Dump Valve Chatter on gear change
18 February 2003, 05:50 PM
#1
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Hi there.
I'm thinking of getting an Impreza turbo real soon and have already started making plans of the mods I would like to do. (Exhaust / air intake system / dump valve).
What I would REALLY like is for the dump valve (waste gate? - correct me if i'm wrong) to make that chattering noise that you hear all the time on the rally cars.
What is needed to acheive this??
Many Thanks
[Edited by cmdcorrola - 2/18/2003 5:51:22 PM]
I'm thinking of getting an Impreza turbo real soon and have already started making plans of the mods I would like to do. (Exhaust / air intake system / dump valve).
What I would REALLY like is for the dump valve (waste gate? - correct me if i'm wrong) to make that chattering noise that you hear all the time on the rally cars.
What is needed to acheive this??
Many Thanks
[Edited by cmdcorrola - 2/18/2003 5:51:22 PM]
18 February 2003, 05:58 PM
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No dump valve! That's the easiest way.
And if you have an IHI turbo, a few spare ones wouldn't go amiss if doing that.
If it's a Mitsubishi turbo though, it should be ok for a while.
There are dumpvalves that apparently sound like the no dump valve method, although seeming that's the ones with the stiffer springs, they probably make the sound like there's no dump valve by not opening. So, basically, no dump valve...
And if you have an IHI turbo, a few spare ones wouldn't go amiss if doing that.
If it's a Mitsubishi turbo though, it should be ok for a while.
There are dumpvalves that apparently sound like the no dump valve method, although seeming that's the ones with the stiffer springs, they probably make the sound like there's no dump valve by not opening. So, basically, no dump valve...
19 February 2003, 11:38 AM
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The chatter on rally cars has nothing to do with dumpvalves.
The chatter on street cars (like mine) is to do with the dumpvalve and the pressure required to move the piston in the DV. I have 2 springs - a red and a blue one. When I put the blue one in the dump valve it makes a chatter, and the red one makes a loud 'whoooosshhhh'!
The chatter on street cars (like mine) is to do with the dumpvalve and the pressure required to move the piston in the DV. I have 2 springs - a red and a blue one. When I put the blue one in the dump valve it makes a chatter, and the red one makes a loud 'whoooosshhhh'!
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19 February 2003, 01:16 PM
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no offence but yall a bit wrong, but it fine as i thought EXACTLY the same years back when i had reno5turbos, and only really worked it out once i had a cossie.
the flutter/chatter noise is whats called "wastegate chatter" even tho its not the wastegate in any way, its air coming out the turbo compressor inlet when the throttle is snapped shut on boost. "Impeller stall" is another more accurate name but no1 knows wat u on about if u say that, lol. "turbo chatter" id call it.
ANYWAY...
NO DUMPVALVE makes that noise, thas jus rumour etc thas spread over the years (even by tuners, before i had a clue, Torque Developments told me the HKS SQV valve made that noise "depending on your induction pipework" but no ANY turbo makes that noise "depending on induction pipework" ESP if no dumpvalve at all).
Let me explain...
Like i said earlier its the noise of pressurised air (from being on boost) escaping back out of the turbo compressor inlet when the throttle is shut. The MAIN reason for std factory fit recirulating dumpvalves like most turbo cars have is to STOP any "chatter" as they decide that it might put customers off (same reason for nigh on silent std exhausts n induction, i even saw a review of the old Ibiza GTi where they COMPLAINED that you could hear induction noise...).
The reason dumpvalves help stop chatter is because it gives soewhere else for the air to escape.
People say its to keep the turbo reliable, well if it IS on a scooby then their turbos must be VERY crap, as 99% of turbos that are specced to do so are fine to 25/30 psi with no reliabilty changes without a dumpvalve, you never see a turbo listed as "can run 2bar of boost, ONLY with a dumpvalve" as its jus legend thas spread across the bloody world (Ive ran without a dumpvalve for 2yrs now, with boost ranging from 25psi peak/22psi held, to 36psi peak/30psi held, and ive had no reliablilty issues with it).
Other things that muffle the sound is the airbox (jus fit a cone), airflow meters, and long induction piping.
