Basic Math On Fuel/air Ratios That Gets Ignored

[Grumpy]

1 cubic foot of air at standard temperature and pressure assuming average composition weighs approximately 0.0807 lbs. (at sea level)
that simply means it takes 12.4 cubic feet of air to equal one pound,
your best engine torque is generally found at a fuel/air ratio near 12.6:1 ,
thats 12.6 pounds of air per pound of fuel.
now lets do some math,
remember the intake stroke is only every other revolution,
lets say you built a 454 chevy engine, 454/8+ 56.75 cubic inches per cylinder.
theres 1728 cubic inches of air in a cubic foot,
thus it takes a single cylinder rotating about 61 revolutions,
to ingest a cubic foot of air,
but of course its a V8 ,
so in reality your looking at about 7.62 revolutions to ingest
that cubic foot of air. (assuming near 100% efficiency)
which can only be achieved with good exhaust scavenging
and correct matched cam timing,
free lowing exhaust and of course decent heads and intake designs

the days of easy access too $.34 cents a gallon SUNOCO 260 are unfortunately now just a distant,
but pleasant memory
but E85 has some significantly increased octane potential if your willing to deal with some issues

think about that, every 7.62 revolutions it sucks in nearly 1 cubic foot of air, if we assume most nearly stock engines idle at about 800 rpm...your looking at the engine at idle ingesting about 105 cubic feet of air every minute at idle speeds. at 6500 rpm, your looking at about 853 cubic feet of air ingested near peak rpms
853 cubic feed of air volume about 1 lb of fuel per 12.6 lbs of air,it takes 12.4 cubic feet of air to equal one pound, that would require about 5.45 lbs of fuel
per minute at peak rpms.
gasoline generally weights near 6 lbs per gallon, so at peak power a 454 could potentially burn almost a 9/10th of a gallon per minute.
that also means that the fuel delivery system must keep up with demand, so in the example above I would suggest nothing less than a fuel system fully capable of providing about 75-80 gallons per hour (remember even if your fuel pump can theoretically deliver 100 gph, theres flow losses in the fittings filters and lines so Id advise a fuel delivery with line sized 3/8" minimum and ideally a full 1/2" inside diameter on any serious muscle car application )

Given Horsepower x .50 lb fuel/hp = lbs of fuel for given horsepower

To calculate Fuel Consumption for a 400 hp Gas engine with a BSFC of .50 lbs/hp/hr:

400 hp x .50 = 200 lbs/hr

To convert this lbs/hr to a more meaningful gallons per hour we use the conversion rate from lbs to gallons which is 6.2 lbs to 1 gallon of gas

200 lbs/hr / 6.2 lbs/gal = 32.25 gph
BSFC .50 / 6.2 = .0806 gallons / horsepower / hour.

Again we calculate Fuel Consumption for a 400 hp Gas engine.

400 hp x .0806 = 32.24 gph

Remember, if you are running E85 or Methanol be sure to use those BSFC values in your formula. To calculate peak fuel consumption for a 800 hp E-85 engine we can use a BSFC of .70 and the formulas below.

800 hp x .70 = 560 lbs/hr 560 lbs/hr / 6.2 lbs/gal = 90.32 gph

OR

BSFC .70 / 6.2 = .113 gallons / horsepower / hour

800 * .113 = 90.40 gph

Note: These gph flow rates may seem high when compared to your daily driver on the highway, but remember these are not averages, these are flow at loaded peak output.

USE THE CALCULATORS to match port size to intended rpm levels... but keep in mind valve lift and port flow limitations
http://www.wallaceracing.com/runnertorquecalc.php
http://www.wallaceracing.com/ca-calc.php
http://www.wallaceracing.com/area-under-curve.php
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php
http://www.circletrack.com/enginetech/1 ... ch_engine/
https://performancedevelopments.com/fuel-flow-calculations-for-horsepower/
http://blog.cantonracingproducts.com/blog/how_to_estimate_your_engines_fuel_flow

be aware that the cross sectional area of both the fuel lines and fuel filter medium,
and the fuel pressure regulator and return line cross sectional area all effect the fuel delivery efficiency
and fuel delivery consistency is critical,, you need a certain, dependable,
fuel volume available, pressure increases only go so far in correcting lack of required fuel delivery issues,
and you might get by with a cars stock 3/8" lines on a dyno , but once your dealing with inertial loads,
and longer duration, high power runs a 3/8" line is usually hopeless on a 750-1000 hp engine

