#### marleyskater420

##### still needs to learn

- Joined
- Aug 14, 2004

I have been meaning to do this for quite some time now, and currently I am tired of staring at blueprints and finally felt like writing this up.

First off, we need to establish a few main terms that I will be referencing.

1) B.S.F.C.= Brake Specific Fuel Consumption. Definition= "Measure of how efficient the engine is combusting fuel at a given RPM".

Basically, how much fuel does your motor require at a certain RPM to make that power. Forget worrying about the RPM you will spin, the greater concern is the actual BSFC number.

A) Keep in mind the BSFC of the same fuel type

B) Why does the crappy flowing motor have a higher BSFC? Because the crappy-flowing motor requires more fuel to make the same power due to the inefficiency of the motor.... basically because your motor sucks at having well-flowing cylinder heads, it takes more fuel to make the same power as a car with well-flowing heads...similar to how guys with stage 2 motors and crazy flowing heads can make power on a turbo at 20psi that it may take a guy with ported iron heads 28-29psi to make. Get the general idea? (before some douche posts "well there are other things that factor in too!" may I remind you that this is a basic 101-level thread and I am trying to simplify this, so stfu and go pick a e-fight elsewhere)

C) For reference:

N/A gas motors have a BSFC of .5-.55 (now some motors may be less, some more)

Turbo gas motors have a BSFC of .6-.65

N/A methanol motors have a BSFC of about 1.1

D) The BSFC of E85 is somewhat contested/varied over what you may find on the internet. I have seen some DOHC 4 cylinders able to use a BSFC .79 for E85, and others I have seen almost hit .90-again, it

2) How the hell do I calculate what this "BSFC" is? Or better yet, now that I know what number I am going to use for my BSFC on my E85 motor, how can I put that to good use?

A) If you want to calculate your own BSFC for your car, and you are able to log and accurately determine how much fuel your engine is consuming, you can use the following equation:

BSFC=

B) Example: BSFC = 160lb/hr fuel flow consumption / 400hp motor = 160/400=.4 BSFC

- That would mean that this motor makes 400hp at the crank, and only consumes 160lb/hr in fuel..that would mean on a 6 cylinder motor, the engine would only be using 26.67lb /hr fuel per-cylinder for all 6 cylinders, and creating 400hp. For reference, .4 BSFC is a very efficient motor.

C) If we know that BSFC = LB/hr in fuel flow / obs. HP, then we also know that ->

-> LB/hr fuel flow= BSFC x Obs Hp

a) This means that if we know what our target Horsepower level is (how much power you want to make) and what our BSFC we want to use is (we already decide on .85) then we can multiply those by each other and determine how much fuel flow the engine

b) EX: If our BSFC is .85, and we want to see how much fuel we need to make 700hp ...

.85 (BSFC) X 700hp (our HP goal) = 595 Lb/Hr in fuel flow!

c) If we need 595 lb/hr fuel for our 6 cylinder engine, we need to divide 595 by 6 -> 595 / 6 = 99.17lb/hr PER INJECTOR IN ORDER TO MAKE 700FWHP USING A BSFC OF .85 FOR E85.

d) If you need to convert Lb/Hr into GPH (Gallons Per Hour) you take the lb/hr number and divide it by 6, and it gives you the GPH total. If you want to go from GPH to Lb/Hr, just multiply the GPH number by 6 and you have the Lb/hr number.

D) What if we want to calculate the fuel needed for our motor using different fuel injector duty cycle percentages?

a) Why does this matter? When you are selecting your injectors, you do not want to pick an injector that would make the HP you are aiming for at 100% duty cycle because of issues with the injector that I won't get into here. Just know that most reputable shops that actually give 2 shits about you and your car will calculate the fuel flow for each injector using a duty cycle of no more than 80% or 85%.

b) To calculate the duty cycle at various percentages, we first need to use our equation to find out how much fuel is needed per injector for our motor.

Q= Injector flow rate in lbs/hr

Max hp= estimate of engines max HP

BSFC= Brake Specific Fuel Consumption for given fuel. We are using .85 for E85

c) EX: Q = 400 (max HP) X .85 (BSFC) / 6 (# of cylinders) = 56.67 lb/hr PER INJECTOR at 100% flow

d) Now that we have our flow rate required per cylinder, we want to find out what the size injector we need if we want to have the injector work at less than 100% duty cycle.

*The formula for this is : lb/hr per injector / .90 (90%, .8 is 80%, etc etc) = injector size needed to flow that fuel amount with a 90% duty cycle.

*EX: If we use our 56.67, it would look like this to calculate what size injector we need if we wanted it to flow that at 90% duty cycle : 56.67 / .90 = 62.97lb/hr

*If we wanted to see what injector was needed at 80% duty cycle, it would look like this:

56.67 / .8 = 70.83 lb/hr

So why does all this math matter, and how can I use it?

