- When it comes to making more power with
just about any engine, forced induction is an obvious solution but there are a variety of options
when it comes to forced induction. We're here with Eric from ProCharger to talk
about centrifugal superchargers. Now Eric, before we dive into the world of
centrigual superchargers, can you just give us the sort of 30,000 ft view of the options
available in terms of forced induction that are out there today? - Well I mean obviously they can do a screw,
a roots, a turbo, I mean there's any way to shove air into a motor. Obviously a ProCharger is a centrifugal
supercharger and I'm just stoked about what we've been able to accomplish in the last about
30 years. Really pushing the envelope of what's possible. - Definitely the technology has come a long way. Before we dive a little further in, let's actually
back up a storage and you've mentioned there roots syle and screw style blowers, and these
are really common, particularly in the V8 market because from a packaging standpoint, it's nice,
they fit in the valley and that's pretty easy so that's one style of supercharger, then you also
mentioned turbocharger and I like to sort of compare superchargers, centrifugal superchargers
and turbochargers because there are a lot of similarities there so let us know what those are. - Well they're so similar because they actually kind
of started in the same place, back in the day of the warbirds in the sky, you had centrifugal
supercharged, big V12s, V16s that eventually got mechanical turbos that eventually because
turbo supercharged so it's actually they all started in the same spot. Obviously when they diverged was when the
one was exhaust driven only and we're primarily crankshaft driven, belt or direct drive. - So when we look at a centrifugal supercharger,
essentially the compressor side of this looks identical to a turbocharger and for all intents
and purposes, it is? - Very similar, the difference would be RPM at
which it operates at so turbocharger, I mean small ones can be upwards of 200,000 RPM. Your bigger race ones are probably in the 180,000,
100,000 RPM range and we like to stick for gearbox purposes, about, 75, take that back,
we like to stay about 75,000 and lower, obviously racers do what racers do, they push
that envelope a little bit so the compressor design has to take that RPM limitation into
effect. - So you've optimised the compressor design
so that it's efficient and works well with that 75,000 RPM speed in mind? - Yes correct that's exactly it. - OK and you've sort of already alluded to the
fact that this is really a limitation just around the design of the gearbox, you can't really
drive the compressor at the sort of speeds a turbocharger is used to seeing? - Right because a turbocharger's going to be
floating that shaft on oil, where we actually have gears and shafts internal to that. So on planet earth there's actually not
a lot of gearboxes spinning 100,000 RPM. It's not a common thing and obviously your
transmission's not doing that, it's again, there's natural gas turbines or something that
do that and then us. What's been great is over the years, machining
technologies, bearing technology, gear and shaft materials all have evolved obviously. Racing keeps pushing that envelope and we keep
adapting to it and making sure that gearbox can keep getting faster and faster and durable and
more durable. - Alright now this always becomes a contentious
topic because those who love their screw style blowers will argue that they're the best. The turbo team are doing the same in their
corner and then of course supercharger. And the reality is, they have their own sets of
pros and cons. Now in terms of the efficiency alone, if we can
just focus on that for a moment. If we look at a common screw style blower,
they've come a long way over the last few decades but essentially for the same amount
of boost pressure, they're not as efficient as a centrifugal blower, we can say that? - Yes that is usually the case. I mean honestly that is our benefit, is the
efficiency if packaged correctly with the correct motor, correct camshaft, etc etc. I mean you could screw that up, you could
run the wrong compressor and you'd have a mess but we like to make sure that when a
customer calls in, you give us all the information about your motor, I mean everything you can
tell us and I can guarantee I've got a compressor that is basically perfect for that and if we
find that there's a niche that maybe we don't, we'll build it and that's what we've always done,
that's why I have a lot of blowers on display, not everybody understands the differences of
them, they look similar, from the outside you might not be able to tell the two apart. However let's say at 600 horsepower there
might be a 20% efficiency difference between those two. - In terms of that efficiency, because let's
follow on from that and what it actually means. When we compress air, no matter how well we
do it, by definition, physics dictates that we're going to introduce more heat. But depending exactly how efficient the compressor
is in its operation, we can end up adding more heat if that compressor's inefficient, compared to
an efficient one and the knock on effect there is for the same boost pressure, we're going to have
more or less power depending on the efficiency? - Absolutely so that's one of the things that
everybody gets hung up on a boost number. And you can make a lot of boost but if you made
a lot of heat with it, you're kind of negating the whole point so the good thing is again, an efficient
compressor, we also have great intercoolers, when you combine both of those, most of the
