Right, let's talk plenums/induction

[Pupp]

If it was desired to run dual plenums, each with a dedicated throttle plate, (say, one over each rocker cover), feeding the inlets individually from there, what would be the preferred cylinder combinations to feed from each plenum so as to avoid or at least minimise crosstalk/charge-robbing?

I suppose I'm thinking of something very similar to the set-up DNB runs but with (I think) a different order of silicone hoses to the 'trumpet base' (for those that can picture it).

No doubt someone will tell me this has been done before...


ETA ok... I make the least incidence of exhast/inlet conflict when 1,4,6,7 and 8,3,5,2 are fed separately. Going for a lie down now

Edited by Pupp on Thursday 11th February 21:25

[spend]

Thats only 180deg separation, and your cam has the adjacent inlets still open. You really need to look at 360deg separation to avoid the cross talk so that each cyl sucks back in what it itself blows out IMHO. Cliff has the only workable design I could come up with, basically a split level warren across the V

[zombeh]

Pupp said:

I suppose I'm thinking of something very similar to the set-up DNB runs

...

ETA ok... I make the least incidence of exhast/inlet conflict when 1,4,6,7 and 8,3,5,2 are fed separately.

Looking at the photos of Dave's crazyness and the standard manifold that's exactly the way his are.

[dnb]

I believe my crazyness (as Steve puts it) does achieve the maximum separation for 2 throttles (ie 180 degrees). To get 360 you'd need 4 plenums, and you may as well have throttle bodies.

[Pupp]

dnb said:

I believe my crazyness (as Steve puts it) does achieve the maximum separation for 2 throttles (ie 180 degrees). To get 360 you'd need 4 plenums, and you may as well have throttle bodies.

Cheers Dave... if I remember right, you're running an H404; did the twin plenum set up resolve any shunting you might have had?

[dnb]

It solved a lot of the shunting, however it created a couple of other interesting issues - the main one being an extremely sensitive (possibly over-sensitive) throttle. And the design of the throttle cable is unique to say the least...

[rev-erend]

I was using a M 404 and did not have any shunting .. but Mark Adams did a super fine mapping session to iron out the issue.

[Slow M]

Pupp said:

If it was desired to run dual plenums, each with a dedicated throttle plate, (say, one over each rocker cover), feeding the inlets individually from there, what would be the preferred cylinder combinations to feed from each plenum so as to avoid or at least minimise crosstalk/charge-robbing?

I suppose I'm thinking of something very similar to the set-up DNB runs but with (I think) a different order of silicone hoses to the 'trumpet base' (for those that can picture it).

No doubt someone will tell me this has been done before...


ETA ok... I make the least incidence of exhast/inlet conflict when 1,4,6,7 and 8,3,5,2 are fed separately. Going for a lie down now

Pupp,

look at this site, it'll make your head !
Please be aware that what intake system will work best FOR YOU, will be very much dependent on cam, port, valve and application specifics. I know there's some software available that would help but haven't played with (that part of) it.
To help confuse you more, some motor combinations actually "like" American style, single plane intake manifolds.

B.

[Pupp]

Thanks; I'd actually got Eliot's site bookmarked but it's been updated loads since I last looked. Have now played (loads) with the mapping and whilst there is still a definite low speed glitch when I think the fuelling gets messed up by plenum effects (just sub 2k rpm), it is now a load smoother and only occurs coming back on throttle after a spell of overrun or at steady low-load throttle. Quite livable with now and the extended rev-range post 6k with power still climbing hard more than compensates. On this cam, suspect TBs is going to be the only way to restore pristine manners