REFLECTOR:Engines - TSIO520

[reflector@tvbf.org]

>>As far as the turbo plumbing, I don't know at this point. <<snip>>The engine I'm looking at has 300 hours on a Millennium reman. <<
Scott, 
What airplane does the engine you are looking at come out of? There are two basic types of the IO-520 series.
Sandcast and Permold. 
Sandcast was used on most TCM powered Cessna singles. Sandcast engines have the oil cooler in the front (front on a Cessna) and the alternator belt driven on the back side of the engine. 
Permold was used on all TCM powered Cessna twins and most TCM powered Beech models. Permold has the oil cooler in the rear and the alternator gear driven off the crank on the front of the engine opposite from the governor. 
In short, if you look in the right cooling intake of a spam can and see a oil cooler it's sandcast. If you see a alternator its permold. (if you see a cylinder it a Lycoming! :) )
There are some pro's and cons to each engine type for a possible Velocity install. 
Since the permold version was used mostly in twins the turbo plumbing is aft of the engine. Basically on a twin this puts the turbo, air filter and intercooler back in the nacelle. The exhaust and intake plumbing is mounted to the airframe and flex couplings are used to isolate them from the engine movement. This makes them MUCH easier to work on in a twin. However since a Velocity does not have all that otherwise empty nacelle space behind the engine this model may not be off to a good start for a Velo. On the other hand, with the permold approach since the turbo components are remote mounted you  may have some more flexibility to squeeze components in here and there where ever you can find room. It might even be possible to hollow out a wing a root? Putting that much heat in wing root would be scary though. 
The sandcast engines were targeted for singles so they have the turbo mounted directly to the engine case but slung low on the right side. Now this is not going to fit in the tight stock Velocity cowling but it's a better place to start than the permold engines setup (IHMO). One real down side of the 520 sandcast for a Velocity is the oil cooler location. Since on the Velo install it would be on the back of the engine getting proper air to it may well be very tough? Perhaps it could be blocked off and the standard Velocity oil coolers be used instead? another down side is that the area between the engine and the fire wall is very, very "busy". There is a lot of stuff wedged in there. I really wonder if there is room?
If you can get past those two hurdles with the sandcast type then you are going to have to put a rather large bump in the lower left cowl to enclose the turbo. From the lower wing root the cowl should probably come straight down a good foot or so lower than it is now then curve back up to the original cowl left of center line. The good news is when the plane is on the ground this big bump would not be too noticeable. The awesome lines of the Velocity won't be spoiled from most angles while on the ground. I would build a sheet metal box and isolate this "bump" area from the main engine compartment mainly to keep radiant heat from drifting up into the main engine area after shutdown. Plus in this location you could build something like the original Velocity armpit scoop but smaller on the left side only to provide the intake air and maybe provide some additional cooling to the turbo area. If you have the turbo "compartment" closed off with light sheet metal you could put a small outflow on the aft edge of your "turbo bump" on the cowl and keep that area relatively cool.   
I'm going to send two large photos of my 210's sandcast install along with some commentary. They are going straight to you Scott since they are too large for the list server. Anyone one else who is interested send me e-mail direct and I will copy you on it. The zip file is going to be 2.6 meg.
>>Maybe I would end up running it as a normally aspirated IO-520?<<
Personally, I would not do that. There is so much extra equipment on a TSIO versus a straight IO that I would not bother. The TSIO has the second oil pump to scavange the turbo oil return, it has a gajillion reference lines to pressurize the mags, spider, each fuel injector, fuel pump and probably a few other things I can't think of right now. Then you have the whole turbo controller and it's associated oil and reference lines.  Nope, if you don't use the turbo then get a straight IO. It would be tremendously easier! Then if you don't turbo then just get the IO-550 kit from the factory! The 550 is a solid engine. That was not available when I got to that point on mine. If I had the choice today between the Lyc IO-540 and the TCM IO-550 it would be a tough call but on balance I would probably still go with the LYC but the TCM 550 is a fine engine. (it's not a jug muncher! :) )
DM Rob
The rest of this e-mail assumes you have the two photo's sent under seperate cover... Look at the photos while you read the rest...
These pictures were taken while the Millennium jugs were being put on. Most of the baffling is off and the intake and exhaust has been dropped. 
DSC00405: 1. First off note the amount of "stuff" between the jugs and the firewall. It is one very busy place. A lot of equipment there. 
2. In this picture you can see a lot of the reference lines. Running fore to aft along the tops of the cylinder you can see a brass colored line. It's disconnected in this shot but that is the fuel injector reference line. You will also note two black rubber hoses above and behind that. Those are the mag reference lines and the spider reference line is inside the fire sleeve you see running along the top. 
3. Look underneath the engine. At about the fore aft middle of the engine  you can see the nose wheel well. aft of that you can see the "odd" oil sump that any sandcast style engine off a 210 will have. This may be a problem in a Velocity cowl but I think it will fit as is because unlike the lycomings the throttle body is not attached to the oil pan. Leading to...
4. It is very hard to see but look just above and behind the battery. You can see just a portion of the throttle body running vertically there.
DSC00406: This side is very important for a potential Velocity install...
As you might notice when this picture was taken two Millenniums are on with one to go...
1. While the throttle is still fresh in your mind, note the intercooler up top and aft of the engine. On the far side of it as seen in this picture it turns straight down and goes into the throttle body. This is a Riley intercooler STC. The '76 was not intercooled stock. 
2. From this side you can just see the black rubber reference line run into the mag case. 
3. Notice in front of the rightmost cylinder there is a piece of sheet metal hanging there. That is the bottom close out of where the oil cooler is on sandcast engines. The oil cooler is there between the cylinder and the prop. Like I said, that will be a challenge to get air too in a pusher install. 

4. To the meat of the matter. Look at that big empty area below the cylinders. All this space is pretty much filed up with the air filter, turbo and wastegate. Now this is a bed type install and the center keel section the engine rests on is also the nose gear well. Notice on the side of the center keel the two motor mount reinforcements running vertically. Now look for the two brackets hanging down between them in front of the two red fire sleeved oil lines that run fore and aft. Those are the turbo mount brackets. This is a real key for the sandcast type engine. Those brackets tie the turbo to the engine and support the turbo's weight. No flex coupling because the engine, exhaust system and the turbo all move together as a single unit. 
You can just see the bottom of the oil sump here. Like I said I think that sump will just fit into a stock Velocity cowling. however you can see how much the turbo system protrudes beyond the bottom of that sump. This is the approximate size and shape of the bump or turbo compartment you would have to build onto the bottom left of your stock cowling. 
Well, I hope all this helps.