Side entry plenum design

[Charlie]

Due to packaging constraints we are running a side entry plenum this year. I've done some simulation work and still am seeing a lot of variance between the center and outside cylinders vs. our old center inlet design. Not much seems to work, in fact the cylinder-style design seems best (though not by much) in the usable RPM range.

We can always trim the cylinder individually, and probably will, but anyone care to share thier methods for equal flow? PM is fine if you prefer. I need to build this this weekend and am pretty much pulling my hair out at this point.

[Brent Howard]

What is you plenum volume??

Brent

[Charlie]

All my modeling was with a 1400cc plenum, not including the restrictor.

[Dan Deussen @ Weber Motor]

Charlie,

we are also running a side entry log this year and I can only confirm the variances. In our case they mainly occur under partial throttle and outside of the power band but I still used four widebands and trimmed each individual cylinder to run at the same A/F ratio.

http://cs.svsu.edu/~dsdeusse/dyno.jpg

I am not sure what other options you have. EGT's usually help quite a bit, if you don't have mutliple widebands available. If you only have a single wideband available, I guess you could trim each cylinder on a one-by-one basis.

Just out of curiosity, what intake are you running on the car that you posted in-car footage of? It seems so scoot along quite well http://fsae.com/groupee_common/emoticons/icon_wink.gif.

[Gary]

hey charlie,
What about if you taper your plenum to counteract the head loss across the plenum due to friction, turbulence and area changes on entry. By placing a slight taper the velocity of the incoming air will increase, aiding in the filling of the far cylinders hopefully producing an even pressure distribution across the four runners. The taper would have to be calculated depending on the amount of pressure difference you are observing across the log type plenum. I have seen this technique used in a few production cars. Just a thought. See how it goes on WAVE might give some interesting results.

[V2-iacoto]

hi, guy,
we have tested the intake system with Ricardo Wave. We would use a 3 litres plenum (intake pipe and restrictor included), with wich we have more torque, but we don't know if the quickness of the egine will be lower.
Someone has used a 3 litres total plenum??
How is the quickness of the engine??
thanks

[Vector006]

would some sort of balance tube arrangement work? By linking the far runner to the first runner by a small rubber tube, so it gets air on the intake stroke from the pressure wave of another cylinder. I dunno. Or: use a turbo! (jk)

[Charlie]

Thanks for the replies and emails I've recieved on this.

A tapered plenum is what I've generally seen from teams who I assume have some good reasoning behind thier powertrain.

However in the simulation I've done in the 10K+ range the taper makes distribution worse. This is still just simulation though.

Our previous plenum (http://www.eng.auburn.edu/organizations/SAE/AUFSAE/03scales.jpg) was trapezoidal with a center inlet, which made it easier to physically test for cylinder distribution.

Anyone with a tapered side entry intake care to share thier design reasoning/testing here or in private I would be very interested to hear about it! Thanks...

[Matthew]

2 questions charlie:

Why do you desire an even distribution between cylinders?

What have you used for simulation?

BTW - our program had a non-taperd side entry in '03 and will again in '05

[ben]

Our plenum is side entry but differs from most others I've seen in that the side entry section and the runners are all tangential to the main plenum cylinder. I'm not pretending to know what's going on inside, but we have consistantly been around 78 - 80hp since adopting the design.

Ben

[Charlie]

So suffice to say everyone is merely guessing or doesn't want to share I guess.

Why equal distribution? Should be best for power and economy the way I see it. Maybe the difference is negligible but differing airflow means differing requirements for timing and fuel to get best results. Very difficult to tune each cylinder on its own as accurately as the whole system if you know your distribution is right.

[Popeye]

What about changing the inlet runner lengths insidehttp://fsae.com/groupee_common/emoticons/icon_redface.gifutside (ratio) the plenum.

Pops

[SimonUK]

Our inlet plenum has a normal 'feed'.

In CFD modelling side entrys caused no 3 and 4 to have less air than the other two.

[Matthew]

simon - what kind of CFD modeling?, we here have access to CFD-unsteady simulation thru WAVE (haven't used it much though - kinda processor intensive)

we've always noticed (on the dyno and in 1-d simulations) that cyl's 1 and 4, and 2 and 3 seem to work together (sim temps(dyno) and voleffs(simulation)) on a side entry plenum.

[nogaro420]

Hey Charlie,

I was just wandering if you thought about incorporating velocity stacks into the design at all, and whether you ahve tampered with hemholtz tuning? It looks as if your plenum might be too small to do that.

Again one of our past teams experimented with a side fed plenum that tapered. Not sure on the results that it produced but i will look it up.

V2 - We used a 3L plenum last year, the quickness was fine, we actually had a problem witht eh throttle response, it seemed to reach full throttle too quickly, but thats another story.

Brian

[Charlie]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by nogaro420:
I was just wandering if you thought about incorporating velocity stacks into the design at all, and whether you ahve tampered with hemholtz tuning? It looks as if your plenum might be too small to do that.
<HR></BLOCKQUOTE>

Sure, absolutely. The plenum bottom is plenty big to incorporate velocity stacks, and helmholtz is about the most basic intake design step IMO.

[gus]

last year, we went to a conical plenum. comparing it to center and side inlet "log type" plenums, it flowed far better. COSMOSFlow shows individual flows varying by less than 5%, while we saw over 20% variation with logs.

http://cyclone-racing.jarviscomputer.com/albums/Lucky/105_0516_IMG.thumb.jpg

[nogaro420]

hey charlie,

can you recomend and good literature on hemholtz tuning. We have some stuff here at school but everything says something different.

I looked at your pic of your intake also, we have an almost exact replica here in our shop from a few years ago, any complaints about feeding the air in from the top of the car as oppsed to the rear?

[Sam Zimmerman]

If you want to look at only Helmholtz tuning, some items I have gotten through inter-library loan are:

The Two Types of Resonance in Intake Tuning - Thompson, Michael P. and Helmuth W. Engleman ASME January 31, 1969

Design of a Tuned Intake Manifold - H. W. Engleman

The Tuned Manifold: Supercharging Without a Blower - H. W. Engleman

Surge Phenomena in Engine Scavenging - Ph. D. Thesis, U of Wisconsin - H. W. Engleman

Perhaps Charlie can give you a wider selection of authors but every paper I have read about Helmholtz tuning is a regurgitation of these pieces with no real advances so I figure you might as well go directly to the source.

[andrewd]

question:

for those i'll informed, such as i, what are velocity stacks????????????????

[Sam Zimmerman]

The runners or intake pipes.

[Charlie]

A velocity stack is just a properly radiused inlet on your intake runners.

[Sam Zimmerman]

You have velocity stacks on that maverick, Charlie? http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Charlie]

Its got a carbmajurator on it. Much more sophisticated than EFI, its like NASCAR uses. http://fsae.com/groupee_common/emoticons/icon_wink.gif

[Chetan]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Charlie:

http://www.eng.auburn.edu/organizations/SAE/AUFSAE/03scales.jpg was trapezoidal with a center inlet, which made it easier to physically test for cylinder distribution. <HR></BLOCKQUOTE>

How was the air distribution with that? We're doing something very similar but smaller due to packaging reasons.

[MattW]

from what i hear they help out with upper end hp and whatnot....here is a pic of one with a k&n air filter on tophttp://saintscarclub.homestead.com/files/Velocity_Stack.gif

some of the old school muscle cars used them...or tunnel rams http://fsae.com/groupee_common/emoticons/icon_biggrin.gif