Discussion: "Porting by Numbers" Darin Morgan

[Darin Morgan]

Wow,..

nice thread starting here, ..

Port shape Plays a significant role in the shock wave tuning
and it's effects.

Darin makes reference to shape, .. consider the difference in port shape from
a 23* small block head to a SB2.2 port.
The 23* is very low, has sharp corner radius and some very severe changes in
shape and area. The SB2.2 on the other hand has a very gentle sloping port
to the valve with a large corner radius, no sharp bends and no
severe changes in shape. The SB2.2 has a much better shock wave pulse.

Darin, .. have you used the pressure transducers in the chamber to
measure chamber pressure?, . . the one that is built into a spark plug??
Can't the data give an indication of cylinder filling and shock wave effects?

As for test pressure, .. it's been hashed over and over here several times.
here's what I have found, .. I use the standard 28" for most tests, ..
and sometimes do a second test at 40" to check for turbulence.
I didn't find any use flowing above 40" for anything, .. I tried over 50" on
some DRCE stuff and SB2.2 and didn't really find anything, ..
in fact buy following the turbulence is bad theory I hurt some heads.

Curtis

Yes we have used pressure tranducers and plug temps to tune with. Thats actually a funny story. we had three engineers in our shop and four laptop computers monitoring plug tip temperature, in cylinder pressure transducers and a multitude of other things. It looked like a gaming convention around the dyno room that day. Bottom line is, You cant tune off plug temp and you can learn some things with in cylinder pressure transducers but its an all consuming project and not one to be taken lightly. You really have to amass a couple months or years worth of data and only after you have a well established base line can you effectively draw a conclusion to any given changes. All to often we look at computers and software to give us the answers almost intuitively. Well, that just does not happen. With any new measuring device comes a learning curve and only after years and years of accumulated data and experiences are we proficient enough to make tuning changes based off that data.

After three days of tuning, we where right back where we started. Just not enouph time to acumilate data to work off of. If you use them every day, they could be a great tool.


Nothing is as simple as it looks. Its always twice as expensive and takes twice as long as you originally thought!

[MadBill]

I'm beginning to understand why SuperFlow's Engine Cycle Analysis package didn't exactly fly off the shelves. Race or run an engine lab; pick one..

[mike_belben]

Nothing is as simple as it looks. Its always twice as expensive and takes twice as long as you originally thought!

and then three more bills come in the mail that day. I'm finding R&D is unprofitable all the way up until the very moment when you sell the results to someone.

[Procision-Auto]

Race or run an engine lab; pick one..

I'll pick, if you fund either one for me?

Other questions:

How do these flow numbers react under wet tests? I hear so much about
flow separation, and wet testing.

Can you touch on the data between a dry and wet test? What fluid is used
for a wet test? Something similar in SG to the fuel used?

[airflowdevelop]

WOW!
Did everyone forget the square port intake on oval port head deal...a couple of years ago, that was the new bread!

Lets get real guys... Have computers replaced the real world!

Lamens terms: scientific method
1. Observation
2. Hypothesis
3. Prediction
4. TESTING


9. Remembering that the wheel is round! Don't forget what you have proved, build apon and understand.

Dennis

[Ron E]

WOW!
Did everyone forget the square port intake on oval port head deal...a couple of years ago, that was the new bread!

Lets get real guys... Have computers replaced the real world!

Lamens terms: scientific method
1. Observation
2. Hypothesis
3. Prediction
4. TESTING


9. Remembering that the wheel is round! Don't forget what you have proved, build apon and understand.

Dennis

I remember the oval port intake on the square port heads. They helped super-class cars with RT/60ft with no top end losses. But, I missed this version.

[cboggs]

Port shape Plays a significant role in the shock wave tuning and it's effects.

So in effect,if a port is "straight" i.e. no area change or taper,and the intake manifold tapers down to the gasket flange, vs. a fully-tapered-from-the-valve-up port/intake combo will tune differently (port volume/cfm being the same for both the tapered and straight port)?
What differences in tuning effects are you seeing?
Does the runner need to be more tapered,or longer/shorter than it would optimally be with a "straight" port/tapered intake manifold than a fully tapered combo?
How big an effect (in hp or %) would you think the difference to be with either combo,at the same cfm?

Sorry if I'm asking a bit too much today...have a headache and just don't want to think

Sorry it took so long to reply, .. just saw your post.

On your first statement, ... yes a strait port VS a port with taper
will pulse tune at a different rpm, .. and can effect it's "tune".
Everything in the shape and how you accelerate the air will effect it
in some way. I think there's a balance to be found here, .. between
taper and pulse tuning.

Differences are dependent on the application, .. the one I've been
working with over the last few months isn't something I can discuss.

I think the effects of pulse tuning can be rather large, ..

In the most basic terms, .. just like ripples from the rock in the lake, ..
anything that can disturb the pules can diminish their effect, ..
I think so anyway, .. so ports that have less changes in shape
like a SB2.2 have a better potential for pulse tuning then
something with many turns & bends.

