dual-port mega-swirl?

[Anonymous]

New to this site, and delighted to find y'all! New to any site, actually, being a computer-challenged olde phart, so if I should violate some protocol or other, bear with me.

Do we have a resident expert on cylinder head airflow, swirl and tumble, etc.? I've been thinking about the divider, the port-splitter, in an Offy Dual-Port manifold. Consider one leg of this manifold. I'm thinking a guy could weld an extension to the port-divider. The extension would reach into the head all the way to where the port turns the corner, almost touching the valve stem. And, ta-da, he could put a twist in the extension . . . I think I'll refer to it as "the splitter" from here on . . . put a twist in the splitter to impart swirl in a non-swirl head.

The first negative is that if you got the length, twist, bend, or taper of the splitter just a little off of the optimal setting, you could really kill airflow. Of course, this project would be for a torque-motor anyway; you wouldn't use a Dual-Port on a performance engine. As amateur ginders-of-ports, we already worry about getting the short-side radius just right so as to avoid the dreaded "detached airflow", and my splitter could sure detach the hell out of the airflow if it were a little off!

But what if a properly twisted port-splitter imparted a strong vortex that flowed around the valve head even better than the normal straight-through airflow? Didn't Coanda, the French engineer from Ricardo's time, achieve an effect like this with exhaust pipes?

Of course, the Aussies and Kiwis would have to twist their splitters the other direction . . . .


or am I wrong?

 

[xctasy]

Seattle Smitty said:-

Of course, the Aussies and Kiwis would have to twist their splitters the other direction . . . .

Absitively!

Welcome SS! You'll just love it here then!

These are my opinions, based on my experience with Fluid Mechanics. Hope I haven't missed the details you have intimated. Looks like you have put substaintial thought into it.

The splitter may work well if you could do an appropriate check on the velocity and flow near the valve, and deal with the behaviour of the fuel particals on departing from the two ports to the valve.

I've seen Australians experiement with Chevy 9 port L6 port dividers, but at the port, velocity goes up as the air fuel mix starts to undergo compression. The flow speed (Q, the velocity) is proportional to the Area (a) of cross-section times the Volume (v) of air at the start. Simple Bernoulli equations will show you what happens. In practice, the fuel/air mix creates a streamiline which will condense atomised fuel, and it will behave like a jets wing in the presence of a humid air layer. Fuel would puddle, and fail to take the turn. The fuel molecules would reform, and behave like rain drops on a gutter.

Big, curved, dull forms are more areodynamic, and I guess the idea that one could guide the flow into the right spots would be fine at a low speed, but it would fail at the 200 to 300 feet per second level.

If you look at the ports of Chryslers late 1990's Magnum 318/360 and early 1981-84 173 Carb Chevy 60 degree V6's, you'll see the use of ramps to create an unstable zone at the base of the port to ensure the fuel air mix negotiates the short turn radius. This was a trick used by David Vizard on his 'Apple Port' 2000 cc Pinto heads in the early 1980's. Rather than cast a two plane guided intake port as you deciribe, the chapps at Ford, Mopar and the General have looked into this.

The engine which would most benifit what you are descrbing would be the 2300 Lima OHC four found in rear drive Fords. If ever there was an oddball intake design that could use the Offy dual plane port transfered into the intake port, it would be that one.

Hope that helped out.

 

[Anonymous]

xtaxi

I feel like a real man of the world now, since that was my first-ever posting of any kind to any website, and yours was the first answer. Had to open a Henry Weinhards (local beer) to mark the occasion.

I'm just a dumb welder, without enough physics to rule out what might be obvious impossibilities to an engineer. Your point that the fuel would come out of suspension makes intuitive sense to me, although it makes me wonder when the effect starts. The primary ports of the Dual-Port manifold are already very small, and velocities very high at or before W.O.T., so does the fuel want to come out of suspension anyway, even without any added gizmos?

My suspicion has always been that the Dual-Port was a clever add-on, but was something that would better have been incorporated into the original engine design, especially as part of a four-valve head design. Nevertheless, what we are left with, while necessarily sub-optimal, makes for interesting home-brew experiments. If the factories built perfect engines, what fun would that be?

