Nitrous?

[440_Magnum]

Re: Nitrous?

I've read in several places that Rare Bear used nitrous during the speed record attempt, let alone at various times while racing. To get the kind of speeds being talked about for Voodoo on their speed record attempt, will they need to use nitrous to achieve that? Is one type of engine better at using nitrous than the other--radial vs. Merlin?

Getting back to the original question, I think all the comments are correct but I would add this. Boosting the power of any engine is about packing more fuel and oxidizer inside the cylinders to produce more power up to the mechanical limits of the engine structure, while preventing detonation. How you do that, be it nitrous, supercharging, or turbocharging, or a combination fundamentally doesn't matter so much to the engine structure, assuming you control inlet temperatures ( a bit of a generalization).

The air race engine builders have always taken advantage of the inherent features of the engines they start with. The Merlin was designed with a supercharger that can, in stock -9 form, deliver a staggering amount of boost, and do so at crankshaft RPMs that the propeller can live with... enough boost to max out the engine structure without any other power-adder like nitrous. That's why the "we can break it easy enough without nitrous" quote is true. The 3350 and most other radials have superchargers, but the way they're designed and geared usually means that they can't easily produce engine-breaking Merlin-level boost at crankshaft RPMs that the propeller needs (which is part of the reason the rare 3350 "slow nose case" is desirable- it allows higher crank rpm -> higher blower rpm -> higher boost for a reasonable prop RPM). So nitrous makes more sense for a radial or an engine like the Shackleton Griffon that also has a single-stage lower-pressure blower than it does with a Merlin with its high pressure blower.

[Lockheed Bob]

Re: Nitrous?

One of the best explanations I have read yet for us laymen. Thanks.