jr
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Registered: 20th May 02
Location: Kent
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bit boring but important as it stops all these people gettign excited over wastegate chatter
writtne by mike rainbird from passion ford btw
WASTEGATES DO NOT CHATTER, WASTEGATES DO NOT "DUMP THE BOOST" WHEN YOU LIFT OFF THE THROTTLE or any other noise that every journalist seems to accuse them of making!
For your information, wastegates dump EXCESS boost pressure in the same way as a pressure release valve on a pressure cooker, i.e. only when it gets to a point that is preprogrammed into the ECU as being too much (being controlled by a sprung loaded actuator and air being bled off / fed to this by an electromechanical solenoid, but that is a totally different kettle of tuna). So a wastegate only dumps boost in full throttle (or heavy load partial throttle) situations. The noise you are actually hearing in your closed throttle scenario (often described as a pigeon noise, or "whoofling" if heavily damped by a factory airbox), is in fact nothing more sinister than turbo stall (or it's correct term, compressor surge). This occurs when the throttle is shut and the air flow produced by the turbo hits the shut butterfly of the throttle body and has nowhere to go but back the way it came (the wrong way through the compressor housing), so the noise you get is the blades of the turbo "chopping" through the air that is bounced back off the closed throttle butterfly. Normally at this point (if fitted) you can hear a "tssssssshhhhh" noise as well, which is the "dump" valve releasing some of this air flow, in an attempt to stop the compressor stalling (and thus trying to reduce the lag when the throttle is reaplied and the turbo has to "spool" back up).
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Dom
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Registered: 13th Sep 03
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good post 
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James R
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Registered: 4th Feb 03
Location: 205GTi16/306GTi16
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WRC cars are good for this cause they have antilag instead of a DV so it makes it louder as they are still trying to boost 18psi with the throttle shut.
got to love it 
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Kerry
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Registered: 5th Oct 01
Location: Norwich
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so to cut a long story short dump valves are bad and u are better with a recirc
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jr
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Registered: 20th May 02
Location: Kent
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quote:
Originally posted by Kerry
so to cut a long story short dump valves are bad and u are better with a recirc
and wastegates dont chatter
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Dom
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Registered: 13th Sep 03
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i take it, antilag is something that the ECU has to have? and just having a quick read, i found out that it put huge stress on the exhaust manifold etc - i take it, its not the sort of thing to have on a "every day" car? 
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CorsAsh
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Registered: 19th Apr 02
Location: Munich
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quote:
Originally posted by Dom
i take it, antilag is something that the ECU has to have? and just having a quick read, i found out that it put huge stress on the exhaust manifold etc - i take it, its not the sort of thing to have on a "every day" car?
Anti lag involves burning fuel in the exhaust housing to keep the turbine spinning IIRC...
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Robbo
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Registered: 6th Aug 02
Location: London
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So does a re-circ make the tishhhh noise or the horse chatter? Trying to identify re-circ and atmospheric (or whatever the other is called lol)
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jr
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Registered: 20th May 02
Location: Kent
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anitlag i belive is wheen the turbo is spooled up and tickover RPM so there is no lag while accelrating
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Kerry
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Registered: 5th Oct 01
Location: Norwich
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my recirc made a slight chatter but not very loud or noticeable
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broster
Premium Member
Registered: 6th Dec 02
Location: Drives: E39
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waste gates only work on full throttle dump valves work on closed throttle......simple
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Adam-D
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Registered: 11th May 02
Location: Cheshire
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i had a dv
i liked the noise more than anything
did make it a little laggy but it was only a small turbo
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Dom
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Registered: 13th Sep 03
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quote:
Originally posted by CorsAsh
quote:
Originally posted by Dom
i take it, antilag is something that the ECU has to have? and just having a quick read, i found out that it put huge stress on the exhaust manifold etc - i take it, its not the sort of thing to have on a "every day" car?
