[beepbeep]

Originally posted by Pete Pranger
Now, for my needs.

This will not be a "cruise only" airplane. I am building this to +8/-6gs and intend to use it as such. I spend my workday cruising straight and level, so I want my off time to be spent vertical and inverted. I need a responsive engine that handles negative as well as positive g loads and will not complain with a lot of rapid throttle movements.

Well you can consider the prop as big "torque converter" anyway, so I don't think properly sized turbo will introduce noticeable lag. You are using hand throttle and not hitting it with your feet so chances are you'll never feel turbo-lag anyway.

I don't really need boost at idle, but I can't have a lot of lag either. What is the normal rpm range of the current stock of turbos? I am only looking for a 2000 rpm window (1000-2800) and I am sure that virtually any turbo can offer that. But then again, I am full of "theory" and short on practical use.

1000-2800 or 2000-5600 it doesn't matter. Engine is just a big airpump and turbo doesn't know how fast motor is spinning. It just cares about mass-flow. With other words, you want a turbo that can boost between 2000 and 5600 RPM on a car engine with volume of 180 cid
There are lot's of turbochargers that will work in those conditions.

I remember you were telling me before that these modern turbos are using engine coolant, so what do I use for an air-cooled motor to keep the bearings cool? Oil?

Most bigger turbochargers are only oil-cooled. Watercooled turbochargers are small units made for soccer-moms that run them hard and then instantly shut off the engine, cooking the bearings. If you let it idle 30 secs after full throttle (which you probably have to when landing) it'll be OK. so it's just one oil-hose doing both lubrication and cooling. You have to have some sort of dry-sump system though if you plan pulling G's or oil will seep trough the bearing-seals and cause lot's of smoke otherwise.

Are you guys running inter (or humor me here "after") coolers? Would you encourage or discourage the use in this application? I think I can plumb one and I might even be able to use the byproduct for cabin heat, but I don't know yet.

Yes. Intercooler is a good thing. It gives you more power, less heat produced in the heads and will also kepp shrapnel from entering the engine in unlikely event of turbine failure.

I know I am beating a dead horse with you here, so I apologize in advance BUT, I know a ton of guys using Paxton/Vortec etc and I haven't heard of one failure (other than belt related) but I won't harp too hard on this, this time because as I said before, I have no way to effectively drive the darn thing. I had however thought of what to do as a back up due to component failure and I was considering a pseudo-alternate air door if you will, downstream of the compressor so that if the compressor is lost, it would run purely naturally aspirated, but again these are very basic thoughts only.

Ehh...if you want some serious power out of those things you are talking about 20-30HP transmitted trough a rubber belt in a vibrating enviroment that's seeing 5G of accelleration. It's your call but I wouldn't feel comfortable with that, even if I found the way to drive it. Those people running Paxton, are they using them on airplanes or cars? If belt snaps, there will be no "failure" on car per definition. Engine will stop and car will coast down. If belt snaps in your application you'll be "out of airspeed and ideas" pretty soon.
Air-door would work as long as it's situated before throttle-body (otherwise MAP will get confused) and EFI is used.

Thanks for your input (and everyone else here) and for the link. I hadn't seen a 2 stage/2 speed supercharger since I flew a Convair 340 (R2800) years ago. I miss those old radials.
Pete

I had never seen one Too young.