# Air/Fuel Ratio for VW motors?? & Tuning Tips?



## NYCMK3Jetta (Oct 21, 2002)

Guys... Im gonna be purchasing a A/F Data logger to tune my turbo along with my EGT and A/F gauges.  On the VW's whats the ideal a/f ratio I know it varies from car to car. Some cars require 12:1 some require 14:1. What does VW recommend.
How do you guys street tune your cars? I just planned to find a open strip and run my car in each gear (1st-3rd) from idle to 6000rpms and then just check out the logged data graph. and adjust the duty cycles on the injectors accordingly with my S-AFC II? 
Anyone have their own backyard tips?


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## need_a_VR6 (May 19, 1999)

*Re: Air/Fuel Ratio for VW motors?? & Tuning Tips? (NYCMK3Jetta)*

Tune way rich and less timing at first. Watch your A/F and EGTs so you don't melt. Be VERY careful as you can easily kill the motor while trying to drive, program and watch all at the same time.


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## mrkrad (Nov 9, 2000)

*Re: Air/Fuel Ratio for VW motors?? & Tuning Tips? (need_a_VR6)*

we recommend you get a buddy that knows how to use a S-AFC to tune while you drive.
lol.


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## NYCMK3Jetta (Oct 21, 2002)

*Re: Air/Fuel Ratio for VW motors?? & Tuning Tips? (mrkrad)*

I plan to have a passenger there reading the gauges and tuning or i'll have my boy drive and I will make adjustments on the fly.
I plan to tune it rich... then cut it back slowly until it fits the ideal ratio.

What Ratio is that on the 2L motors? 12:1? 11:1?


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## need_a_VR6 (May 19, 1999)

*Re: Air/Fuel Ratio for VW motors?? & Tuning Tips? (NYCMK3Jetta)*

I used to 3mm tune my Rabbit to roughly 12.5:1 on a narrow band, god knows what that is on a wideband though. Rougly .87v O2 voltage at WOT. That was an all motor car though.. so you might want to go a touch richer.
Problem is you're not going to find your "ideal" A/F on the street with a gauge.. you need a dyno.


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## SILVERADO (May 16, 2002)

*Re: Air/Fuel Ratio for VW motors?? & Tuning Tips? (need_a_VR6)*

Take it on a long stretch of road,slightly uphill if possible,close the windows,and since you are adjusting only air/fuel then your fuel quality,compression,setup etc. will determine your max boost.I don't know how to tune a race car,but I can tune a street car decently,so my mixtures are a little on the rich side,but we are looking for reliability and power.I would start at lower boost settings and work my way up,for onset of boost,try 13.5-13.1then past 4psi try 12.8-12.3,then past 12psi try 11.5-10.9.These are safe values,but since you don't have a way to adjust timing,you might be able to run higher boost with richer mixtures.I have read that turbo cars make the best power in the 13.0-12.5 range,but for street gas,the richer mixtures are just a "little insurance",you'll make good power,and hopefully not melt the pistons!ABA pistons have skinny ringlands!BTW,the windows are up so you can listen for "pinking",when you hear it,tell your driver to let off and either lower the boost or richen the mixture.(if you had piggyback or standalone ,you could also pull out timing)but you will be relying on your "knock sensors" to make a igntition map for you.And disconnect your O2 sensors from the ECU,no matter what you do,the ECU will try to "trim back" your fuel if you are running closed loop,open loop you can maintain the mixture you are trying to program in with your Apexi unit. 


_Modified by SILVERADO at 8:08 PM 5-9-2003_


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## Jefnes3 (Aug 17, 2001)

