Supercharger vs Turbo

Discussion in 'Forced Induction & Tuning' started by chickendreamer, Mar 14, 2006.

  1. chickendreamer

    chickendreamer Well-Known Member

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    Supercharger vs Turbo

    The same question arises over and over, what’s better Supercharger or Turbo? Comparatively both have their advantage & disadvantage and both will have fans telling one is better than the other but bottom line a turbocharger will produce more horsepower per psi than a supercharger. This of course has to be under the assumption that both the supercharger and turbocharger produce the same amount of flow.

    For superchargers there are 3 different kinds, there is a roots style, twin-screw and centrifugal supercharger. The main difference between each of these superchargers is how they push air into the engine. Roots and twin-screw superchargers use meshing lobes of differing design where a centrifugal supercharger uses an impeller to draw air into the engine. Although all of these designs provide a boost, they efficiency of them varies considerably. Each type of supercharger is available in different sizes depending on the amount of flow desired.

    The Roots supercharger is the oldest design. The Roots supercharger is the oldest designed patented in 1860 by Philander and Francis hence the term “roots†supercharger. As the meshing lobes spin via a belt driven by the engine crankshaft, air trapped in the pockets between the lobes is carried between the fill side and the discharge side. Large quantities of air move into the intake manifold and "stack up" to create positive pressure. For this reason, Roots superchargers are really nothing more than air blowers, and the term "blower" is still often used to describe all superchargers. Roots superchargers are usually large and sit on top of the engine. They are popular in muscle cars and hot rods because they stick out of the hood of the car. However, they are the least efficient supercharger for a few reasons: They add more weight to the vehicle, they move air in discrete bursts instead of in a smooth and continuous flow and also they are limited to a relatively small maximum amount of flow. However, these superchargers typically have the quickest response in power and produce enormous amounts of low end torque which allow the driver to smoke the tires under 3000rpm. They give the best low end power but top end power is restricted because the blower can only flow so much.

    A twin-screw supercharger operates by pulling air through a pair of meshing lobes that resemble a set of worm gears. Like the Roots supercharger, the air inside a twin-screw supercharger is trapped in pockets created by the rotor lobes. But a twin-screw supercharger compresses the air inside the rotor housing. That's because the rotors have a conical taper, which means the air pockets decrease in size as air moves from the fill side to the discharge side. As the air pockets shrink, the air is squeezed into a smaller space. This makes twin-screw superchargers more efficient, but they cost more because the screw-type rotors require more precision in the manufacturing process. Some types of twin-screw superchargers sit above the engine like the Roots supercharger. They also make a lot of noise. The compressed air exiting the discharge outlet creates a whine or whistle that must be subdued with noise suppression techniques. Similar to roots style, the twin-screw produces enormous amounts of low end power to the engine. Kenne-bell superchargers use the twin screw type of arrangement. Twin screws also give excellent low end response but are limited to top end rpm power.

    The final type of supercharger is the centrifugal which is Vortech, Paxton or Procharger. More of each of these brands I will discuss later but for now I will stick with how they work. A centrifugal supercharger powers an impeller, a device similar to a rotor, at very high speeds to quickly draw air into a small compressor housing. An impeller is similar to a rotor. Impeller speeds can reach 50,000 to 60,000 RPM. As the air is drawn in at the hub of the impeller, centrifugal force causes it to radiate outward. The air leaves the impeller at high speed, but low pressure. A diffuser, a set of stationary vanes that surround the impeller, converts the high-speed, low-pressure air to low-speed, high-pressure air. Air molecules slow down when they hit the vanes, which reduces the velocity of the airflow and increases pressure. Centrifugal superchargers are the most efficient and the most common of all forced induction systems. They are small, lightweight and attach to the front of the engine instead of the top. They also make a distinctive whine as the engine idles.

    Turbochargers like superchargers compress the intake air and push it into the engine. In order to achieve this boost, the turbocharger uses the exhaust gases from the engine to spin a turbine, which in turn spins an air pump. The turbine in the turbocharger spins at speeds of up to 150,000 rotations per minute (rpm) which is the reason you here a whine as turbo’s spool up. And since it is hooked up to the exhaust, the temperatures in the turbine are also very high which is why typically turbocharger systems are intercooled.

    Both superchargers and turbochargers drain power from the engine in order to produce the power. Superchargers require the engine itself to turn over the lobes or impeller. To test the efficiency of a supercharger Campbell Automotive did an interesting test using a centrifugal supercharger.