1) If you want to figure out how injector you need for a certain horsepower target, you can now use the formula Q= Horsepower X BSFC / # of cylinders (where Q is the injector size in lbs/hr)

So if you want to know what size injectors you need for 850fwhp on E85, you can use that formula easily=

850 X .85 / 6 = 120.41 lb/hr (this is at 100% duty cycle)

If we want to know what size injectors we need if we only want an 80% duty cycle, we can use the other formula= 120.41 (calculated from the previous formula that tells us how much fuel we need) / .80 = 150.51 lb/hr injectors to flow enough for 850fwhp on E85 an only have a 80% duty cycle.

So, some basic HP ratings for those who just want the easy way out and don't bother to learn.

600fwhp = 85 lb/hr

650fwhp = 92 lbs/hr injector at 100% duty cycle

700fwhp = 99 lb /hr

750fwhp =106.25 lb/hr

800fwhp = 113 lb/hr

850fwhp = 120 lb/hr

900fwhp = 127.50 lb/hr

950fwhp = 135 lb/hr

1000fwhp = 141 lb/hr

Now there is another way to calculate all of this and still be on the safe side, and that is to calculate the fuel requirement (BSFC X HP = fuel flow required) and multiply that number by 40% to be on the safe side. Yes, E85 uses roughly 30% more fuel, but in life there are things like tolerances/pressure increases from the fuel line plumbing/safety net, so using 40% is a very safe way to calculate things as well. You would use a BSFC of .65 for a gasoline turbo engine, and calculate the flow with that, and then add 40%.

So- a 600fwhp gas turbo motor X .65 BSFC = 390 lbs/hr

Then- 390 X .40 = 156 lb/hr

Then- 390 lb/hr + 156 lb/hr = 546 lb/hr, which when divided by 6 (number of cylinders) gives you 91lbs/hr, which you will see is even higher than the number I calculated using .85 for E85 BSFC.

You can do it either way. For whatever it may be worth, Kinsler Fuel Injection uses the 40% addition method-calculate the fuel required on a boosted gas motor, and add 40% to that.

Hopefully this comes in handy to someone looking to find out what injector size will work for them.

Alright Go down a few posts to learn how to select what type of fuel pump will work with your setup.

First off, we need to establish a few main terms that I will be referencing.

1) B.S.F.C.= Brake Specific Fuel Consumption. Definition= "Measure of how efficient the engine is combusting fuel at a given RPM".

Basically, how much fuel does your motor require at a certain RPM to make that power. Forget worrying about the RPM you will spin, the greater concern is the actual BSFC number.

A) Keep in mind the BSFC of the same fuel type

__vary from motor to motor. Since one of the operative words in the definition is__**CAN**__efficient__the BSFC for a OHV N/A V6 with crappy head flow will be higher than a DOHC N/A V6 with 4 valves per cylinder, and lots of headflow.B) Why does the crappy flowing motor have a higher BSFC? Because the crappy-flowing motor requires more fuel to make the same power due to the inefficiency of the motor.... basically because your motor sucks at having well-flowing cylinder heads, it takes more fuel to make the same power as a car with well-flowing heads...similar to how guys with stage 2 motors and crazy flowing heads can make power on a turbo at 20psi that it may take a guy with ported iron heads 28-29psi to make. Get the general idea? (before some douche posts "well there are other things that factor in too!" may I remind you that this is a basic 101-level thread and I am trying to simplify this, so stfu and go pick a e-fight elsewhere)

C) For reference:

N/A gas motors have a BSFC of .5-.55 (now some motors may be less, some more)

Turbo gas motors have a BSFC of .6-.65

N/A methanol motors have a BSFC of about 1.1

D) The BSFC of E85 is somewhat contested/varied over what you may find on the internet. I have seen some DOHC 4 cylinders able to use a BSFC .79 for E85, and others I have seen almost hit .90-again, it

__depends on the engine combination, but to solve that for us, I will be using a number of .85 that will pretty much cover any Buick combination you have-so guys with entirely stock setups can use .85 and be completely fine with the number they arrive at. Obviously those who have high-flowing heads may choose to use something more around .83 or .81, but I have learned that the LAST thing you want to do, is skimp on your fuel system when making high horsepower..____. Kinda easy to remember, no?__**For the sake of argument, and to keep things on the safer side, we will use a BSFC of .85 for E85**2) How the hell do I calculate what this "BSFC" is? Or better yet, now that I know what number I am going to use for my BSFC on my E85 motor, how can I put that to good use?

A) If you want to calculate your own BSFC for your car, and you are able to log and accurately determine how much fuel your engine is consuming, you can use the following equation:

BSFC=

**LB/Hr in fuel flow**(for the entire motor)**/**(**divided by**)**Observed Horsepower**B) Example: BSFC = 160lb/hr fuel flow consumption / 400hp motor = 160/400=.4 BSFC

- That would mean that this motor makes 400hp at the crank, and only consumes 160lb/hr in fuel..that would mean on a 6 cylinder motor, the engine would only be using 26.67lb /hr fuel per-cylinder for all 6 cylinders, and creating 400hp. For reference, .4 BSFC is a very efficient motor.