*Re: Air/Fuel Ratio for VW motors?? & Tuning Tips? (SILVERADO)*

Silverado is right:
For all vacuum conditions run as close to 14.7 as you can get it, for best emissions.
I have seen cars run 15.0-15.5 at part throttle really light load, this will
save gas, more than you realize. its easiest to aim for 14.5-14.7...
best power on ANY motor is approx 13.0 - 13.5 A/F
This is easy to run NA, but is too close to the 'edge' for and NA motor
coverted to FI. For a reliable street car there is no way you can run so 
lean for a long time...
My basic rules of thumb: 
most vacuum conditions = 14.7
the 'last' column on your fuel table before you break into boost = 13.5
low boost to ~2 psi = 12.9
mid boost to ~10 psi = 12.5
over 10 psi = 11.9 - 12.0
Any more fuel to run richer hurts power. i.e. any mixture richer than 'best' power
(around mid 13's) causes a loss of power. You can see this if you
try and run A/F around 10, lots of black smoke and not much power.
If you need richer than 11.5 to solve a 'problem' then fix the problem
don't just smother it with fuel. Run less boost, take out some ignition timing,
whatever, you're not making 'more' power just because you increased the boost
and burried it with fuel.....
just the way I tune cars
Jeffrey Atwood


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## SILVERADO (May 16, 2002)

*Re: Air/Fuel Ratio for VW motors?? & Tuning Tips? (Jefnes3)*

Thank you JA,I am happy that somebody agrees with me for once!


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## XthetraderX (Feb 23, 2003)

*Re: Air/Fuel Ratio for VW motors?? & Tuning Tips? (Jefnes3)*


_Quote, originally posted by *Jefnes3* »_
Any more fuel to run richer hurts power. i.e. any mixture richer than 'best' power
(around mid 13's) causes a loss of power. You can see this if you
try and run A/F around 10, lots of black smoke and not much power.


If you are experiencing this... would EGT's climb steadily?
As of right now, im rollin on a F U C K E D up ATP chip and cartech... EGT's cimb steadily at WOT.... they would continue past 16 if i stayed on the gas (probe in center of manifold). I have given up on this, and am looking into other methods... but i wonder for the sake of knowledge.


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## Jefnes3 (Aug 17, 2001)

*Re: Air/Fuel Ratio for VW motors?? & Tuning Tips? (XthetraderX)*

EGT will go down if you run rich. Provided you are richer than 14.7 to start with.
If you KNOW your A/F is good, i.e. I use a Motec PLM, and your egts are high
its is because you are retarding ignition timing alot and basically
burning fuel after its left the head.....not very good for your exhaust valves.
At this point you have reached the 'end' of your current config.
You need more octane, or lower compression to go further...
This is how the egt guage only tells you part of the story, are you lean or
are you just running very retarded ignition timing?
Jeffrey Atwood


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## mrkrad (Nov 9, 2000)

*Re: Air/Fuel Ratio for VW motors?? & Tuning Tips? (Jefnes3)*

definitely need to read your plugs, they tell more truth than any egt/wideband/etc.


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## TheDeer (Sep 21, 2000)

*Re: Air/Fuel Ratio for VW motors?? & Tuning Tips? (mrkrad)*


_Quote, originally posted by *mrkrad* »_definitely need to read your plugs, they tell more truth than any egt/wideband/etc. 


Yeah romp on it and shut it down, cause if you let it idle, the plugs won't tell the tale of what happens under boost.


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## Agtronic (May 14, 2001)

*Re: Air/Fuel Ratio for VW motors?? & Tuning Tips? (TheDeer)*


_Quote, originally posted by *TheDeer* »_
Yeah romp on it and shut it down, cause if you let it idle, the plugs won't tell the tale of what happens under boost.

So basically, you have to shut the engine off with the turbo glowing red right? Damn, that would feel so wrong!


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## jhillyer (Feb 17, 2002)

*Re: Air/Fuel Ratio for VW motors?? & Tuning Tips? (XthetraderX)*


_Quote, originally posted by *XthetraderX* »_
If you are experiencing this... would EGT's climb steadily?
As of right now, im rollin on a F U C K E D up ATP chip and cartech... EGT's cimb steadily at WOT.... they would continue past 16 if i stayed on the gas (probe in center of manifold). I have given up on this, and am looking into other methods... but i wonder for the sake of knowledge.

I'll defend Cartech here, in case someone thinks that comment was a slam. Their RR FPR/FMU is a fine quality device, and easily tuned. I did not consider its large size before I bought -- had to move a couple things to make space. It works.


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