Robin
Premium Member
Registered: 7th Jan 04
Location: Northants Drives: Clio 182 Cup
User status: Offline
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right, there is a civic jordan on the estate where i work, and its got either a turbo or a supercharger, thing is, i dont know which it is
it makes a darth vader esque whooosh instead of the pttttttttsssssssssshhhh of a DV, could it be a low pressure turbo? or is it an SC?
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broster
Premium Member
Registered: 6th Dec 02
Location: Drives: E39
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superchargers often have a wining noise
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ed
Member
Registered: 10th Sep 03
User status: Offline
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Superchargers don't have dump valves?
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Robin
Premium Member
Registered: 7th Jan 04
Location: Northants Drives: Clio 182 Cup
User status: Offline
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quote:
Originally posted by 1800ed
Superchargers don't have dump valves?
they do, otherwise the pressure created would keep going into the engine when you back off the throttle and keep the revs up, which isnt good, they have a sort of by-pass valve to prevent this
and broster, its a vtech civic with jap exhauts and induction kit, you cant hear the engine until about 8krpm
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richard_syko
Banned
Registered: 17th Dec 03
Location: Newport, Wales
User status: Offline
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quote:
Originally posted by robmarriott
quote:
Originally posted by 1800ed
Superchargers don't have dump valves?
they do, otherwise the pressure created would keep going into the engine when you back off the throttle and keep the revs up, which isnt good, they have a sort of by-pass valve to prevent this
and broster, its a vtech civic with jap exhauts and induction kit, you cant hear the engine until about 8krpm
Dont think they do mate 
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Robin
Premium Member
Registered: 7th Jan 04
Location: Northants Drives: Clio 182 Cup
User status: Offline
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believe me, they do, they are driven off the engine, so the engine is still spinning the charger up when you back off, forcing air into the engine, when the car is not putting as much fuel in... this is not good
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TNM
Member
Registered: 5th Apr 04
Location: Nottingham Drives: VW Tiguan
User status: Offline
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i cant remember any one know whos had a super charger having a dump valve!
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Robin
Premium Member
Registered: 7th Jan 04
Location: Northants Drives: Clio 182 Cup
User status: Offline
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not an actual DV turbo style, but a pressure release valve all the same
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Robin
Premium Member
Registered: 7th Jan 04
Location: Northants Drives: Clio 182 Cup
User status: Offline
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"the power delivery is less thrilling than that of a turbo, but you get boost earlier and ther is no lag, so you always have boost on tap. you can also run a dump valve, which fires out the excess boost, saving engine internals"
taken from last months MAX hardcore
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CorsAsh
Member
Registered: 19th Apr 02
Location: Munich
User status: Offline
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S/Cs do have a sort of dump valve. Anyone who doesnt believe this should do a search for a film of a Datsun 240Z with a chevy engine... can actually see the valve working.
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Robin
Premium Member
Registered: 7th Jan 04
Location: Northants Drives: Clio 182 Cup
User status: Offline
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quote:
Originally posted by CorsAsh
S/Cs do have a sort of dump valve. Anyone who doesnt believe this should do a search for a film of a Datsun 240Z with a chevy engine... can actually see the valve working.
Ta very much
still dont know what this civic is though
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Mattb
Member
Registered: 2nd Feb 03
Location: Under your sisters bed
User status: Offline
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a super charger would have to run with a dump valve, be it atmospheric or recirculating. if it didnt, boost pressure would hit the closed throttle body and head for the only exit, back the way it came, trying to spin the chargers compressor turbine in the opposite direction to what the engine is
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Robin
Premium Member
Registered: 7th Jan 04
Location: Northants Drives: Clio 182 Cup
User status: Offline
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quote:
Originally posted by Mattb
a super charger would have to run with a dump valve, be it atmospheric or recirculating. if it didnt, boost pressure would hit the closed throttle body and head for the only exit, back the way it came, trying to spin the chargers compressor turbine in the opposite direction to what the engine is
although, as the inlet does not close instantly, it would still force air into the engine, creating a very lean fuel/air mix and bugger the engine, and keep the revs up, it'd be like having a sticky throttle
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Rebrabuk
Member
Registered: 28th Mar 04
Location: North East
User status: Offline
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My V6 makes a 'Whooooosh' sound.. 
