Ventilation is a commonly overlooked aspect of engine test cell room design. Proper airflow through the test cell is by far one of the most influential factors when assessing the power of your engine.
Fundamentally, air is a critical property of the combustion process. Without air it’s really hard to make any power. So why would you starve your engine of the one thing it needs most? It’s a lot of work to get your test cell to flow air correctly, let alone enough CFM. Realistically, most HVAC techs do not understand how much air is needed through a cell.
Typical guidelines are 10-15 times the cubic feet of your room in cubic feet of airflow per minute. Those requirements could be higher depending on your power level. A heat balance should be done to ensure you have enough airflow.
Below is a graph from a 493.9 HP alcohol circle track motor. As you can see, there was a 25.6 HP and 14.63 lb. –ft. gain by just providing adequate airflow through the room.
These discoveries almost cost an engine builder his life with the excess alcohol and exhaust fumes when he entered the test cell after only one run. Not only can there be power left on the table, it can be deadly. Understandably test cells cost money. There are also many ways to make your test cell usable and safe.
(The difference in performance for correct room ventilation.)