(a) General. Chemical balances of fuel, intake air, and exhaust may be used to calculate flows, the amount of water in their flows, and the wet concentration of constituents in their flows. With one flow rate of either fuel, intake air, or exhaust, you may use chemical balances to determine the flows of the other two. For example, you may use chemical balances along with either intake air or fuel flow to determine raw exhaust flow.
CFR 40-1065.655-2014 history
2014CFR 40-1065.655-2014 Protection of Environment. Part1065:Engine-testing procedures. Section1065.655:Chemical balances of fuel,intake air, and exhaust.