Upstream of

Hello,

I am translating a rather technical table, where the following appears all the time:
Temperature upstream of diesel en­gine
Temperature downstream of diesel engine
Pressure upstream of startup valve
Pressure downstream of startup valve

Is it wrong to interpret it as Temperature above the diesel engine etc. ?

From the use of this term I assume that there is a flow of some kind involved. This may be an actual flow of some kind of fluid or it may be a process flow.
>>> indicates the direction of flow.

Upstream ..... >>> .... engine or valve .... >>> ...... downstream

The meaning is clearer for the valve, because I assume the valve controls flow of a fluid.
It's a bit less clear for the engine because I don't know anything about the wider context.