slate blue

By Greg BBRD
Ok these are Nascar Port molds, they don't make this overly clear but if you look close before the seat area you can see a reduction in that area. You can also see it in the stock mold.



Here's some more of Darin's work, it is a Nascar SB 2.2 Chevy Head



This area near the seat you refer to Greg is the throat, you don't get it on 4V engines, 2V engines need it for turning the air at low lifts. Different sized throats are used to alter the flow curve, tighter throats for better low lift numbers in general.

Again you can see how similar this port is to my port, as I said I didn't copy the Suzuki port but it is very similar, however I did copy or tried to copy the features of this port. Obviously the chamber is the wrong way round on our heads. This is where my friend is planning to experiment with changes to the chamber. The diffusion of the flow most probably will have considerable effects. For this final flow test I have played with the chamber also. Sometimes you do go backwards, this port is very sensitive. I suppose this is the reason it is called an experiment!



You can see how the short side is straight, no throat in that area, flow will go backwards if there is a throat there. N.B this area (the throat) is round, mine is 48 mm in diameter. Also there is no throat on the very long side as the flow has momentum in that area. It is the sides that really need it. I have changed the throat area in tests.

The pic also shows the worlds most efficient port too! That is on a flow per sq" basis. Peak flow around 114 cfm per sq" of valve area at 0.800" . Note the cant on the intake valve. Our wedge heads don't have that, the flow cannot be equaled with a wedge head. If you plug in the 4V Porsche head valve area you will see how good that Chevy head is.

Those heads, SB 2.2 flow around 99 cfm per sq" at 0.500". I have achieved 85 cfm at 0.500" and 97 cfm at 0.800" I am hoping we come out at 85 cfm at 0.500" and 100 cfm at 0.800" That then hits the bench marks for max flow of a wedge head. It should also get me up to around 315 to 320 cfm at 87% of cam lift or peak piston demand.

On the weekend I will try to draw the intake system, when you see it, I think you will like it, I think everyone will like it, it is conventional in design, spider intake but like the port key changes to assist with flow. It will have a consistent 2 degree taper to the mouth.

To beentherebaby, I am being conservative with airflow numbers, that is running highish airspeeds and my throat is 88% as you would know that is conservative, more of a street port not an all out race port.

Greg

slate blue

O.K another small update and good general info for the bank. This port was 5% bigger than the previous port, it is the one that is on the right of the three port moulds. I was hoping for better results. However I need to qualify how I do the development to make things clear.

I develop two ports and always leave the best one. The port that we were working on had its chamber opened to 104 mm where my pistons are for a 103 mm bore. So I closed the bore down with some putty in the head. This shrouds the valve and cuts the flow. So the last test was down on this bore so the numbers may be a bit artificially high, not much but some.

I probably took a bit too much out of the short side, again not too much but say 2 mm and that can make a big difference when you are chasing small gains. I also had a play with the chamber but I think I screwed up just don't know how bad? That is what the flow guy said to me today. The fellow providing the main technical help has not seen it yet and I will let him sort out the pressure recovery aspect. That is not where there is the biggest deficit in design.

Below is some info from a valuable source, Darin Morgan. Here's an except and he is talking about race engines, you can't run 55 degree seats on the street.

Quote:

There are many proponents of the " flow curve must match the camshaft lift curve" theory but I am not one of them. Some people still believe that if the camshaft has a maximum of .700 lift that the area under the flow curve must be maximized in this area as well and anything that happens to the flow curve after .700 lift is of no consequence. Nothing could be more incorrect I assure you! Its like that old theory about 30 degree seats. They flow more down low ( .050 to .350 lift ) so they should make more power for cam profiles at or slightly above .400 lift because they maximize the area under the curve in that area,right? Wrong. You can put a properly designed 55 degree seat and chamber, decrease the flow at .050 to .400 lift and make more power with cams with only .400 lift. You have to design the thing correctly and its tricky. You cant just throw steep angle seats in any head and have this work. You must have convex chambers and good pressure recovery in the chamber or its disastrous. The steeper the seat angles and the larger the throat area, the more important the chamber design becomes.

You turn the air less, use less energy doing so.
You maximize the potential flow in an area more conducive to flow from a piston speed stand point.
You have proper pressure recovery in the chamber ( Equal exit velocity around the entire circumference of the valve head. A controlled deceleration of the air like a venturi divergent angle.)
You get more air fuel mixture in the cylinder.
It makes more power.