Back to my port-splitter, and agreeing that fuel-separation would probably render it useless in any case, tell me about airflow alone, and my uninformed speculation about inducing a vortex around the head of the intake valve. If, repeat, If it were possible to get a whirlpool effect going (in the tiny amount of time available), would that increase the flowrate or choke it down? I just don"t know the physics. But I do remember a simplified drawing of a Coanda-designed exhaust pipe from the 1920's that (I thought) worked by creating a vortex. Coanda found power increases on a couple of test engines, but I have never seen this invention applied anywhere. If I knew how to create a drawing here, with sweeping curves, I'd post it. It looks like it could be incorporated into a 2-stroke expansion chamber, which I intend to try, once I've done some research on Coanda's original idea. I believe Coanda went on to pioneering laminar-flow studies.

 

[xctasy]

Firstly, the airflow techniques are best talked over with a plane technician. Someone who works with airflow everyday. I don't. I steal and plagurise all my info from other sources, then sit down and suss out what lines up with the physics. Going right into the math will mess you up, the main idea is know the principals.


I'd look at the ancient Pommy guys. I'm gonna go under my house, and PM you a list of the guys I have learned from most.

They are absolute nuts who have some bizare ways of port-mismatching the stock intakes to create controlled vortex intakes, ehxasts, and intake ports.

All I learned about gas flow comes from:-

a) an English book 1980's called Practical Gas Flow, where an air craft technician applied his aero experience to little Limey Ford Escorts. Made a home-made flow bench, and did Silcast mock-ups with Plaster of paris, and then found out what worked.

b) David Vizards books. A briliant Anglo American guy who is a typical theoretical English engineer... who then got his hands dirty and started working in the real world!

c) There is another later book on Flow Management, Pommy again. It's a 1997 book. It is very good.

I'll get some of the details together, but some of the books are out of print becasue people would rather look at EFI books which no-one can afford, than take simple instructions which anyone could copy.


You Americans lead the way in flow measurement, cams, and intake manifolds, period. All flow managaement is still done in CFM, and thats proof! The cash-stapped Poms then beat the crap out of the rest of the world because they use there technoolgy on little engines. In the USA, big engines like mountain motors rule, and it clouds what is happening with airflow. You could have a 460 with really bad heads loosing 100 hp on some of the better ones, and then make up for it with a brilliant cam and manifold because you've got the best intake and cam guys in the world. With tiny engines from Englishmen who race in the weekends on limited funds, it creates a funny atmosphere where quaint Poms excell. They sit behind there pint on Guiness thinking how the hang they are going to beat so-and sos Mini Cooper S by shear trial and testing. In Australia, New Zealand, USA, Canada, the testing is done on bigger engines by teams or people with bigger budgets, but we loose site that all were trying to do is make a better fire pump. I get more sense out of back-yard Poms becasue they argue and winge more about what they know. The rest of the world, even the Australasian AVESCO and Nascar, IndyCar, etc, are less inclined to take a risk on bizare ideas becasue the team boses, accountants or rule makers may not like it.

Any way, these English guys do use swirl inducing ramps and techniques just as you describe. They check operation of the quirky ideas on little engines that they can afford to modify in a week, apply the technique, and analyse it. One weekedn they may weld up a cylinder head with a blob of weld on the intake, then they drive around in all sorts of club events, and verify if the change has given them power and economy. It's kind of hard to ananlyse the effectiveness of a mod on drag strip only running, or on wide open tracks. The English are stuck with no garage room, and cars which they have to drive to the circuit, or test and develope all day just to qualify.

I have seen Raymond Mays Swirl intakes on V12 jags, and the HSC chambers on 2.3 and 2.5 Ford front drivers, the ill-fated 1986 EFI 5.0 heads, the late 1986 to 1993 X-flow Ford heads use swirl inducers work well. They often loose some hp, but gain massive amounts of efficiency.

Best person to talk with would be Mark P. This guy havs dealt with CVHH Hondas and Stratafied Charge Engines which were being developed in the 70's to get by emission and corporate fuel average regulations.

Maybee FrenchtownFlyer could help out. He's a 300 For guru!

another one is Panic. This guy is a Mopar man with one H-U-G-E list of technical articles. He follows the info and looks at text book and imperical precedent. That means, if it works, he p[ublishes it on his site. Have a look and use it! I've found that his articles are the best to start with.

Last thing is this. There are no new ideas...only old ones reheated.

If I was you, I'd grab and old junker F150 , Mustang 2.3 or Tempo 2.3, and have a go making a split port you describe work. The 2.3 ohc engine can take the dual plane Offenhauser intake designed for a 390 cfm four barrel on the earlier 2.0 liter Pintos. The Offy manifold for 300's is fairly cheap. The Tempo has a seperate intake which you could cut and section at a minimum of cost. There are plenty of junked heads which you can cut with a band saw, and do a mock-up of your ideas without spending big sums of money.

