Topic: tuning the a4

[jm]

run lean and overheat the head?

[SpeedyDTP247]

run lean and overheat the head?

yes i run alittle bit on the lean side. overheat the head, you mean cylinder head?

[Hawk296]

run lean and overheat the head?

Running lean can drastically raise Exhaust gas temperatures. This can burn valves, melt pistons, spark plugs etc etc etc. This is even worse on a boosted engine. On my Subie, I am running a max of 11.4:1 AFR under WOT, full load. That is as lean as I dare to go. I use an Innovate LC1 wideband 02 and also measure EGT at every port at the same time. I have seen max EGTs of alittle over 1,600 degrees F. If this was a track car where I was continually full throttle full boost, I would probably enrich the mixture a bit back towards 10.8:1 and keep the temps alittle lower. But that would require something bigger than these 550cc injectors too.....

[SpeedyDTP247]

should i get a egt gauge? where would i tap into the exhaust on the 2.8 30v? i only have an adjustable fpr on the car and checked with my vag-com (looking at the fuel trim level) and i got it into the acceptable (sp?) range but i think it needs more fine tuning. i was told adding bigger injectors really wont help? i have stock b5 s4 injectors which is the same (iirc) flow rate as the rc injectors that came with the pes kit

[Hawk296]

When tuning AFR I personally would only do it with both a wideband 02 sensor and EGT gauge. I am not too familiar with the 2.8 but I would tap the exhaust manifold close to the port, and I would do it on the leanest cylinder (if there is a traditionally lean cyl on these motors).

[SpeedyDTP247]

When tuning AFR I personally would only do it with both a wideband 02 sensor and EGT gauge. I am not too familiar with the 2.8 but I would tap the exhaust manifold close to the port, and I would do it on the leanest cylinder (if there is a traditionally lean cyl on these motors).

i guess i need to do more research

[Dark Lightning]

EGT can be useful but is a much better tuning tool when combined with a wideband.

[Dark Lightning]

Two important notes:

Wideband - The wideband O2 sensor should be installed as far away from your engine as possible, BUT must be placed before the catalytic converter and also be placed after your headers join together.  If placed after the catalytic converter you will not be reading the proper air/fuel mixture.  If placed before the header union you will only be reading one bank of cylinders (the left or right three); this can be overcome by having one wideband O2 sensor per cylinder bank, but this would greatly increase the cost.

EGT Gauge - Should be placed as brutally close to the motor as possible, typically within the first inch of header leaving the motor.  Any farther away and you'll be reading the temperatures after the air has had a chance to cool; even 2-3 inches is too far honestly.

[Hawk296]

Agreed

[Theta Tau 87]

Two important notes:

Wideband - The wideband O2 sensor should be installed as far away from your engine as possible, BUT must be placed before the catalytic converter and also be placed after your headers join together.  If placed after the catalytic converter you will not be reading the proper air/fuel mixture.  If placed before the header union you will only be reading one bank of cylinders (the left or right three); this can be overcome by having one wideband O2 sensor per cylinder bank, but this would greatly increase the cost.

How far is ideal if there is no cat in the exhaust?  My supercharged Corrado has been running rich since I swapped in a 2.0L 16v with a twin screw charger and I would like to tune it in much the same way Speedy is considering.

[SpeedyDTP247]

Two important notes:

Wideband - The wideband O2 sensor should be installed as far away from your engine as possible, BUT must be placed before the catalytic converter and also be placed after your headers join together.  If placed after the catalytic converter you will not be reading the proper air/fuel mixture.  If placed before the header union you will only be reading one bank of cylinders (the left or right three); this can be overcome by having one wideband O2 sensor per cylinder bank, but this would greatly increase the cost.

EGT Gauge - Should be placed as brutally close to the motor as possible, typically within the first inch of header leaving the motor.  Any farther away and you'll be reading the temperatures after the air has had a chance to cool; even 2-3 inches is too far honestly.

damn this sounds like its getting expensive it looks like i need to buy 2 wideband a/f sensors because my exhaust joins together after the cat in front of the resonator.

[Samantha]

no project worth doing is cheap.

[SpeedyDTP247]

no project worth doing is cheap.

especially when you have 2 project cars

[Dark Lightning]

How far is ideal if there is no cat in the exhaust?  My supercharged Corrado has been running rich since I swapped in a 2.0L 16v with a twin screw charger and I would like to tune it in much the same way Speedy is considering.

Sorry, didn't see the replies else I would have chimed in earlier.

General recommendation is at least 18" post-turbo, but there are other considerations.

Heat and pressure destroy wideband oxygen sensors, which is why it absolutely can't be pre-turbo and why immediately after the turbo will lead to a short(er) lifespan.  However, if you have a stock cat on an A4 (for example) your only option is to install the wideband in the first O2 sensor's position.  Most decent widebands are fully capable of faking an narrowband (standard) O2 signal so the loss of the first O2 isn't a big deal.

Additionally, you want as few joints as possible because exhaust leaks can throw the reading off; in the case of the A4, assuming you have a testpipe, the best location is somewhere in the downipe after you make sure that everything between the motor and the wideband is sealed tight.  I can't speak intelligently about S4 exhausts so I'm no help there, but you get the idea.

[xr4tic]

how do you know you're running lean?

As for piggy-backs, they work for a lot of cars, but keep the following in mind:
If your MAF is maxing out, a piggy back wont do anything until you get a bigger MAF
If your injectors are maxing out, a piggy back wont get you more fuel.
A piggy back is good for FINE tuning.  If you're way off, it may cause more problems then it solves.

Check your fuel trims, make sure it isn't leaning out the mixture under normal driving.  If it is, then it may be bad tuning (since normal driving should be real close to 0 fuel trim) or bad sensor(s) somewhere

If possible, check your fuel pressure, make sure it rises with boost - change the fuel filter if it's been a while.