Well I'm a firefighter,and i've been having to much time to think of stupid sh*t,and I was just wondering ! Well i've been admiring the turbo that's on our Engine,it's about as big as my head. And i was like wow ! Well i looked up the spec and Our fire engine is a 4 cyc, with 400 Hp at 2200 rpms and has 970 lbs of torque at 2200 rpms. Well is it possible to get a turbo off a fire truck or Semi and slap it on. I know there's alot other things you have to upgrade along with it,but that's a big turbo,blows away T78 ,well in size!

 

Housing size is the last thing to worry about when picking a turbo. Too big could actually be bad(and in this case it is)
Basically, YES you can take just about any turbo, custom a manifold, custom fittings and lining, custom your hood to fit that monstter , and do it.
Where would you make boost?At 500rpms before redline. Would that boost be 'good' air? No you'd more than likely be sitting to the left the turbos efficency range and due to this there is NO telling where you would be boosting. Spikes all over the place.

Turbo size, boost and anything else is NOT the important thing. FLOW is what makes power

When picking a turbo you need to think of a few things:

1> the engine you are working with
2> how much power you want to make
3> what you are going to use it for (drag auto)

based on your engine and using math, you can figure out the how much that engine will flow. Then you can match several turbos to that engine, then pick the turbo that fits your application