Air fuel ratio comparison

[Rider57]

The nominal (chemically correct) air fuel ratio is 14.64:1 by mass (not volume) for burning 100% gasoline, but in practice the nominal air fuel ratio for most 100% gasoline fuel injection systems ranges from about 14.6 to 14.7 for a typical nominal value, depending on manufacturer, with the ratio of 14.7 being slightly preferred for increasing fuel economy under light load conditions.

The attached table shows the range of air fuel ratios typically used for burning gasoline, E85, and pure ethanol (E100) under an assortment of assumed operating conditions.


The term AFRst refers to the air fuel ratio under stoichiometric or ideal air fuel ratio mixture conditions. (See stoichiometry.) FARst refers to the fuel air ratio under stoichiometric conditions, and is simply the reciprocal of AFRst.

Equivalence ratio is the ratio of actual fuel air ratio to stoichiometric fuel air ratio; it provides an intuitive way to express richer mixtures. Lambda (λ) is the ratio of actual air fuel ratio to stoichiometric air fuel ratio; it provides an intuitive way to express leanness conditions (i.e., less fuel, less rich) mixtures of fuel and air.
The estimated required E85 summer blend air fuel ratio compares very closely to the value of 9.765 given in the table. In practice, though, the exact stoichiometric air fuel ratio for gasoline varies as a function of the exact blend of gasoline, which, in turn, is varied by time of year by refineries to increase or decrease volatility, prevent vapor locking, etc., for better matching seasonal climatic changes. This ratio is also varied with non-E85 gasoline during seasonal changes by the various additives used by vendors of national blends.

Deviations from stoichiometric combustion computed values are required during non-standard operating conditions such as heavy load, or cold weather operation, in which case the mixture ratio can range from 10:1 to 18:1 for burning 100% gasoline. Slightly wider ranges than even this on the low end of the air fuel ratio, dropping to below 8:1, are required for burning all possible blends of E85 and gasoline efficiently under all conditions of engine loads and inlet air temperatures.

All of these theoretical stoichiometric combustion estimated values should be taken only as approximations to what may really be required for achieving perfect combustion. The lambda sensor is what ultimately confirms whether stoichiometric combustion is taking place in practice.

Additionally, the ideal stoichiometric mixture typically burns too hot for any situation other than light load cruise. This is the target mixture that the ECU attempts to achieve in closed-loop fueling to get the best possible emissions and fuel mileage at light load cruise conditions. This mixture typically can give approximately 95% of the engine's best power, provided the fuel has sufficient octane to prevent damaging detonation (i.e., knock).
It is this 95% issue that causes problems in the common unmodified MOCO engine.

Lambda, typically used for referring to lean versus rich air fuel mixtures, is normally measured by the lambda sensor] (also known as an oxygen sensor.)

This is just a FYI.
I will post some more information once I am back in Houston.



[attachment removed after 60 days by system]

[Steve Cole]

This should be a little of an eye opener for some and good reference material for others. With all the blends that are being done today after the fuel leaves the refinery it's quite a range that the engines see today. The most common blends across the US today are not completely blended at the refinery! So what you get from one station may well not be the same as from another station event when it's the same brand. They get things add or blended in at the distributor level and that just screws with tuning all the more. They will load gasoline into the tanker truck then add the ethanol into the tanker truck, mixing is done by nothing more than driving the truck to the station where it get dumped into the storage tank.

[Rider57]

Trying to put what I have into understandable terms for the forum is the challange.
I have much more information on the various additives and what they do, who uses them and what is the end result in the MOCO engines.

[7hogs]

Thanks for posting this!

[Rider57]

Gasoline additives increase gasoline's octane rating or act as corrosion inhibitors or lubricants, thus allowing the use of higher compression ratios for greater efficiency and power, however some carry heavy environmental risks. Types of additives include metal deactivators, corrosion inhibitors, oxygenates and antioxidants.

The Clean Air Act was put into place in January 1995 in the United States of America as part of the efforts of the Environmental Protection Agency. This act requires deposit control additives (DCAs) be added to all gasolines. This type of additive is a detergent additive that acts as a cleansing agent in small passages in the carburetor or fuel injectors. This in turn serves to ensure a consistent air and fuel mixture that will contribute to better gas mileage.

* Additives *
Hybrid compound blends are:
Combustion catalyst: an organometallic compound which lowers the ignition point of fuel in the combustion chamber reducing the temperature burn from 1200 degrees to 800 degree F.
Catalyst additives prolongs engine life and increases fuel economy.
Burn rate modifier increases the fuel burn time, resulting in an increased fuel efficiency.
Polymerization increases fuel ignition surface area resulting in increased power from ignition.
Stabilizer/demulsifier/dispersant: prolongs life of fuel and prevents water contamination.
Corrosion inhibitor prevents corrosion of tank and fuel system.
Deposit control additives, acting as detergents, clean the engine.

