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Discussion Starter #1
There are a few posts in the Go fast forum that are just packed with quality info... The FAQ's, the Turbocharger options post (the one I did)... I'll be doing a Supercharger some time after next week...

But there is no real solid post about the exact differences between Turbochargers and Superchargers from a generic standpoint... Let's see how sucessful this thread can be...

PLEASE KEEP THIS POST CLEAN!!!! NO DISCUSSION... just post info that is useful...

If you have nothing to add to this future FI encyclopedia, dont post! Links are good, as long as they are actually useful... You ARE welcome to post any questions you have though, once you've given the FI savvy a chance to give as much info as they have...

The Question that will be exhausted once and for all in this post:

What are the differencees between Turbochargers and Superchargers? Technicalities, benefits, types, EVERYTHING! GTE, Hyper, herez your chance to spill...

If you find anything wrong or inaccurate in this post, please PM the person who posted the info so he can fix it. Thx to a couple of people who have cleared up a few misconceptions in my posts...

<font size=-1>[ This Message was edited by: ZaKapitan on 2002-05-25 16:30 ]</font>
 

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Discussion Starter #2
I'll begin with the basics...

It's easy to pump more gasoline into a cylinder. But the problem comes from getting enough oxygen in there to burn all that fuel...

Naturally Aspirated engines rely on displacement to fill their cylinders with enough air. Not good enough; you can never get anything more than atmopsheric pressure in there, and so you're limited to the amount of fuel that can be burned using the available oxygen.

Enter Forced induction: Forced induction is a way to get more OXYGEN into your cylinders. Nitrous does it in chemical form... N2O has a large amount of oxygen to volume ratio: 33% of the volume is oxygen, compared to the maximum of 20% in air.

The other way to get more oxygen is just to force more air into the cylinder, by putting it under pressure... through turbocharging or Supercharging.

Both of them operate on the same principle.. Put an air pump on the intake side, and you can pressurize the air entering the cylinder. In this case, they're basically fans that spin very fast...

Superchargers use a belt connected to the engine to turn this fan... Superchargers are always pressurizing the air going into an engine, as long as the engine is running, so many superchargers usually also have a Bypass valve/wastegate to keep the engine from being boosted at lower RPMs.

By changing the size of the pulley connected to the drive shaft, you can make that "fan" spin faster, and raise the pressure of the air going into the engine.

Turbochargers work a little differently... they use the exhaust coming out of the engine to turn the fan... The exhaust side of the turbocharger is connected to a turbine, which spins and powers the intake side. You'll realize that you get a vicious circle going on here... the more exhaust comes out, the faster the turbocharger spins, hence the more air goes in, and eventually goes out to turn the turbocharger even faster...

While superchargers act as basically pumps and allow no room for leakage around the fins, turbochargers are free-flowing.. air can flow around the fins.. it's more like a fan. Because of this, it takes a certain RPM to start this chain reaction... and it also explains why there is a certain "lag"... it takes time to spin a turbocharger up to 60,000 RPMs...

Also, since the turbocharger's boost is dictated by how FAST THE TURBOCHARGER IS SPINNING, there really is no solid way to regulate how fast it's spinning, or to put a limit to the boost... So we put on either a Wastegate or a Blow-off valve...

A BOV is installed on the intake side... and it's basically a valve that opens after a certain pressure... After 10PSI, for instance, the BOV will allow all the extra pressure to just get released, allowing only 10PSI of pressure into the engine. That's how you regulate a turbocharger.

A BOV also helps to keep you from having too much air going into the engine when you change RPMS very quickly. For instance, between gears, your RPMS might go from 6000 to 2000 vey quickly, while that turbocharger is still spinning itz ass off... that's where you get the PSSSHHHH... It releases all the pressure and allow it to build up naturally without throwing the Air/fuel ratio out of whack...

A wastegate or bypass valve opens up at a set level of boost, like the Blow off valve. For instance, if you've set your turbocharger to 10PSI, a wastegate will open up and let any pressure out more than 10PSI... that'll keep your turbocharger from overboosting your engine (Overboost)

You use either a BOV or a wastegate, not both...

Realize that a Wastegate on a supercharger works in the reverse of a Turbocharger wastegate... A Supercharger's wastegate is open at lower RPMs, and closes to allow the boost at higher RPMS. Turbocharger wastegates open when boost gets too high.

_________________
"Men who get well with women, are usually those who know how to get on without them." -- Lord Mancroft

i am young jedi. i learn from sensei. i practice on you.

