A buddy of mine has a connection with ProCharger and was just talking about a good deal he can get on a universal Sport Compact supercharger kit. Got me thinking about if it was possible to adapt this kit to my EJ25 and if it would be worth it. I'm not a big fan of Turbo setups but a supercharger might be a viable option.

Someone slap me in the face with an obvious reason this has not been done yet...

Subaru already has an out-of-the-box turbo setup, and good at that.

If you can get it to work, roll it man.

That would be sweet.

Esp with a big belt, so you can hear it whine

b

I've been thinking about doing this too.... The only reason I can come up with is that the EJ25 is fairly high compression to start with. But there must be something to do about that.

If you look on Nasioc therea re a number of Supercharger kits avaialble. I haven't researched them a LOT but there are a bunch of people trying out different stuff. Its potentially a very very cheap way to get more power. Supercharger, intercooler and programable ECU are the major components, most of which can be gotten cheap (used charger, megasquirt, etc.)

-Tony

A supercharger is for instant power but it does rob power from the engine to drive

it. Turbocharging is driven off the exhaust with almost no loss of power. The type of

driving that I have done with mine I don't need full power right off the line.

If you are going to use yours for the 1/4 mile than why not. But if you are

going to use it for what it was designed for TURBO....

I've drivern a WRX and the tubro lag sucks ass. I'm sure that can be fixed with some fairly simple mods, but a supercharger on a 2.5 would be fun. I say go for it! And then I'll copy whatever you do

-Tony

I'm sure it would supercharge nicely - if you could get the compression down on the atmo 2.5 engine. I bet you could run a lower boost number and have quite a bit of excitement just taking it as is....

C'mon guys, you are supposed to be talking me OUT of doing this... Eh, its all a pipe dream right now but there is no better time to do it than while I have it all torn apart.
Much more research is needed but I'll start diggin into it.
Thanks for helping me spend even more non-existant cash!

Just get some dished bus pistons and go at it...

bring out some JB weld too.

b

Both superchargers and turbos suck engine power. One is just less noticable by *only causing an exhaust restriction. Meanwhile, both provide forced induction- which results in a net power gain.

I'm not a supercharger kinda guy myself. My NHRA man tells me that the biggest fallicy is that it, based on the pump design, literally starves for air at high rpms. Big problem for racers. Pro drag cars have them setup to provide the best boost right at takeoff, and then let the supercharger overheat or eat crap for the next 5 seconds. My guy runs his cars NA, though. Nothing compares to the kind of boost you can put in with a roof scoop on your 914....

a wrx motor in the midst of it's lag is still stronger than my stock 1.7 was...

And the lag goes away realllllllly quick when the car weighs nothing.

BJH

to get serious power from it then you might as well use a turbo motor as all the right equiptment is there (internally that is) and it should handle it, if you want just a bit more then up to the 4-6psi (most factory supercharged setups run at this) would be ok for an atmo hi comp motor without too many problems

this would be good on a six

IMHO the 2.0 engine is not quite torquey enough for the 3000lb WRX - which seems to make the lag a bit annoying. The same effect can be observed in our 2.5GT at high altitude where there just isn't enough torque before the turbo spools up. Once everything is spinning though - it's as exciting as ever.

In a 914 there seems to be plenty of torque and when the boost kicks in, it's just voracious. I am hoping in the future to switch to a ball bearing turbo, perhaps something with a titatium rotor ( depending on the dollars ), will be interesting to see how that compares.

I'm sure with 4-6lbs of boost on a 2.5 motor you'd have a LOT of fun. I'm only running 7-8psi right now on the 2.0 and it's fine. With proper intercooling and what not I'm sure it would be really a lot of fun. I would be worried about 1st gear though, although pulling off from 2nd would almost certainly not be a problem.

Been done a few times....even offered as a kit from some company in Colorado (Rippy or ripplen or RXXXX something )

There is also at least one supercharged Subaru over on NASIOC..

Supercharger install on Subaru,. homemade setup

Click to view attachment

the turbo has the advantage of being done thousands of times....you'll be on your own pretty much with the supercharger...

You could lower the compression on a N/A 2.5 with thicker copper head gaskets, but you'd mess up your cam timing. I don't know if it's enough to matter.

Oh, there's no doubt that it could be done, but it's going to up your fuel mileage vs. turbo (like that's a concern for a sportscar), cause the turbo is doing its job under load and the supercharger does its job fulltime, and it will make less peak power than a proper turbo setup without going to crazy extremes.

The way I see it, there's a few ways to go, listed approximately in order of cost effectiveness

1) Learn to drive fast despite turbo lag. It can be done.