* Oxygenates *
    Alcohols:
Methanol (MeOH)
Ethanol (EtOH)
Isopropyl alcohol (IPA)
n-butanol (BuOH)
Gasoline grade t-butanol (GTBA)

   Ethers:
Methyl tert-butyl ether (MTBE) Now outlawed in many states for road use.
Tertiary amyl methyl ether (TAME)
Tertiary hexyl methyl ether (THEME)
Ethyl tertiary butyl ether (ETBE)
Tertiary amyl ethyl ether (TAEE)
Diisopropyl ether (DIPE)

*Antioxidants, stabilizers *
Butylated hydroxytoluene (BHT)
2,4-Dimethyl-6-tert-butylphenol
2,6-Di-tert-butylphenol (2,6-DTBP)
p-Phenylenediamine
Ethylene diamine

* Antiknock agents *
Tetra-ethyl lead
Methylcyclopentadienyl manganese tricarbonyl (MMT)
Ferrocene
Iron pentacarbonyl
Toluene
Isooctane

Lead scavengers (for leaded gasoline) These chemicals are no longer use but can be purchased at most auto stores.
Tricresyl phosphate (TCP) (also an AW additive and EP additive)
1,2-Dibromoethane
1,2-Dichloroethane

* Fuel dyes, most common:
Solvent Red 24
Solvent Red 26
Solvent Yellow 124
Solvent Blue 35

* Fuel additives in general  *
Ether and other flammable hydrocarbons have been used extensively as starting fluid for many difficult-to-start engines, especially diesel engines.
Nitrous oxide, or simply nitrous, is an oxidizer used in auto racing.
Nitromethane, or "nitro," is a high-performance racing fuel.
Acetone is a vaporization additive, mainly used with methanol racing fuel to improve vaporisation at start up.
Butyl rubber (as polyisobutylene succinimide, detergent to prevent fouling of diesel fuel injectors).
Picrate improves combustion, increases fuel mileage.
Silicone is an anti-foaming agent for diesel fuel, but may damage oxygen sensors in gasoline engines.
Tetranitromethane can increase the cetane number of diesel fuel, improving its combustion properties.

[FBRR]

"Equivalence ratio is the ratio of actual fuel air ratio to stoichiometric fuel air ratio; it provides an intuitive way to express richer mixtures. Lambda (λ) is the ratio of actual air fuel ratio to stoichiometric air fuel ratio; it provides an intuitive way to express leanness conditions (i.e., less fuel, less rich) mixtures of fuel and air."

Said another way,  Lambda is AFR/AFR (stoich) and Equivalence ratio is the inverse of Lambda. Both define rich or lean state as it relates to stoich!

[wurk_truk]

Steve is correct about additives being added at the "Distributor Level".  Gasoline is a commodity.  ALL gasoline made in the United States is made in just TWO Blends.  87 and 91.  WHO makes it does not matter.  It is made so that ALL of it goes into various pipelines.   

So....  BP Chicago orders 1,000,000 gallons of regular.   Somebody in Texas diverts a 1,000,000 gallons into the pipeline to Chicago.   BP Chicago IMMEDIATELY pulls their gasoline of at the terminal end.  It was NOT the 1m gallons just applied into the other end at Texas.  THAT gasoline will be ultimately pulled out by a different terminal.   Pipelines run in batches.  Batches are broken up by like a big balloon called a PIG.

Gasoline has to be mfg at exact SAME standards so that ANY terminal can pull ANY gasoline out.

Terminals add all of the additives.  Stupid crap like Invigorate, or Nitrogen Rich.... etc.  That make commodity gasoline into BRANDED gasoline.

Branded gasoline is made at the terminal.  PERIOD.

I think (its been awhile), that E10 and E85 IS made how Steve says... dumped separately into the actual tanker.  If mixed too far ahead, the alcohol would evaporate.

For BEST results... one needs to pick a Tier One brand and stick with it.  Google Tier One Gasoline.

I try at all times to run Shell, a Tier One supplier/brand.  Tier One can make for some consistency in fuel blends.

But... this is not always possible.

When out in the country... one needs to try to buy gasoline from the newest and nicest looking stations one can find.

ALL gasoline ends up with water in the underground tanks, simply based upon condensation, if nothing else.  The newer the station... the better the tank monitoring system (generally).   Time and time again..... I see stations go into the back room and turn off the water alarms on the monitoring systems.  It IS a crap shoot.

NEVER EVER in life would I buy E85 and run that in my bike.  E85 has a LARGE tendency to 'make' water in the tanks.  As the alcohol eveaporates, air is drwn in the tank, and an 'air conditioner' effect can slowly start... dropping the moisture thats in the air out into the tanks.

High volume stations will always beat a low volume station, if for nothing else.... gasoline turn over is high.

Problem for us is we like to run Premium grade fuels...   NOBODY sells much premium.  It CAN sit in tanks for a year or more.   If one wanted to narrow THAT down.... buy gasoline in a RICH neighborhood.  The more CARS that buy Premium, the faster the turnover.

I am seriously considering tuning to 89 to eliminate some of the hassle.  Sure... the bike will have a tad bit less power... but its NOT a drag bike, and I seriously doubt I would SOP much of a change.

I have 10:1 with Singh grooves.  My CCP is 185ish... so I truly think the 87 is a doable thing.

Gasoline is simply going to get worse and worse and time goes on.  I know of more than 1-2 stations that have eliminated Premium completely.

89, 92, 93, These grades are eithe done by AT THE DISPENSER mixing... like 89.  Or by adding octane enhancers at the terminal.

[Rider57]

Pretty much says it all!
Many have taken home various "additives" from the local parts store and thrown it in the tank not knowing exactly the total outcome. It said it is a "octane booster", but what else does it do?

Tolulene is one that comes to mind. Works great! Dont breath the fumes or the exhaust though.
It is a known cancer causing chemical and caused birth defects in pregnant women.
Acetone is another. You should see what it does to the fuel lines and injectors after a while.

Be cautious when using these or any other additives.
Like wurk said, stay with a tier 1 brand and use it all the time.
Use 87/89 and tune your bike for it. The power loss is small, you can still run with the pack and if tuned properly for it, your bike will still deliver the ride your looking for.