Carb CFM Calculator now up

Sandy · 10-17-08, 01:22 PM

Still hacking some code for fun, simple Carburetor CFM calculator with some charts to help visualize the CFM at specific RPM and VE.

Carburetor Size Calculator

Others here

Tire Size Calculator
Tire Size Calculator

Next Up -
Fuel Injector size Calculator

Compression Raito Calculator

Other Calc Suggestions???

Sandy

Rick · 10-26-08, 05:10 PM

This works real well(???)
I think my 48 IDA's are to small:

Carburetor Size Calculator
Engine Size
Maximum RPM
Volumetric Efficiency (VE)
Carburetor Type
Carburetor CFM
Carburetor Size CFM

Sandy · 10-26-08, 05:39 PM

I guess I had better add a bit more error (fool proofing) checking on user input...

Try 0.90 instead of "90" you had entered for the VE that should yield better results. These number may not work well with IR (weber) CFM ratings.

I'm going to need to see your dyno sheet too -

From the CarbCalc page

Quote:

Stock Engines VE = 0.75 - 0.85
Mild Built VE = 0.85 - 0.90
Racing Engines VE = 0.90 - 1.0
Anything more then that needs a dyno sheet to prove it!

Sandy

Jac Mac · 10-26-08, 05:49 PM

For your VE use the decimal point, ie 90% = .9, 100% = 1.00 .

Doesnt really work for webers as you have to use one cyl vol. eg ; approx 36 cu in for 289.

Jac Mac · 10-26-08, 05:53 PM

Quote:

Originally Posted by Sandy

I'm going to need to see your dyno sheet too -

From the CarbCalc page
Sandy

Sorry, not available!

Sandy · 10-27-08, 01:55 PM

CarbCalc page updated to issue a helpful message if VE out of whack, and a disclaimer about Weber Carbs ;-)

Injector calc almost done, initial view (no charting) is here -

Hit the "Sample" button to get an idea how to work the values. I'll be adding help and charting for these as time permits.

Injector Size Calculator

Sandy

JimmyMac · 10-28-08, 04:31 PM

Guys,
Do these formulae work with a Ford / Autolite in-line carb & Cross Boss manifold set-up ?
I would appreciate any help.

Jac Mac · 10-28-08, 05:06 PM

James,
If your throttle bores are 1-11/16 then its 850cfm ( Trans Am), if its 2-1/4' its 1400cfm ( Nascar ). Assume you dont require the p/n's

That little 289 is going to be a hummer to use that airflow!!!

JimmyMac · 10-28-08, 05:27 PM

Jac,
I bought one recently with a pile of spares and three sets of manuals but the paperwork could be for a moon lander vehicle for all I know. I need to learn about these things.

I was told that these carbs beat the Webers hands down for progression.

Sandy · 10-28-08, 05:34 PM

I would imagine if they have a plenum under them they might be close. If IR under the hood then maybe not so much, but would be something of a start. These calcs are really estimates for more conventional setups but always a good starting point as it is easy to visualize a Holley like carb ;-)

I have seen a few of the autolite setups and they are as cool looking as webers, maybe more so since they are from Autolite and hens tooth rare I'm guessing.

Sandy

JimmyMac · 10-28-08, 05:41 PM

Quote:

Originally Posted by Sandy

I would imagine if they have a plenum under them they might be close.
Sandy

That's exactly what I was thinking Sandy.
I also agree that it's a pretty cool lump of kit and I would like to give it a go some day. I have an ambition to do a nice Mustang some time so I decided to buy this as a reminder.
Many thanks for posting the calculator.