Originally Posted by Tempest245
Gord, Hud, et al.. What was your motivation for doing this? Keeping the heat out of the cabin
? Is this a lower latitude issue? Or does it improve engine performance?
Yes, yes, and yes.
From (2) earlier posts:
Engine Room/Compartment Ventilation
The maximum temperature of the engine room should never exceed 140 degrees F, within 3/4" of any electrical equipment
(Alternator), and should never exceed 115 deg. F anywhere in the engine compartment.
The approximate cooling
ventilation (this is in addition to combustion air requirements) rate may be determined by the following formula:
CFM = (1000 x H.P.) ÷ T
HP = maximum engine horsepower
T = allowable temperature rise, ‘F. (often specified at 15 degrees)
Hence, for a 22 H.P. engine:
CFM = (1,000 x 22) ÷ 15 = about 1,500 CFM Cooling
which (@ ± 1,000 FPM velocity) would utilize (2) 224 square inch ducts - both make-up air & exhaust (2 @ 16" x 14", etc)
Engine room Ventilation
The maximum temperature of the engine room should never exceed 60 degrees C (140 F) within 20mm (3/4") of any electrical equipment
, and 45 C (113 F) at the air intake.
Ventilation Requirements for Yanmar Diesel
Duct Sizes (2 Required - 1 Supply In & 1 Exhaust Out)
Engine Square inch = Diameter
3.02 sq. in = 50mm = 2" dia.
6.0 sq. in. = 75mm = 3" dia.
100mm inside diameter tube duct area is 78.54 cm2
50mm inside diameter tube duct area is 19.7 cm2
4 inch inside diameter tube duct area is 12.57 inches2
2 inch inside diameter tube duct area is 3.15 inches2
Note: TWO ducts the same size are required, one inlet and one outlet.