Flowing at higher depressions

[coulterracn]

[msj442]

hey ray what is your capacity at 36"? bruce said he designed the bench for 28" mainly for depression , so i jsut assumed it wouldnt be a good idea. jmo



max

[bruce]

The PTS DM only uses sensors that range up to 38" for static, I'm working on a prototype now that has 100" sensors.

If you use the PTS bench design I'd add in a few corner braces and make sure you have screws closer together for added strength. This has been discussed in the PTS Plans area

[coulterracn]

[bruce]

Not everyone is going to take the same direction on their build hence the "caution" of adding in bracing.

I used construction adhesive and glue on my joints and I agree with you, it's not going anywhere

[msj442]

i was just mainly thinking about the area of panel , which im sure you have addresssed bruce in your r&d.
what was your capacity at 36" ray?
max

[slracer]

"I can go higher than 36" without any complications. I had to keep it at 36" because of the vertical manometer being only 36" in length. I'll have to fabricate a 48" vertical manometer for the bench and use the 36" for probing."

I can't find the thread right now, but I seem to remember reading (somewhere here on the Forum)that the probe manometer should be higher than the vertical? Does anyone know where that is (or if it is)? I'm getting reday to add a probe to my bench and a shorter one would fit a lot easier.
Thanks, Doug

[coulterracn]

[jfholm]

[coulterracn]

John

I am using the 20" Dywer incline meter with red oil. I used Ed's spreadsheet to draw the precent scale I'm using.

I admit I am having trouble with the math and required values to calculate actual cfm for a given orifice size. I was trying to use a spreadsheet I downloaded from this forum to calculate the 3" orifice. I realize the 732cfm is way off base.

Now that I know I'm able to flow at higher depression I'll spend the next few days reading about calibrating the bench.

I've been porting cylinder heads for 37+ years. I have read every book and article I can find on cylinder heads and air flow including the ten set CD's from Speedtalk. I know what a flowbench is used for and understand it's pricipal but I am lost and confused with with some of this stuff.

Ray

[bruce]

Knowing the vertical rise of the Dwyer 20" manometer you would size your orifices based on this number. Somewhere on here is the exact measurement of that rise. TomV would have that info, Tom you out there?

Once you have that number calculate your orifice hole sizes using that number as your Dp.

[coulterracn]

[coulterracn]

I was surfing the net for port velocity information when I found an article co-written by Chuck Jenckes and Jim Mcfarland. go to www.strokerengine.com/HeadTech.html






Process of Evolution

Upon evolution of an economical airflow stand or bench, engine builders were quick to see the tool was an effective way to quantify airflow performance of one port relative to another. The flow bench is most effective when used to develop cylinder heads that are closely related to production parts. The reason is that airflow performance of a production part is so restricted that any gains in flow will most likely increase engine power.

Most flow bench testing is performed at a depression of 28 inches of water. At best, this is accurate only twice during a full inlet cycle (See Chart #1) This chart shows an inlet port that sees negative pressures up to 2.6 psi (73 inches of water), much higher than the 28 inches of water used on an airflow bench. A true representation of cylinder head flow performance would be using a three-dimensional plot of flow at varying lifts and depressions. Flow benches become less effective as cylinder head design is less restricted and mass flow increases. For example, heads developed for CART, IRL, Pro Stock drag racing, or Outlaw sprinter engines are less likely to be successfully developed on a standard airflow bench.

Further, an intake port must flow fuel and air. Engines running methanol operate at air/fuel ratios more than twice the richness of those on gasoline. The large quantity of fuel, much heavier than air, clearly impacts the performance of an intake port. Wet flow benches that can operate at much higher flow depressions make a better tool for such engines. Some engine builders working on these engines simply use the dynamometer to test cylinder head improvements. The flow bench becomes a quality control tool, much like a go/no-go gauge, to verify a finished head compares to its prototype. The point here is that the Saturday-night racer should not become overly dependent on airflow benches. The dynamometer is a superior engine evaluation tool.


Ray

[msj442]

sure wish i could afford a dyno. looks like i will have to just stick with the flowbench. thanks for the article ray.b

max

[jfholm]

Ray,
I have noticed that there are "experts" out there that like to get on a soap box for a certain area and beat it to death or diminish the need for something. In this case the flow bench. I still feel that the flow bench is a valuable tool, especially when used at higher depressions. I also feel this is even more important when you do start getting heads like Pro Stock, F1 etc.

I think the that "all" the tools are needed and to be coordinated together. The only trouble is on my budget I can only afford to build a PTS flow bench which we have proved to now be one of the best to have.

Dynos are great! But unless you really know what is going on even Dynos can lead you down a wrong path, especially when people get focused on peak HP and TQ.

Best place and tool is the race track. We built an engine in the mid '70s that had much better heads, long rods and a ton more HP. We thought we were going to thunder. We only picked up .05 seconds in ET and 3 mph. The car would not recover fast enough between shifts.

Now in retrospect the heads were too bid in the CSA. The engine was just a 331 SBC shifted about 7800 rpm. Now if we could have gotten the little bugger to shift about 11000 rpm we probably would have set some records.

Another thing on wet flowing look back at my comment in "why wet flow" My 360 SB Chevy is only using .0035 oz of fuel per firing. Alcohol would be approx twice that at .007 oz. I drool more than that.

John