    “We did a test with a 8.5:1 compression 510" BBC with a D1 procharger. We ran it N/A with no belt and the engine make 595 HP. With the belt hooked up but not pushing air into the engine it make 425HP and wouldn't pull a stiff cock out of a pail of grease in July. The blower took 170HP to turn at 6500rpm, Now granted the engine makes 1000hp with the blower all hooked up is cool, but imagine if it was a turbo.â€Â

    As tested, it is clear to understand that a turbocharger will produce more power per psi than a supercharger because of the above test. However, turbochargers are not 100% efficient like some people make it out to be. One cause of inefficiency of a turbo comes from the fact that the power to spin the turbine is not free. Having a turbine in the exhaust flow increases the restriction in the exhaust. This means that on the exhaust stroke, the engine has to push against a higher back-pressure. However, turbochargers still have less inefficiency than a supercharger. Another loss of the efficency is turbo chargers significantly increase the intake air since the exhaust flow heats up the turbocharger so much. However, this is easily remedied by adding an intercooler to a turbocharger system which is very common.

    Often times the costs of a supercharger are usually lower than turbocharger system… well, that’s what people think on first look. If we were to compare all of the supporting mods we need with both a supercharger and turbocharger it becomes clear the price usually adds up to be close in the end. Let’s do a comparison with a Paxton novi 2000 for a 94-95 mustang and a HP Performance turbocharger kit with supporting mods.

    Novi 2000 - $3,420.00
    Injectors - $300.00
    Maf - $250
    Headers (short) - $200
    Total - $4170
    (includes fuel pump)

    HP Performance Turbocharger kit w/ T60 - $4500
    (includes maf, injectors, fuel pump, also includes intercooler)

    So after adding up the numbers you can see the turbocharger system isn’t much more money, also if you ended up getting an intercooler for the supercharger kit, the supercharger system will cost you more.

    Performance wise, a supercharger on a 94-95 mustang with H/C/I around10psi will give you rougly 400rwhp/400rwtq on a mustang dyno. Where for a turbocharger system, like my car I produced 467rwhp/506rwtq at 9.5psi.

    However, installation of a supercharger is usually much easier than a turbocharger. Of course if we do install the supporting mods of headers and an intercooler with a supercharger then the difficulty of the installation isn’t much different.

    Finally, a turbocharger puts less strain on the engine block since the engine crank isn’t turning over an extra accessory like the supercharger needs too. And for the 302 guys anything over 400rwhp is block splitting territory.


    If you want any additional information regarding turbo mustangs check here: http://www.turbomustangs.com/turbofaq.php
     
  2. Lightning Struck

    Lightning Struck Well-Known Member

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    very good info, well done :thumb:
     
  3. bkstang95

    bkstang95 Active Member

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    Very well written. I must say that i am a turbo person myself. There are more pro's than con's for running a turbo (in my opinion).
     
  4. Downshift

    Downshift Well-Known Member

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    I have seen 5.0 Turbos but I havnt seen any 4.6 Turbos. I just havnt looked. But I head the 4.6 are a bitch for just getting headers on, would it be like impossible to do a turbo kit on them? Just curious.
     
  5. Downshift

    Downshift Well-Known Member

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    Btw good write up :dancing6:
     
  6. Lightning Struck

    Lightning Struck Well-Known Member

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    you better believe its a MAJOR BITCH to put headers on a 4.6 :mad:
     
  7. chickendreamer

    chickendreamer Well-Known Member

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    I'll do some more updating like what kits are availible, the advantages of twin over single turbos, etc.
     
  8. Dalamar

    Dalamar Well-Known Member SN95 Supporter Retired Staff

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    Excellent write up. I agree with you on all the info.
    I've been looking into blowers and moved to turbo's over the last few years.
    Haven't quite had enough money to get one, so I've just been researching for "fun"

    I'm also convinced that the turbo is the best way to go.
    I like how you get decient low end response, like a root's type, and some increase in power
    on the top end, like a centrifigal. Kind of a "best of both worlds" setup.
    Plus turbo's sound sweet.

    I priced out a KB, with long tubes, and an X pipe, ect
    vs a HP twin kit, and the KB with exhaust costed more! case closed for me.

    Any blower is a big improvement, don't get me wrong, KB makes a very nice blower, and has all
    the accessories you would want.


    ChiknD - where did you find the HP kit for that price?
    I am working towards doing a Twin kit,
    I was looking at HP, but they can't deliver, and they're setup has a few flaws.
    So, I'm looking at the Turbohorsepower kit.

    do you have any recommendations for me.
    (aside from a shortblock...)
    Any advice would be appriciated.

    And - congrads on the new moderator position. :bunny3:
     
  9. VulcanGT

    VulcanGT Active Member

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    very nice write up man! i was looking into getting a turbo for my 95 GT. i think this has sealed the deal, plus i love the sound of a turbocharged V8 :pimp2:
     
  10. jimgt95

    jimgt95 Well-Known Member

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    Nice write up. I disagree however that twin screw superchargers are noisey. My KB is silent driving around and I can only hear it whistle a little bit at parking lot speeds in 1st and 2nd gear. Of course I've never heard any other brand of twin screw, so maybe that is the noisey one.