<font size=-1>[ This Message was edited by: ZaKapitan on 2002-05-26 02:17 ]</font>
 

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Discussion Starter #3
INTERCOOLERS:

Why do you need an intercooler? what is an intercooler?

For all you people who remember ANYTHING from physics, you know that compressing a gas makes it hotter. And Hotter gases expand! so here you are compressing the air to get it into your engine, and it gets hot and expands again... USELESS!!! USELESS I TELL YOU!!!!

An intercooler is basically a radiator for your intake air... After the air is compressed by your turbo/supercharger, it goes through an intercooler, which allows the hot compressed air to cool down and contract a bit... That way, you can get more out of your FI system.

Here's the way it goes...

1) Intake: air is sucked into the engine through that high performance filter of yours...

2) Charger: your turbocharger/Supercharger spins really fast and compresses the air... the air gets compressed, heats up, and expands...

3) Intercooler: The pressurized warm air runs through an intercooler, which functions the same way as a radiator... the air cools down a bit, and contracts.. so now you have high-pressure contracted air. great!

4) ENGINE: it goes into your engine, allowing you to burn more fuel, and make more power!

k that's all I know...
 

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<TABLE BORDER=0 CELLPADDING=0 CELLSPACING=0 ALIGN=CENTER WIDTH=85%><TR><TD COLSPAN=2><font size=-1>Quote:</font><HR></TD></TR><TR><TD> </TD><TD><FONT SIZE=-1>
On 2002-05-25 05:25, ZaKapitan wrote:
Also, since the turbocharger's boost is dictated by how high the RPM is, there really is no solid way to regulate how fast it's spinning, or to put a limit to the boost... So we put on a Blow-Off Valve...

A BOV is installed on the intake side... and it's basically avalve that opens after a certain pressure... After 10PSI, for instance, the BOV will allow all the extra pressure to just get released, allowing only 10PSI of pressure into the engine. That's how you regulate a turbocharger.

A BOV also helps to keep you from having too much air going into the engine when you change RPMS very quickly. For instance, between gears, your RPMS might go from 6000 to 2000 vey quickly, while that turbocharger is still spinning itz ass off... that's where you get the PSSSHHHH... it releases all the pressure and allow it to build up naturally without throwing the Air/fuel ratio out of whack...

_________________
"Men who get well with women, are usually those who know how to get on without them." -- Lord Mancroft

i am young jedi. i learn from sensei. i practice on you.

<font size=-1>[ This Message was edited by: ZaKapitan on 2002-05-25 05:34 ]</font>
</FONT></TD></TR><TR><TD COLSPAN=2><HR></TD></TR></TABLE>

Correct me if I am wrong but a BOV is what is installed within the intake track. This, as Zak has stated, helps reduce the pressure that builds up after the throttle is closed (i.e. intake pipe doesn't blow off or other damage, etc.)

A "waste gate" on the other hand, is the mechanism that is controlled electronically, by vacuum or both to specifically reduce the overall boost pressure that is sent into the engine.
 

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Superchargers are not always on when the engine is on. Many superchargers have a bypass valve that allows the supercharger to be passed entirely when not needed (highway cruising for instance) allowing less wear on the engine.
 

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Depends upon the application, and your use for the car?

p.s.
Anyone wanna post a defintion of boost spike, boost creep, and detonation.....

<font size=-1>[ This Message was edited by: mateo on 2002-05-28 18:46 ]</font>
 

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Discussion Starter #7
TURBO TIMERS:

A turbo Timer is a mechansim that keeps the engine running for a couple of minutes after you take out the key and get out of the car.

See, because Turbochargers are lubricated with your dirty motor oil and get so hot, there is a film of oil that stays on the hot turbocharger after you turnoff the engine. This oil can burn and leave a residue all over the moving parts, called "coking"...

Itz kind of like cooking butter in a pan and forgetting to put in the eggs... it gets all burned and sticks to the pan...

A turbo timer allows your engine to run for a while, circulating the oil for a while until the turbocharger can cool. Usually you can set them for how long you want it to run. A turbo timer is no different from just sitting in your car and letting the turbocharger cool down for 5 minutes before you get out of the car, it's a convenience thing.
 

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The Great Debate, it will never end!
"What is better - a supercharger or a turbo?"

We only wish the answer were that simple, but unfortunately it is not. The simple answer is:
"It depends."
Both superchargers and turbos have distinct advantages and disadvantages. Selecting the right kind of forced induction for your vehicle will depend upon your driving habits, your power preferences, your needs and budget.

