Confusing Uses of the Word "Backpressure"

I too have seen the term used either way, more often for upstream pressure. The context has ordinarily made it clear, but I can see how it might be confusing in some cases. The terms "upstream pressure regulator" and "downstream pressure regulator" seem more precise.

I think you're mis-interpreting the Wikipedia article - it is referring to the increase in pressure upstream of the exhaust pipework - i.e. at the engine exhaust port, just as the second reference describes the pressure upstream of the valve.

Your confusion lies in your use of the word "reference" when attempting to define "back pressure" in the two contexts above.

Back pressure is back pressure, regardless of the point of reference.

"Back pressure is back pressure, regardless of the point of reference."

Very true. Ex Mrs. Doorman was never confused about the point of reference whenever my backpressure became evident.

I tried to blame the dog but that never worked very well.

bean-o there.

done-o-that.

I have yet to get confused. The situation sets it in the right frame, normally.

That valve you put up as an example is for regulating the backpressure, where backpressure is the discharge pressure, of what ever it is fed from.

The literature says the valve works by controlling the inlet pressure of the valve and the inlet of the valve is fed from the discharge of whatever is pumping. ie the valve's inlet pressure is controlled to control the discharge pressure of what ever it is appended to.

That first paragraph in the literature is pretty clear I think and then gives an example too.....

Thanks to everyone who has contributed. The combination of your comments helped clear the confusion.

Cheers.