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| The Pub For General Automotive Related Talk |
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20-07-2006, 12:15 PM
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FF.Com.Au Hardcore
Join Date: Apr 2006
Posts: 784
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this has probably been asked a million times,but dose anyone know what the best air fuel ratio is.
i got mine checked the other day and it was 16 to 1 at cruise and 13.8 to 1 at WOT.is this running to lean? thanks jake |
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20-07-2006, 12:34 PM
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Regular Member
Join Date: Dec 2005
Posts: 112
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Not sure of the ratio, but if you lean till peak CHT, then enrichen 25degrees, you'll be on the ball.
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20-07-2006, 12:42 PM
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meow
Join Date: Dec 2004
Location: Where the Pirates are.
Posts: 2,744
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I'm no expert, but ~13:1 is stoichiometric ratio.
16:1 sounds just a *tad* lean. |
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20-07-2006, 01:15 PM
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#4 | ||
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Hello
Join Date: Dec 2004
Location: Mt Barker, SA
Posts: 4,300
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13.8 may be a bit lean. Mine is tuned to 12.8. I THINK it depends on the car though.
__________________
2008 FPV TERRITORY F6-X Silhouette, window tint, roof racks, 3rd row seats, ROH Mantis 19s, black custom plates 'FPVF6X' and no stripes.  : Cobra :
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20-07-2006, 08:13 PM
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Performance moderator
 
Join Date: Feb 2005
Location: St Clair..N.S.W
Posts: 14,875
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WOT should be around 12.5 ...I know blown motors should be around 11.5
Coming back to 14.7 on light cruse..
__________________
Real cars are not driven by front wheels,real cars lift them!!... BABYS ARE BOTTLE FED, REAL MEN GET BLOWN. Don't be afraid to try something new. Remember, amateurs built the Ark...Professionals built the Titanic! Dart 330ci block turbo black pearl EBXR8 482 rwkw.. Daily driver GTE FG.. Projects http://www.fordforums.com.au/showthread.php?t=107711 http://www.fordforums.com.au/showthr...8+turbo&page=4 |
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20-07-2006, 08:58 PM
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#6 | ||
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Regular Member
Join Date: Dec 2004
Posts: 35
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The stoichiometric ratio is 14.7:1 for petrol (that means for complete combustion of the petrol you need 1 unit petrol, and 14.7 units air).
Full load AFRs are generally in the range of 12.5 to 13.5. The best setting depends on octane rating (richer mixtures are less likely to detonate?), combustion chamber design etc. Some cars do run VERY rich from the factory - around 11:1 at full load. Leaning out the air:fuel ratio at cruise can improve fuel economy, at the cost of higher NoX emission I think? Anyway, there is nothing wrong with your ratios as long as you aren't getting detonation. Maybe there is more power there, if that is what you are chasing. There are plenty of professional tuners on this forum, hopefully one of them will weigh in with all the facts for you. |
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21-07-2006, 01:06 AM
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#7 | ||
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Boost Addict
Join Date: Jan 2005
Location: North Brisbane
Posts: 1,151
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same as dynos, its an indicator, very well depends where the probe is placed.
however assuming its a stock car, i dont see anything wrong with those ratios. remember under cruise the narrow band will adjust the AFRs to a target value in order to preserve fuel efficiency on long distance travel and stoich is 14.7:1. ideally value are to hover plus minus 1 around that value at low and medium load, -2 under heavy load and +2 on cruise EDIT: BlueJ beat me to it ....  :
__________________
N12 Pulsar - sold Gen1 Liberty Turbo - sold VP Commodore Turbo - sold LN65 Hilux Turbo - sold EL31 Corolla Turbo - sold Ford AU Ute Turbo - sold Ford AU XR8 Sedan - 5.4l V8 Turbo (in the build) Ford BA XR6T Ute - daily driver Ford FG XR6T Sedan - cruiser do you see a general trend? I DO  Can't live with it, can't live without it! |
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21-07-2006, 07:25 AM
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building the xe...
Join Date: Aug 2005
Location: western sydney - home of the mullet
Posts: 2,473
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can go up to 18 on decel... down to abot 10 or 11 on flat stick... but it all does depend on the car to start with, then the setup...
skylines run very rich from factory, anyone seen the black smokethey bellow out at full throttle... same with the xr turbos... turbo cars run very rich from factory... look at the evo for instance... 2.4l turbo, average consumption is approx 12.5l per 100k... standard lancer 2.4 gets about 9l per 100k... they both have mivec cam timing... evo is set up a lot more for performance then economy, like who is buying an evo that would be worried about fuel economy... |
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21-07-2006, 07:27 AM
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#9 | ||
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building the xe...
Join Date: Aug 2005
Location: western sydney - home of the mullet
Posts: 2,473
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even your base s***ter falcon runs richer than most cars out there... its all comp controlled these days though...
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AFR's
Hybrid Mode