got any ideas? al

[M@tt 77]

sounds like your doing a similar project to me, i havent actually started any of the building yet though!

 

any way i've opted to use a cossie inlet plenum as it has the inlet in the centre and the throttle body points to the left which is better for the pipe work routing.

 

 

It doesn't have any sort of tapering in it so i'm not sure how much of issue it will be but as cossies can run big BHP with these i wouldn't have thought it would make much difference especially as the distance the air is travelling over isn't that far once inside the plenum, although i could be wrong (never really paid any attention in my fluid dynamics course!! )

[allanallen 528 2 Cars]

 

i guess the tapering wouldnt matter so much on the cossie manifold because of the inlet being central. Its a nice looking piece of kit though, dont think i could squeeze that onto my motor though

 

I'm just gonna put a steady taper onto my manifold and 'suck it and see' to how well it works. theres nothin like a bit of improvisation. al

[M@tt 77]

bit of a thread revival but if you have a look at this months PPC (1 in readers cars, 1 in walkers workshop) you'll see 2 examples of tapered inlet plenums for forced induction, so i take back my previous comments about it probbaly not making much of a difference (they look like factory plenums)

 

The first is a 1.8 Audi Turbo lump that was dropped into a 1.2 clio and the second was a very very bling BMW. I'll try and scan the pics if i can get my scanner working with vista and put them up here.

[Malachy 0]

ill find some info out i have on this for you once i get my scanner working too, i too am designing a plenum but for a turbo setup.

 

edit:

here ya go if your interested in the runners bit ill scan that too

 

http://www.aoxv99.dsl.pipex.com/ipd1.jpg

http://www.aoxv99.dsl.pipex.com/ipd2.jpg

http://www.aoxv99.dsl.pipex.com/ipd3.jpg

Edited April 14, 2007 by Malachy

[DrSarty 90 1 Cars]

This is when one of my forum new abbreviations could be genuinely used: NAPL =

 

Need Another Puma Lecture

 

This is when I would hope Dave Baker's obvious engine/flow/dynamics knowledge could be extremely beneficial to us all.

 

DrS

[allanallen 528 2 Cars]

ill find some info out i have on this for you once i get my scanner working too, i too am designing a plenum but for a turbo setup.

 

edit:

here ya go if your interested in the runners bit ill scan that too

 

http://www.aoxv99.dsl.pipex.com/ipd1.jpg

http://www.aoxv99.dsl.pipex.com/ipd2.jpg

http://www.aoxv99.dsl.pipex.com/ipd3.jpg

 

cheers for this, i'm a bit crap with computers though and your links are to small to read and if i print them i only get half a page. can anyone blow them up or something.......please, cheers al.

[sonofsam 5]

If you hover your mouse over the picture you should see a small magnifying

glass appear, click it and it should make the image larger, looks like an interesting read

[allanallen 528 2 Cars]

If you hover your mouse over the picture you should see a small magnifying

glass appear, click it and it should make the image larger, looks like an interesting read

 

top man

[allanallen 528 2 Cars]

interesting stuff, thimk i'm gonna have to alter mine a little. Ive got the slope to the end runner but it stops sharply after it. i'll have to see if i can extend it a bit.