Clearing Up Confusion

According to Merriam-Webster's dictionary, a supercharger is defined as:
"a device (as a blower or compressor) for pressurizing the cabin of an airplane or for increasing the volume air charge of an internal combustion engine over that which would normally be drawn in through the pumping action of the pistons".
A turbocharger is defined as:
"a centrifugal blower driven by exhaust gas turbines and used to supercharge an engine".


According to Webster's, a turbocharger is included in the definition for superchargers - it is in fact a very specific type of supercharger - one that is driven by exhaust gasses. Other superchargers that do not fall into this category - the kind that we are all used to hearing about - are normally driven directly from the engine's crankshaft via a crank pulley. So in reality, it is not fair to compare all superchargers to turbochargers, because all turbochargers are also superchargers. For the purpose of this discussion, however, a supercharger will be considered all superchargers that are are not driven directly by the engine, while turbochargers will be considered all superchargers that are driven by engine exhaust gasses.

Similarities

Both superchargers and turbochargers are forced induction systems and thus have the same objective - to compress air and force more air molecules into the engine's combustion chambers than would normally be allowed at atmospheric pressure here on Earth (14.7 psi at sea level). The benefit of forcing more air molecules into the combustion chambers is that it allows your engine to burn more fuel per power stroke. With an internal combustion engine, burning more fuel means that you convert more fuel into energy and power. For this reason, supercharged and turbocharged engines normally produce 40% to 100%+ more power (depending on the amount of boost) than normally aspirated engines.

How They Work

A supercharger is mounted to the engine and is driven by a pulley that is inline with the crank (or accessory) belt. Air is drawn into the supercharger and compressed by either an impeller (centrifugal-style supercharger), twin rotating screws (screw-type supercharger), or counter-rotating rotors (roots-type supercharger). The air is then discharged into the engine's intake. Faster crank speed (more engine rpm) spins the supercharger faster and allows the supercharger to produce more boost (normally 6 to 9 psi for a street vehicle). Typical peak operating speeds for a supercharger are around 15,000 rpm (screw-type and roots style superchargers) and 40,000 rpm (centrifugal-style superchargers).

A turbocharger operates in much the same way as a centrifugal (internal impeller) supercharger, except it is not driven by pulleys and belts attached to the engine's crank. A turbo is instead driven by exhaust gasses that have been expelled by the engine and are travelling through the exhaust manifold. The exhaust gas flows through one half of the turbocharger's turbine, which drives the impeller that compresses the air. Typical operating speeds of a turbocharger are between 75,000 and 150,000 rpm.

Head to Head Comparison

Now it's time to evaluate the turbocharger versus the supercharger according to several important factors.

Cost
The cost of supercharger and a turbocharger systems for the same engine differ, the turbocharger system is slightly higher so cost may be a factor.

Lag
This is perhaps the biggest advantage that the supercharger enjoys over the tubo. Because a turbocharger is driven by exhaust gasses, the turbocharger's turbine must first spool up before it even begins to turn the compressor's impeller. This results in lag time which is the time needed for the turbine to reach its full throttle from an intermediate rotational speed state. During this lag time, the turbocharger is creating little to no boost, which means little to no power gains during this time. Smaller turbos spool up quicker, which eliminates some of this lag. Turbochargers thus utilize a wastegate, which allows the use of a smaller turbocharger to reduce lag while preventing it from spinning too quickly at high engine speeds. The wastegate is a valve that allows the exhaust to bypass the turbine blades. The wastegate senses boost pressure, and if it gets too high, it could be an indicator that the turbine is spinning too quickly, so the wastegate bypasses some of the exhaust around the turbine blades, allowing the blades to slow down..
A Supercharger, on the other hand, is connected directly to the crank, so there is no "lag". Superchargers are able to produce boost at a very low rpm.

Efficiency
This is the turbo's biggest advantage. The turbocharger driven primarily by potential energy in the exhaust gasses that would otherwise be lost out the exhaust, whereas a supercharger draws power from the crank, which can be used to turn the wheels. The turbocharger's impeller is also powered only under boost conditions, so there is less parasitic drag while the impeller is not spinning. The turbocharger, however, is not free of inefficiency as it does create additional exhaust backpressure and exhaust flow interruption.

Heat
Because the turbocharger is mounted to the exhaust manifold (which is very hot), turbocharger boost is subject to additional heating via the turbo's hot casing. Because hot air expands (the opposite goal of a turbo or supercharger), an intercooler becomes necessary on almost all turbocharged applications to cool the air charge before it is released into the engine. This increases the complexity of the installation along with oil feed lines. A centrifugal supercharger on the other hand creates a cooler air discharge, so an intercooler is often not necessary at boost levels below 10psi.

