Superlite Ltd.
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Registered: 9th Jan 07
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quote:
Originally posted by P1CK4D
Nice one. By looking at that though, it looks like it starts before the turbo. How can that work?
It dumps exhaust gas so it doesn't go into the turbo
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Ste L
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Registered: 3rd Jul 06
Location: Manchester Drives: 106 16v Rallye
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as above, basicaly all the waste from the waste gate,
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P1CK4D
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Registered: 19th Jun 06
Location: Around Essex Somewhere
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Sorry for seeming dumb guys. But doesnt a Turbo work by the exhaust gases pushing it round? Why would dumping gas before the turbo benefit it?
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Superlite Ltd.
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Registered: 9th Jan 07
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If all the exhaust gas went into the turbo it would psin toooooo fast. Wastegate dumps abit of it out 
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jr
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Registered: 20th May 02
Location: Kent
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usally Waste gaste gasses vented back into exhaust system with internal wastegate
scremer pipe vents into atmosphere via external wastegaste
[Edited on 30-08-2007 by jr]
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deano87
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Registered: 21st Oct 06
Location: Bedfordshire Drives: Ford Fiesta
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My car is bit of a screamer. In every gear passed 3krpm
[Edited on 30-08-2007 by deano87]
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Ste L
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Registered: 3rd Jul 06
Location: Manchester Drives: 106 16v Rallye
User status: Offline
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quote:
Originally posted by P1CK4D
Sorry for seeming dumb guys. But doesnt a Turbo work by the exhaust gases pushing it round? Why would dumping gas before the turbo benefit it?
The wastegate is a valve that allows the exhaust to bypass the turbine blades. The wastegate senses the boost pressure. If the pressure gets too high, it could be an indicator that the turbine is spinning too quickly, so the wastegate bypasses some of the exhaust around the turbine blades, allowing the blades to slow down.
[Edited on 30-08-2007 by Ste L]
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P1CK4D
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Registered: 19th Jun 06
Location: Around Essex Somewhere
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Why would spinning too fast be a bad thing? Wouldn't it just make you go faster? I actually do enjoy learning new things 
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Stu
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Registered: 3rd May 00
Location: Madchester UK Drives: 2014 BMW M135i
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Basically when you reach the required amount of boost the wastegate stops pushing the exhaust gases round the turbo and vents them off. Usually they are vented off into a pipe which is then routed back into the exhaust system - Obviously not 100% ideal as it creates a restriction and turbulence. So all a screamer pipe is, is the vent pipe NOT going back into the exhaust system but straight to atmosphere (uncatted and unsilenced)
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Stu
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Registered: 3rd May 00
Location: Madchester UK Drives: 2014 BMW M135i
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Screamer pipe
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Superlite Ltd.
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Registered: 9th Jan 07
User status: Offline
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WASTEGATE
The wastegate is the valve that allows exhaust gases to bypass the exhaust turbine of the turbo. Bypass more gas (open the wastegate further) and the turbo will slow, reducing the amount of boost being developed. Close the wastegate, and more exhaust gas is forced through the turbine, increasing turbo speed and thus the boost level being developed. The easy rule to remember is that closing the wastegate increases boost. Wastegates are typically built into the turbo, but some cars (like the one pictured) use external wastegates.
WASTEGATE ACTUATOR
The opening degree of the wastegate is controlled by a wastegate actuator. This device comprises a diaphragm backed by a spring. The
spring holds the wastegate shut, while boost pressure deflects the diaphragm against the spring, so opening the wastegate. If a 7 psi
spring is fitted to the wastegate, and the other side of the wastegate is connected straight to a source of boost pressure, the turbo will develop 7
psi boost. Lowering the pressure that the wastegate actuator sees (eg by a bleed) will mean that the wastegate doesn't open as far, causing in this example boost to be higher than 7 psi. Often the term 'wastegate' is used when the person really means 'wastegate actuator'.
BOOST CONTROL SYSTEM
A boost control system is used to vary boost pressure. Factory turbo cars usually use an electronic system to do this, with boost level varied depending on engine coolant temp, the occurrence of detonation, throttle position and so on. When applied to a modified car, a boost control system is invariably designed to increase boost above the level set by the manufacturer.
WASTEGATE CREEP
This is the term given to the slow opening of the wastegate prior to the peak boost level occurring. For example, if the wastegate is at its maximum opening at 7 psi boost, in many cars at 3.5 psi boost it will already have started opening ('creeping'). Nearly all factory boost control
systems allow this to occur so that boost does not come on in such a rush; wastegate creep allows much better driveability and gives a flatter torque curve. However, it also reduces acceleration over that which is possible without any creep. It's the 'coming onto boost' part of the full-throttle curve where reduced creep makes a performance difference. However, with good boost control systems, the part-throttle behaviour can also be very much changed if wastegate creep is reduced or eliminated.
BOOST SPIKE
A boost spike is a sudden overshoot from the designated boost pressure. For example, if boost is set to 15 psi but during hard acceleration rises
for 1 second to 20 psi before again dropping back again to 15 psi, a spike has occurred. Boost spikes that occur when the engine is coming on
boost are common in poorly set-up bleed systems.
