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Title: Single turbo V-engine, dual O2 sensors pre-turbo or one in downpipe? Post by: nubcake on March 28, 2017, 10:11:11 AM Hi guys!
I'm currently building my car with a single turbo. Let's assume I have the possibility to sort out all the ECU stuff (ME7.1.1). But from a pure mechanical perspective, what is the best config to pick for a mostly street car? A pair of pre-turbo sensors or a single post-turbo one? As I understand, pre-turbo ones are exposed to higher temperatures & pressures, therefore their accuracy might drift a bit? However, it will still allow me to keep bank-specific trims and better track if one bank is not healthy. Any opinions on which way to pick and why? Title: Re: Single turbo V-engine, dual O2 sensors pre-turbo or one in downpipe? Post by: jameswalker on March 28, 2017, 11:10:03 AM If I had to do over, I would have a single sensor post turbo. For only 1 reason, no other. Fear that the lambda may not like its new elevated temperatures, shooting out metal into the turbine and having the car off the road.
That's my pure mechanical reason, as per your request! Title: Re: Single turbo V-engine, dual O2 sensors pre-turbo or one in downpipe? Post by: nubcake on March 28, 2017, 12:04:34 PM If I had to do over, I would have a single sensor post turbo. For only 1 reason, no other. Fear that the lambda may not like its new elevated temperatures, shooting out metal into the turbine and having the car off the road. That's my pure mechanical reason, as per your request! That was one of my concerns initially. I spoke to local Subaru guys (some of those cars have lambda pre-turbo from the factory) - and they told me that they never heard of such issues over the years. Title: Re: Single turbo V-engine, dual O2 sensors pre-turbo or one in downpipe? Post by: aef on March 29, 2017, 12:35:58 AM depends on the manifold too
Lets say you have to buy a expensive rothe turbo manifold for r32, would you drill and weld to it? Dont think so. I would run 1 post turbo. Title: Re: Single turbo V-engine, dual O2 sensors pre-turbo or one in downpipe? Post by: nubcake on March 29, 2017, 08:27:00 AM depends on the manifold too Lets say you have to buy a expensive rothe turbo manifold for r32, would you drill and weld to it? Dont think so. Everything will be custom, so that's also not a problem. I would run 1 post turbo. But why? :) Title: Re: Single turbo V-engine, dual O2 sensors pre-turbo or one in downpipe? Post by: passerati on March 29, 2017, 11:42:30 AM I deal with lambda sensors at work...
The only pre-turbine sensor i know is the BOSCH LSU adv lambda probe. All other types BOSCH LSU 4.x and NTK ones are always post turbo. Main reason is the static and dynamic pressure dependency of the probes. Here the LSU adv is less sensitive to pressure gradients. Also the material of the protection tube is more heat resistant. Further on modern ecus own a pressure and temperature compensation calculation of the O2 signal. Temperature dependency is also reduced due to closed loop heater controls. But on ME7 i think you wont find temperature compensation. Title: Re: Single turbo V-engine, dual O2 sensors pre-turbo or one in downpipe? Post by: nubcake on March 29, 2017, 12:37:22 PM I deal with lambda sensors at work... The only pre-turbine sensor i know is the BOSCH LSU adv lambda probe. All other types BOSCH LSU 4.x and NTK ones are always post turbo. Main reason is the static and dynamic pressure dependency of the probes. Here the LSU adv is less sensitive to pressure gradients. Also the material of the protection tube is more heat resistant. Further on modern ecus own a pressure and temperature compensation calculation of the O2 signal. Temperature dependency is also reduced due to closed loop heater controls. But on ME7 i think you wont find temperature compensation. Okay, thank you! However, LSU ADV is wideband. Do you know about any narrowband sensors that can operate pre-turbo? I have the following scheme in my head at this point: Use single narrowband in downpipe, operated by stock ME7 algos. And then add 2 pre-turbo LSU ADV with external controller fed back into spare ECU inputs with some custom code to monitor bank-specific AFR deviations and maybe modify trims a bit. Need to check the price of those ADV controllers now. :) |