Surge
Because a turbocharger first spools up before the boost is delivered to the engine, there is a surge of power that is delivered immediately when the wastegate opens (around 3000 rpm). This surge can be damaging to the engine and drivetrain, and can make the vehicle difficult to drive or lose traction.

Back Pressure
Because the supercharger eliminates the need to deal with the exhaust gas interruption created by inserting a turbocharger turbine into the exhaust flow, the supercharger creates no additional exhaust backpressure. The amount of power that is lost by a turbo's turbine reduces it's overall efficiency.

Noise
The turbocharger is generally quiter than the supercharger. Because the turbo's turbine is in the exhaust, the turbo can substantially reduce exhaust noise, making the engine run quieter. Some centrifugal superchargers are known to be noisy and whistley which, annoys some drivers (we, however, love it!)

Reliability
In general, superchargers enjoy a substantial reliability advantage over the turbocharger. When a a turbo is shut off (i.e. when the engine is turned off), residual oil inside the turbo's bearings can be baked by stored engine heat. This, combined with the turbo's extremely high rpms (up to 150,000rpm) can cause problems with the turbo's internal bearings and can shorten the life of the turbocharger. In addition, many turbos require aftermarket exhaust manifolds, which are often far less reliable than stock manifolds.

Ease of Installation
Superchargers are substantially easier to install than a turbos because they have far fewer components and simpler devices. Turbos are complex and require manifold and exhaust modifications, intercoolers, extra oil lines, etc. - most of which is not needed with most superchargers. A novice home mechanic can easily install most supercharger systems, while a turbo installation should be left to a turbo expert.

Maximum Power Output
Turbos are known for their unique ability to spin to incredibly high rpms and make outrages peak boost figures (25psi+). While operating a turbocharger at very high levels of boost requires major modifications to the rest of the engine, the turbo is capable of producing more peak power than superchargers.

Tunability
Turbochargers, because they are so complex and rely on exhaust pressure, are notoriously difficult to tune. Superchargers, on the other hand, require few fuel and ignition upgrades and normally require little or no engine tuning.

Conclusion

While the turbo will always have its place in a more specialized market. Superchargers generally provide a much broader powerband that most drivers are looking for with no "turbo lag". In addition, they are much easier to install, making them more practical for a home or novice mechanic.


Mike
 

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This is something I have seen mentioned so far, is that most people believe that a Turbo will require more maintenance however this is not necessarily the case as you have to maintain the SC belt along with its usually external sump which is separate from the motor and will frequently need to have oil added and or replaced as often or even more so then a turbo as the oil pool is smaller...
 

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True true, but remember, that the Supercharger is only being used approximately 5% of the time, so even though your point is correct, its not really all that bad.
 

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hey mateo, your post is full of incorrect info. either edit it to the correct info, or get rid of it. if you want examples, i'll show you

"Also with a turbo, the intake charge is much cooler"

"A BOV (blow-off valve), not only regulates boost pressure"

"or boost creep"

"Supercharger's are usually a very easy "bolt-on" way of acheiveing boost."

"this is loss is very small and isn't a big deal"


"this only means you have to change your oil every 2,000 miles instead of every 1,000 miles"

"Supercharger's also run very hot, their intake charge is much hotter than with a turbo. This creates what is called detonation, this is bad for your engine"




all of this is misinformation, and you are awful confident to be so misinformed. if you want, i can edit your post to read correctly, not opinion wise, but factually wise, if you aren't able to come up with the correct information. i can also PM you the proper information if you would like. now i am not trying to bust your balls, but people are going to read that and believe you, and then the wealth of misinformation will spread even further.

as for your question about
"Anyone wanna post a defintion of boost spike, boost creep, and detonation....."

boost spike = when boost climbs above a preset level (done by a wastegate or wastegate with a boost controller) upon the initial surge of boost, but then begins to settle as rpms increase beyond its peak. it is usually do to an inadequate boost controller, inadequate turbo or inadequate exhaust system.

boost creep = when boost reaches a preset level at "x" rpm (usually well below redline) and then boost continues to increase uncontrollably, above the initial settling point and preset level. it is usually do to an inadequate wastegate or inadequate area for exhaust gases to bypass the turbine wheel.

detonation = is uncontrollable preignition, where as the air and fuel in the motor are ignited at non-optimal points, and sometimes very damaging points, during the rotation of the motor. it all centers around cylinder pressure and cylinder temperature.

lmk what you decide

-gte






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On 2002-05-25 13:42, mateo wrote:
Turbos 101a: Turbos, after what Houston and Zak said, also run off the engine's own oil system, making it even more important to change your engine's oil. Turbo's also create better horsepower overall, their effciency rating is much higher (66% i believe). Also with a turbo, the intake charge is much cooler, which means, as Zak said, MORE HORSEPOWER!!!!!