time, most of our kits are back down within 10° of ambient, somewhere around there. Makes a lot of horsepower. - Alright let's talk about the differences now
between a turbocharger and a centrifugal supercharger because as we've already discussed,
essentially on the compressor side of things, we've got a very similar technology, you mentioned
there differences in the compressor designed based on the operating RPM but obviously the turbocharger
is exhaust driven, the centrifugal supercharger is belt or crank driven? - Yeah belt or crank for us in most cases. So with the turbocharger, especially on pump
fuel, obviously it's now introduced back pressure which is going to dictate how you build your
timing curve. Again turbochargers have come a long way and
they are doing better than ever just like we are but if you're talking abut a street car guy, it's
running pump gas or he's octane limited, there are some key areas where we have some
great advantages because we can let the car run basically its normal timing torque ratio that it
wants to run before we start inducing a bunch of airflow. 'Cause we have not put any restriction on it. - So as far as the exhaust side of the engine is
concerned, it's operating like an aspirated engine? - Oh absolutely. And the thing that we've seen most recently
is people are now changing their minds, they're not talking about camshafts being a turbo
camshaft or a supercharged camshaft, that's finally kind of going away, people just
now realise that treat the motor as an air pump, get air in, get air out, just make the most
horsepower you can. - And this moves a little off topic but when we are
speccing a camshaft, that exhaust back pressure that we see with a turbocharger is a big factor
on the cam that we would choose. - Right, not so much on the centrifugal side. - Because again you've got basically naturally
aspirated as far as the engine's concerned on the exhaust side. - OK let's talk about the way the centrifugal
supercharger works in terms of its boost curve because this is one area that is
substantially different to an exhaust driven turbocharger so what's a typical boost curve
look like? - Well I mean the easy and short of it is
you could draw 45° angle. 'Cause I mean like if we had a very radial
compressor, that's what it's going to do, it's going to be very linear from start to
finish. Now that doesn't hold true for most of our
newer compressor designs because again they're more of, I mean we'll call 'em almost
like a turbo style wheel, kind of is what it is, very laid back blade, a lot more protrusion
out into the inducer and we actually are relying a lot more on compressor RPM so
if you size the compressor incorrectly you would have a big lull before that blade
came up to speed and really moved into that efficiency zone. Again, we work with the customer to make sure
that that doesn't happen so that way we get an impellor that starts out at that 45 and actually
tapers in a lot harder if that's what they would like it to do. - But essentially, all other things being equal,
we're never going to have 20 psi of boost just off idle, it's going to be that somewhat linear
curve because the compressor speed is obviously driven either directly or indirectly
via crankshaft speed. - Right and honestly I don't want 20 pounds
of boost at idle, it's ridiculously hard on rods and pistons, you can't run any timing at that
point, you're going to have to pull so much timing out of it, you're almost going to negate
a lot. So truely a small amount of boost, I mean even
a screw does have that kind of curve, they gain as RPM gains so having a lower amount of RPM
boost at a low piston speed or rod speed's not really a bag thing, again as long as it has a
properly built timing table, you can really optimise that. And let's talk about variable cam timing, that's
really changed the game and helped us there too so we can make really a lot of robust torque
by moving the cams into different positions and putting let's say two or three pounds of
boost down low, so we haven't exceeded the cylinder pressure that the octane of the fuel could handle. - In terms of driver feel, essentially you're, because
you're crankshaft driven, zero lag, when you get into the throttle, the compressor is already at
whatever speed that's dictated by the crankshaft speed so zero lag, is this essentially going to feel
from the driver's foot pedal, like a bigger capacity naturally aspirated engine? - That's exactly what everybody always said,
it takes a big block and makes it feel like it's twice a big block, it's a very linear power band
and that's probably the number one reason why we're selling more race blowers than
ever before. Because racers, especially at the 4000 horsepower
level, I know it sounds crazy, they need a driveable linear power curve. Something that hits hard right at the very
beginning, they're obviously trying to reel in all that power and then try to put it back in. Where our curve is actually now starting to fit
promods more naturally than ever before. Because it's a usable power band from start
to finish. - Alright let's talk a little bit about the
complexities around fitting a ProCharger to a vehicle. Obviously you need to get access to something
to drive it so you're somewhat limited in where in the engine bay this supercharger is likely to
be able to fit correct? - Yep we are, we obviously, in most cases,
except for a few exceptions, we're driving off the front accessory drive. Now what we've done is we obviously can do
driver's side mount, passenger side mount, we've done a lot of reverse mounts lately
where the blower actually is flipped around the other direction, got cold air facing forward. It really just depends on the engine bay of the
vehicle. The other thing that we've spent a lot of time
