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Per cylinder AFR in a turbocharged vehicle

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I recently saw a Papadakis racing vehicle on youtube (I don't remember exactly but I think it was the drift corolla) with a wideband fitted to each cylinder on the exhaust manifold runners pre turbo. I have researched and installed an aftermarket wideband and gauge in my 2014 genesis coupe (has another installed by the OEM as well) and all of the install guides I have seen tell you to fit the wideband post turbo at 36 inches from the exhaust port (18 inches for NA) and to mount it at 0 - 15 degrees to prevent moisture from entering the sensor. The OEM gauge was also mounted this way. I know these instructions are meant to preserve the life of a sensor in one of the most inhospitable parts of the car, so it made sense to follow them.

This is interesting to me because the factory intake manifold for the genesis coupe is known to cause cyl. 1to run rich and cyl. 4 to run lean, and sometimes by a good margin due to poor factory QA and casting (I have ported/polished my intake manifold, but the design will still cause a slight imbalance). I am planning an exhaust manifold/turbo upgrade soon and may want to fit a bung in each exhaust runner to get a more accurate AFR per cylinder, and hopefully tune with a higher safety margin.

So my question is, did Papdakis get a special sensor, or is this an acceptable way to mount a normal wideband and the gauge manufacturers/OEMs are being very conservative in their instructions? If it is a special sensor, what make and model is it? Did they perhaps lengthen their exhaust manifold runners to reach a safe distance (it looked far closer than 36 inches, but it was a video and I may not have realized that it actually is downstream by a good length)? Is it something else I didn't identify?

Sorry if this is a common knowledge question, and I am sure this probably isn't worth the effort I'll expend to do it, but I love metrics and would always rather more data to parse than less :)

You can use a Bosch LSU ADV lambda sensor which is designed to be installed pre-turbo. Maybe this is what is on that vehicle. Pretty sure NTK also has a lambda sensor for pre-turbo installation.

A simpler way is to run individual EGT probes in each cylinder. This also tells you if one is running hotter than the others etc. and you can adjust your fueling and or timing accordingly.

Thanks Christoph! I already have the thermocouple expansion box for my Haltech ECU and will certainly be adding an EGT sensor to each cylinder as you mentioned. Is the Bosch LSU ADV a newer wideband sensor? I have heard from a friend that the NTK sensors are very accurate, so I could see them being more robust as well. I am currently using two Bosch LSU 4.9 sensors. I appreciate you putting me on the right track.

Edit:. A quick google search let me know it is a different/newer sensor, and when I was trying to find what Papadakis was using in their car I never managed to find it. Great info Christoph, now I just have to ask Haltech if their wideband controller can use this sensor or if I'll have to source a different one.

You will need a controller that can apply emap correction to the reported lambda data, I dont think the Haltech controller can.

LSU sensors are generally preferred for per cylinder lambda over NTK sensors as they are less sensitive to back pressure.