With a super charger it takes power to make power. With a turbo its free. Hey theres your answer to the $$$ its free.

 

The more boost, more HP it takes to spin a blower. Turbo is free for the taking!

 

I think there's advantages to a centrifugal supercharger. For one, with a turbo you build exhaust backpressure. Additionally, the shorter uneven length pipes hurt exhaust scavanging. Of course the boost makes up for this and then some, but it's not exactly free.

Neither does a centrifugal supercharger always stress the bottom of the motor. The stress on the bottom is ultimately controlled by your foot, which is what ultimately determines motor stress with ANY motor, forced induction or not. Of course with a supercharger it's going to take a few HP to spin it, but that's nothing that a motor making hundreds of HP cant handle. The AC compressor probably puts a bigger strain on the motor.

All just my opinion.

 

From what I have been reading, most of the energy driving the turbo is heat energy, not backpressure. This is why they suggest mounting the turbo as close to the exhaust flange as possible.

Also, exhaust scavenging (as I understand it) is a method of drawing more air/fuel mixture into the cylinder during the overlap phase on a normally aspirated engine. In the case of a turbo or supercharged engine, scavenging is unnecessary as the intake tract is under pressure, and in many cases there is no overlap.

A centrifical supercharger has the advantage of being easier to install, easier to select, and easier to change boost, but at a price. The boost in a supercharger is linear. This means that max boost must occur at max RPM, otherwise you would be overboosting at max RPM. The trade-off is that at half-max RPM you have half boost, and at lower rpm you have virtually none. For example, if I have 14psi at 6000rpm on a supercharged engine, then I will have 7psi at 3000rpm. On a turbo motor, that isn't the case. You can have 14lbs at 3000 and 6000. This would mean the TC motor would be making over twice the HP at 3000rpm as the SC motor. I say OVER twice because not only does it have twice the intake pressure, but it isn't using as much of it's HP to run the compressor.

Having said that, Jay Brown is making over 1,000HP on his FE with a centrifical supercharger.

Each option has it's place for sure.

-Scouder

 

Hence they run zoomies on the really high horsepower nitro drag cars.

 

Ya but...

I'm not sure I'd believe the info on a turbo charger site about super chargers.

There's no way it takes much power to turn a centrifigal blower. I think Rusty's right that it takes more power to run the AC compressor. And there's no way putting a giant fan in your exhaust pipe doesn't affect exhaust performance. It's got to be a wash.

And the numbers I've seen from blower companies don't show the linearity talked about. From what I understand you get boost from the lowest RPM. Blowers are all about tremendous throttle respones.

I just like the simplicity of the plumbing of a centrifugal blower. My head hurts thinking about the bends required to build a set of headers with a turbo in it. But once it's done, I'd love to see it.

Peter

 

Its not that I believe there statements but I believe what I see in there videos.... The mustang that is just Raping the dyno is proof enough for me that a turbo is good stuff. I mainly like the way a turbo drives as opposed to a SC.

 

you can't get something for nothing. The turbo is spun by the exaust pressure. that pressure is made by the piston pushing up on the gasses during the exaust stroke. Its robbing the engine of a few horsepower to spin that turbine, which is meeting resistance from the air. If it was a perfect system, with no energy loss, then 16 pounds of boost would take 16 pounds of torque to make. The same holds true for the Supercharger. Their power loss through the act of spinning is about the same for both types.

Turbos have an additional problem, though. they restrict the exaust flow, robbing some initial power the engine makes before boost. Turbos more than make up for the loss with they power you gain, but it's not free. It ends up being less efficiant becuase it had to overcome a higher powerloss. Less efficcent means the engine will build more heat, and use more gas for the same power output.

On the other hand, Turbos are non liner and so are power curves, so you can potintialy tune a turbo system to better match your power curve.

Superchargers are more efficent, and generate less waste heat, but they are liner, so you have to build an engine with a linier HP ramp to make the most of them, and then you basicly have a drage racing motor. With less parisitic losses, 16 pounds of supercharger boost will make more Horsepower than 16 pounds of turbo, but the RPM band will be much smaller and less usebale. Perfect for a dragster, less so for a street rod.

 

What about bearings in them? Some 25 years ago when I left that line of business turbos, especially with some models were known for chewing up bearings, in the turbo that is. The problem was heat and fresh oil getting to the bearing for the next start up. I would think no such problem accompanies a sc. Have the turbo companies gotten them to be more reliable?

 

Superchargers are more efficient? This just isn't the case. It is widely known, and documented, that turbochargers are more efficient than superchargers. It's simple. A SC gets all it's power from the crank. 100% of it's power is derived from crank energy. TCs get MOST of their power from heat energy that would have been dissipated out the exhaust anyway. That part IS free. The remainder is generated by pressure. The percentage of crank energy that is lost to pressure is significantly less than the energy lost to the drivebelt on a SC. The power loss is NOT about the same.

These are generally accepted as true:

For any given HP output, the TC will use less fuel than SC.
For any given boost, the TC will create more flywheel HP than SC.
For any given max boost, a TC can provide it over a wider RPM range than SC.

Yes, a SC system may be easier to install, and may make boost in .2 seconds where a turbo takes .5, but to try to defend it on the merit of efficiency is a losing battle. There is a reason that turbos are the current trend in HP, and why they are penalized in weight or displacement in most forms of competition.

All of this is easy to find on the Internet, and it isn't just the turbo companies saying it. The more I reasearch this topic, the more sold I am on turbos. There is no magic bullet, for sure. Every system has disadvantages, but after evaluating them, it's a turbo for me.

-Scouder

 

It would appear so. I haven't been reading anything about reliability problems, and the SC guys would be jumping on that if it were the case. Also, the diesel pickups are getting hundreds of thousands of miles out of them.

-Scouder

 

I've been looking into the turbos myself, Not so much as to really get a lot of boost but just to bring things back to "normal sea level cold day" kinda thing...LOL. Ok, so that's not such a technical term but you probably get what I'm talking about. In my case here in Houston TX we are at basically sea level but it's so dang hot here all the time that I've got less dense air to play with. From what I've researched, I think turbos mounted directly after the headers could work well for this and not be that difficult to install.

Tracy

 

Dont turbo's add more heat to the incoming air charge than a supercharger?

 

It depends on where the air inlet is. Back in the early 90's I was into the Buick V6 turbo regals. I ran a ram air scoop into a cold air box/filter. From there it was a straight shot into the turbo. But that was with running a intercooler to the intake also. A chip to bypass the 85 mph limit set from the factory and some upgrades and the car was very fast. 3800 stall converter...that car would hookup and scoot!

I can only imagine the power your 511 would get from twin turbo's. OMG!

G.

 

I can only go by what I've read, cuz I'm still learning, but I was reading today that it's not any worse than a roots type supercharger. I would imagine that a centrifical has a cooler charge. All of them make heat. You can't compress air without it. After you pass it through the intercooler it comes back down anyway.

-Scouder