That's my theory and I am sticking with it until someone can come up with a better one.LOL

So that is encouraging on a couple of fronts, one I have more gains to come from chamber work and when you see the flow curve you will see that above the peak cam lift is some big numbers which Darin is quite keen on. I was always designing my ports to peak near my peak cam lift. Darin does say in his CD airflow secrets that any port that backs up in flow numbers is disaster for power. I guess the fact the the numbers still rise is just taking that theory a bit further.

Anyway he goes on to publish his flow numbers from various engines, mainly SB2.2 orientated. Remember they are canted valve heads.

SB2.2 4.000 bore 2.070 valve, 29.5cc chamber, for small 4cylinder comp eliminator engine
____________________Porsche 928 head 4.055" Bore and 2.10" Valve
.2 136_______________0.200" 135
.3 227 ______________0.300" 191
.4 297 ______________0.400" 244
.5 348 ______________0.500" 281
.6 360 ______________0.600" 314
.7 371 ______________0.700" 336
.8 382 ______________0.800" 346 _____This is 100 cfm per sq" of valve area
.9 384 ______________0.900" 348
1 388 ______________1.000" 350

SB2.2 Standard NASCAR head from 2002. 48cc chamber 4.185 bore 2.180 valve

.2 161
.3 236
.4 312
.5 371
.6 402
.7 405
.8 412
.9 415
1 418


SB2.2 Standard NASCAR head 2005. 38cc chamber, 4.185 bore 2.180 valve


.2 145
.3 225
.4 300
.5 375
.6 415
.7 426
.8 443
.9 451
1 453

SB2.2 2.200 valve 4.200 bore. 38cc chamber

.2 152
.3 226
.4 305
.5 375
.6 418
.7 429
.8 446
.9 453
1. 456

When Darin asked about these SB2.2 heads on the flow bench, the reply was.


Greg

beentherebaby

Keep in mind that designing a port and airflow profile for drag racing is much different than for road racing or street use. Wet flow can also be much different than dry flow... When you chase high valve lift/peak airflow for HP gains you usually lose torque over the usable RPM range and this hurts vehicle performance. If we raced flow benches and engine dynos it might be different, but we don't.

slate blue

I am exploring in a new direction with the combustion chamber on the 2V, I hope it doesn't cause me dramas but sinking the valve further may give some gains, perhaps sizeable as the chamber controls the diffusion. When the valve gets bigger the front part of the wedge chamber, that is where the chamber goes flat is lost. The airflow can't diffuse their anymore. I noticed that different valve angles where making a difference, especially the top cut. So that could be the diffusion secret. This is how I will do the chamber.

http://www.hotrod.com/techarticles/e.../photo_08.html

I will drop the intake valve and develop an area in front of it, much like the Yates head, the best diffusing head on the market. This could explain why I haven't been able to increase the flow on a per sq" basis of valve area. The standard Porsche figure at 0.500" is extremely good for an old wedge head at 86 cfm per sq". If I was bale to match or better this say 90 cfm the heads would flow in the 310 cfm range at 0.500" and in the 340 plus range at max cam lift which is currently 325 cfm. Those numbers support over 700 hp in a normal race engine but if you read the link below you will it can do in excess of 800 hp.

The rest of the article here, it is an engine that has the same essential size and airflow even the valve angle is the same at 20 degree, hence the relevance to the 928 heads but is a drag engine. It has very high lift cams.

http://www.hotrod.com/techarticles/e...sor/index.html

That engine doesn't have a dry sump either not the coatings, so even more power is available but he is obviously trying to keep the price down, so that is why 700 hp should be doable at 8,500 rpm. Also when you compare the flow numbers to the 4V engines you can see if the same revs were used they would produce much more power than they do today, obviously camshafts would need to be changed etc. For those interested compare those flow figures in the article to the figures for the 4V I have posted before

Greg

slate blue

Small update, the port on the right did quite well, it achieved 305 cfm at 0.500" however it fell off after that, at 87% cam lift it did 306 cfm which is still an improvement but it would have been much higher if my peak numbers didn't fall off. The peak numbers were 325 cfm at 0.650" and now are 316 cfm, I was hoping for 335 to 340 cfm at peak lift.



So I have turned my attention to the chamber. The pic below is of the Chevy SB 2.2 head.





This pic is the Yates head.