Darin, .. I was involved in a chamber pressure test some years ago, ..
and I'm glad to see you have the same feelings I did at the time, ..
But I'd still like to find a way to measure this stuff, ..

Curtis

[rmcomprandy]

Geez RonE ... Mercruiser only has THOUSANDS of them out there in the narine market.
All these experts on here and no-one can offer a reason why this works.
It seems actual data and results are only sometimes accepted here, except whenever they dissagree with a good theory; personally - I'll believe the results.

[Ron E]

Geez RonE ... Mercruiser only has THOUSANDS of them out there in the narine market.
All these experts on here and no-one can offer a reason why this works.
It seems actual data and results are only sometimes accepted here, except whenever they dissagree with a good theory; personally - I'll believe the results.

Easy now. I'm not disputing your posts. I've just never heard of them. 1st guess would be that it applies to a more constant-RPM engine, which fits marine applications better than automotive. I seems like major puddling of fuel would result from the dam on the floor. It also seems the exposed edges of the head would shear fuel from the mixture further hurting the mixture condition.

I also believe results. If something works and doesn't make sense to me, it means I don't understand it. i'm trying to get by that phase on this right now.

[Procision-Auto]

Some ideas:

Are these marine engines injected? Where is the fuel presented into the
air stream? Close to the head port?

Do you think the oval/rectangular port combination has the same effect
on a carbureted engine as it would on an injected engine where intake
runner flow is comprised of only air?

[Sir Yun]

I reckon it is a bit of a hit 'n miss/bandaid afair. I have heard about 2/8 inch mismatching in the floor producing better power in the engines i work on. ..maybe introducing turbulence in the port on the floor did something to improve the very short SSR..who knows.

On the Mercruser I could be a multitude of things.. large slow (on a low RPM engine) ports that benefit from a bit of extra excitement to keep fluel suspended?? or maybe you end up a newly blown boundary ( as Mr Widmer seems to call it).

but on a more of less no compromise design i would put money on keeping things as orderly as possible in the port.

[rmcomprandy]

These Mercruiser marine engines are carbureted with a Q-Jet 4 barrel on a 180° intake manifolds. On both the B.B.Chevy and B.B.Ford engines the intake floors still seem to align; it's the rest that's WAY off.

The reason I keep bringing this up is that I don't understand either why it works but, SOMETHING must be happening here.

On one, I sort of port matched it by rounding off and funneling the head port about an inch or so past the flange to somewhat match the intake manifold and it lost LOTS of low end torque. I'm talking 1000 rpm to 2500 rpm though didn't change the max horsepower at all.
Whether it's just plain volume or air shearing or another pulse or just the engine seeing the sharp edge as the end of the runner -- I'm at a loss as to whatever the reason.
Bee's can't fly either 'cause they don't have enough wing area but surely they do.

[Darin Morgan]

These Mercruiser marine engines are carbureted with a Q-Jet 4 barrel on a 180° intake manifolds. On both the B.B.Chevy and B.B.Ford engines the intake floors still seem to align; it's the rest that's WAY off.

The reason I keep bringing this up is that I don't understand either why it works but, SOMETHING must be happening here.

On one, I sort of port matched it by rounding off and funneling the head port about an inch or so past the flange to somewhat match the intake manifold and it lost LOTS of low end torque. I'm talking 1000 rpm to 2500 rpm though didn't change the max horsepower at all.
Whether it's just plain volume or air shearing or another pulse or just the engine seeing the sharp edge as the end of the runner -- I'm at a loss as to whatever the reason.
Bee's can't fly either 'cause they don't have enough wing area but surely they do.

I am going to take a stab at this one.

The reason the low end TQ at 1000-2000rpm is better due to the mismatch is due to shear effect on the air fuel mixture. It atomizes the mixture at an RPM that is to low to instill any mixture velocity there by increasing burn rate and cylinder pressure. Go turn on your wet dry vac in the garage and pour a stream of water down the open ended sharp edge nozzle to visualize this. When wet fuel hits high speed air it vaporizes big time!

The reason it doesn't hurt the top end is because there is just enough volume and area to support the engines needs at those rpms. Put a bigger cam in them and they would more than likely choke.

I find it difficult to imagine this scenario taking place in any high RPM engine where there is sufficient air speed.

[rmcomprandy]

Darin - that's as good an explanation as any I have heard or come-up with myself.

Atomization is one of the few phenomina which can actually be helped by this. A few years ago I had to replace those heads I modified to get back to the same results as original and it has been in the back of my mind ever since like a bad penny.

Being that it is a low RPM, off-idle thing lends itself to this kind-of explanation.

[beth]

The secondaries of a quadrajet do a very poor job of atomizing fuel. Opening them at lower rpms always results in a loss of torque that does not occur with a similar flowing Holley.