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O2 sensor position

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this may have been covered , but i haven’t read it

in many of the engine pictures there are O2 sensors close to the head , I understood they had to be a distance down the pipe 1/2 m comes to mind ,

if its a wideband, they usually recommend 18 inches past the turbo with the tip pointing downward so not to collect moisture. at least thats what my AEM uego recommended. and Ive seen similar specs with others. Try not to get too caught up in the "time delay" that you'll hear people talk about relative to positioning. When you do the math at reasonable engine speed any signal delays seem to be mostly in the devices sending/picking up the signals. unless you have CAN comm which is said to be pretty fast.

Edit: I assumed turbo haha. I believe the same 18 in applies from the cylinder head on an NA engine.

no not turbo ,HPA has a photo on their Instagram pics , it’s 4 cyc with temp probes at the head flange , and then O2 sensors close to them , I will be running an Hayabusa with 4 short pipes ( maybe less then 500mm ) and had expected to us a sensor at the end of one pipe ( i would like to.use 4 , it’s. $s thing — i still may in the long term do that ) was surprised to see. O2 sensors so close to the “ fire” the Bosch 4.9 instuctions give a distance ( I think it’s something like not less than 500mm — that’s from memory so maybe wrong )

500mm =18”. i’m an old Ozzi i can converse in both , We went metric in the 70s

Yes I believe its a heat thing for the 4.9 sensors which is what I was thinking of. If its just a stoich standard type unit those can be much closer. Like you I have seen many pictures of sensors immediately in line with cyl heads and turbos. I was too afraid to ruin my sensor like that in a permanent mount application. If its temporary for tuning purposes maybe the story is different.

It completely depends on your powerplants sustained EGTs and where you're seeing them. Max intermittent is something like 1000c and sustained is sub 950c. Somewhat annoying when you've got a chicken or the egg problem on a config you're building. Need the lambda sensor to tune, wont know your EGTs until its tuned.

edit: Just looked it up with Bosch, it's < 1030c and < 930c respectively.