http://garage.grumpysperformance.com/index.php?threads/setting-up-your-fuel-system.211/#post-26636

http://garage.grumpysperformance.co...-big-a-fuel-pump-do-you-need.1939/#post-21738

http://garage.grumpysperformance.co...e-required-octane-for-compression-ratio.2718/

related info
http://garage.grumpysperformance.co...e-required-octane-for-compression-ratio.2718/

http://garage.grumpysperformance.com/index.php?threads/calculate-fuel-injector-size.1200/

http://garage.grumpysperformance.com/index.php?threads/how-big-a-fuel-pump-do-you-need.1939/

http://garage.grumpysperformance.co...engine-volumetric-efficiency.6254/#post-55061

http://garage.grumpysperformance.com/index.php?threads/intake-runner-question.12899/

https://www.raceworks.com.au/calculators/injector-hp-calculator/

http://garage.grumpysperformance.co...es-restrict-fuel-flow-rates.12859/#post-66683

http://garage.grumpysperformance.co...ss-fuel-pressure-regulators.12776/#post-65998

http://garage.grumpysperformance.com/index.php?threads/bits-of-427-bbc-build-related-info.15543/

http://garage.grumpysperformance.co...-sizing-return-vs-feed.3067/page-3#post-61157

 

[Grumpy]

if you don,t read the links and sub links ,
in the threads posted on this web site,
and use the provided calculators your probably missing well over 80%
of the info you need to build a potentially impressive and durable engine.
yes Im aware some guys would rather skip the research and reading,
those are inevitably the guys wondering

HOW COME THE CAR JUST CAN'T GET DECENT TRACTION
WHY DID THAT PART BREAK?
HOW DO YOU INSTALL OR TEST THIS?
HOW COME THE OTHER GUYS CAR IS FASTER?
WHY DID HE BUY THAT PART?
I WISH THEY MADE A TOOL FOR THAT? (THEY PROBABLY DO)
WHY CAN'T I GET THIS CORRECTLY ADJUSTED?
WHY DOESN'T THE PART FIT CORRECTLY?

https://www.jepistons.com/blog/compression-ratio-theory-and-how-to-calculate-in-powersports

https://www.hotrod.com/articles/0311em-power-squeeze/

http://www.bgsoflex.com/crchange.html

http://www.wallaceracing.com/hp-cr-chg.php

http://garage.grumpysperformance.co...c-vs-static-compression.727/page-2#post-94269

http://www.wallaceracing.com/Calculators.htm

http://garage.grumpysperformance.co...ing-parts-and-a-logical-plan.7722/#post-85144

it generally helps to have a few diagnostic tools at hand, they don,t need to be top quality but you do benefit from experience and the knowledge of what your trying to accomplish and an isolate and test mentality

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14 Function Digital Multimeter with Sound Level and Luminosity

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Fuel Pump and Vacuum Tester

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Amazon.com

 

[Indycars]

1 cubic foot of air at standard temperature and pressure assuming average composition weighs approximately 0.0807 lbs. (at sea level)
that simply means it takes 12.4 cubic feet of air to equal one pound,
your best engine torque is generally found at a fuel/air ratio near 12.6:1 ,
thats 12.6 pounds of air per pound of fuel.
now lets do some math,
remember the intake stroke is only every other revolution,
lets say you built a 454 chevy engine, 454/8+ 56.75 cubic inches per cylinder.
theres 1728 cubic inches of air in a cubic foot,
thus it takes a single cylinder rotating about 61 revolutions,
to ingest a cubic foot of air,
but of course its a V8 ,
so in reality your looking at about 7.62 revolutions to ingest
that cubic foot of air. (assuming near 100% efficiency)

think about that, every 7.62 revolutions it sucks in nearly 1 cubic foot of air, if we assume most nearly stock engines idle at about 800 rpm...your looking at the engine at idle ingesting about 105 cubic feet of air every minute at idle speeds. at 6500 rpm, your looking at about 853 cubic feet of air ingested near peak rpms
853 cubic feed of air volume about 1 lb of fuel per 12.6 lbs of air,it takes 12.4 cubic feet of air to equal one pound, that would require about 5.45 lbs of fuel
per minute at peak rpms.
gasoline generally weights near 6 lbs per gallon, so at peak power a 454 could potentially burn almost a 9/10th of a gallon per minute.

I tried to follow your calculations, step-for-step. If you consider the table below it should progress
from the first column to the last column.



To make it easier to digest the data, I provided the graph below .....



Or if you prefer, there is the graphic below that has both Data and Graph in ONE image.



