Dual Plenum Design

[Alan_RHIT]

Anybody have the pros and cons of a dual plenum design? I have read a few papers but I still have a few worries about the true performance possibilities of this design. Any comments would be awesome.

[wagemd]

Originally posted by Alan_RHIT:
Anybody have the pros and cons of a dual plenum design? I have read a few papers but I still have a few worries about the true performance possibilities of this design. Any comments would be awesome.


Are you referring to 2 plenums in series or in parallel (ie 1 plenum feeding 2/4 cylinders, and another feeding the other 2)?

[Sormaz]

If I were going to do this, from a packaging standpoint I would want to have one plenum feeding cylinders 1+2 and the second feeding 3+4 however from a functionality standpoint, they should be split 1+4 and 2+3 as, at least on an f4i those are the companion sets.

Interesting...

(assuming parallel plenums on a 4 cyl and that my intuition is somewhat correct)

[Alan_RHIT]

Yeah its a f4i so i was thinking 1 and 4 and 2 and 3....

[Nath_01]

Are you talking about a dual volume plenum?
The idea has been tossed around our team in the past where there is a smaller volume chamber that is used for low RPM (better throttle response and less over run) and progressively 'switches' to a larger volume for high RPM, High power.

It was tried in the past, im not entirely sure why it didnt work.

It should be noted aswell that we run a single and currently our large plenum volume is a pain in the butt to get started (takes a few strokes to clear the plenum, pull some vacuum and then fire once the cylinder and exhaust is nice and full of fuel http://fsae.com/groupee_common/emoticons/icon_wink.gif )

I would be interested to hear if any teams have attempted this aswell!

[Alan_RHIT]

I was thinking more along the lines of a single plenum for 1 and 4 then a separate plenum for cylinders 2 and 3 the idea is that as one draws air the pressure is restored to the plenum before 4 draws air....at least i think this is the idea...but the low and high rpm idea is also interesting....

[Adambomb]

Hmm, sounds a lot like a dual plane intake manifold commonly seen on carbureted "V" engines. With those the idea was to increase the vacuum signal to the carb at low speeds, which sounds to me like what you're talking about. They did suffer up top though, I'm pretty sure you don't get as strong of resonance at high rpm. Pretty much all the max-performance V8 intakes are all "single plane" (like a typical FI intake.

As for other examples of similar designs, I remember the Opel V6 modified by Cadillac for the late '90s Cateras had this goofy set of trap doors in the intake to get multiple effective plenum volumes. They were trying to get "Cadillac low-end torque" out of the German V6. It had basically two intake pipes, two throttle bodies, two plenums (one for each bank), and the trap doors were in a 3 stage configuration: at low rpm, the whole systems were separate, resulting in what seemed to the engine like a smaller plenum with a longer intake pipe. Then in the mid-range a butterfly between the two intake pipes before the throttle body opened up, making it seem like single larger diameter pipe. Then finally at high rpm a butterfly on the back of the engine between the two plenums opened up making the two plenums seem like one larger plenum. I don't remember what sort of gains they were quoting, but FWIW it made it past the Cadillac bean counters.

[ST]

Ferrari V8's have an interesting system, 2 plenums each connected to one bank of the V. There is a throttle body for each plenum to atmosphere and a third throttle connecting each of the plenums together. Perhaps this gives them the top end power single plane V8's have with the throttle response of a split plenum.

Wonder if you'd get a similar benefit with a split plenum on a 4 cylinder with the restrictor?

[wagemd]

Originally posted by ST:
Ferrari V8's have an interesting system, 2 plenums each connected to one bank of the V. There is a throttle body for each plenum to atmosphere and a third throttle connecting each of the plenums together. Perhaps this gives them the top end power single plane V8's have with the throttle response of a split plenum.

Wonder if you'd get a similar benefit with a split plenum on a 4 cylinder with the restrictor?

In past years we have experimented a little with dual volume plenums, but its really hard to say how much of an impact it had. There are so many variables, such as cylinder pairing and manufacturing tolerances, that it can be a challenge to isolate improvements.

I think its definitely something worth looking into. You might try doing some Ricardo Wave modeling and physical testing.

[Nayrsiemanym99]

I am a new member to the forum so bare with me. Last year was my first year in FSAE but now I am the Engine Subteam Leader.

We experimented with the duel plenum design on our single cylinder engine last year. For packaging reasons we had two side branch plenums, one a small volume and another a large volume. This proved to be very difficult to start and tune for cranking and Idle. We spent weeks on our dyno trying different things but ended up not finding anything that work well every time.

When we did finally get it running and on a chassis dyno it proved very useful though. From just a simple Venturi into our engine the year before, we had a 8hp increase and far greater torque with two peaks in our torque curve (From the two volumes).

Its an interesting idea and there is definitely the potential for great things but it will take time to make it work properly. Go for the gold!

Ryan

[Demon Of Speed]

Originally posted by Nayrsiemanym99:
When we did finally get it running and on a chassis dyno it proved very useful though. From just a simple Venturi into our engine the year before, we had a 8hp increase and far greater torque with two peaks in our torque curve (From the two volumes).

Ryan

We run a single as well, how ever we run a single plenum design. Because of resonance we have two (2) peaks in our torque curve as well. I am wondering why you didn't have the second plenum set for a different resonance so you would get four (4) peaks in your torque curve. Please note I am not an engine guy.

[wagemd]

Originally posted by Nayrsiemanym99:
I am a new member to the forum so bare with me. Last year was my first year in FSAE but now I am the Engine Subteam Leader.

We experimented with the duel plenum design on our single cylinder engine last year. For packaging reasons we had two side branch plenums, one a small volume and another a large volume. This proved to be very difficult to start and tune for cranking and Idle. We spent weeks on our dyno trying different things but ended up not finding anything that work well every time.

When we did finally get it running and on a chassis dyno it proved very useful though. From just a simple Venturi into our engine the year before, we had a 8hp increase and far greater torque with two peaks in our torque curve (From the two volumes).

Its an interesting idea and there is definitely the potential for great things but it will take time to make it work properly. Go for the gold!

Ryan

Interesting... Multi-plenum is certainly easier to work with on more than a single cyl. On a single cyl, you could possibly gain more from a simple Helmholtz resonator branch off the airstream somewhere...

Depending on your intake and runner diameters, those 2 plenums might just be acting as 1 larger volume. Placing some sort of flapper valve between them would combine those 2 ideas and give you more tune-ability (abeit more required tuning).