Recent Topics
Bad steering
by ridgerunner. 10/18/18 08:48 AM
iPad Login
by willbur. 10/18/18 08:44 AM
Shell Helix Ultra 0w-30 AV-L, 19236km, Saab B202L
by turboseize. 10/18/18 07:43 AM
F1 - 2018 United States Grand Prix
by gofast182. 10/18/18 05:54 AM
Volvo ACEA A5/B5 vs. VW 504.00/ 507.00
by kakraemer. 10/18/18 02:11 AM
Walmart CANADA Supertech
by Snagglefoot. 10/17/18 11:13 PM
Possible plumbing leak in 19 year old house...
by gregk24. 10/17/18 10:43 PM
Pinched air filter - how much possible damage?
by pezzy669. 10/17/18 10:29 PM
Russians have no sense of humor
by rubberchicken. 10/17/18 09:36 PM
Know how Paul Walker felt when....
by Marco620. 10/17/18 08:48 PM
2013 v6 accord
by lilspenny. 10/17/18 08:24 PM
351 Windsor locked up from sitting
by ram_man. 10/17/18 08:02 PM
5 Gallon Buckets
by RayCJ. 10/17/18 07:52 PM
Nexen Winguard Ice Plus Winter Tire
by ValkyrieIS21. 10/17/18 07:25 PM
Need help figuring out what this generator is.
by joegreen. 10/17/18 07:11 PM
new subaru owner what oil to use?
by lucerne06. 10/17/18 06:18 PM
Microwave Ovens
by paulri. 10/17/18 06:17 PM
Newest Members
ston123, chevymad1, TJR4617, Papac0rn, FBM4130
66240 Registered Users
Who's Online Now
98 registered members (badger05, A310, ABomb369, Ablebody, Alfred_B, Anduril, 9 invisible), 1,864 guests, and 40 spiders.
Key: Admin, Global Mod, Mod
Forum Statistics
Forums67
Topics292,117
Posts4,874,523
Members66,240
Most Online2,494
Oct 17th, 2018
Donate to BITOG
Previous Thread
Next Thread
Print Thread
Hop To
air fuel ratio #4768338
05/25/18 10:11 PM
05/25/18 10:11 PM
Joined: Jan 2018
Posts: 233
KS
red7404 Offline OP
red7404  Offline OP
Joined: Jan 2018
Posts: 233
KS
What characteristic of a liquid fuel sets the A / F ratio?

Re: air fuel ratio [Re: red7404] #4768402
05/26/18 12:15 AM
05/26/18 12:15 AM
Joined: Mar 2016
Posts: 1,467
Western S.C. since 1996
CR94 Offline
CR94  Offline
Joined: Mar 2016
Posts: 1,467
Western S.C. since 1996
Air/fuel ratio is not a characteristic of the fuel. It's the ratio air mass to fuel mass in the fuel-air mixture. Stochiometric ratio for air:gasoline is about 15:1.


2011 Toyota Prius now at 93K
1981 Mazda GLC (323) retired at 606K
1972 Subaru DL retired at 190K
1954 Chevrolet retired at 121K
Re: air fuel ratio [Re: red7404] #4768561
05/26/18 08:58 AM
05/26/18 08:58 AM
Joined: Mar 2018
Posts: 139
Hammehead Offline
Hammehead  Offline
Joined: Mar 2018
Posts: 139
Stochiometric ratio is a result of the calorific power of the fuel. The higher the cp, less fuel is used in the stoichiometry of its mix.

Last edited by Hammehead; 05/26/18 09:00 AM.

ToYota Corolla XEI 2010 1zzfe
Kawasaki Ninja ZX9R B4
Taurus GL Vulcan
Citroen C5 phase I
I used to use syn, now whatever is on sale and never had problems. This noob knows stuff.
Re: air fuel ratio [Re: red7404] #4768573
05/26/18 09:22 AM
05/26/18 09:22 AM
Joined: Nov 2008
Posts: 12,682
NH
supton Offline
supton  Offline
Joined: Nov 2008
Posts: 12,682
NH
Not a chemist but what the heck, I'll play one for now.

Most fuels are composed of hydrogen and carbon. In order to fully release all the energy stored in the fuel, there is an ideal amount of oxygen required for the chemical reaction. Too little air and it doesn't fully react. Too much, seems hard to occur but it certainly does inside of an internal combustion engine (due to the small window of time for it to do "useful" work and the need for the flame to go from combustible molecule to another one). Ultimately you get carbon dioxide and water--and heat which is what is usually we are after--and to do that there is a proper amount of oxygen (from the ambient air) required.

Now I realize fuels can be other than hydrogen and carbon based, and often there is stuff in the fuel which also requires combusting (which may or may not help with releasing heat) but most stuff that we like to burn is largely hydrogen&carbon (oil, gas, wood, coal).


2011 Toyota Camry, base, 2.5L/6MT, 169k, hers
2010 Toyota Tundra DC, 4.6L/6AT, 144k, ours
1999 Toyota Camry LE, 2.2L/4AT, 192k, his
Re: air fuel ratio [Re: red7404] #4768580
05/26/18 09:26 AM
05/26/18 09:26 AM
Joined: Mar 2014
Posts: 3,315
NJ
Leo99 Offline
Leo99  Offline
Joined: Mar 2014
Posts: 3,315
NJ
When we talk about the stoichiometric ratio, that the is the ratio of air to fuel for a "perfect" burn. For gasoline it's 14.7:1. If other fuels can burn with less oxygen, the A/F goes down. If they need more oxygen, the A/F goes us.