Anti lag involves burning fuel in the exhaust housing to keep the turbine spinning IIRC...
yea, retards the engine when the throttle is closed to keep fuel mixture and values opened (sometihng like that).
Just curious, if its something you could have on an every day car? but it sounds like things will break a lot quicker when using it 
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Kerry
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Registered: 5th Oct 01
Location: Norwich
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thats why i have a spare
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Robbo
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Registered: 6th Aug 02
Location: London
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quote:
Originally posted by Robbo
So does a re-circ make the tishhhh noise or the horse chatter? Trying to identify re-circ and atmospheric (or whatever the other is called lol)
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Drew
Banned
Registered: 24th Nov 01
Location: County Durham
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quote:
Originally posted by jr
anitlag i belive is wheen the turbo is spooled up and tickover RPM so there is no lag while accelrating
this is correct, thou vibs had to disagree with me and laugh at me when i said this, as he claimed that the turbo couldnt spool without boost, until he did his research and admitted i was correct afterall 
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Kerry
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Registered: 5th Oct 01
Location: Norwich
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quote:
Originally posted by Robbo
quote:
Originally posted by Robbo
So does a re-circ make the tishhhh noise or the horse chatter? Trying to identify re-circ and atmospheric (or whatever the other is called lol)
chatter
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Drew
Banned
Registered: 24th Nov 01
Location: County Durham
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quote:
Originally posted by Robbo
So does a re-circ make the tishhhh noise or the horse chatter? Trying to identify re-circ and atmospheric (or whatever the other is called lol)
i 1st told u mine sounded like a horse  u laughed at me Rob 
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Robbo
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Registered: 6th Aug 02
Location: London
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yesh i remember lol
so a re-circ makes a horsey noise like dres and an atmospheric sneezes lol
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Dom
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Registered: 13th Sep 03
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quote:
Antilag is used to keep the turbo spinning at a high speed even when the engine doesn't need a high volume of air. As a result, when engine does need that increased amount of air, the turbo doesn't have to build up - hence no lag. This is what creates the backfire noise on the rally cars.
How it works
When the driver lifts his foot from the gas pedal the ignition timing is altered with sometimes 40? or more delay (retard) and the intake air and fuel supply mixture is made richer . This results in an air/fuel mixture that keeps getting in the combustion chambers (through an additional bypass valve) when the driver no longer accelerates. The ignition being delayed, the air/fuel mixture reaches the exhaust tubes mostly unburned. When the spark plug fires, the exhaust valve is starting to open due to the ignition delay mentioned above. With the exhaust temperature being extremely high, the unburned fuel explodes on contact of the exhaust tubes close to where the turbo sits and the explosion keeps it turning (otherwise it would slow down since its intake, the exhaust gases, is cut-off). The effect is a vastly lower response times. Antilag puts huge stress on the exhaust manifold and pipes (mounted on a street car a bang-bang system would destroy the exhaust system within 50-100 km)
just read some more and people dont recommend antilag for road use as you will be replacing parts fairly often
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jr
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Registered: 20th May 02
Location: Kent
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see, eveyone is learning, this post should be topped for educational reasons
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Drew
Banned
Registered: 24th Nov 01
Location: County Durham
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gt4 wrc's have an antilag option, the turbos are reported to last around 7000 miles, so no, not really a good opion for road use
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Dom
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Registered: 13th Sep 03
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quote:
Originally posted by jr
see, eveyone is learning, this post should be topped for educational reasons
aye mate, it is really useful info
although doing some more research, people recon turbos/manifolds dont seem to last longer than a few weeks using antilag
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Drew
Banned
Registered: 24th Nov 01
Location: County Durham
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last longer than a few weeks (from what ive read)
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jr
Member
Registered: 20th May 02
Location: Kent
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quote:
Originally posted by Drew
gt4 wrc's have an antilag option, the turbos are reported to last around 7000 miles, so no, not really a good opion for road use
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