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CorsAsh
Member
Registered: 19th Apr 02
Location: Munich
User status: Offline
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My 1.2 8v whines like its supercharged. But it's not. 
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nickyboy01
Member
Registered: 10th Sep 03
Location: Oxford-ish
User status: Offline
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Supercharger sounds like this
http://www.nloc.net/~bigd/Vids/WRX%20vs%20Lightning.wmv
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R Lee
Member
Registered: 15th Aug 03
User status: Offline
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honda's respond very well to suprecharging.
so, i'm guessing its supercharged.
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richard_syko
Banned
Registered: 17th Dec 03
Location: Newport, Wales
User status: Offline
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A recirculating dump valve is mostly used where dumping the charger air to atmosphere would lose metered air - that is, air that has already been measured in the ECU by a Mass Air Flow meter. Losing this air to atmospehere would cause incorrect fuel/air ratio - make it run rich.
The valve is driven from the amount of manifold pressure seen after the throttle body.
At idle and part throttle settings there is (generally) a partial vacuum in the manifold. At these times, the valve would remain open and recirculating the air from the charger outlet back to the charger inlet.
At wide open throttle the manifold pressure is near to atmospheric then goes positive as boost comes on. At these times the valve shuts tight and so no boost is lost back to the charger inlet - its all going into the manifold/engine.
With a supercharger, whether a positive displacement type (G60, Eaton etc) or Centrifugal (Z-Eng, Vortech etc) the air would be recirculating all the time there is a part throttle setting. As soon as you gun it, the valve shuts and all the boost enters the engine. Change gear quickly, and you will get a chuff as when you let go of the throttle, vacuum happens in the manifold, valve opens, vents - you get the picture.
So the choice of using a recirculating dump valve, or an open to air one, and where to locate it, can be made by looking at your charger setup. As long as you start metering the air entering the engine after the 'loop' or open part of the circuit, you are OK - otherwise, like I said, you will lose metered air.
NOW - heres something to bake your cookie:
Would fitting a recirc valve to Centrifugal Supercharger setup (Vortech, Z-Eng etc) cause more drag on the engine? Doesnt it go that load on the Supercharger is directly related to air flow through it - so increasing the flow will increase the load?
Think about a hair dryer - cover the exit nozzle up with your hand (make sure its on a cold setting!) and you will observe that the motor inside races faster and faster. Thus you have reduced the flow, the load on the motor dropped, so it went faster. Let your hand go, and the motor slows down as its now flowing air.
Work that one out!
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Marc
Member
Registered: 11th Aug 02
Location: York
User status: Offline
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quote:
Originally posted by CorsAsh
My 1.2 8v whines like its supercharged. But it's not.
1.2 16v's do too 
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vibrio
Banned
Registered: 28th Feb 01
Location: POAH
User status: Offline
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S/C would just sound like a normal car but with a whin. turbo makes a specific sound from the exhaust.
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Marc
Member
Registered: 11th Aug 02
Location: York
User status: Offline
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Ross is correct
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Kerry
Member
Registered: 5th Oct 01
Location: Norwich
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could be a bov as opposed to a dv
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vibrio
Banned
Registered: 28th Feb 01
Location: POAH
User status: Offline
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quote:
Originally posted by Kerry
could be a bov as opposed to a dv
I love it when people talk about stuff when thay have no clue abotu the subject
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Kerry
Member
Registered: 5th Oct 01
Location: Norwich
User status: Offline
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why do i not have a clue? i have had both and they both have a totally different sound 
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vibrio
Banned
Registered: 28th Feb 01
Location: POAH
User status: Offline
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quote:
Originally posted by Kerry
why do i not have a clue? i have had both and they both have a totally different sound
a DV and a BOV are one in the same thing. a bailey DV sounds different from a forge DV and a forge DV on my car sounds different to a forge DV on a supra or a ERST etc
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