A BOV (blow-off valve), not only regulates boost pressure, but it also acts as a safety from boost spikes or boost creep. Both are very bad for the engine and for the actual turbo itself.....so beware.....

Superchargers 101a: Supercharger's are usually a very easy "bolt-on" way of acheiveing boost. Supercharger's create more torque than turbo's, supercharger's also have a small drag percentage on the engine. Like Zak stated, they run off a belt, that runs of the crank in the car, this causes a drag on the engine and the engine loses horsepower, this is loss is very small and isn't a big deal. Supercharger's usually have their own oil system, this only means you have to change your oil every 2,000 miles instead of every 1,000 miles. Supercharger's also run very hot, their intake charge is much hotter than with a turbo. This creates what is called detonation, this is bad for your engine.

In other words....

Turbo = tire screaming speed

Supercharger = massive torque

CHOOSE YOUR POISON WISELY!!!

p.s.
Anyone wanna post a defintion of boost spike, boost creep, and detonation.....
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mmmmmmmmmmmmmmmm booost.
 

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My question in pretty general. I love forced induction, and would love to have either SC or Turbo. BUT, my question is driveablity of the car. As for me, the IS is my only car and have nothing else to drive.

A Turbo, Generally requires more maintanence than the SC, but my stupid question is, what about fuel economy and driveablity of the car.
I have an idea of what it would be, but i do not have first hand experience with FI on the IS300. Only on my other car which was sold 3 days ago.

Let me know, Thanks alot.
 

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As for fuel economy, I think Turbo's are better off than Superchargers because there is "constant" boost for a Supercharger while you can decide whether or not to boost with the gas pedal on a Turbocharged car.
 

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Discussion Starter #17
Good question...

GAS MILAGE AND FORCED INDUCTION:

Adding more pressure to a cylinder will always increase efficiency. Any combustible mixture will burn faster and more efficiently under pressure.

Try it yourself... you strike a match, and it burns... If you were to press on the match head with your finger and snap it accross the lighting strip of the matchbook, it'll pop instead of flaring up...

A stick of dynamite works the same way... if you were to take the dynamite out of it's sheath and light it, it will just flare up... Same thing with a firecracker... I'm sure many people have hammered the bottom of a piccolo pete and watched it explode at the end...

So you'd think that forced induction would increase the fuel economy too simply because of the higher pressure, right? You're right... Pressurizing the combustion chamber more will increase efficiency, and you will get better gas mileage with the same amount of gas being burned.

The thing is, with all these 300+ HP IS3's you see on the board, they also increase the gasoline going into the engine... the Toyomoto kits, for example, all include fuel system upgrades to accommodate the added fuel. So although the fuel is being burned more efficiently, the car is tuned to use more gasoline.

If you were to get yourself some form of forced induction and kept it at like 2PSI (an example) simply to burn the already-there gas more efficiently, you WILL get better gas milage.

A turbocharger is more economy efficient than a supercharger because the supercharger draws its power directly from the crankshaft. This added load makes the engine work harder, and in turn you get robbed of efficiency. This translates into minute HP and gas milage losses.
 

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just a fyi, not ALL s/c's are like what mentioned above.

for example, mercedes benz's s/c unit uses electronic(or was it something else?) clutch on the s/c so that it doesn't use gas too much.

well, that's all i gotta say; some s/c's are smart.
 

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well i have got to say a very very very informative post. I knew nothign about SC before and now i feel like an expert :smile: thanx alot guys
There are some questions i have that i would rellay appricaite if some one answered
1. amount of MODs requiired to get the Turbo or the Super? What do you have to get done to your car before you can do any of these?
2. The diffrence between horse power gain or torque gain which one is more important and why ?
3. any one here got the SRT SC charger installed ? if they did how much gain are we talkign about? and if possible 0-60 and 0-100 numbers and 1/4 miles will be greatly appriciated.
 

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And this is what a turbo looks like,



This is a Mitsubishi TD04HL-19T with integrated wastegate and BOV (recirculation valve).

<font size=-1>[ This Message was edited by: Johann on 2002-05-28 04:51 ]</font>
 
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