I must have really enjoyed creating the graphics above, I spent several hours playing
with them !!!

Open to suggestion for more graphs or changes to the above.

Download the Excel file below .....
.

spark plug info

spark plug info..SO!...read thru the links theres a ton of good info, but its spread over all the links, if you can get that skill mastered your well ahead of most guys who fail to take the time and effort to learn that skill guys frequently ask me what plug gap to use, Provided your ignition...

garage.grumpysperformance.com

reading plugs

YOU REALLY NEED TO READ THRU ALL THESE THREADS AND SUB LINKS TO GET A GOOD BASIC UNDERSTANDING http://www.4secondsflat.com/Spark_plug_reading.html http://www.strappe.com/plugs.html http://garage.grumpysperformance.com/index.php?threads/383-with-ignition-knock-issues.14293/#post-72961...

garage.grumpysperformance.com

Basic Math On Fuel/air Ratios That Gets Ignored

1 cubic foot of air at standard temperature and pressure assuming average composition weighs approximately 0.0807 lbs. (at sea level) that simply means it takes 12.4 cubic feet of air to equal one pound, your best engine torque is generally found at a fuel/air ratio near 12.6:1 , thats 12.6...

garage.grumpysperformance.com

you want a controlled burn (that generally takes 30-50 thousands of a second)
where a rapid increase in pressure above the piston forces it down the cylinder,
and you want to avoid detonation, that will rapidly damage a piston

A spark plug only functions completely when its center electrode temperature is between these temperatures of about 500°C and 950°C.
keep in mind just rapidly compressing the fuel/air mix rapidly raised the mixtures temperature enough that it can cause it to self ignite
(detonation) one reason you use quench & squish in the combustion chamber design to get the ignition to start and burn uniformly, and ideally starting in the near center of the combustion chamber and racing out toward the outer edges rather than self ignition near the edges that will rapidly result in piston damage from excessive pressure and heat.
remember at 850 rpm (idle speed ) your compressing a new cylinder full of fuel/air , 7 times a second at 6000 rpm it is 50 times a second.

The following examples detail the typical temperatures of various combustion-related engine parts during normal operation:

• Intake valve: 475° F
• Exhaust valve: 1,200° F
• Spark plug: 1,100° F
• Piston face: 575° F
• Cylinder wall: 375° F

"The most commonly known flammable liquid is gasoline.
It has a flash point of about −50° F (−65° C). The ignition temperature is about 495° F (232(232° C) [sic], a comparatively low figure."
The temperature of the burning gases inside the combustion chamber is typically around 2,800° F. In a diesel engine, this temperature remains fairly steady. In a gasoline-powered engine, the temperature can climb to 4,500° F or more under certain circumstances. However, the vehicle's engine cooling system keeps the walls of the combustion chamber at a temperature of between 265° F and 475° F.

Heat Range | Basic Knowledge | SPARK PLUG | Automotive Service Parts and Accessories | DENSO Global Website

An explanation of the relationship between the degree of dispersion of the heat the spark plug is subjected to and vehicle speed.

www.denso.com

detonation issues???

Hi guys, I NEED some advise here... I have a 350 sbc motor that has been bored out 40 over, 6" piston rods, dished out piston heads at 20cc, 3.750 stroke crankshaft, my deck clearance is -.006, Trick flow 175 cylinder head chamber size is 56cc, mild Elgin 923 cam, and an .042 head gasket... I...

garage.grumpysperformance.com

What is the temperature inside the combustion chamber of an engine?

Answer (1 of 9): As there appears to already be some engineering based answers, I will defer from a scientific answer, and give you my real world aviation experience. Flying my PA-31–325 Navajo, it being equipped with two turbo charged, air cooled six cylinder engines producing 325 horsepower eac...

www.quora.com

calculate required octane for compression ratio

What else influences your car's octane requirements? IF YOU DON,T LIKE READING SUB-LINKS, AND LOOKING AT CHARTS , AND DOING A BIT OF MATH 'AND INDIVIDUAL CALCULATIONS, YOUR UN-LIKELY TO BENEFIT FROM MOST OF THE THREADS, ON THIS WEB SITE! LIKE IN MOST AREAS ITS KNOWLEDGE AND THE ABILITY TO THINK...

garage.grumpysperformance.com

How Hot Does A Combustion Chamber Get In A Vehicle? [The Answer Might Surprise You!]