 

[Anonymous]

Since planes have been mentioned, I'll stick this in.

Couple years ago I became interested in ultralights. I remember reading an article with regard to the installation of pairs of small ribs in a slight V on the upper wing surface. The idea is to create a small flow of very fast moving air between the ribs that would flow over the surface of the wing to prevent stalling. I believe they were known as Vortice Generators and were actually standard fare on some large scale commercial aircraft.

The short side curve of an exhaust port would/should/kinda-sorta maybe have the same problems with breakup of low speed air that causes stalling of wings on planes. This may or may not have bearing. But if you could stabilize the low velocity airflow, you could probably keep your fuel in suspension. This might allow you to run a port larger than normally acceptable for low R's but big enough to really let it sing.

Idea is probably half-baked, and no good to begin with, but think it over and see if you like it.

 

[Anonymous]

http://142.26.194.131/aerodynamics1/controls/Page4.html

http://www.bcchapel.org/pages/0003/Vort ... ators.html

http://www.thomasaviation.com/172175.pdf

 

[Anonymous]

Heathdaily

I've been around airplanes for a long time, though I hadn't seen those links you posted. The kit for the C-150 looks interesting; I'll get back to it another time.

The port-splitter I had envisioned would not work in the manner of aircraft "vortex generators" (which I think are mis-named), even though my idea is to create a vortex, a whirlpool like the one that's formed when you drain your bathtub. By contrast, aircraft vortex generators are analogous to roughing up the surfaces of an intake port. You've noticed that most of the advice you've read about porting over the last 25 years says do not polish the ports. What you're hoping to avoid is a thick "boundary layer" of very slow-moving air that has the effect of reducing the size of the port. Some have suggested "dimpling" the port surfaces (where you can reach!), possibly with a very small, like 1/8", rotary file to get a golf ball surface. I've done this on some 2-stroke engines, but of course I've always made other changes at the same time, so I've never isolated the effect of dimpling. I keep putting off building a flow-tester, which is inexcusable because it is a simple project. One thing I can say is that it's easier to make neat-looking dimples in aluminum than cast iron. A way to make raised dimples is with a center-punch. Raised dimples would, I bet, be effective on the short-side radius of a 4-stroke port, well, any port with a turn, such as up in the intake manifold. And raised dimples over the surface of a short-side radius would (should) work just like aircraft vortex generators, to prevent detached-airflow or stalling. But how do you center-punch a port? Some kind of very compact, hand-held pneumatic jackhammer with a right-angle head?

I remember Smokey Yunick writing that the best shape for the short-side radius was not a smooth sweeping curve, but a succession of small flats such as you get around a valve-seat after grinding it to three or four angles.

I'm still wondering about that bathtub drain . . . .

 

[Anonymous]

xtaxi

I've got a copy of Practical Gas Flow being held for me at a used book store. I already have two of Vizard's later books. He would seem to lead a great life: run experiments on the dyno all week, and blast around a racetrack with other amateurs on weekends!

I've been searching for a very old magazine article on Coanda's exhaust pipe investigations. I know I have it, somewhere . . . .

I share your appreciation of those Englanders who are willing to get dirt under their nails in order to wring the last bit of power out of small and unpromising engines. I was at a hot-rod show recently, and somebody showed up with an old Austin Mini. Somebody was snorting at the little bitty engine with it's crappy siamesed exhaust, and I said, "You ought to go to the track and see what fifty-some years of racing development can do with an engine like this . . . these cars absolutely haul ass!"

 

[rbohm]

8) having met, and had him as an instructor, david vizard, i can tell you that he is brilliant, and well versed, and funny also. if you want to encourage a swirling airflow in the ports, you want to try to emulate what the factories are doing these days as best you can. however they are generating their swirl as the a/f mix enters the chambers, rather than try to induce a swirl in the ports. you can generate swirl in the ports, but you tend to lose airflow that way, and that hurts performance. also if you try to induce swirl as the mixture enters the chambers, becareful again as to how you do it. the early 4.6 sohc heads(91-98), while flowing very well above .500 valve lift, has poor low lift flow due to the swirl generator ford cast into the head. cylinder head guys have found extra power by removing the problem section.

 

[Anonymous]

Man, I wish I had a Henry's. I used to live in Portland, but they don't have em down here in Atlanta.

-Dan in Atlanta