Without data you're just another person with an opinion. W. E. Deming

2003 Corolla 250,000 miles
2004 Rav4 359,000 miles
2015 Camry 59,000 miles
Re: air fuel ratio [Re: red7404] #4768665
05/26/18 11:20 AM
05/26/18 11:20 AM
Joined: Jun 2003
Posts: 5,926
Illinois
SHOZ Offline
SHOZ  Offline
Joined: Jun 2003
Posts: 5,926
Illinois
My A/F gauge can be programmed for whatever stoichiometric ratio you want. I use E10 all the time so I set it at 14.2. Lambda is much better to use.


2008 Hyundai Accent 1.6L 5 sp manual hatchback
2010 Hyundai Genesis Coupe Track 2L Turbo 6sp manual
Re: air fuel ratio [Re: Hammehead] #4768727
05/26/18 12:30 PM
05/26/18 12:30 PM
Joined: Jun 2003
Posts: 33,250
ME
eljefino Offline
eljefino  Offline
Joined: Jun 2003
Posts: 33,250
ME
Originally Posted By: Hammehead
Stochiometric ratio is a result of the calorific power of the fuel. The higher the cp, less fuel is used in the stoichiometry of its mix.


This is a good answer.

Another is that if you examine the exhaust gases, neither oxygen nor fuel particles remain as everything was used up and converted.

If one introduces nitrous oxide, they have to run much richer fuel. But they make more power as the oxygen content of the "air" inside is higher than 21%. Some NOS systems are "wet" and include the needed fuel; others require ECM mods and bigger injectors.

The Space shuttle had to carry liquid oxygen so it could have a stoichometric burn in outer space where there was otherwise no other oxidizer available.

Ethanol for all its issues splits apart and leaves a little extra oxygen in the combustion chamber, so if you're tuned for it, even 10%, you can make more power than with pure gasoline alone.

Re: air fuel ratio [Re: red7404] #4768732
05/26/18 12:39 PM
05/26/18 12:39 PM
Joined: Apr 2018
Posts: 46
Texas
talest Offline
talest  Offline
Joined: Apr 2018
Posts: 46
Texas
Originally Posted By: red7404
What characteristic of a liquid fuel sets the A / F ratio?


As mentioned, for pump gas it is 14.7 to 1, or 14.7:1

This would be the ideal mix for the best, and most complete, burn in combustion per stroke.

Re: air fuel ratio [Re: talest] #4768757
05/26/18 01:14 PM
05/26/18 01:14 PM
Joined: Jun 2003
Posts: 5,926
Illinois
SHOZ Offline
SHOZ  Offline
Joined: Jun 2003
Posts: 5,926
Illinois
Originally Posted By: talest
Originally Posted By: red7404
What characteristic of a liquid fuel sets the A / F ratio?


As mentioned, for pump gas it is 14.7 to 1, or 14.7:1

This would be the ideal mix for the best, and most complete, burn in combustion per stroke.
And the highest exhaust temps.


2008 Hyundai Accent 1.6L 5 sp manual hatchback
2010 Hyundai Genesis Coupe Track 2L Turbo 6sp manual
Re: air fuel ratio [Re: red7404] #4769057
05/26/18 09:10 PM
05/26/18 09:10 PM
Joined: Mar 2018
Posts: 139
Hammehead Offline
Hammehead  Offline
Joined: Mar 2018
Posts: 139
Yes with ethanol, the 14.7:1 doesn´t apply for ages. Only for the scarce E0. E15 may use 13.9:1 or even a tad less, hence the higher fuel consumption of these oxigenated gasolines, since you´re adding a lesser cp to the final fuel.

And thank you Eljefino

Last edited by Hammehead; 05/26/18 09:13 PM. Reason: cp

ToYota Corolla XEI 2010 1zzfe
Kawasaki Ninja ZX9R B4
Taurus GL Vulcan
Citroen C5 phase I
I used to use syn, now whatever is on sale and never had problems. This noob knows stuff.
Re: air fuel ratio [Re: red7404] #4773551
05/31/18 03:57 PM
05/31/18 03:57 PM
Joined: Jan 2011
Posts: 211
California
DGXR Offline
DGXR  Offline
Joined: Jan 2011
Posts: 211
California
Shell fuels provide the best air-fuel ratio :P


1995 Corvette coupe LT1 6-speed
2006 Tacoma 2.7 2wd access cab
1999 Yamaha YZ400FL
2003 Honda XR400R
Re: air fuel ratio [Re: DGXR] #4776956
06/04/18 08:19 AM
06/04/18 08:19 AM
Joined: May 2010
Posts: 1,093
Ocala, Florida
racin4ds Offline
racin4ds  Offline
Joined: May 2010
Posts: 1,093
Ocala, Florida
Originally Posted By: DGXR
Shell fuels provide the best air-fuel ratio :P


Let me fix that for you-

The vehicle's ECM or tune provides the best air-fuel ratio wink

Last edited by racin4ds; 06/04/18 08:19 AM.

Just say NO to thin oils and M1!
05 F350 Powerstroke
05 Hyundai Tucson
08 Legacy GT
Re: air fuel ratio [Re: racin4ds] #4779274
06/06/18 03:21 PM
06/06/18 03:21 PM
Joined: Jan 2011
Posts: 211
California
DGXR Offline
DGXR  Offline
Joined: Jan 2011
Posts: 211
California
Originally Posted By: racin4ds
Originally Posted By: DGXR
Shell fuels provide the best air-fuel ratio :P


Let me fix that for you-

The vehicle's ECM or tune provides the best air-fuel ratio wink


Clearly. We really need to develop a sarcasm font. I thought my tongue out thingy would indicate a comment in jest.


1995 Corvette coupe LT1 6-speed
2006 Tacoma 2.7 2wd access cab
1999 Yamaha YZ400FL
2003 Honda XR400R

BOB IS THE OIL GUY® Powered by UBB.threads™