A close up with no valves



Particular attention is paid to the diffusion of the flow after the air passes the edge of the valve. That is the curved chamber area and the recessed area. They do this also with top end 4V heads like some Hondas.

So I have applied the same principles to the Porsche 2V head and here is what a rough prototype looks like.










Anyway it certainly looks the goods as far as the way the air is angled after it finishes with the valve. I think the exhaust is more likely to improve, if I was a betting man I would be more confident on that side as the chamber seems to direct the gas towards the exhaust valve more now. I will try to get it tested before the year is out.

Greg

toofast928

Excellent work Greg. Did you do the shaping of the chamber by hand?

slate blue

Hi Tony we sunk the valve by machine and will need to re-touch up the seats, then the rest by hand. It will have to be done by CNC for production as it would be too hard to replicate. I will hopefully be able to post a few more pics before Chrissy. The one with the molded silicone in the ports is interesting as you can see the way the air will approach the chamber because of the angle on the back of the valve.

Greg

GregBBRD

Greg:

Nice. That's a lot of airflow!

Do you have any idea how close you are to "water" in that right hand port? Do you think that you will be able to duplicate that port in all four ports of the heads? I ask, because some of the heads seem to have considerable core shift.

slate blue

Greg, it seem at this stage there is less metal in the end intake port, it gets down in some parts to 2.5 mm or 0.100". To achieve this port what I am doing is welding up the spring seat and that allows for the straighter more optimal port. It also incorporates more installed height for the springs by creating a spacer plate between the head and cam box.

I am using 944 heads even though the head shown is a 928 head. Now the one thing with core shift and wall thickness etc is that the 944 heads have different valve placement. The intake is the same but the exhaust is not. The exhaust is better placed and then I will move the intake over to meet the exhaust.

What this means is that I hopefully wont have wall thickness issues due to the fact that between the 944 valves is solid and what I am doing is creating a diaginal port. This of course stems from the fact that the port is wider spaced. This may have the effect also of unshrouding the valve due to the fact that the majority of the flow is heading away from the bore wall. If you don't follow I will have another go as I know I may not be clear in my explanation.

Cheers

Greg

slate blue

First pic shows the ports how they are currently with the altered and hopefully better diffusing chamber. You can see the extra diffuser at the front of the port nearest the key. That would not normally exist and the air would just break away at the seat.



This one shows how the port relates to the valve and the short and long sides.





This gives an idea about the area the air has to flow into after hitting the back of the valve. Hopefully it gives an idea about how the air diffuses of the chamber and how the chamber isn't just chopped out to give max clearance rather shaped to keep flow attached.




This pic still has the port molds still in place to show the valve angles and how they affect the flow into and out of the chamber.



The ports haven't been tested as yet, the reality is that I can't make them any bigger, the pinch or choke point is still a bit small at 2.15 to 2.2 sq" average port size is around 2.46 sq" or approx the same size as a standard S4 port.

Even if the top end flow is bigger than before it will not be able to be utilized as it will choke in the tightest part of the port, luckily this is only is very small distance around 12 to 15 mm near the valve stem so hopefully that wont be as bad as the whole port being that size. However if the low lift flow can be improved that will be good.

The thing is that the port may choke at max lift however just slightly below that point is the most important area 87% to 90% of max lift and the flow will be at its fastest to give the best cylinder filling. It also means at the time of closing of the intake valve the air will still be running very fast and give excellent ram effect and as such the driveability should be great too.

Greg

IcemanG17

update on this? Great thread.....I am impressed that the 16V head can flow almost equally to the 32V....very impressive!!!

slate blue

Hi Brian, thanks for your words, I haven't been out to the head place as it about 25 miles away and he wasn't answering the phone, I think a well deserved break for him but I will try next week and then that new chamber will be tested. I am really happy with how the port relates to the chamber and valve but we have to wait for the numbers, been wrong before.

Greg

slate blue

So got the numbers, it went backwards, so not worth doing, the numbers are still respectable, i.e 290 cfm at 0.500" but that is still less and it is more work and you run a risk with this style of chamber as it is bigger in area. So in a way this is good news.

Other good news is I have all the info I need to have on these round ports. I may need more info as I think I will run the oval port as these ports are better suited to a lower revving engine due to cross sectional area issues. To say conservative and away from water jackets a cross sectional area of say 2 sq" or less.

