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

Beemer2

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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?
 

Steve@Avantgarde

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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.
 

star

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Plus turbo lag will be much less.
 

Naraic

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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.

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

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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
 

SL63 Mark

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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.
 

grober

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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.
 

Naraic

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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.

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

wireman

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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.
 

FIBAMAN

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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.

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).
 

Bolide

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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
 
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mersum1es

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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).

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.
 
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FIBAMAN

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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 over a foot in diameter. Shame it wouldn't fit under the bonnet of a road car...

Nick Froome

When are they going to start fitting fold out wings?
 

richardN2O

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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 :)
 
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Beemer2

Beemer2

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  • Thread Starter
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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.

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?
 

wireman

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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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