Background:
A discussion about the temperature beneath the engine cover prompted an investigation to see if the temperature changes with the engine cover removed versus when it is in place.
Test Procedure:
An RTD temperature sensor is placed above the engine and the air temperature is recorded during routine driving.
The engine cover is then installed and the air temperature is recorded again during similar driving conditions.
This data was NOT recorded over a fixed course. The exact duration of the drives as well as vehicle speeds were not replicated for each session.
A cold start is a session that was preceded by 12 hours wherein the engine was not operating.
A warm start is a session that begins when the engine has been operating 1-2 hours prior to the start of the session.
A hot start is a session that begins when less than 1 hour has passed since the last engine operation. No hot starts were recorded.
Test Results:
Note: OVR_ENG, represented by the Green line, is the air temperature above the engine.
Engine Cover Removed:
Engine Cover Installed:
Summary Chart:
Note: Dashed lines are used to show when the cover was removed, and solid lines show when the cover was installed.
In the legend for the chart above, R indicates the cover was Removed, I indicates the cover was Installed. C indicates a Cold Start, and W indicates a Warm Start.
Comparing Temperature Data from 600 seconds and beyond:
On average there is no significant difference. (The mean temperature with the cover installed is 3 degrees less than with the cover removed.)
Conclusions:
In both cases the air temperature trends toward approximately 130 degF during the early part of the drive.
After approximately 15 minutes the temperatures appear to vary roughly around the 130-degree range with changes in the vehicle speed.
This investigation served as a screening experiment to inform a decision on whether a more robust experiment would be worthwhile for assessing the contribution of the engine cover to air temperature above the engine.