OVERBOOST
An overboost is a short-term increased boost level that rises above the constant level. It is the same as a spike except for two aspects - it occurs
for a longer period (eg 3 seconds) and it is a desired feature of the control system! Boost control systems (both electronic and pneumatic) can be set up to allow short-term overboosting in some driving situations. An uncontrolled and unwanted excessive boost level should not be called an overboost. Some aftermarket systems call overboost 'scramble'.
BOOST FALL OFF
This occurs when the boost level reaches a peak (eg at max torque) and then gradually falls in level through the rest of the rev range. This can
occur in pneumatic systems (which don't have any feedback loop) as compressor efficiency drops off or pressure inadvertently builds again
in the wastegate line because of control problems.
SURGING BOOST (full throttle)
If the boost at full throttle constantly varies up and down (eg by a few psi) the car is said to have a full-boost surge problem. This is common in
poorly set-up or badly designed electronic boost control systems featuring feedback. It is easily felt on the road.
SURGING BOOST (part throttle)
While similar in name, this is a quite different characteristic, where maximum boost is available on small throttle openings. It is a characteristic of most aftermarket electronic boost controllers, a few factory electronic boost controllers, and just a very few aftermarket pneumatic boost controls. It is achieved by reducing wastegate creep, and
so this characteristic is a trade-off between excellent part throttle torque and a resulting lack of fine throttle control.
BOOST CUT
A Boost Cut is actually either a fuel or ignition cut, triggered as a result of exceeding the factory boost limit. A device (either electronic or neumatic) which overcomes the Boost Cut. Both types work by reducing the boost or airflow levels seen by the ECU.
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JM_16v
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Registered: 17th Oct 05
Location: Essex Drives: GLC63S
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kool superlight
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scottyp1989
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Registered: 29th Jul 07
Location: Warley, West Midlands
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http://cgi.ebay.co.uk/SAXO-CORSA-ASTRA-GOLF-ANY-EXHAUST-TURBO-SOUND-WHISTLE_W0QQitemZ320152081112QQihZ011QQcategoryZ9895QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
thats what the whistle is if you havent got a turbo. my mates got one on his vr6 an my other mate on his astra and they dont sound bad
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Ben ev
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Registered: 23rd Oct 05
Location: kingslynn / torquay
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quote:
Originally posted by Steve
good if you want to wreck your turbo and hinder its performance
care to explain that one steve?
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Steve
Premium Member
Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
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if your achieveing this by blocking off the dump valve, you cause the turbo to stall
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Ben ev
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Registered: 23rd Oct 05
Location: kingslynn / torquay
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quote:
Originally posted by Steve
if your achieveing this by blocking off the dump valve, you cause the turbo to stall
acheiving what exactly?
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Superlite Ltd.
Member
Registered: 9th Jan 07
User status: Offline
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quote:
Originally posted by Steve
if your achieveing this by blocking off the dump valve, you cause the turbo to stall
What the fuck has fitting an external wastegate and screamer pipe got to do with blocking off the dump valve? 
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Steve
Premium Member
Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
User status: Offline
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pressure to be forced out the external wastegate
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Steve
Premium Member
Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
User status: Offline
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quote:
Originally posted by Superlite Ltd.
quote:
Originally posted by Steve
if your achieveing this by blocking off the dump valve, you cause the turbo to stall
What the fuck has fitting an external wastegate and screamer pipe got to do with blocking off the dump valve?
well if you dont seal off the dump valve pressure will be lost through that route
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Superlite Ltd.
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Registered: 9th Jan 07
User status: Offline
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wastegates and dump valves are not dumping the same pressue steve
You can have both fitted to your car
[Edited on 30-08-2007 by Superlite Ltd.]
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Ben ev
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Registered: 23rd Oct 05
Location: kingslynn / torquay
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i can only assume your talking about having a ew on a kkk turbo with a integrated bov
still think your getting wires crossed slightly fella
[Edited on 30-08-2007 by Ben ev]
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Steve
Premium Member
Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
User status: Offline
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most people block off there dump valves forcing the pressure out the wastegate, its not a good thing
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Steve
Premium Member
Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
User status: Offline
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quote:
Originally posted by Superlite Ltd.
wastegates and dump valves are not dumping the same pressue steve
You can have both fitted to your car
[Edited on 30-08-2007 by Superlite Ltd.]
yes i know, people force more pressure back through the turbo out the wastegate though by sealing off there dump valve
[Edited on 30-08-2007 by Steve]
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whitter45
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Registered: 15th Nov 02
Location: Norton
User status: Offline
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quote:
Originally posted by P1CK4D
Why would spinning too fast be a bad thing? Wouldn't it just make you go faster? I actually do enjoy learning new things
as with any thing fluid dynamics palys a part. Tip speed on turbines etc are critical and at excess speeds air flow will changed
also got to remeber load on the bearing etc are all affected by spool speed.
The turbo will be designed to operate at a given rpm and pressure etc thus control measures need to be put into place
Some turbo's reach amazing rpm speeds
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Superlite Ltd.
Member
Registered: 9th Jan 07
User status: Offline
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quote:
Originally posted by Steve
quote:
Originally posted by Superlite Ltd.
wastegates and dump valves are not dumping the same pressue steve
You can have both fitted to your car
[Edited on 30-08-2007 by Superlite Ltd.]
yes i know, people force more pressure back through the turbo out the wastegate though by sealing off there dump valve
[Edited on 30-08-2007 by Steve]
Oh!
Why the hell do people do that
[Edited on 30-08-2007 by Superlite Ltd.]
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