O2 sensor location for turbo
O2 sensor location for turbo Researching for my first turbo build, low buck 5.3 with a GT45. I have seen setups with both O2s in the down pipe, as well as one O2 sensor in the down pipe tied to both O2 bank inputs. I get that the wideband has to go in the down pipe since it is only one sensor, but I have been thinking about the common issue of the #7 cylinder running leaner than the others, or at least that has been the explanation I have seen on why #7 is often the one to fail. Wouldn't it be better to keep the factory O2s in the exhaust manifolds before they go into the turbo to get more accurate bank to bank readings? Or maybe at least leave the drivers side in the manifold and passenger side in the down pipe with the wide band, since the passenger side would be getting both banks exhaust gas (assuming passenger side turbo mount)? Tuning in open loop would have to be done with the wide band, but when going back to closed loop each bank would have its own sensor for corrections just as factory. I would think this would help keep the drivers side bank fueling more accurate than if reading both sides combined on the down pipe.
Make sense or reading too much into it?
Make sense or reading too much into it?
The problem with narrow band O2 sensors is that their accuracy diminishes under pressure. Pre-turbo exhaust can have a lot of pressure, while the downpipe has much less (like a lot less).
Andrew
Andrew
I ran the factory O2 sensors in the manifolds with my front mount turbo kit and had the wideband a couple two, three feet downstream from the turbo in the down pipe.
Never had an issue with any of the sensors, current car is set up the same way but with a fender dump and has been flawless.
Additionally, I wouldn't suggest installing the wideband too close to the turbo (extreme heat is bad) or the exhaust cutout if you run one, (inaccurate readings), make sure the orientation in the pipe is correct as well and you shouldn't have any issues.
Never had an issue with any of the sensors, current car is set up the same way but with a fender dump and has been flawless.
Additionally, I wouldn't suggest installing the wideband too close to the turbo (extreme heat is bad) or the exhaust cutout if you run one, (inaccurate readings), make sure the orientation in the pipe is correct as well and you shouldn't have any issues.
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Same here , NB sensors pre turbo - good for data logging and getting the fuel dialed in without boost, use wideband for boost tuning . At least that's how I do it. No problems with the NB sensors, I just don't look at what they're doing under boost .
Exactly, I wired my WB into the boost controller and HP Tuners, all WOT tuning is done referencing that.
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Not an expert but I fumbled my way through it . Lots of info out there on this. Basically you log the fuel trims and end up with a graph of rpm vs kpa and add or remove on your VE table until you end up with near zero in all the boxes, that puts it at stoic/14.7 or close at most rpm and load conditions, then use PE /BE richen where you want /need it , can also lean it for cruise by enabling the lean cruise. Of course monitor the wideband especially in the early stages and make adjustments right away if too lean or way too rich. If you need more help I will try, but there are others here way better at it than me and plenty of info available on line and you tube. The sloppy mechanics wiki has info also
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The factory O2s can be pre-turbo without issue since they are only used at idle/part throttle anyways so pressure won't have much if any effect on them. You don't want both of them trying to read both banks together though so no single downpipe, at least one of them needs to be on the corresponding bank of airflow only so that bank is balanced, the other may see the sum of both banks as it will adjust as if the other bank was already "zero". Of course the best most accurate way is each side just reading the individual banks though.
The wideband however needs to be in your downpipe so pressure doesn't skew the readings.
The wideband however needs to be in your downpipe so pressure doesn't skew the readings.
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Verdad Gallardo Not an expert but I fumbled my way through it . Lots of info out there on this. Basically you log the fuel trims and end up with a graph of rpm vs kpa and add or remove on your VE table until you end up with near zero in all the boxes, that puts it at stoic/14.7 or close at most rpm and load conditions, then use PE /BE richen where you want /need it , can also lean it for cruise by enabling the lean cruise. Of course monitor the wideband especially in the early stages and make adjustments right away if too lean or way too rich. If you need more help I will try, but there are others here way better at it than me and plenty of info available on line and you tube. The sloppy mechanics wiki has info also
The factory O2s can be pre-turbo without issue since they are only used at idle/part throttle anyways so pressure won't have much if any effect on them. You don't want both of them trying to read both banks together though so no single downpipe, at least one of them needs to be on the corresponding bank of airflow only so that bank is balanced, the other may see the sum of both banks as it will adjust as if the other bank was already "zero". Of course the best most accurate way is each side just reading the individual banks though.
The wideband however needs to be in your downpipe so pressure doesn't skew the readings.
The wideband however needs to be in your downpipe so pressure doesn't skew the readings.
Thank you all for your help!.
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Thanks, understand on the method, I just thought the VE cells were being filled from the wideband input, so I was mistaken if they are in fact being filled based off the narrow band input. So the wideband is only used for keeping track of AFR and the narrow bands are providing the data for the VE cells, is that correct? Then the PE/BE tables can be used to richen up the fuel based on how the VE table was set up.
As far as I know the wide band hooked up is for data logging ( I didn't hook mine up) just log it by eye lol. By logging the STFT as a graph you will get the info you need to add or subtract from the VE table , that's how I did it anyway. I'm sure someone here can explain it much better. I'm guessing you are going 2,or 3 bar SD ?
GMCGreg is correct.
You wanna creep up on it, make short hits gradually moving up in rpm while watching to make sure you don't run lean.
Then you add or subtract fuel via the ve table from a histogram you'll make.
Trial and error, take it slow and you'll be fine.
You wanna creep up on it, make short hits gradually moving up in rpm while watching to make sure you don't run lean.
Then you add or subtract fuel via the ve table from a histogram you'll make.
Trial and error, take it slow and you'll be fine.