Semi threadjack as requested by Iggy in PM . . .
Expanding on my Procharger -vs- Vortech comments, both are capable units with different drawbacks and benefits. I have had the opportunity to work with several Vortech models and a few Procharger models both on vehicles and test benches purpose built to measure flow, temperature rise, etc. Based on this testing I tend to prefer Vortech units over Procharger when possible. As many of you will recall, I work primarily on aircraft so the factors that are of paramount importance to me are different from the average automotive hot-rodder but there is still some carry over.
I have a friend with a dedicated 1/4 mile car who runs the largest unit Procharger makes, pretty much as hard as he can run it. He runs high 8's and the blower is working beautifully. We use a Procharger C2 on one of our aircraft kits and it changes the capabilities of the aircraft. It runs cool and does pretty much everything we could have hoped for. Another plus for Procharger is that they offer a MUCH wider range of sizes. The A,B and C blowers are small enough to run on motorcycles efficiently. I don't believe there is currently another supercharger manufacturer out there that can claim the same. The location flexability of an internally lubricated blower not much bigger than a football can be the determining factor when designing a custom system. So why do I prefer Vortech??? We will start with the compressor wheel design. The beautiful swirly bit that fills the snail that we all love. Look closely at this picture of a Procharger C-2 model blower.
If you look closely you can see what looks like lines on the compressor wheel deeper down inside the volute. Along the fins themselves you will see what looks sort of like an orange peel pattern. I can assure you those are all tall enough to feel with your finger/fingernail and cover every surface of the compressor wheel. Procharger machines their compressor wheels and does not clean them up perfectly smooth. If they do coat them with some sort of Teflon or other anti-corrosion product it is not thin enough to noticeably smooth out the machining marks. While the performance offered is still terrific I can't help but wonder if they could get a little better flow if those important surfaces were smooth. But since the performance is there it doesn't matter too much on that front. Where it does matter is during catastrophic failure. More on that in a moment. Beyond the compressor wheel, the gear cases themselves tend to be thicker and heavier than Vortech blowers (not sure if there is any benefit because I have never seen a Vortech case crack), the bearings are on par with Vortech, shaft/gear life is the same, but we have had better luck with the seals on the Procharger units for some reason. Basic volute and compressor wheel design and pairing however is far below the Vortech standard though. Again, more about that in a moment. As for unit longevity, we have not had Prochargers in our product line long enough to have any real data here. I expect they will be on par with Vortech but only time will tell.
Vortech units also run exceptionally cool and (for our aviation applications anyway) are fabulously efficient. They are super light, easy and inexpensive to rebuild if needed. If you look closely at this picture of a Vortech compressor wheel you will notice some differences from the Procharger unit.
The entire surface is completely smooth save for a couple of notches at the center. Upon closer investigation you will notice that the tolerances between the fins and the volute are tighter and the fins themselves appear thicker. None of these are illusions. Both the finish of the wheel and it's fitment to the volute are far better. While the thickness difference can be measured in .001 of an inch it is of vital importance. Other important notes specific to my experience with Vortech blowers . . . some of them will slowly seep a film of oil from the input shaft, some never do. This is more of a nuisance but it is noteworthy. Also, if you are not using an internally lubricated unit you need to be absolutely sure you have a downhill run on your oil return. Any pooling of oil inside either brand will cause the same conditions as it being starved for oil. As I stated before, I don't have any real data on how Prochargers will last under these conditions but I do know that Vortech shafts and bearings will last far longer than I would dare tell anybody to push them and still function, albeit at a diminished capacity. I have seen some seriously discolored, chewed up internals that you could hear and feel grinding when you turned them by hand, but the customer only complained about "less boost these days".
