Freezing the hat

Question:

Drag racers seem to unanimously agree that freezing is an issue and many de-ice the blades after a burnout. But, the monster truck guys who're in and out of the power for much longer periods of time say it's not a problem. Can someone clarify if this really is a problem with BA or if it's more or less a falacy that everyone in drag racing bought into?

 

I have never driven one before, but could it be that in the monster truck world they are like you said "in and out of the power for much longer periods of time", probably the majority of the time full throttle or close?

The icing problem with a blown alcohol motor in drag racing is that we have to leave the line at RPM, which requires fairly fine control of the throttle blades. So when the blades are iced up even a little bit the throttle gets a little sticky, then you have to push a little harder on the pedal - then boom, it breaks loose and you've either jumped through the beams or are way too high in RPM.

 

Chris, I have driven my car 10 miles round trip to alameda for a car show and had no issues with ice, it was really cold in the AM when I drove it and the hat would frost up but never had any hard core ice issues on the butterflies that would impair it's functionality

-Jalil

 

Worse with the screw blowers,
probably the trucks with the small blowers arent drawing near the amount of air thru the blades
I know mine never needed de icing with a roots

 

Iv had a hat ice up so bad during a warm up when someone forgot to unpack the de icer
that the blades were actuly stuck with solid ice not a little frosting I also noticed when we ran a jbr hat opposed to the cbd mk 7 lt that we ran now it hardly ever had icing probs on the same engine with the same tune up,

This year were back on the jbr....

 

canter hit it... humidity

and i think the biggest issue is the volume of air being moved as the blowers get more efficient and and the overdrives increase with the screws. more volume, higher velocity makes for more pressure/temp drop

 

Agreed on the humidity playing a large part in all of this. As well, the screw blowers do move more air, which means at idle, the blades are much more closed.

I am guessing that most monster trucks are set up pretty fat, with the blades open a bunch. None of them are trying for a .900 60'.

 

The monster trucks only turn the blowers 10 percent by rule and most of them just use hat nozzles. Almost all of them don't use any gel lube and the blowers are not stripped very often so they are not pushing a large volume of air.

 

You hit the nail on the head. Most gasses under pressure create endothermic reactions when going from a compressed state to lower pressure state and air is no different. When the air is sucked through the injector, the gasses are relieved of pressure created by the atmosphere (roughly 14.4 psi). Doesn't sound like much pressure, but it is dictated by surface area and volume displacement(more volume = larger surface area to compress against).

 

anyone notice the carbon hats do it less than the mag or aluminum? My camaro will freeze and stick throttle wide open if we dont de ice it. The dragster with a carbon hat does not seem to have any ice issue