These people saying "chatter on street cars is nothing to do with chatter on rally cars" are wrong, it EXACTLY the same thing. "my chatters because i got a stronger spring in my dumpvalve so my dumpvalve makes the noise" thas HALF right, having the stronger spring is stopping the dumpvalve opening partially or completley as the cars vacumn isnt strong enough to open it so most/all the air has nowhere to go but back out turbo, so TWTWTWOOOOOO, fookin chatter laddy.
So to sum it up, take off std resirc dumpvalve n plug the pipes, fit an induction kit, n go booting up down the road to the sound of chatter.
Dumpvalve woooshes are a bit gay anyway, kinda old news.
Cheers, Steve
Oh,BTW dumpvalves have no noticable effect on reducing lag between gearchanges either, thas another old wives tale, btu it you got a massive turbo with very long compressor blades (T4 or bigger) then a dumpvalve might be good for very high boost (30psi+) as longer blades are mre likely to snap when turbo stopping suddenly.
And rallycars etc dont run dumpvalves becasue, 1- no need, and 2- it makes the anti-lag not work as well as the air escapes out the dumpvalve when u let off which is exactly what you DONT want it to do when running ALS (belive me i tried it).
the flutter/chatter noise is whats called "wastegate chatter" even tho its not the wastegate in any way, its air coming out the turbo compressor inlet when the throttle is snapped shut on boost. "Impeller stall" is another more accurate name but no1 knows wat u on about if u say that, lol. "turbo chatter" id call it.
ANYWAY...
NO DUMPVALVE makes that noise, thas jus rumour etc thas spread over the years (even by tuners, before i had a clue, Torque Developments told me the HKS SQV valve made that noise "depending on your induction pipework" but no ANY turbo makes that noise "depending on induction pipework" ESP if no dumpvalve at all).
Let me explain...
Like i said earlier its the noise of pressurised air (from being on boost) escaping back out of the turbo compressor inlet when the throttle is shut. The MAIN reason for std factory fit recirulating dumpvalves like most turbo cars have is to STOP any "chatter" as they decide that it might put customers off (same reason for nigh on silent std exhausts n induction, i even saw a review of the old Ibiza GTi where they COMPLAINED that you could hear induction noise...).
The reason dumpvalves help stop chatter is because it gives soewhere else for the air to escape.
People say its to keep the turbo reliable, well if it IS on a scooby then their turbos must be VERY crap, as 99% of turbos that are specced to do so are fine to 25/30 psi with no reliabilty changes without a dumpvalve, you never see a turbo listed as "can run 2bar of boost, ONLY with a dumpvalve" as its jus legend thas spread across the bloody world (Ive ran without a dumpvalve for 2yrs now, with boost ranging from 25psi peak/22psi held, to 36psi peak/30psi held, and ive had no reliablilty issues with it).
Other things that muffle the sound is the airbox (jus fit a cone), airflow meters, and long induction piping.
These people saying "chatter on street cars is nothing to do with chatter on rally cars" are wrong, it EXACTLY the same thing. "my chatters because i got a stronger spring in my dumpvalve so my dumpvalve makes the noise" thas HALF right, having the stronger spring is stopping the dumpvalve opening partially or completley as the cars vacumn isnt strong enough to open it so most/all the air has nowhere to go but back out turbo, so TWTWTWOOOOOO, fookin chatter laddy.
So to sum it up, take off std resirc dumpvalve n plug the pipes, fit an induction kit, n go booting up down the road to the sound of chatter.
Dumpvalve woooshes are a bit gay anyway, kinda old news.
Cheers, Steve
Oh,BTW dumpvalves have no noticable effect on reducing lag between gearchanges either, thas another old wives tale, btu it you got a massive turbo with very long compressor blades (T4 or bigger) then a dumpvalve might be good for very high boost (30psi+) as longer blades are mre likely to snap when turbo stopping suddenly.
And rallycars etc dont run dumpvalves becasue, 1- no need, and 2- it makes the anti-lag not work as well as the air escapes out the dumpvalve when u let off which is exactly what you DONT want it to do when running ALS (belive me i tried it).
19 February 2003, 07:37 PM
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cmdcorrola,
I have a Forge VTA Dump Valve - not that expensive - something like £120 - Sounds great - I usually change the springs over every now and again depending on if I'm in chatter or whooosh season!
Cheers!
I have a Forge VTA Dump Valve - not that expensive - something like £120 - Sounds great - I usually change the springs over every now and again depending on if I'm in chatter or whooosh season!
Cheers!
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