While the head flows a lot more air on the bench, the velocities have to be checked. Say 280 cfm could be useable, then the sum of 280 * 2.4/311 fps=an area required of 2.16 sq". However on a street engine and to setup nice wave tuning. You aim for mach 0.62 to 0.64. I'll add more on this later (311 is mach 0.55 at 28" depression on a flow bench.) So when you drop the port down to 2sq" or so that puts you in that range. It also allows a smaller valve with a better discharge coefficient and less shrouding. So these goals become easier to achieve.

I have also decided to build my own flow bench, it is too expensive paying people for this work, apparently. it is quite reasonable to do and you can get a 3 phase motor and run an eaton supercharger as the vacuum and this can pull upto 60" on smaller heads. A project for the future.

Greg

slate blue

Just bought one of these late model 2V heads from the 944, I will adapt them which is not too hard, this will solve any worries I have about the port walls becoming too thin and not enough cross sectional area for the amount of airflow they are capable of



They have 48 mm valves on the intake and 40 mm exhausts. Nice flat floor to slow air on the short side. They will still need building up on the short side and some "high" porting.

Here is some great articles from Chevy Hi Performance, just an except below.

vhttp://www.chevyhiperformance.com/te...ign/index.html

http://www.chevyhiperformance.com/te...ign/index.html

CFM and Velocity

Darin Morgan: "Make no mistake, velocity is the primary variable in the design of the entire induction system. I often say that my job title should be Velocity Manager instead of Cylinder Head Designer. Air speed is 10 times more important than raw flow numbers. If you kill the velocity by 10 percent, you will kill almost 40 percent of the wave and ram energy that dynamically fills the cylinder! Raw airflow cfm is an important variable as well; it's just not as important. If you buy a cylinder head that is properly sized for a flow of 400 cfm and your engine is only asking for 350 cfm, you will not only fail to achieve the power potential that the 400 cfm would have given you, you will also fail to reach the power that the 350 cfm would have given you. That's because you killed all the air speed in the induction system. If your engine is asking for 350 cfm and you give it a properly sized cylinder head flowing 350 cfm, your airflow demand is matched and your air speed is matched. You then have a chance of achieving the power potential that 350 cfm can give you.
"How much power potential can 350 cfm give? Well, that depends on a host of variables such as engine speed, overall induction system design, and piston speed. To put it in basic terms, the less restriction you have in the induction system and the more freedom you have to attain increased engine speeds, the easier it is to extract the full potential of the 350 cfm available. Most people don't know how much airflow their engine is actually asking for! This leads to builders wanting to purchase cylinder heads with way more airflow than their engines can possibly use. The end result is a low air-speed induction system that can't properly fill the cylinder by means of dynamic inertia and harmonic supercharging, which means the engine will never reach its full power potential.

"That said, a good cylinder head port design will flow a lot of air for its valve size. The bad news is that a bad port design will flow just as much if not more air! Airflow alone won't tell you if a port design will reach its power potential with 100 percent certainty. Everyone knows that it's easy to compare two 23-degree small-block Chevy heads with 220cc ports. Just pick the one with the most flow, right? That's about all the average builder can do, and in a lot of cases it's hit-and-miss. There are multitudes of ways to achieve that 220ccs. You can have a big pushrod pinch section and a very small bowl area, or a huge bowl area and a super small pushrod pinch area. One 220cc port can actually be choked off at the pushrod, short-turn radius, or throat area, hurting top end power. Another 220cc port design can have too small of a bowl area and too large of a choke and hurt power and torque equally across the entire power range. Having extra airflow isn't always bad, but it can't come at the expense of air speed. The ports must be sized properly. The amount of air Pro Comp Eliminator engines are asking for are exactly how much the heads flow, and that's not a coincidence. People want to make cylinder head design simple, but it's not. It's very complex and interdependent on a massive amount of variables."
CFM and Power

Darin Morgan: "If you use a 235cc port flowing 340 cfm and they hurt power over a set of 210cc ports flowing 300 cfm, then the air velocity was to low in the 235cc heads. It's not always that simple, but that's the general idea. The 210cc port heads may have flowed less, but their air speed matched the engine combination more closely than the higher-flowing cylinder heads. This scenario shows the end result of installing a cylinder head that flows too much air without enough air speed, but what if we reverse the situation? If you install a 220cc head flowing 300 cfm on an engine that needs a 235cc port flowing 340 cfm, you will decrease the engine's rpm range and peak power.

