By Fergus Ogilvy

Demon Bow-thru carburetor - overhead viewBowling Green, KY: For turbocharged and centrifugal supercharged applications using a bonnet, Demon Carburetion offers three Mighty Demon Blow-through carburetors. Operating with up to 18psi of boost they are available in 650, 750, and 850cfm.

To increase the vacuum signal to the carburetor under boost and to enrich the calibration, they are equipped with annular boost venturii, large screw-in power-valve channel restrictors in the metering blocks, and 0.130in needle-and-seat valves in the fuel bowls. The bowls also contain non-collapsible solid nitrophyl floats, unlike their brass counterparts. Air bleeds are appropriately sized.

These new calibrations are said to hold a flat fuel curve. Even at higher rpm the main circuits sustain constant BSFC (Brake Specific Fuel Consumption) values and air-fuel ratios. The idle circuits, which often carry the responsibility for part-throttle cruising, demonstrate fine non-boosted drivability.

On the bottom side of the base plate, machined, right-angle channels are visible. These introduce a source of boost pressure to four machined grooves on the throttle shafts. This innovation seals the shafts and prevents pressure escaping from the carburetor. For security, screw-in vacuum fittings replace the common pressed-in types.

Other interesting properties of these carburetors introduced by Demon in the late nineteen-nineties are easily recognizable. These include billet metering blocks and base plate with the distinctive Idle-Eze air valve as well as replaceable air bleeds, and idle-feed restrictors. To prevent galling in the bores of the aluminum base plates, the throttle plates are mounted on Teflon-coated throttle shafts.

Introduced in late 2013, their part numbers are as follows:

650cfm 5282020BT

750cfm 5402020BT

850crm 5563020BT

For further information contact:
Demon Carburetion

To learn about boost referencing blow-through carburetors read the story below.