Whether you're a weekend DIY mechanic, a diehard gearhead, or just a vehicle owner curious about how your car works, you may want to know more about how the engine burns fuel to create power. Many common questions center on what causes engine overheating. You may be wondering just how hot it...

vehq.com

Heat Range | Basic Knowledge | SPARK PLUG | Automotive Service Parts and Accessories | DENSO Global Website

An explanation of the relationship between the degree of dispersion of the heat the spark plug is subjected to and vehicle speed.

www.denso.com

https://www.researchgate.net/figure...w-the-change-of-the-crankshaft_fig4_355930276


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[Grumpy]

wow, thats impressive,
its also rather reassuring to find someone,
actually reads these threads and linked info/

 

[Indycars]

Thanks !

Any changes you would like to see ?

 

[Grumpy]

Fuel Line Sizing -- What Size Do I Need?
https://ipgparts.com/blogs/blog/fuel-line-sizing-what-size-do-i-need
November 16, 2012 • -10an • -6an • -8an • an fittings • an line size • an to inch conversion • fuel line horsepower requirements • gas • General • horsepower fuel • how much fuel do i need • Technical Articles • what size fuel line

Lots of strange information out on the internet regarding fuel line sizing and it seems like most of the time people run way more diameter fuel line than they need. This is an interesting article that I came across that seems to be pretty relevant. Quick reference for AN to Inch line conversion: -6AN = 3/8" -8AN = 1/2" -10AN = 5/8" -12AN = 3/4" Fuel Line Sizing A question that is often asked of me when dealing with high horsepower applications is: “My fuel line is nominal 3/8” id. Don’t I need to increase the size of the fuel line to at least ½” id (from a #6 to a #8 or #10) to support say 600 HP”? The answer is “NO”! A 3/8”id fuel line can easily support 600 HP given sufficient “pump head”! Given a big enough pump a 3/8” steel line could support 1000 HP. The simple way to know is to install an electronic fuel pressure gage. If the pressure falls as the engine RPM’s go up you need more pump head. More pump head can be achieved with a bigger pump, higher pump voltage and/or increasing the line size. But before you do check out the following (and remember a dirty fuel filter is often the culprit of falling fuel pressures!). The reason most people do not understand why is because “back in the day” when carburetors ruled and everybody ran a Holly electric fuel pump running at 14 psig then into a rail mounted PRV set to 6 psig the “pump head” was insufficient to overcome the pressure drop thru the 3/8” line: particularly if the pump was at the front of the vehicle. Let’s see why today this is what I call a “wives’ tale”. For this example I will use gasoline. If we use alcohol we need about double the flow or with E85 we need to increase the flow numbers by around 30 % . At WOT (Wide Open Throttle) a BSFC (Brake Specific Fuel Consumption) of ½ pound of fuel per horsepower is quite safe: resulting in A/F ratios of 11:1 or richer. Remember that maximum HP occurs at an A/F ratio of 13:1. We won’t go into why one chooses such rich air fuel ratios; suffice to say that using a BSFC of .5 is generous. Since gasoline has a weight of 5.994 lbs/gallon (@ a SG of .7201 typical) then in round numbers we need 1 gallon of gasoline per 12 HP (5.994/.5). The reason I am making all these conversions for you is because typical fuel pump measurements are made in volume versus mass although mass is more accurate. OK stay with me now as we calculate how much gasoline fuel we need to support say 1000 HP. 1000 divided by 12 = 83.3 Gallons Per Hour or 315 Liters Per Hour. Now we are going to calculate the pressure drop thru a 3/8” steel line for a typical vehicle at a flow of 83.3 gph or 1000 HP. Most of you know that the pressure drop thru a straight pipe is less than an elbow or a 45 (same principle as your air ducting from your blower thru the piping and on into the engine). Lets assume we have about 10 feet of 3/8” fuel line. Let’s double that to say 20 feet to take care of the bends in the steel pipe from the gasoline tank up to the engine fuel rail. Ingersoll-Rand publishes an engineers’ handbook called “Cameron Hydraulic Data”. In there they list the “Friction Of Water” thru various types of pipe. Using the pressure drop thru a new steel pipe of .364” id at 1.388 gpm (83.3 gph) we get a head loss of 35 feet per 100 feet of pipe with water as the medium. 2.31 feet of water = 1 psi therefore 35/2.31 = 15 psi per 100 feet. If I use 20 feet of steel pipe then that is 1/5 of 15 or 3 psi using water (gasoline is less viscous and flows more freely). A Fuelab Model 41401 can deliver 90 gph @ 70 psig. Can I tolerate a 3 psig drop if I need the fuel delivered at 60 psig? Yes. Will increasing the line size to ½” help? Yes the pressure drop thru a ½” line is a nominal 5 feet versus 35 feet for the 3/8” id fuel line. The ½” line will result in a ½ pound drop versus the 3 pound drop for the 3/8” line at the stated flow of 83.3 gph (enough to support 1000 HP at a BSFC of .5). The pressure drop at 1320 HP thru a 3/8” steel line might be around 5 psi. The key to sufficient fuel supply is pumping power. As another example let’s look at a flow of 1 gallon per minute at a required fuel rail pressure of 70 psig. That is enough fuel to support 720 HP. The pressure drop thru a 3/8”id line at 60 GPH is less than 1 psig! Switching to a ½” id line would result in a pressure of about 1/10 of the 3/8” line. However, given sufficient pumping power, a one (1) pound drop versus a tenth (1/10) pound drop is insignificant. At 500 HP the pressure drop is even less. VISCOSITY SG plays no role in friction loss. The key factors are viscosity and surface tension of the liquid being pumped. Gasoline has lower viscosity and much lower surface tension than water, which is why it flows more easily thru a pipe. Consider that most greases have a lower SG than water but much higher viscosity. Which do you think flows more easily thru a pipe? SG becomes a factor if there is vertical lift of the liquid involved or very long pipe runs (which represent a large physical mass of liquid.) SG simply determines the weight of the liquid per unit volume and it boils down to more weight requires more power (HP) to move it. Friction loss is the mechanical resistance exercised by the pipe wall on the liquid. Low surface tension and/or low viscosity liquids overcome that resistance more easily. Here is a little experiment you can try. Water has relatively high surface tension. Alcohol greatly reduces that tension. Place a small drop of water on a counter top. (The counter top is analogous to the pipe wall) The water lies on the counter as a small bubble. Don’t touch the water but let a very small drop of alcohol drip into the water. Watch the water immediately spread out on the counter top. The alcohol broke down the surface tension and the water molecules were free to move. If you put a drop of gasoline or alcohol (low surface tension liquids) on the counter top you see they immediately spread out. BTW, this is an area of misunderstanding with people. Sourced from http://www.blowerworks.biz/docs/fuel-delivery-basics/fuel-line-sizing/