    And another thing, as far as making top end power with a KB, on my dyno graph I make peak HP at 5700 rpm (I don't take my stock block into redline). It's very linear on the HP side and a huge jump on the TQ side and then nearly flat on top (a slight arch from 2K to 5700). I, however, don't have that "burst" like a turbo or especially a centrifugal supercharger at the top of the tach.

    The reason I really like my KB is because it's a street oriented supercharger. It makes great power where I need it, from off idle to before redline. In terms of cost I made my mods with an eye towards adding a KB down the road (over the course of several years) so the impact was considerably less on my pocket book when it came time to put on the s/c. Other pluses: install was a breeze and it looks badass on top of the engine.

    We could debate this forever, but bottom line is get what you are happy with. For my combo and use (key words there), the KB was and is the way to go.
     
  11. Tattoogod

    Tattoogod Well-Known Member

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    ive been looking into every possible thing where ias turbo,single or twin. roots style blower,or a paxton style. im leaning more torwards tohe KB blowzilla..cause if i blow a head gasket or something else.i want me repair to go kinda quick.and from what ive heard,not seen but to do spark plug changes and peeps blowing head gaskets like crazy with turbo. it sounds like turbos create more power with less boost,but comes with more work to tune and to keep stable.where ive ridden in a kb blown 94 on a stock motor at 10psi. and it was sick enough for me.


    btw what does H/C/I mean..its on the top of my tongue and i cant remember it lol..driving me nuts here.
     
  12. jimgt95

    jimgt95 Well-Known Member

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    Heads/Cam/Intake

    That's why I bought my KB Blowzilla. I wanted a good street supercharger that I didn't have to change the cam (yes I am running the stock cam), get crazy with the exhaust and intercooling (turbo/centrifugal), and buy a whole new upper and lower intake to utilize the forced induction (found a cheap gt40 lower at WFC8). I also wasn't interested in going to the drag strip every weekend and competing. I just wanted a good powerful car that would be fun on the street and not handle like a tank. The KB is a great option for those purposes.
     
  13. Matt94GT

    Matt94GT Well-Known Member SN95 Supporter Retired Staff

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    Im still debating kb or turbo...
     
  14. Spyder

    Spyder Well-Known Member

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    IMO turbo is the only way to go. POer comes on fairly fast as long as the turbo is sized correctly to the engine combo, you make more power with less boost, and not everyone has one. I have been in a single turbo 5.0 that is putting down about mid 500's and i must say, that thing is stupid fast when you puch it. ive never seen anything take off like that before, its insane. But the cool part, its a stock cam so it idles perfectly, its as calm as an old lady when you keep your foot out of it, and you get better gas mileage compared to a supercharger.
     
  15. Matt94GT

    Matt94GT Well-Known Member SN95 Supporter Retired Staff

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    I just dont want to worry about blowing headgaskets or other major issues...
     
  16. 97GTS

    97GTS Well-Known Member

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    Turbo (esp. BIG ONES) only way to go IMO
     
  17. Spyder

    Spyder Well-Known Member

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    Head gaskets will blow reguardless which way you go. Matt i hear you are debating whether you wanna go KB or Turbo. If you only worry is head gaskets, then dont let that keep you from buying a turbo. The way i see it boost is boost and if the boost is gonna blow out your head gasket than it doesnt matter if its from a KB or a big turbo. If anything i would think that the turbo would be less likely to blow out due to the fact that the motor is working a hell of a lot less to make the same amount of power. Turbos will make the same amount of power with less boost, which eguals less stress.


    As far as big turbos rockin, that is true to a point. One thing that you have to consider when getting a turbo is getting one that is suited to both your driving situations and your motor combo. There are two sides to the spectrum; a small turbo that spools near instantly but doesnt put out the goals that you want, or the huge turbo that lags like a bitch but will give you more than enough power. Now a properly sized turbo for a v8 will spool somewhere between 2500 and 3500 depending on your boost controller, and will not give up on the top end. Its all about finding your sweet spot and keeping your goals realistic.
     
  18. Dalamar

    Dalamar Well-Known Member SN95 Supporter Retired Staff

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    +1 to what Spyder said. exactamundo Matt.
     
  19. Matt94GT

    Matt94GT Well-Known Member SN95 Supporter Retired Staff

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    yeah good point makes total sense, I just allways hear and read about turbo tuning issues and stuff blowing up.
     
  20. Spyder

    Spyder Well-Known Member

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    The reason stuff is so easy to blow up on turbos is all your need to do to get more power, is turn a little knob!! you set it, then get used to it and say , "Self, we need more powa" and then turn the knob and watch you block scatter across the pavement.