C) If we know that BSFC = LB/hr in fuel flow / obs. HP, then we also know that ->

-> LB/hr fuel flow= BSFC x Obs Hp

a) This means that if we know what our target Horsepower level is (how much power you want to make) and what our BSFC we want to use is (we already decide on .85) then we can multiply those by each other and determine how much fuel flow the engine

__needs to make that power!__**as a whole**b) EX: If our BSFC is .85, and we want to see how much fuel we need to make 700hp ...

.85 (BSFC) X 700hp (our HP goal) = 595 Lb/Hr in fuel flow!

c) If we need 595 lb/hr fuel for our 6 cylinder engine, we need to divide 595 by 6 -> 595 / 6 = 99.17lb/hr PER INJECTOR IN ORDER TO MAKE 700FWHP USING A BSFC OF .85 FOR E85.

d) If you need to convert Lb/Hr into GPH (Gallons Per Hour) you take the lb/hr number and divide it by 6, and it gives you the GPH total. If you want to go from GPH to Lb/Hr, just multiply the GPH number by 6 and you have the Lb/hr number.

D) What if we want to calculate the fuel needed for our motor using different fuel injector duty cycle percentages?

a) Why does this matter? When you are selecting your injectors, you do not want to pick an injector that would make the HP you are aiming for at 100% duty cycle because of issues with the injector that I won't get into here. Just know that most reputable shops that actually give 2 shits about you and your car will calculate the fuel flow for each injector using a duty cycle of no more than 80% or 85%.

b) To calculate the duty cycle at various percentages, we first need to use our equation to find out how much fuel is needed per injector for our motor.

__Formula:__Q= Max H.P. X BSFC / # of cylinders (that means= The max HP you want to make, multiplied by the BSFC for that fuel, divided by the number of cylinders in the engine)Q= Injector flow rate in lbs/hr

Max hp= estimate of engines max HP

BSFC= Brake Specific Fuel Consumption for given fuel. We are using .85 for E85

c) EX: Q = 400 (max HP) X .85 (BSFC) / 6 (# of cylinders) = 56.67 lb/hr PER INJECTOR at 100% flow

d) Now that we have our flow rate required per cylinder, we want to find out what the size injector we need if we want to have the injector work at less than 100% duty cycle.

*The formula for this is : lb/hr per injector / .90 (90%, .8 is 80%, etc etc) = injector size needed to flow that fuel amount with a 90% duty cycle.

*EX: If we use our 56.67, it would look like this to calculate what size injector we need if we wanted it to flow that at 90% duty cycle : 56.67 / .90 = 62.97lb/hr

*If we wanted to see what injector was needed at 80% duty cycle, it would look like this:

56.67 / .8 = 70.83 lb/hr

So why does all this math matter, and how can I use it?

1) If you want to figure out how injector you need for a certain horsepower target, you can now use the formula Q= Horsepower X BSFC / # of cylinders (where Q is the injector size in lbs/hr)

So if you want to know what size injectors you need for 850fwhp on E85, you can use that formula easily=

850 X .85 / 6 = 120.41 lb/hr (this is at 100% duty cycle)

If we want to know what size injectors we need if we only want an 80% duty cycle, we can use the other formula= 120.41 (calculated from the previous formula that tells us how much fuel we need) / .80 = 150.51 lb/hr injectors to flow enough for 850fwhp on E85 an only have a 80% duty cycle.

So, some basic HP ratings for those who just want the easy way out and don't bother to learn.

**:**__THESE NUMBERS ARE THE FLOW RATES PER INJECTOR AT 100% DUTY CYCLE__600fwhp = 85 lb/hr

650fwhp = 92 lbs/hr injector at 100% duty cycle

700fwhp = 99 lb /hr

750fwhp =106.25 lb/hr

800fwhp = 113 lb/hr

850fwhp = 120 lb/hr

900fwhp = 127.50 lb/hr

950fwhp = 135 lb/hr

1000fwhp = 141 lb/hr

Now there is another way to calculate all of this and still be on the safe side, and that is to calculate the fuel requirement (BSFC X HP = fuel flow required) and multiply that number by 40% to be on the safe side. Yes, E85 uses roughly 30% more fuel, but in life there are things like tolerances/pressure increases from the fuel line plumbing/safety net, so using 40% is a very safe way to calculate things as well. You would use a BSFC of .65 for a gasoline turbo engine, and calculate the flow with that, and then add 40%.

So- a 600fwhp gas turbo motor X .65 BSFC = 390 lbs/hr

Then- 390 X .40 = 156 lb/hr

Then- 390 lb/hr + 156 lb/hr = 546 lb/hr, which when divided by 6 (number of cylinders) gives you 91lbs/hr, which you will see is even higher than the number I calculated using .85 for E85 BSFC.

You can do it either way. For whatever it may be worth, Kinsler Fuel Injection uses the 40% addition method-calculate the fuel required on a boosted gas motor, and add 40% to that.

Hopefully this comes in handy to someone looking to find out what injector size will work for them.

Alright Go down a few posts to learn how to select what type of fuel pump will work with your setup.

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