 

[Grumpy]

Fuel Line: What Sizes Do You Need
https://www.jymfg.com/fuel-line-what-sizes-do-you-need/

A fuel hose（https://en.wikipedia.org/wiki/Fuel_line） is a hose used to bring fuel from one point in a vehicle to another or from a storage tank to a vehicle. It includes Fuel injection hose, Marine fuel hose, Farm fuel hose, Diesel fuel hose, Fuel transfer hose. It is commonly made of reinforced rubber to prevent splitting and kinking.

The United States Environmental Protection Agency defines a fuel line as “all hoses or tubing designed to contain liquid fuel or fuel vapor. This includes all hoses or tubing for the filler neck, for connections between dual fuel tanks, and for connecting a carbon canister to the fuel tank. This does not include hoses or tubing for routing crankcase vapors to the engine’s intake or any other hoses or tubing that are open to the atmosphere.



Marine fuel hose is specifically designed and branded for use in supplying fuel to motors in boats or marine vessels. USCG Type A1 hoses are designed for fuel feed applications where the fuel is constantly in the hose, whereas Type A2 hoses are designed for fuel fill type hoses only. The “A” refers to meeting flammability tests and the “1 or 2” differentiates the hoses for fuel permeability tests – “1” being suitable for constant fuel contact where as “2” would not meet constant fuel permeability.

Fuel Hose Sizes
AN Size Tube or Hose OD Tube or Hose ID
-6 3/8” .297”
-8 1/2” .391”
-10 5/8” .484”
-12 3/4” .609”

http://garage.grumpysperformance.co...-blow-bye-and-related-info.16790/#post-102614

With a wide selection of durable fuel hoses, JYM makes it easy to find the perfect solution for any material-handling application. From high-pressure braided and spiral hoses for hydraulic systems to low-pressure, small-bore industrial hoses, JYM manufactures each fuel hose to match the requirements of the application and never compromises on quality. JYM fuel hose safely handles a wide variety of petroleum based fuels in depot, dispenser, dock, engine fuel line, in-plant transfer, transport and tank truck suction and discharge service. The hoses are compatible with many fuels such as av gas, bio diesel, diesel, gasoline and jet fuel, and are available in a diverse range of pressures, sizes and temperature capabilities.