Mustang Tech

Oz,
That's why I brew my own. An infinite supply of dancing juice.....hahahaha

ozbilt wrote:

Astro wrote:Surely you two could have just put all this in a PM to each other?

Cheers

J

Possibly you do not understand talk about calculators because you still use an abacus.

Hands up - you got me Oz

Cheers

J

I am a post count whore....

Geez some of you blokes are hard to please.

I think is a great new feature - I really do. Hats off to you.
I am sure it will expand.

The carbi sizing calculator is wrong. The result tells me it is the traditional (and wrong) formula at it is for a 1.5hg pressure drop which is to high and offers to much flow resistance. Hence every single dyno will show higher performance from a larger carbi than the formula suggests.
Modern carbis work fine with very low pressure drops such as 0.5hg.

It's only a guide boof.
If it returns 520CFM, you're going to buy a 600 anyway.

In the end, a carb designed specifically for your engine and by a pro will be able to go bigger because it will atomise as best as possible, but then if you were getting a carb built to suit your engine, you wouldn't be looking at this calculator.

By all means, send through your formula and I will change over to yours. I was trying to keep it as simple as possible for the average person.
I mean most of us have no idea even what our VE is - lets face it. And that is one of the most important parts of it really.

The current formula is (MaxRPM x EngineSize) / 3456) x VE

I also just found this on edelbrocks website:

CFM and Carburetors:
Carburetors are rated by CFM (cubic feet per minute) capacity. 4V carburetors are rated at 1.5 inches (Hg) of pressure drop (manifold vacuum) and 2V carburetors at 3 inches (Hg). Rule: For maximum performance, select a carburetor that is rated higher than the engine CFM requirement. Use 110% to 130% higher on single-plane manifolds. Example: If the engine needs 590 CFM, select a carburetor rated in the range of 650 to 770 CFM for a single-plane manifold. A 750 would be right. An 850 probably would cause driveability problems at lower RPM. A 1050 probably would cause actual loss of HP below 4500 RPM. For dual-plane manifolds use 120% to 150% higher.

So they are suggesting 10-30% for a single plane manifold and 20-50% on a dual plane.
Adding those percentages may bring the values closer to what yours would suggest.

Interesting - I agree with what they are saying but most people think the number mean X carbi with no magic adjustment - any way change the constant to 2820 and it will be closer to the formula I will be presenting.

Done - now with your new value, it's the closest larger carb to the value produced?
No adding a percentage on top?

Yes - go up to the next size. So a 347 with .95 VE, 6000-6500 RPM will be just over 700cfm so a 750 is the go.

Ok cool. I will remove the Edelbrock text tomorrow.