LT4POWR

It’ll probably never be a sticky because some people on this board can’t seem to quit bashing other people. It’s seriously getting old. Almost every cam thread turns into a LE/BRE vs Joe O cheerleading competition, and every head thread turns into a LE vs Ai battle.

jerrysta

They are all good and so is the guy doing my heads.


There IS more than one guy or company that knows how to make a cylinder head flow.

Allow us to soak in the education and quit bickering. I would think all of you guys bring some value to the table.

jkipp84

Sometimes you gotta take the bad with the good..

I think it should be a sticky, there's great info here.

IllusionalTA

Wonder if they can cleanse it of the bashing.. From my POV i'm not using either to do my heads but value both's opinon, as well as brett's as he's always answered all my question and lit the spark under my *** to get some "ok" 23 deg heads..

Mindgame

I love the Roadrunner stuff, lol.


Well, well... you actually do "figuring" LR. I haven't ever seen you post any figuring you didn't get from your program so maybe you can set the record straight here...

I have a valve, 2.02" in diameter. At .500" lift the flow (28" H2O) is 260 cfm. What is the discharge coefficient gonna be for the rest of my figurin'?

Pie are round and cornbread are what again?????

Time to put up or... well you know the rest.

For the rest of you, we'll move on to a technical discussion once we can figure out who needs to stay out of the frying pan.

-Mindgame

blackz97

Does the frying pan work good at low/mid lift? where can i get one?

Steve

Mindgame

To move this thread closer to it's original intent.... guys who are interested in porting or just understanding it better should check out this thread,

http://64.65.63.61/forums/showthread...=368633&page=4

And especially this post,

http://64.65.63.61/forums/showpost.p...6&postcount=49

The airflow velocity stuff (to me) is very important as it correlates directly with volumetric efficiency. If we could get the "pros" to talk on that subject then I'd be all ears. I know what the few people I deal with are striving for and I know what most of the airflow theory prescribes. Would like to know how some of these other guys are applying the theory though.

-Mindgame

1racerdude

OK I'm putting up.
I am by no means a fluid dynamics engineer but I get buy. MG I generally charge for this type of service but I will do it JUST cause ya are a good guy.


"I have a valve, 2.02" in diameter. At .500" lift the flow (28" H2O) is 260 cfm. What is the discharge coefficient gonna be for the rest of my figurin"

Well by my figurin your discharge coeffient is .562 ya got a effective flow area of 1.781 and a actual flow area of 3.171.(didn't know wether ya wanted the "ideal"or "actual" figurin) Not a bad head

Time to put up or... well you know the rest.










Damn man if ya keep doing that ya gonna hurt yoself

FASTFATBOY

Here is a MOST excellent, jam up thread also for you "readers" ,that includes me.

http://ls1tech.com/forums/showthread.php?t=416169



David

Denny McLain

Still Trying to figure out if this was a good thread or not. Enjoyed the technical aspect but was a little disappointed in the gamesmanship that parts of it turned into.

I will say this……. Lloyd is one of the nicest individuals anyone could possibly ever meet and I’ll bet the people at AI along with everyone else whom contributed are probably also.

Amazing how keyboards say things that people one on one never would. Still the best and most imformative board going.

Mindgame

Not a bad head but not great either.

BTW, you should show your work.

And just for that, I won't charge you for explaining HOW the program works LR.

Ok, for the technical side of this discussion. Those of you who got the mean mach paper I mentioned will see that the the discharge coefficient is used for the Mean Mach calculation. This is the formula EAP uses to calculate this. A discharge coefficient is simply a mathematical respresentation showing how efficient a given area is at moving air. In the example above, the port is ~56% efficient. The closer we get to 100% of theoretical flow, the better the efficiency.

When LR shows the work you will see how the numbers are derived.

Taylor draws a direct parallel between Mach speed and volumetric efficiency. Depending on the port, Taylor and countless others have shown that port choke will occur somewhere between .5-.6 Mach. If you look at a head flown at 28" of H2O then this correlates with ~260-340 feet/second. You'd need a pitot probe to check this but from what I've gathered, at 340-350 ft/sec TQ starts to fall off rapidly in a live engine.

The point in pushing the Mach to the highest speed the port can endure without choking is to maximize volumetric efficiency. If the air speed is high enough (inertia is high) then the cylinder continues to fill even as the piston moves away from BDC. This is called "inertial supercharging" and is the principle behind achieving a volumetric efficiency greater than 100%. On the other hand, if the air velocity is low (inertia is low) the charge may not produce as much "fill" or may revert back up the port. This is why overly large ports with low velocity are sluggish at low engine speeds.

If I run the calcs on some of the really good stuff I've seen, I end up with numbers like...

3.1, 3.8, 4.6
3.5, 4.2, 5.0
3.8, 4.6, 5.4

Calculate enough of these out and you'll see that the MEAN is right in the 4.2 range just as stated. If you don't know the definition of Mean in mathematical terms, well I'll throw you a bone.... it's the "average".

Just a little backrgound on how a program like EAP works and what the output actually IS.

-Mindgame

thesoundandthefury

Just out of curiosity, how much does cylinder displacement/stroke/piston speed factor into determining real world mach #'s? Is this something that a flow bench can compensate for or does it basically come down to guesstimates? Or does it even matter?

I'm trying to get an idea if there would be any difference in how a head would "behave" if you bolted it on a (350 main) 3.875" stroke 396 vs. something like a (400 main) 3.25" stroke 358 with longer rods, with otherwise identical valvetrains.

("Behave"= will mach numbers vary?)

1racerdude

What didn't ya think I knew that EAP gives the discharge coefficient?
The thing is it uses the 137CFM/SqIn constant.
The figures in my figurin were using the 146CFM/SqIn constant.
The 146 is more in line with the present thinking of the pro's.

Dude I ain't teaching school. Never have turned in my scratch pad just the answers
I got the right answer do I get a gold star.

1racerdude

What you are considering "long rod" is 5.7-6.0. There is not enough difference to matter. Now if it where 5.7 to 6.5 it will make a difference and the 5.7 will win on the suction deal and getting the air column in the cyl. IMO the MACH numbers are a guess unless ya measure it on a engine dyno with your particular set up. That hasen't been done much if at all.I have been told if ya wanted to get into a big R&D program on the subject ya could install pedot tubes or static pressure caps in a intake to measure it.

thesoundandthefury

I think the longest rod you can stuff into a zero decked 400 block with a 3.25" stroke is 6.350." Are you saying the 5.7" rod will produce more suction on the 3.25" stroke crank or the 3.875" stroke?