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What does a "twin" turbo do that a single turbo does'nt?

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by Beemer2, Oct 23, 2012.

  1. Beemer2

    Beemer2 Active Senior Members

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    My W212 is a twin turbo. How is this different from a single turbo?

    Secondly what was the significance of the word Kompressor on certain models?
     
  2. Steve@Avantgarde

    Steve@Avantgarde Forum Supporter Authorised Forum Supporter

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    Before you may have 2 exhaust chambers merging into 1 powering 1 large turbo, now you have 2 seperate chambers with 2 smaller turbos. Better power output, depending on the design maybe more efficient.

    Kompressors are superchargers, so rather than using recycled exhaust gasses, it uses fresh air forcing it into the engine at a higher rate.
     
  3. star

    star Forum Supporter Authorised Forum Supporter

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    Plus turbo lag will be much less.
     
  4. Naraic

    Naraic Moderator

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    ...and superchargers are crank driven...and have no lag as compared to the turbo charger.
     
  5. Wirral_guy

    Wirral_guy Active Senior Members

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    From how I understand it - the 2 turbochargers are set-up to operate most efficiently at different parts of the rev range - effectively spreading the boost more evenly.

    As has been said - a kompressor (compressor\supercharger) is a mechanical way of achieving the same thing as a turbo (i.e. forcing more air into the engine) run from the engine itself rather than the exhaust gasses.

    Dave
     
  6. Still Learning

    Still Learning Senior Member

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  7. SL55 Mark

    SL55 Mark Senior Member

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    As Malcolm says, the twin turbo system traditionally used by Porsche (and possibly other manufacturers ?) uses one small turbo with lower inertia which spins up quickly at lower revs (from memory around 1,500-3,000) and one large turbo which kicks in from 2,500rpm and delivers maximum grunt. The idea is to reduce turbo lag, always the bane of single large turbo engines.

    As far as I recall Porsche introduced it with the 959 , in the mid 1980s, and followed it up with more mainstream cars like the 993 and 996 TTs from the
    '90s on.

    I'm trying to remember the layout, I think exhaust gases from both cylinder banks were unified and the turbos were effectively in-line ? I can check later.
     
  8. grober

    grober Senior Member

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    In reply to your question - possibly cost a helluva lot more to replace if one of the twin turbo's goes AWOL.
     
  9. Naraic

    Naraic Moderator

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    Malcolm posts a lot...but not in this thread so far.;)
     
  10. grober

    grober Senior Member

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  11. wireman

    wireman Senior Member

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    There are two approaches to twin turbo charging, the complicated big one little one with fancy manifolds and the two same size smaller ones which offers much reduced lag and decent high output performance without complex manifolds, on a six pot cyls 123 drive one turbo and cyls 456 the other, all in cheaper than one big one and far better for road use.
     
  12. EmilysDad

    EmilysDad Senior Member

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    I hope you don't do the spannering ........ :shock::shock:
     
  13. FIBAMAN

    FIBAMAN Senior Member

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    Car manufacturers have tended to follow industrial engine developments, I recall first seeing a turbo charger on an engine built in 1953 / 54. Last one I worked on had 3 turbo chargers (9 cyl Sulzer 900mm bore 23,500 shp).
     
  14. Bolide

    Bolide Senior Member

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    Porsche and BMW are triple-turbocharging car engines now

    I remember seeing a Porsche 928 V8 on a stand at the Motor Show at Earls Court. It had been prepped for offshore powerboat racing and had two turbos, each about a foot in diameter. Shame it wouldn't fit under the bonnet of a road car...

    Nick Froome
     
    Last edited: Oct 23, 2012
  15. mersum1es

    mersum1es Senior Member

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    Jep, and lot of development still going on in industrial side (both 2-stroke and 4-stroke diesels) due to new emission standards, for example
    http://www.abb.com/product/ap/seitp324/996d26edc83f4a81c125770b0053247f.aspx I believe we may see someday these Miller-cycles etc. also in passenger cars too.
     
    Last edited: Oct 23, 2012
  16. FIBAMAN

    FIBAMAN Senior Member

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    When are they going to start fitting fold out wings?
     
  17. SL55 Mark

    SL55 Mark Senior Member

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    Sorry, it was wirral_guy :D.

    I saw the avatar and got them mixed up. :shock:
     
  18. richardN2O

    richardN2O Senior Member

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    Nothing todo with Mercs, BUT when my mate has finished his "Street Legal" Dragster, I'll post some photo's.
    His Twin Turbo'd 9 Litre V8 has turbo's the size of buckets :)
     
    Last edited: Oct 23, 2012
  19. OP
    Beemer2

    Beemer2 Active Senior Members

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    If I recall correctly the Saab 900 had a turbocharger that only kicked in at higher revs. Does the MB twin run continuously or only at higher revs?

    I'm still enjoying the thrill of the acceleration from around 30mph up and it seems as if the acceleration is not linear but increases which is making me think that the turbo system is a factor in this?
     
  20. wireman

    wireman Senior Member

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    Turbo chargers work off exhaust gas, the engine produces more gases at higher speeds and hence the turbo's turbine generates more power for its compressor, so yes all turbo charger systems work more at higher engine speeds, the trick is to size the turbo for the required application and provide controls that are effective in regulating its behaviour, in days gone by the waste gate was the only control, hence the early Saab's small(ish) turbocharger led to awful narrow power band engine characteristics, today we have variable turbine nozzles which can greatly widen the operating range of a turbo system.
    Modern applications significantly improve part throttle economy and reduce emissions, in my opinion the only valid reason to add the complication of a turbo.
     

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