Converted CFM vs Real CFM

[larrycavan]

I've had several requests to tweak FlowSoftExcel to capture the converted CFM value during flow testing. While I can make some changes to allow that, I think it's important to understand that converted flow information is NOT a good indicator of a ports shape or size being correct. Don't be mislead into thinking that because you have a port behaving well at a low test pressure that it will continue to behave well at a higher test pressure.

Larry Meaux did a good write up regarding this several years back. It's probably on SpeedTalk.com if you do a little research. However, in short it comes down to one simple thing. If you can't test at higher pressures [above 25"] and you're serious about trying to make power from your porting efforts, you need to upgrade your flow bench so it will "safely" pull a higher depression that you can "accurately" measure the pressure drop at.

The same holds true for port mapping.

This information in this link should be read by anyone who ports heads. http://maxracesoftware.com/bulletinboar ... f=26&t=822

Larry C
Cavanaugh Racing Heads
http://www.cavanaughracing.com

[Hotz]

hi Larry....

Please any information to access the forum MaxRace how to do?
Just buy the program!

very good your site
congratulations!

[larrycavan]

hi Larry....

Please any information to access the forum MaxRace how to do?
Just buy the program!

very good your site
congratulations!

You need to join that forum to read the info.... I forgot about that. Just join it. Good forum!

[johnsmith]

Hi Larry,

I added a column myself on the data sheet which shows calculated flow at 28" and modified the charting to point to this instead of the actual CFM.

I'm hoping my changes won't affect any of the other calculations in flowsoft. I was planning to do some testing today using both the old and the modified spreadsheets to make sure I haven't buggered anything up.

Problem I have is that I only have domestic 13A supply and 3 vacuum motors. The heads I am doing will only allow me to get 26" at max lift but I want to compare my results with other publicized flow data at 28".

Cheers.

[larrycavan]

Hi Larry,

I added a column myself on the data sheet which shows calculated flow at 28" and modified the charting to point to this instead of the actual CFM.

I'm hoping my changes won't affect any of the other calculations in flowsoft. I was planning to do some testing today using both the old and the modified spreadsheets to make sure I haven't buggered anything up.

Problem I have is that I only have domestic 13A supply and 3 vacuum motors. The heads I am doing will only allow me to get 26" at max lift but I want to compare my results with other publicized flow data at 28".

Cheers.

That's the beauty of having an Excel application. You can add whatever you like

The only things I can think of is you'll have to clear those cells manually and the calculated data won't be reflective of the converted number. It's the calculated data that you want to be looking at as well as volume. CFM/Sq.IN & Coefficient in particular. Coefficient number doesn't change much when flow conversions are done.

In your case the conversion value is minor. The change in flow conditions shouldn't be drastic.

Let's say you were going from 3" to 28". In a situation like that, the spread is significant and the behavior of the port [tendency to go turbulent] as pressure is increased is unpredictable. As the FPS increases, the shape of the port may need some attention in various places. That article on Maxracesoftware's forum will open your eyes to how critical air speed is when it comes to making horse power.

Nothing is absolutely carved in stone, of course. But at least be aware of the potential for being mislead by converted numbers.

[Hotz]

hi Larry....

Please any information to access the forum MaxRace how to do?
Just buy the program!

very good your site
congratulations!

You need to join that forum to read the info.... I forgot about that. Just join it. Good forum!

Larry ....
Registration blocked ...
There appears to the local application ...

or am I too blind

[RandyW.]

Was told you have to buy the pipemax program before being able to register.

[Flash]

Not that much money, and a vary good program!

[Malvin]

Here is the page Hotz
It is a very good program as Flash has written http://maxracesoftware.com/

[Hotz]

Thanks guys ...
saw the program ..
It is certainly very good ...
My bench stop construction ..
Now is not the time of the program ...
I wanted to enter the forum to better understand just ...
Good value to buy...

Things for the future

how many here use the program?