Portable generators.

[HoneyBadger]

An insulated box with some decent fans blowing in/out would circulate enough air I think. You'd have to build about a 4'x4' box to stick it in so it has plenty of breathing room, but can't you direct the exhaust away from the engine and through a sound deadening baffle? Am I talking crazy here? I'm thinking I could build this type of box for about 50 in materials if I had the tools. (circular saw is necessary, nailer would be nice)

[00tec]

An insulated box with some decent fans blowing in/out would circulate enough air I think. You'd have to build about a 4'x4' box to stick it in so it has plenty of breathing room, but can't you direct the exhaust away from the engine and through a sound deadening baffle? Am I talking crazy here? I'm thinking I could build this type of box for about 50 in materials if I had the tools. (circular saw is necessary, nailer would be nice)

You could, but by redirecting and baffling the exhaust, you will reduce the engine's power.