2) Get a twin turbo engine from Japan

3) Get a single turbo engine, then replumb it to take two smaller turbos. This is probably a bit less work than trying to supercharge. Might require aftermarket ecu, but so might the supercharger setup.

4) Use an anti-lag system like rally cars. The downside is that you'll go through turbos like potato chips, upside is that you'll shoot flames and loud bangs out your exhaust when you let off the throttle, making small children cry, and making veterans duck and cover. Checkout the pro-drive street car with anti-lag, Top Gear segment

Personally, I'd like to drive around in a car that sounds like squirrels are being forced into the engine.

As somebody already pointed out, superchargers AND turbochargers both rob power from the motor to compress the intake charge. With a supercharger its more obvious, cause there's a belt. With a turbo its a little deceptive, but just think of it as a humongous exhaust restriction. But both devices will produce more net power due to the increased air intake. A turbo charger is inherently more efficient (less "robbed" power for the same amount of net power output), or so says Corky Bell.

If you're looking for a reason *not* to supercharge a 914, you definitely want to keep that inefficiency in mind. All that wasted energy has to go somewhere, and basically it's gonna end up as extra heat; i.e., even more than a turbo for comparable power. So before you just "slap in a supercharger", make sure you've got a cooling system that can handle it. My impression is that water-cooled 914s are usually at the "just barely adequate" end of the spectrum, but I could be wrong.

It's not just as simple as ineffiency. It's where the ineffiency lies. With a turbo, by the time you're spooled up, there is no longer much of an exhaust restriction. With the supercharger, at the top rpm, everything is shaking loose and it can't find enough air to feed the pump. With natural aspiration, drag. The one thing that you absolutely must do is find a method to make far more power than you're losing. Some early turbo cars used a series of swing valves to redirect ehaust and intake around the turbo when it wasn't spooled. I'm doing an exhuberant n.a. component on my car, but the air will pass through the chassis without stopping at certain speed/rpms. And I haven't thought too much about a supercharger. Maybe a clutch on the drive pulley and a valve to redirect air to a n.a. scoop at 60mph?

I know this is drifting away from the original post, but's always intersting (to me, anyway) to talk/think about this kind of stuff. When I used the term "exhaust restriction" in reference to a turbo, I meant that the turbo is actually extracting energy from the engine, energy that would otherwise show up at the wheels. And this "robbing" of energy does NOT decrease at higher RPMS or when the turbo is already spooled up. Lets say you're spooled up and running at high RPMs. So a whole lot of air is being compressed from atmospheric pressure to some considerably higher pressure; this requires power - quite a bit of power. It's a common misconception that the work of compressing the intake charge is somehow accomplished for free, but that would violate the laws of thermodynamics.

It's beeen a while since I read Corky Bell's book on Tubochargers, but the point he raised about turbo- vs super-charging was that superchargers are inherently more inefficient than turbos in a fundamental, thermodynamic sense. I *think* the point was that since the exhaust gas is expanding and cooling as it passes through the turbine, there is some extra work (P * dV) that can be extracted from the "working fluid" (e.g., exhaust gas); so *some* of the work a turbo extracts is energy that would otherwise have been wasted, but not all of it (not even most of it). A supercharger, OTOH, is driven mechanically, so there is no more energy to "extract".

I'm not suggesting that Turbos are "better", just that for comparable gains in power seen at the wheels, a supercharged engine is gonna burn up more fuel and generate more heat than a supercharged one. And if its sitting in a 914, getting rid of that extra heat is something to think about.

BTW, The Subaru EG33 (6 cylinders, from the SVX) takes the same sized pistons as the EJ22, so there are commonly available low-compression pistons. And I recall that someone was "working on" a supercharging kit for that engine. That might make for a fun little project...

Yeah, alpha, it's a funny thing you mention this. I think Saab re-invented this back in the late 70s, but the idea was actually first used on the Chrysler turbine car! It had vanes that could redirect gasses to the power turbine that would be used to reduce the amount of time it would take to spool the turbine, and even turn the gasses around to provide an "engine braking" effect like piston engines, because they wanted the car to be familiar to a piston driven car.

But it's a funny thing you mention it because the new Porsche 911 turbo uses vanes on to also reduce the apparence of lag, and eliminate the need for a wastegate. I think the VW TDIs with the red "I" in North America also have variable vane turbos, as well do many large diesel tractors. It's more efficient than the wastegate, and it delivers boost across a wider RPM band. Cool stuff.

edit: wanted to put this cool gif animation of a VVT turbo up, for everyone to really see what goes on: