It hurts to hear Darin Morgan say for so many years, he was ruining heads when he ported them. So if he was ruining them, I'm sure lots of other folks are too.

And when adders like turbos, NOS, etc. are involved, it is easier to turn up the boost rather than get the wet low right. (Of course at the highest levels of competition, everything has to be optimized.)

So that leaves me with the $64 question: "How good is the wet flow of the ported heads in my car?"

I have One Data Point:

• Improved wet flow will make engine run richer.
• It will also produce more HP for the same CFM port flow numbers.
• VE will be increased.
• And given good wet flow, CFM now merely determines what rpm range the torque will appear.

 

More theories:

Bad WF means big gobs of fuel not burned and pass out the exhaust.
IF TRUE, there are 2 potential issues:
1) they slow combustion down requiring more advance (probably true) and
2) could make more HP if more right size fuel droplets could be introduced.
QUESTION while showing pig rich due to unburnt fuel, would further enrichening produce more HP due to more good sized droplets?

RICH could mean 1) bad WF, or 2) good WF actually running rich.

It may also mean mixture tuning should be based on HP and not A/F ratio. In which case bad WF may be indicated when more HP is obtained by running "excessively" rich.

THE PROBLEM: I don't think it is possible to get a canned tune for ported heads, the WF characteristics of which are not known. So how to assess WF? I'm thinking cold start open loop A/F ratio.

 

One way to look at it,, almost nobody in NASCAR or F1 or Indy ,,, hand ports heads,, and RPM's are everything, CNC owns the hi-rpm world..

 

CNC is just a manufacturing process it has nothing to do with port or combustion chamber design. I assure you all the top levels of competition have much invested in optimal WF port design. And like Darin says, no one is talking because those secrets are what win races.

 

But it guarantees repeatability of the port or chamber design that hand porting cannot. Once that primo port or chamber is done once then entered into the CNC machine, it can be endlessly repeated as long as the tools are sharp. Not true with hand porting

 

Keep in mind that a CNC program is only as good as the original port work and that may differ according to who initially did the work and the work of person who digitized them and the person setting them up on to be CNC'd. Also there are differences in ports according to each cylinders flow characteristics so cylinders 7-8 may be different than 3-4-5-6 so just copying the best port out of several and repeating it isn't always the best way to go about it. I have a set of AFR CNC heads that were sent out to get worked over by hand by a well known porter and they picked quite a bit and the intake and heads were port matched while they were there.

 

I'd bet that they aren't pulled off the cnc and built without someone touching them up somewhere by hand.

 

I think AFR is not gong to do the job since it cannot determine unburned HC in the exhaust.

I think an exhaust gas analyzer would be required to measure HC in the exhaust.

Improved WF would burn more fuel (AFR becomes richer) and reduce HC's.

HC's might be the critical measurement. (Actually a 5-gas analyzer might reveal a lot more.)

TOPIC: Using 5-gas exhaust gas analyzer to assess ported head wet flow


EDIT: CO may be another useful measurement

 

from http://www.hughesengines.com/TechArt...inderheads.php

For all these years engine builders have worked with flow of "dry" air thru the intake system, and power has increased in great part because of it. However, the true medium flowing thru the ports is a mixture of air and liquid fuel. This A/F (air/fuel) mixture acts differently and responds differently to ports shapes and modifications than the wet A/F mixture. This situation has lead to the seeming contradictory situations where small, low flowing ports produce more power than larger high, flowing ports. This fact flew in the face of the rule of More, if some (air flow) is good More (air flow) must be better! Now the cylinder head ads that had listed massive air flow numbers started changing their heads to "high velocity". The higher velocity was a better answer, but the velocity needed to be harnessed, as not all high velocity heads produce good power. What the higher velocity did was atomize the fuel much better and that resulted in a more burnable mixture in the combustion chamber. Shazam! More power out of the same engine.

 

From what I have been told by people working around engine development in NHRA Pro Stock, the CNC just roughed in the port and chamber designs before being finished by hand. The CNC machines just reduced the amount of time to go from raw casting to a finished product. In some cases, the induction package isn't even done in house and can be contracted out among several cylinder head specialists and tested to see which will be run in competition.

The same people also told me wet flow was something they had looked at, learned a few things from, and moved on. Ultimately, competition race engines are not designed around achieving "good" or "bad" wet flow or even the highest dry flow numbers. They are designed with the goal of achieving the fastest ET or lap times. .

 

Are you saying that wet flow and CFM are no longer important these days?

 

I'm saying that's what I have been told. I don't have personal experience working in a Pro Stock or NASCAR shop, but I have spoken with guys who have and who were open to talk about their observations after rule changes kneecapped the engine development. .

CFM hasn't been very important in a long time except for advertising. It's more common to use a flowbench in port development for testing velocities with a pitot tube rather than for testing raw flow numbers. Wet flow testing came along and showed people what certain characteristics in the induction path make for good or bad wet flow, but some say it was a waste of time, and some say they learned a few things to apply to their designs, and never really needed to wet flow a head again. There is something to wet flow characteristics, but wet flow testing doesn't seem to be as common place as it was in the first years since Mondello made it popular.

My personal thoughts are that opinions will vary because A) you have to correctly interpret what you see happening in a wet flow test to gain anything from it rather than recording actual data to tell you if you're going in the right direction or not, B) for some people, wet flow testing might not tell them anything that they didn't already know from observing combustion patterns on the chamber and piston face, and C) due to the nature of racing, you might only develop one type of head (ie Hemi, DRCE, SB2, R07, etc) and once you "fix" that head and get good wet flow characteristics, there's no more need to develop that particular head with wet flow testing.

To tie all this in with your original posts, a CNC program isn't always designed by the vendor you bought them from. Sometimes that work is contracted out and might be done by someone who does value wet flow testing and uses it as part of their development work. I don't think there's really a way to asses the wet flow of your particular heads without testing them though. There are lots of other variables in an engine that can affect the fueling of an engine that wouldn't correlate to wet flow. I wouldn't get too hung up on it.

 

What you are describing is the evolution of competitive racing head technology.

This is not what my post topic is about.

The topic is you acquire a car with ported heads done by an unknown person and no tune, what tests can be done with engine in car to determine if heads are worth investing money in a thorough tune and more mods? If the porting job was bad, throw a canned tune on the car and forget about it. BUT if the porting was done by a person with expert knowledge, further investment is justified.

I focused on wet flow assuming that the porting job was good enough to NOT go turbulent. If flow goes turbulent, the heads are ruined and wet flow is irrelevant.

Hope that makes sense.

Thanks for the post..

 

I strongly suggest that Darin Morgan's youtube videos should watched to get a basic understanding of wet flow.

What has evolved is that various rules and practices have been adopted with promote wet flow resulting in an empirical knowledge base. The problem with this is that there is no understanding of why stuff works. And without understanding, advancements are left to chance - throwing stuff on the wall until something sticks. Example: people learn which aftermarket cylinder heads produce the most HP and which should be avoided. Again this is empirical and good enough for people playing catchup. Those at the forefront are discovering the physics.