on is again intercooling to make sure that again they're getting back down or as close
to ambient as possible and we've spent a lot of time educating people that even if the
air filter is in the engine bay, it's actually not as detrimental as some people might actually
think. The reality is the intercooler cools it back down,
there's not that much heat load once the car's moving one mile and hour, two mile an hour,
there's a lot of airflow through an engine bay. - One of the concerns of course with any belt
driven supercharger is the belt failing, falling off, becoming loose, slipping, whatever that may
be and obviously in competition that's not ideal. What is needed in order to combat that,
what are the complexities around making sure that element is reliable? - Well so back in the day, just like everybody,
we would rely on factory tensioners or something another company made as a
tensioning device. Here in the last couple of years, we just
went to build our own so for a street car guy that's running an eight rib, or a six
rib, or an eight rib or a 10 rib belt, we now manufacture the tensioner ourself. It has a huge range of travel and it obviously
is a very tight tensioner so it's going to apply a lot of force without exceeding what the
crankshaft can handle. Which has changed the game. I mean now on our belt driven stuff, I'd want
to say, eight rib stuff is now approaching 1400 horsepower fairly reliable on the mustang
platforms and stuff, 10 ribs even a little further than that. - Os the limit here in terms of how much power is
required to actually drive the supercharger as you approach these higher boost airflow regions? - It's actually that, RPM and belt stretch. What a lot of people don't take into account
was as you keep upping in power, the belt stretches over time and a lot of the times the
tensioner would run out of travel. So it's putting pressure in, pressure pressure and
then it hits a stop, or then the belt goes slack and that's game over. So again, once you've exceeded what a belt can
handle, because of the drive power, then we'd recommend, we have the gilmer style belts,
or cog if some people call 'em that. And then for guys that are 2000 horsepower and
above, honestly most of them are now going to either a reverse belt drive that's very short or
they're going to a crank drive blower and that has been the game changer for all big big,
2000, 3000, 4000 horsepower setups. - Crank drive makes a lot of sense. One of the questions I've got around that is
how then do you adjust the blower speed to affect boost pressure? I mean obviously if a belt drive, you can change
the size of a pulley and change the drive ratio between crankshaft and supercharger, not quite
so simple on a crank drive? - It's actually really easy, I'll actually show you
over here since we have one on display. So we can change the blower speed in about
five minutes. So we actually have an intermediate gearbox
that goes right between the crank and right between the blower, it actually uses, we wanted
to make sure it was industry standard, easy stuff so the gears inside are just gears out of a
quick change rear end. Quick change rear ends don't blow up, they
run a lot of horsepower through 'em and they have almost zero reliability issues so we made a
bearing structure that could work within that RPM, whatever use range and then therefore
that's what then speeds up the blower. So all you did was eliminate the belt, turned
it into gears. - Makes a lot of sense, gets rid of a potential
failure point. Now before we came on camera you did
mention some of the advances with modern cars these days and how they're actually
helping centrifugal superchargers essentially do a better job and this is around gearing. So tell us what you're talking about here. Well in the last I don't know, let's say 10 years,
six speed trannies came around, then there was some seven speeds, eight speeds and now the
10 speeds have become very common on most of the performance muscle cars and what's great
about those transmissions is you can't have more than half throttle before it's automatically going
to downshift and put you way up in the RPM. It's going to put it in our sweet spot as I'd like
to call it. We're going to live in the upper RPM range
with very small RPM drops on gear changes. So it's no shocker to everyone, we make peak
torque, very high up in the RPM range. So if you're in a car and you just put your foot
more than halfway down, you just went to the point where we make the most torque which
is wonderful. - So the higher gear count really just gets
around the fact that the centrifugal supercharger, the boost comes up slowly, you're straight away
in the meat of the power band as soon as you put your foot down? - Yeah absolutely I mean somebody the other day
was like what do you do about something at 2500 RPM and I was like, well your vehicle won't ever be at
2500 RPM, you drive a Chevy truck, it's actually impossible to be at full throttle at 2500 RPM
and he was like oh yeah I didn't even think about that so it was perfect. - Alright thanks for your time there, great to learn
a little bit more about centrifugal superchargers and hopefully that's broken down some misconceptions
and misunderstandings for our viewers. Thanks for your time there Eric. Actually, if people do want to find out more
about ProCharger, how are they best to do that? - procharger.com, we have a lot of resources
on the website, we've got downloadable brochures that go into a lot of tech, otherwise just pick
up the phone, you can call us any time, we'll be glad to answer any question you've got. - Perfect thanks a lot. - No problem, thank you. - If you liked that video
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