All this Head porting and flow talk had me researching flow benches ??

Sorta off topic but on a turbo motor has anyone actually slowed down because of too much head flow? Not including situations suffering from the valve being blocked by the cylinder walls?
 
TRs don't pull air into the cylinder at WOT the air is forced into the combustion chamber. So why test a head with a vacuum system that its purpose is to flow forced air? What am i missing?

There are quite a few reasons to test a forced induction head with a vacuum system, with the main reason being how we calculate energy loss. Selecting a certain size turbo for your application after knowing your cylinder head cfm is critical, as you can then tailor your valve events with that cfm and bore and stroke which essentially dictate how fast your turbo will spool, and where that power is going to be. This is what separates the men from the boys. Anybody can force more boost in and make power, but only a few can tailor their setup and make tremendous power all over the curve with immediate spool time, lower egt's, and even lower boost pressure, when knowing all of these particulars. Also remember that vacuum and boost go hand in hand, so when testing cfm through a vacuum system, you're forcing its' double at 15-psi.
 
Consider for a moment the process of just flowing air into the cylinder minus all other engine operating effects. You have to have pressure differential in order for there to be flow. Regardless of turbo or NA, for the sake of discussion consider at TDC the cylinder pressure is equal to the manifold pressure which is equal to the pressure at the throttle blade (WOT case at this point not considering any residual pressure, just pumping air). As the piston moves down the pressure will want to drop in the cylinder, the air flowing in wants to equalize the pressure, how big of a pressure drop you get is based on the restriction of the intake port and runners…. In each of my previous examples, the pressure drop was 1 psi, so regardless of turbo or NA, a 1psi pressure drop will net the same ACFM(actual cubic feet per minute) of air. ACFM is measure of air volume, not air mass. Since the pressure of the turbo motor is higher, the mass of air for 1 ACFM is higher than the NA case, but the volumetric flow(ACFM) we are considering is the same. Since the flow bench is measuring at roughly 1 psi pressure drop, it gives a good representation for both the turbo motor and the NA motor in my simplified example, since it is volume flow that your are looking at. It takes a little while, and little study and by no means do I have it all nailed down.


In reality, the turbo motor will have higher pressure at TDC on the exhaust stroke than the manifold, unless you have a turbo that can run on less back pressure than the compressor produces in boost, and a well designed NA motor will start at a lower pressure at TDC due to scavenging. This is not considered in my simple example. The intent is to show that for the 1 psi pressure drop ACFM flow is the same for both turbo and NA.
 
Just trying to figure out if there is such a thing as a too much much porting? besides not being balanced with the other cylinders?
I am going to give this dumb idea of mine a shot, i get the guys with actual knowledge on the subject saying that it isn't necessary or that the other method can be applied but isn't that just a theory of what should happen? No matter what teams look like on paper the game is still played because of some unexpected variable that might show up.
the plan.
1- Garbage can
2- Vacuum / blower combo
3- Wood
4- Iron buick head
5- PVC pipe and fittings
6- LS1 MAF
7- Translater
8- PowerLogger
9- Buick ecm
10- 2 MAPS
11- Engine harness
12- ????

yes it's winter
 
Last edited:
It takes a little while, and little study and by no means do I have it all nailed down...

We thought about using a shop vac a la Vizard some years back with a floating pressure drop, but never got around to it. Which flow bench are you using for your research?
 
I mentioned earlier that I don't have head porting experience, between my education and a decade of power plant engineering experience, and quite a bit of experience around aircraft, the explanations were geared toward flow behavior and what to expect. Also, why the current benches should be good enough considering what you are asking them to do. The flow explanations are based in sound physics and engineering. Floating pressure drop would be interesting to see the results. I'm getting ready to head out of town, so I won't be on for a couple of days, but interested in continuing the discussion. So many other variables, that others have likely experimented with, but maybe want to keep for business or competition reasons.
 
Just trying to figure out if there is such a thing as a too much much porting? besides not being balanced with the other cylinders?
I am going to give this dumb idea of mine a shot, i get the guys with actual knowledge on the subject saying that it isn't necessary or that the other method can be applied but isn't that just a theory of what should happen? No matter what teams look like on paper the game is still played because of some unexpected variable that might show up.
the plan.
1- Garbage can
2- Vacuum / blower combo
3- Wood
4- Iron buick head
5- PVC pipe and fittings
6- LS1 MAF
7- Translater
8- PowerLogger
9- Buick ecm
10- 2 MAPS
11- Engine harness
12- ????

yes it's winter

http://www.flowbenchtech.com/forum/ is a great resource, whether you just want to learn how it all works or how to build your own bench.
 
Top