[EagleAutosports]

This applies whether your engine is naturally aspirated, boosted or nitrous assisted. Of course this is just a guideline, some slight interpretation to your particular combo will be required.

[RLG34750]

Good and well needed post....

[Dave]

You might want to check out the FRPP catalog for a lot more on proberly sizing your fuel system requirements. They do show a difference in having a NA vs blown hp injector sizing.
Ford Racing Performance Parts [Ford Racing Parts Catalogs]
Just down load the catalog for an always handy refererce guide. Think the fuel sytems area starts around page 134

Dave

[EagleAutosports]

In order to select the correct size injector for your application, you might wish to use one of the following formulas.

horsepower x B.S.F.C. divided by the # of injectors X .80 (duty cycle)

Find HP value of Selected Injectors:

Injector size (lbs/hour), 31.25 X (80% duty) / .50 B.S.F.C.



In most cases a naturally aspirated engine will have a B.S.F.C of .50. This means that the engine will use .50 lbs. of fuel per hour for each horsepower it produces. Turbocharged engines will want to be at .60 lbs. per hour or higher.

Most injectors will max out at 80% duty cycle and this is the accepted industry standard.

B.S.F.C is brake specific fuel consumption - How much fuel you are using per horsepower per hour



Conversion Formulas

To convert cc / min to lbs. / hr. - Divide by 10.5
To convert lbs. / hr to gal. / hr. - Divide by 6
To convert cc / min to gal. / hr. - Multiply by .015873

[Bullitt95]

The BSFC of N/A engines does vary quite a bit so 0.5 should only be used as a guide. The more efficient you make the engine, the lower the BSFC will become and the % increase in HP/TQ may be much higher than the % increase in injector flow required.
A bone stock 5.0 has a BSFC of about 0.52 but with H/C/I and intake/exhaust bolt-ons, it could drop down to about 0.43 or less.

[EagleAutosports]

These will answer many questions.

HORSEPOWER:

horsepower (HP) = torque (ft lbs) X rpm DIVIDED by 5252

DISPLACEMENT:

cubic inch displacement (cid) = bore X bore X stroke X .7854 X number of cylinders

REAR WHEEL HP CONVERTED TO FLYWHEEL HP:

rear wheel HP DIVIDED by 80 = flywheel HP

TORQUE:

torque = horsepower X 5252 DIVIDED by rpm

CARBURETOR SIZE:

carb cfm required = CID X max rpm DIVIDED by 3456

SAE/METRIC CONVERSION:

.061 cubic inch = 1 cubic centimeter

ESTIMATED HORSEPOWER BASED ON CFM:

HP = .2575 X CFM (at 28" of water) X number of cylinders

COMPRESSION RATIO:

compression ratio = S.V. + C.V. DIVIDED by C.V.

S.V. = 3.1416 X bore X bore X stroke DIVIDED by 4

C.V. = (chamber volume - gasket volume + deck clearance volume + gasket volume) X .061

[EagleAutosports]

Anyone have something to add to this, go ahead like the guys have about the injectors. Anything productive is encouraged, we're here to help our Mustang brothers.

[V8Demon]

Yes, Fuel pressure and it's effects on an injectors flow....

New flow rating = [square root of (new pressure /old pressure)] x old flow rating

Example:
New flow rating = [square root of (45 PSI / 39.6 PSI)] x 20.0 lbs./hr = 21.3 lbs./hr

According to FoMoCo all of their injector ratings are based on 40 PSI.


1 gallon = 3.8 liters. = approximately 6.5 pounds for one gallon/liter of gasoline.

Using 6.8 pounds/gallon we get:
HO injectors = 19 lbs/hr = 2.79 gal/hr = 10.62 liters/hr
8 HO injectors = 84.96 liters/hr

Using 6.5 pounds to the gallon we get:
HO injectors = 19 lbs/hr = 2.92 gal/hr = 11.108 liters/hr
8 HO injectors = 88.862 liters/hr

Using 6.2 pounds to the gallon we get:
HO injectors = 19 lbs/hr = 3.06 gal/hr = 11.645 liters/hr
8 HO injectors = 93.161 liters/hr

See how important it is to upgrade your pump as well as injectors?!

Now, gasoline does expand and contract a decent amount with temperature (colder gas is denser gas -- a gallon will weigh more when cold) Believe me on this one. You can ask anyone who has worked on aircraft and had them filled up overnight only to watch them vent gas an hour or so after sunrise. Different gases/fuels have different density as well.

Also, let me add that changing fuel pressure changes flow rates for both injectors AND pumps. As you raise pressure, injectors will actually flow more, however a fuel pump will flow less. More pressure on the pump means more restriction upstream. More pressure to an injector means more force behind the gas coming out of it, simply put anyway........

[t1320t]

Here's a simple link..
Autolounge.net | Calculators | Fuel Injector and Pump Sizing

[gbmust92]

Eagle,I'm trying to figure Compression ratio? I think I've got it all but deck clearance volume. I have a zero deck height. Does that make the volume zero? If it does I'm coming up with like 11:1. I am running a 331 with 61cc chambers. Thanks

[EagleAutosports]

Whoa, sorry for the slow response... just 4 months behind. If you're doing the calculation right, then it would be zero deck. If you figure on zero deck and then coming up with 11:1, then that should be close.

[EagleAutosports]

This was provided by a member and it's a good resource for fuel injection information.

[dudeboy]

for CR, why ignore the volume of space between the piston and cylinder wall down to the first ring?

[lugnutz08]

i know volume and pressure are seperate, and very confusing!!!

[MU3ST5ANG1]

Originally Posted by dudeboy

for CR, why ignore the volume of space between the piston and cylinder wall down to the first ring?

well technically, you wouldnt, however when you measure(using a cc plate and burette) the actual volume of that space(block pour) you would bring the piston to true TDC and seal off the space with grease, then add in 1cc to your other numbers (block pour, chamber,head gasket) to compensate for the grease.