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Why anti-lag instead of supercharger?

Posted by jacobfrey121, May 31, 2020

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  1. jacobfrey121

    jacobfrey121 Probationary Member

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    I searched the subreddit here (and el goog) to no real answer. I also read the wiki, so apologies if somehow this has been answered before.



    Why do some race car series use anti-lag systems (a continually spooled turbo) instead of a supercharger? Isn't a supercharger effectively no lag, as well?



    There must be some power advantage (superchargers can be street legal but I'm assuming anti-lag systems aren't) to do this in a racing setting, right?
    10.0.0.0.1. 192.168.1.254
     
    Last edited: Jun 1, 2020
  2. lasershark

    lasershark Proven Member

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    turbos are more efficient without parasitic loss... what platforms are you speaking of?
     

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  3. ThunderChild

    ThunderChild Supporting VIP

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    It comes down to packaging, weight and overall power capabilities. Sizing a supercharger correctly can be difficult for smaller engines, and when at low rpm or when overspun they have issues one mall displacement engines. While it is a possible idea, you're going to add significant weight or have to account for massive heat buildup.

    Antilag systems use the already installed system that is light and responsive, and when you're replacing entire engine assemblies that often they done really care.
     

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  4. DogWhistle

    DogWhistle Supporting VIP

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    We have both the N/A 3.8L and the S/C (roots type) 3.8L in nearly identical GM cars, of the same year. Yes, the compression ratio is lower on the S/C car.

    The N/A car is more responsive from a start since you don’t have the S/C impellers to restrict airflow before they spin up to speed. I can appreciate that 4 cylinders do not have the torque to overcome the air restriction while the S/C is spinning up.

    The gas mileage is about 3% better on the N/A car.

    Having said all of that, the S/C has a very linear response, with virtually no lag. You can control the amount of boost you want with your accelerator pedal, which, for a street car is very nice.

    And, the exhaust system is not restricted with a convoluted piping path, allowing the air to flow freely down the exhaust, and not causing heat build up under the hood.

    The N/A is nicer for city driving, but it is more fun to drive the S\C for highway driving.

    There are companies that produce a S/C which looks like a turbo, except it is belt driven. The limited space in our DSMs would make for a challenging install, but the fan style blades would not block as much incoming air. But, perhaps the biggest challenge would be to select a drive ratio (speed) that would work well for all driving situations since 4 cylinders are torque challenged.
     

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  5. ThunderChild

    ThunderChild Supporting VIP

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    Supercharger rotors are not a "restriction", as long as sizing is not vastly off, they are always pumping at least the same or a larger amount if air into the engine than it can ingest.

    What CAN happen is the addition of rotational weight and physical drag that the supercharger induces when going full throttle and the bypass closes. Load will go up exponentially, increasing the torque demand to drive the supercharger. On a low tq engine (like a 4g63) this can cause a "lag" feeling, as well as more load on other components that wouldn't normally see these kinds of Loads/situations.

    Once again, it all comes down I necessity and overall function, as well as weight of the system as a whole.
     

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  6. 1990TSIAWDTALON

    1990TSIAWDTALON Moderator

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    Just throw a 150 shot on it............:sneaky:
     

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  7. ThunderChild

    ThunderChild Supporting VIP

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    You kids and your nitrous... LOL
     

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  8. stillrunning

    stillrunning Proven Member

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    Turbos are the most flexible, can adjust hp on the fly or dial it back and are probably the most efficient overall at compressing air

    Centrifugal superchargers are just basically belt driven turbos and have a very linear boost curve that goes with rpm

    Positive displacement superchargers have near instant response since by nature since they displace more air volume than the engine can take in they have boost as soon as the bypass valve closes but can generate more heat at higher pressure ratios than turbo's or centrifugal superchargers.

    Positive displacement superchargers give you the impression of having a much bigger engine since they deliver near instant response

    While turbo's don't take power directly from the crank via a belt drive it does take power to drive the turbine wheel hard enough to generate needed pressure and volume with the compressor wheel, exhaust restriction which the pistons work against to push the exhaust through the turbine.
     

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