So, why all the attention to the compressor wheel and comments about catastrophic failure? First, being held to aviation certification standards we have had to perform "rotor burst" tests on every model of blower we have presented to the FAA. This is normally done by introducing "foreign debris" into the supercharger while it is running. A spectacularly painful and expensive test to execute I assure you, but the results have been awe inspiring. Passing small metal objects (nuts, scrap sheet metal, etc.) into the vortech created some horrible gouges in the compressor wheel, dings in the volute, and lots of metal particles shooting out the end of the ductwork across the parking lot from our test bench . . . but the blower kept producing boost! Introducing the end of a metal wire produced hundreds of dings on the ends of the fins and lots of metal dust on the output . . . but the blower kept working. The FAA insists that the "rotor bursts". In the end we had to drill a series of holes in the compressor wheel and cut it with a die grinder to make it weak enough to fly apart inside the volute. The result? Since the remaining portion of the rotor was so strong, and the tolerances were so tight the free pieces got wedged against the wall of the volute, the blower froze in place and the belt overheated and snapped off. That blower was rebuilt and is flying today. Starting the same test with the Procharger unit was also the end. When we introduced a small piece of sheet metal a chunk (not a nick) of a fin broke off with it, the both broke off more fins, and much like dropping a ping pong ball on a mousetrap, they all proceeded to rip the compressor wheel into a thousand pieces of it's former self. Unlike the Vortech it kept spinning, but created zero boost. Procharger now has thicker fins on the compressor wheels of at least the C-2 model blowers, not sure about the rest of the model line. Long story short, the Vortech contained all but the smallest particles of itself inside the volute when the compressor wheel exploded, the Procharger ripped itself into many sizes and sent them all across the parking lot, which would have been your engine. While neither are good, I think dust passing through the engine has a smaller chance of causing catastrophic engine failure than random dust including dime sized chunks. Oddly enough, both passed the FAA's test since neither of them caused the entire blower to come apart. The burst was "contained" within the volute by both. Since sharp corners in metal are more prone to cracking than smooth surfaces or rounded corners I suspect that all of the machining lines on the compressor wheel contributed greatly to it's failure mode in addition to the thinner design.
The second important point to make on the importance of the compressor/volute design paring comes from the need for smooth flow into and out of the snail. One of the things we all love about turbos and superchargers is blower whine/whistle. The Vortech does this wonderfully at idle but quiets down as the RPM go up. Sort of disappointing but exhaust (and for me propeller noise) are going to drown out most or all of it anyway under load. The Procharger C-2 is the only model I have had on my test bench and it once again is an entirely different beast. In fact, the first time my father tested it I called him a liar, declared he was doing something wrong, then came back to work that day to prove it . . . only to see what he had already claimed. At idle the Procharger sounded like a tornado. No whine at all. Just the noise you get when you stick your head out a car window going 55mph. Strange, but it will make sense in a minute. As we increased the RPM up to full operation the noise from the blower didn't seem to change much but again, it is difficult to tell with all of the other noise going on around. Back down to idle and the sound of rushing wind again. What the hell is that? Turns out it is air being forced back OUT of the inlet. You read that right. Only about 75% of the radius of the blower inlet was sucking air in. The other 25% was pushing air back OUT of the blower. As part of our testing we restrict airflow into the superchargers by holding a piece of sheet metal over the inlet. Holding it over that side of the inlet it kept getting blown out of the way, not sucked flat. At higher RPM this behavior appears to go away, but at idle it is very much there and very easy to demonstrate. Talking with our sources at Vortech they reported having the same problem with some of theirs and fixed it by changing the shape of the intake portion of the volute. I have not had the chance to run the same test on other Procharger models but that kind of problem unchecked on one model doesn't inspire confidence. Fortunately, for most applications this doesn't really cause a problem, but if you plan on designing a draw-thru carbureted design you better plan on a fair amount of ducting between the carb and the blower. All carburetors are is a calibrated air leak, and air pushing its way back through the carb is going to be extremely difficult (read impossible) to tune.
All that said, we use, sell and endorse both. As with any part in any application you work within or around the limitation of the parts you MUST use. If everything were equal I would have elected to use a Vortech instead of the Procharger for that kit, but Vortech doesn't offer anything close to as small as the Procharger unit and for it's flaws, it still works exceedingly well. I doubt anybody would be disappointed in either unless they just happened to get a bad one from the factory. Lets face it, every product will have a flaw come out from time to time. Just sharing my opinion at Iggy's request based on my actual experiences over 2 decades of testing.
