What is the proper AirFuel Ratio for turbo car???

[white_bird]

Hello~
Juz wanna know.. wad is the better air fuel ratio for turbo car?? ofcoz i mean in hi rev with full boost.. 10? 11? 12??

 

[blur_civic]

Actually the optimum Air Fuel Ratio is 14.7:1.. But the problem is at high revs.. the engine requires additional oil to help it cool down (among some other things).. Therefore at high revs (or when turbo kicks in for your case) fuel starts guzzling in at a richer rate..

One thing I like to highlight (and ask for opinion too) is that i've come across many forums which mentioned that 10:1 is way too much.. no matter how highly tuned a car is... any feedbacks on this one?

Thanks.. :)

 

[Joeker]

Overly rich conditions results in excesive carbon build-up, overtime compression increases causing pre-ignition.

Also, carbon will also deterioate lubrication efficeicncy due to sludge.

 

[white_bird]

ermm.. wad abt 12?? is it ok with 1.1 bar boosting??

 

[blur_civic]

ermm.. wad abt 12?? is it ok with 1.1 bar boosting??

There are alot of factors involved to decide if 12:1 is "ok" with 1.1bar...

And I am not qualified to explain about it.. hahaha... :p

 

[blur_civic]

Overly rich conditions results in excesive carbon build-up, overtime compression increases causing pre-ignition.

Also, carbon will also deterioate lubrication efficeicncy due to sludge.

Pardon my ignorance but mind telling me what is overtime compression? :)

 

[vteckiller]

in our hot climate we should be running something like 11.8 afr at 0.9 bar to 1.1bar and 11.7 if 1.2 bar to 1.3bar to be safe and 11.6 if 1.5bar to 1.7bar and 11.2 if 1.8bar to 2bar of boost to be safe and not sorry. for anything like 0.7bar and below 12 is fine.

for n/a car on the other hand maximum high revs 12.5 should make max power

anyway hope this helps a bit..

coz usually overseas car run 12afr even at 1.6 bar or even more but always remember our humidy and our hot climate will never b the same..
better safe then sorry.
so if u running at 1.something bar and runing at 12something better richen the car.

anyway happy motorsports!

cheers
Joshua
Millennium Motorsports

 

[stroker_kit]

double posting...sorry

 

[stroker_kit]

if the AFR is 12, it means 12kg of air over 1kg of fuel, right???....
so r u saying that in malaysia, if one car AFR =12 compared to a car in Japan(cooler country) that also runs with the same AFR value, , the one in Japan, which also uses 12Kg of air molecules, burns more air than in malaysia????

do u guys remember a trick question when u were a small kid?? it goes like this--> 1kg of cotton and 1kg of rock...which is heavier?? im sure u guys knows the answer.....

so, how can 12kg of air in Japan is heavier(more air molecules) than 12kg of air in Malaysia??? cos if u say the air molecules is more, the weight should also increase....

correct me if im wrong, cos im still learning too.....

 

[gentleman]

interesting.....so 14:7:1 is
14= air in kg?
7= fuel in kg?
1= ?

help....

 

[stroker_kit]

nope..

its 14.7kg of air : 1kg of fuel

 

[skunkwok]

in our hot climate we should be running something like 11.8 afr at 0.9 bar to 1.1bar and 11.7 if 1.2 bar to 1.3bar to be safe and 11.6 if 1.5bar to 1.7bar and 11.2 if 1.8bar to 2bar of boost to be safe and not sorry. for anything like 0.7bar and below 12 is fine.

How bout 1.9 bar on SR 20 DET engine ? What the ideal ratio ? engine with JUN 272 cam , holset turbo charge ( like ar 70 infront / .58 back) , 550cc injector , 2 additional injector ( 450 cc / 850cc ) 2 fuel pump , hks piston , 1.5mm gasket , with side exhaust out from the bumper , Microtech MTX - 8 ecu..

rite now the ARF at 14.7 .

 

[apisanif]

owh...so which is the best for 1.2 bar???

 

[stroker_kit]

most of dyno tuners in Malaysia would tune the AFR soemwhere in between 12-13...unless beign requested by the owner to use different AFR.... u can also refer to this diagram for ur reference...

 

[white_bird]

erm... most of them will set 11.8 to 11 le.. coz i saw few dyno b4...

juz my 2 cents..

 

[stroker_kit]

maybe ur right also...
however, Speedwork set my turbo engine AFR at 12 for 4K rpm above...
my friend (using NA) went to LINKS, also around 12... so, thas why i tot most of them set around 12...sorry if my info is not universally correct ..hehe...

 

[flamefox850]

bro stroker kit, i try to answer on behalf of joshua..can aa josh ? correct me if i'm wrong.

yes bro stroker, mass is still mass. the colder the air means more air mass or to be precise the more O2 mass in a volume of air.

more O2 mass in japs mean they have to push more fuel in their engine to get the 12.X:1 ratio also. same here. low O2 mass need less fuel.

but what josh means i think is for safety purpose...not to make power. lower than 12 is consider rich already but unburned fuel can act as coolant in our combustion chamber. even though fuel is a very2 weak coolant agent but i will prevent knock by this little effect.

correct me if i'm wrong.


p/s: use water as coolant agent is better than choking the engine with more fuel than needed IMHO

 

[dolly]

just my 2sen,

unburned fuel doesn't actually help with cooling like water would. Adding more fuel just causes the fuel to burn slower -> lower temperatures

adding more fuel helps with knock, but adding too much will encourage knocking.

as for what is the optimum afr, no idea man, all engines will be different, just stick ur car on a dyno, dont change the temperature/boost/timing and adjust afr, see which gives a better readout (also look out for knock)

 

[stroker_kit]

flamefox,
so, in a cooler country, a 12kg mass of 02 should take a smaller volume compared to a hotter country, where the O2 mass of 12kg takes a bigger volume to occupy..... but still, both engine supply 1kg of fuel to 12kg of air mass to get AFR 12...only that in a cooler country, the engine doesnt need to suck in air as hard as an engine that runs in a hotter county to get the same amout of air mass of 12kg..the less hard work the engine do, the more hp it can produce, is that what ur trying to say??? still wondering whether theoritical=practical..... =)

 

[Joeker]

flamefox,
so, in a cooler country, a 12kg mass of 02 should take a smaller volume compared to a hotter country, where the O2 mass of 12kg takes a bigger volume to occupy..... but still, both engine supply 1kg of fuel to 12kg of air mass to get AFR 12...only that in a cooler country, the engine doesnt need to suck in air as hard as an engine that runs in a hotter county to get the same amout of air mass of 12kg..the less hard work the engine do, the more hp it can produce, is that what ur trying to say??? still wondering whether theoritical=practical..... =)

At any given volume, lower temperature air intake will be denser than that of higher temperature.

Therefore, given the same atmospheric presurre, boost pressure, stroke & bore, static compresiion, i.e a controlled test with identical parameters, the engine operating at the lower tempeture ambience will give higher A/F reading.

There is not hard and fast rule wat A/F ratio is MOST IDEAL.

There is a very thin line between performance and reliability when comes to A/F ratio tuning.