"Air speed is the most important tuning factor when designing a port, intake manifold, or any induction system component. It's not the only one, just the most important. People are infatuated with cfm numbers because that's all they have to judge a cylinder head's worth. It's extremely frustrating for people in the cylinder head business. Blindly sacrificing air speed for airflow is a fool's errand. When a customer demands the most airflow possible they are not always correct in doing so! The problem is when customers fail to ask for the most airflow possible within the limitations of the air velocity and sizing constraints for his particular engine. This is and will continue to be the root of the problem."

"It's not often that a head with lower advertised cfm figures makes more power than a head with higher cfm figures, but it does happen. The reason for this is velocity just about every time. When you sacrifice air speed for airflow, you may be getting yourself into trouble. This of course depends on the engine combination you're dealing with and the airflow requirements of that engine. Today, professional port designers have been able to develop ports that do both. I have ports that flow a lot of air and have an exceptional velocity profile. I always try to get the most air possible, but never sacrifice air speed in order to achieve it. That is unless I can get away with such a trick, which is very rarely."

Valve angle

Darin Morgan: "There is no substitute for a low valve angle head design just as long as you raise the port high enough to make it work properly. Low valve angles let us increase valve size, decrease chamber burn time, reduce pumping losses, reduce detonation or pre-ignition sensitivity, reduce chamber shrouding, and achieve discharge coefficients higher than any other cylinder head designs. Low valve angle heads in the 7- to 12-degree range with port heights of 1.250 inches or more are the most efficient designs possible today. Pro Stock heads are 9- to 10-degrees for a reason. If you look at the most powerful normally aspirated engines, you will find an overwhelming percentage of low valve angle heads. When comparing the flow numbers of a 22-degree BBC head versus a spread-port head, we see that we need to look at the overall induction system design and package. A low valve angle head with low ports that flows high cfm numbers will not outpace a cylinder head with a low valve angle and high ports flowing the same cfm. With the early LS-series engines, there were underhood packaging considerations that the factory engineers had to consider. The short-side radius on the LS1 and LS6 heads is what we call hypercritical, and is not conducive to high flow above a certain lift point. They are great heads, but GM saw the light when they came out with the LS3 and LS7 cylinder heads. These heads have a low valve angle and high ports, not to mention a really nice chamber designs. These heads are the most efficient heads ever to come from GM, and unlike other OEM heads they have room for the high-performance enthusiast to expand upon."

Combustion Chambers

Darin Morgan: "A properly shaped combustion chamber is a balance of pressure recovery, wet flow, and flame travel. These three factors can make or break you. The pressure recovery dynamic is simply the chamber shape being an extension of the valve seat angles, and letting the airflow decelerate at the proper rate once the valves open. A chamber that is laid back too far is a disaster and causes a total loss of pressure recovery, flow control, and wet flow. When the valve opens, it's supposed to open evenly all around the valve. The SB2 heads have the best pressure recovery characteristics of anything I've ever seen. Something as simple as milling the heads to increase compression can kill pressure recovery on the short-side radius area and kill airflow. Likewise, peak volumetric efficiency will be reduced when the pressure recovery is undermined by a chamber that has been laid back too far. Every cylinder head is different, and with heads with low valve angles ranging from 7- to 14-degrees, it's very easy to design and manage all three factors. With very low valve angles, the chamber can come right off the valve seat like a venturi. With higher valve angles, you need to have a deep concave chamber to help pressure recovery. Deep concave chambers are more difficult to work with, but laying them back too far is somewhat difficult as well. Deeper concave chambers, like the ones found in 24-degree BBC heads, often have poor wet flow and reduced pressure recovery due to valve shrouding. Many times there is little you can do about it. Wet flow benches let us take these poor burning chambers and manipulate the seat angles, valve job, and chamber design in order to improve their poor wet flow characteristics."

simos

Thanks Greg, again great bunch of information. I have read all of the
information you have written and linked to this thread, several times.
It's been great learning process for me.

You wrote that you are going to flatten the port floor to slow air on the short
side. Some time ago, I read the following document, which explains the reason
for using D-shape or trapezoid style port. Is this, what you are going to achieve?

http://www.team-integra.net/sections...sp?ArticleID=7


Also, I have now understood the importance of valve seat form. There is
another good document, which explains the topic quite well.

http://www.s2forum.com/forum/showthread.php?t=21320

Keep going to post your progress!

Simo