Digital vs Water Guages - Comparison of measurin tools and methods

[larrycavan]

[cspeier]

I'm working on a SB2.2 for a 4-cylinder G/EA. I know going from 28 to 36 inches finds ALL the problems. In the beginning I just used 28. After I had the port done, I decided to try 36 inches. WOW. What an eye opener. Needless to say, I've redone the port. I was talking with Darin Morgan from Reher-Morrision and he was going to Dart Machinery last week. Maskins bench will flow 50 inches. It takes one #### of a bench to flow a 500+cfm pro stock head at 50 inches. He also made the comment, that the Mondello wet flow was by far more important in finding ET and cfm than anything he's ever tried. Like I've said so many ways to acheive the end result.

Chad

[larrycavan]

I'd be interested in a comparison test between the two versions of the porting. Not just the FB results but the real world numbers of the engine's actual performance. The tricky part may come down to camshaft. Obviously it would have to remain the same cam for both versions of the test for an apples to apples comparison while on the other hand, the higher test procedure and associated porting changes may influence the selection of an entirely different cam to take advantage of the changes. As usual, each twist presents yet another knot...That's the best part of all this work. It never ends..there is never true satisfaction....progress continues...

Larry

[cboggs]

Yes hight test pressures are important, .. you can find turbulence
not found at lower pressures.

I think the key here is the simple fact a flowbench is steady state while
flow in a live engine is dynamic. I'm sure the flow speeds we see in a live
engine are much higher then we test at.

Chad has proven a simple flowbench "fact", .. try flowing a head at 10"
then again at 28", .. and again at 36", .. chart the flow curves, .. they will
not be the same.

We test at 28" and shoot for ports with an air speed around 300 fps, ..
a live engine will double that at close to 600 fps.
Big difference in my book.

I've had a fair amount of flowbench to dyno to race track test results, ..
when I started working at higher test pressures and addressing the things
I found, dyno power went up and track ET's went down, ..

Curtis

[larrycavan]

I received a paper from a well respected expert in the field that indicates the average pressure of a normally aspirated engine, running at full throttle is on average aprox. 25" of water with short lived spikes up to aprox. 50-60" water. It also says target velocity should be .55-.57 Mach, which is considerably higher than the 300fps figure.

I have no doubt that the results you obtain are valid. I'm not questioning them in any way. It is interesting though about the velocity speed target difference.

Each target has it's practical application. For street use, the higher number seems more appropriate.

Accurate Velocity measurments are my main consideration for moving to digital equipment.

Larry