A conical shroud is absolutely more efficient, that's not debatable. However there are space limitations and I believe Mike's piece has enough bypass slots that it shouldn't be an issue. It may actually pass more air than my setup with the black magic 180 which has a proper conical shroud.
The black magic uses a 3300 cfm rated 15" fan. It doesn't cover the entire width of the core, there's an inch to inch and a half on each side. Some air is passing through that section, but the basic area for air to pass for the core with this fan is 176.71 sq/in. Not accounting for the relief flaps, the flat shroud with dual 12" fans has a passable area of 226.2 sq/in. Let's take 10% out of that for the area the fans protrude onto the end tanks. You end up nominally around 200 sq/in of passable space.
I'm not accounting for motor area here of course, but I think if you actually measured everything on my current setup to one of Mike's shrouds, there's a decent bit more relief area.
The proform fans have a rated CFM of 4200 for the pair against the 3300 CFM rating on my current fan. Let's again take 10% off that for inefficiency of the protrusion onto the end tanks. So a theoretical 3780 CFM or nominally 13% more theoretical airflow. Is that enough to solve my tiny amount of creep at idle and slow speeds? I don't know, but it's worth trying on my end I think.
__________________
-Jason
1969 Pontiac Firebird
|