AF ratios

[Pappu1]

what do u falaz and girls think is a safe tune

i have been told by a reputable tuner that 12.5 is good for subaru (as in good compromise of economy and power and not too much exhaust temps)

some people swear by 11.5 so unsure..

this is of course only meant for standard engines with mild mods (so no race car stuff) and for good street driving with some decent power

[Guest]

You will get more power with a leaner tune but it's not as safe.

And it depends on what boost your running etc etc - run 5psi and of course its not so much a problem

I'd say 12.5 is pretty much on the edge for a normal sti - it would only take a bad batch of fuel or abit of overboost on a cold day or your brother driving it... bit of det and rebuild time.

11.5 is safe enough

Subaru std tune is richer again

[Durty-Sanchez]

Std tune is ~ 9 .. 11-11.5 is where I'd go if the fueling is safe (i.e. split rail).

[Pappu1]

hahaha yea the brother driving sure will kill even the std sti..hahaha how did u know his much publicised extrovert driving style ..jhahaha

hmm.. wonder why this tuner was adamant 12.5 is the way to go.. ???

[dubbedup]

doesn't want a blown up motor coming back?

[Bazza-NZ]

Reading this has confused me a little

I have a air fuel gauge in my car in which i monitor a little bit when driving this sit at 14.3-14.8 most of the time, does this mean I'm running lean or does the gauge has a different reading from what you guys are talking about?

[funkytown]

the question is confused..

You never have a constant AF ratio. Look in the dyno thread as there a bunch of plots in there.

AFRs have a common downward to the right (on a graph) appearance. on the Y axis is the AF ratio and on the X axis is RPM (will check this to be 100%).

Thus (if downward to the right), as you increase rpm(and inheriently boost / load skyrockets) your AF ratio gets lower.. Ie more fuel to air.. i.e richer.

Mine is around 11.2 on full boost, but much closer to 14 or 15 at low rpm.Thus you dont get just one figure.

edit: in the results section under dyno runs, see my last picture in the last post, its AFs ploted with Boost and is a very good illustration. of the AFRs moving with load / rpm / boost

[Pappu1]

i was asking more like a avarage sort of af ratio under boost..

yea it will change but generally sits at 12.5 in my plots and the tuner has assured me that that is fine and running less is just wasting fuel (more safer yes but dont need to as 12.5 is safe enough)

so in summary - is 12.5 good under boost?

[Guest]

 Bazza-NZ said:

Reading this has confused me a little

I have a air fuel gauge in my car in which i monitor a little bit when driving this sit at 14.3-14.8 most of the time, does this mean I'm running lean or does the gauge has a different reading from what you guys are talking about?

For a start you only have a narrow band a/f gauge i would bet - which works off the o2 sensor. It is not accurate and also only operates over a narrow range probably 14.3 to 14.8 !

A wideband sensor is what a tuner would use so they can tune richer when on boost

[Pappu1]

anyone can confirm if the front o2 sensor in the manifold - what ratios does it read?

is it a 0-1v output?

[Guest boostin]

Front sensor on a V7 is what Subaru call an "Air/Fuel Ratio" sensor. Earlier (V6 and before) were simply Oxygen sensors.

Oops, forgot to say it should be 0 - 3V output.

[Pappu1]

 boostin said:

Front sensor on a V7 is what Subaru call an "Air/Fuel Ratio" sensor. Earlier (V6 and before) were simply Oxygen sensors.

Oops, forgot to say it should be 0 - 3V output.

does that maea it is a wide band (the v7 ones i mean)

[Guest]

no

[V8eta]

I wouldn't be happy with 12.5, id richen it up to 11.3 - 11.5:1 personally on pump gas incase you get a bad batch as Qwerty has said.

[Bazza-NZ]

 Qwerty']

[quote name='Bazza-NZ said:

Reading this has confused me a little

I have a air fuel gauge in my car in which i monitor a little bit when driving this sit at 14.3-14.8 most of the time, does this mean I'm running lean or does the gauge has a different reading from what you guys are talking about?

/quote]

For a start you only have a narrow band a/f gauge i would bet - which works off the o2 sensor. It is not accurate and also only operates over a narrow range probably 14.3 to 14.8 !

A wideband sensor is what a tuner would use so they can tune richer when on boost

Sweet thanks for clearing this up, nope i get the full range from 10-20 but now i understand what they are talking about, plus i did some research

I'm putting the car on the dyno next year mid jan so will have to check it out then

[Pappu1]

 Bazza-NZ']

[quote name='Bazza-NZ said:

Reading this has confused me a little

I have a air fuel gauge in my car in which i monitor a little bit when driving this sit at 14.3-14.8 most of the time, does this mean I'm running lean or does the gauge has a different reading from what you guys are talking about?

/quote]

For a start you only have a narrow band a/f gauge i would bet - which works off the o2 sensor. It is not accurate and also only operates over a narrow range probably 14.3 to 14.8 !

A wideband sensor is what a tuner would use so they can tune richer when on boost

Sweet thanks for clearing this up, nope i get the full range from 10-20 but now i understand what they are talking about, plus i did some research

I'm putting the car on the dyno next year mid jan so will have to check it out then

where did u get the sensor fro? what sort of output does it have? 0-1v or 0-3v?

[Guest boostin]

It will run off the factory O2 sensor.

[dimin]

Ive tuned mine to 11.3ish to 1, richening up to under 11 at redline. 12.5 seems really lean with a tmic, youd have to pull a bit of timing under boost to stave of detonation I would of thought. I would rather tune it richer with a lil bit more timing, but different tuners have different methods i suppose.

[Bazza-NZ]

 pappu']

Reading this has confused me a little

I have a air fuel gauge in my car in which i monitor a little bit when driving this sit at 14.3-14.8 most of the time, does this mean I'm running lean or does the gauge has a different reading from what you guys are talking about?

For a start you only have a narrow band a/f gauge i would bet - which works off the o2 sensor. It is not accurate and also only operates over a narrow range probably 14.3 to 14.8 !

A wideband sensor is what a tuner would use so they can tune richer when on boost

Sweet thanks for clearing this up, nope i get the full range from 10-20 but now i understand what they are talking about, plus i did some research

I'm putting the car on the dyno next year mid jan so will have to check it out then

where did u get the sensor fro? what sort of output does it have? 0-1v or 0-3v?

[quote name='boostin said:

It will run off the factory O2 sensor.

What he said --^

Runs off the o2 sensor wire so probably isn't very accurate at all really But thats alright as its one of those multi Apexi turbo timer thingys with bat, timer, a/f and o2 (o2 monitors the voltage)

[Pappu1]

anyone seen the jaycar af ratio display kit - i was thinking of making one and using the factory front 02 sensor

[philr8]

 pappu said:

anyone seen the jaycar af ratio display kit - i was thinking of making one and using the factory front 02 sensor

the factory 02 sensor is located in the headers or up pipe and is inaccurate for open loop fueling, save your money and get a wideband sensor and gauge!

[Pappu1]

thanks for that.. yea i was just thinking it it were accurate then wud have been a nifty little kit on a cheap budget too haha

ah well...