"Chatter" sound dumpvalve
31 May 2005, 10:48 PM
#1
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"Chatter" sound dumpvalve
whats the craic on the "chatter" sounding dumpvalve mostly associated with rally cars?
can be got for a road goin impreza?
can be got for a road goin impreza?
31 May 2005, 11:01 PM
#3
rally cars don't use a dump valve, the noise comes from the air rushing back through the turbo when backing off the throttle. The more boost you have when backing off and the larger the turbo the louder and more sustained it is.
31 May 2005, 11:03 PM
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Originally Posted by Pavlo
rally cars don't use a dump valve, the noise comes from the air rushing back through the turbo when backing off the throttle. The more boost you have when backing off and the larger the turbo the louder and more sustained it is.
31 May 2005, 11:11 PM
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Originally Posted by ALi-B
Put a strong spring in any dumpvalve and you'll get the wastegate chattering 
chattering dumpvalve me ****! lol
31 May 2005, 11:16 PM
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and the turbine stalling?
Originally Posted by Pavlo
rally cars don't use a dump valve, the noise comes from the air rushing back through the turbo when backing off the throttle. The more boost you have when backing off and the larger the turbo the louder and more sustained it is.
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i run without a DV, chatters like a good one
01 June 2005, 02:47 PM
#10
Originally Posted by richie rich
and the turbine stalling?
If using a big turbo with a MAF sensor this causes problems, as it can happen when you go from large to small throttle opening as well as just closing the throttle. If it does happen, the MAF sensor measures the air going in and back out again and thinks there is much more airflow than there is, resulting in overfuelling, jerkiness and generally feeling not great to drive. But unless you are looking at a turbo at least as big as a TD05/06 20g this will not be a problem.
Paul
03 June 2005, 02:56 PM
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if you don't mind your turbo disintegrating and the bits being sucked into your engine then this a good mod (disregarding the fact that you'll get more lag). i think you'll find a wrc turbo is built to a somewhat higher spec than a road car.
03 June 2005, 04:41 PM
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Originally Posted by TonyFlow
Do you not reduce lag by running without a DV (the whole point in doing it)?
so to keep it spinning when the throttle closes momentarily (ie gearchange) the air is vented either to atmosphere or to before the turbo (recirculated). removing the dv entirely causes the air to back up between turbo and throttle plate on gearchanges, and eventually go backwards over the blades - so called compressor stall. it's a bad thing generally because the air is trying to force the blades back the opposite way they're going. eventually, they will shatter and the resultant mess will end up in your valves - nasty.
06 June 2005, 07:02 PM
#21
Removing a dump valve will generally reduce lag between gearchanges. However fitting a "performance" dump valve will often reduce lag between changes when compared to a soft OE setup. It usually manages this by reducing the amount of air that's bled off and how fast it bleeds off.
Many people run without dump valves of any sort, and for the most part it will not harm the turbo, although the more boost you run, the more severe the effects of not running a DV will be. I don't know anyone that has removed the dump valve and had the turbo fail, certainly not within a year, and beyond that it's difficult to say whether the DV was a factor at all.
Paul
Many people run without dump valves of any sort, and for the most part it will not harm the turbo, although the more boost you run, the more severe the effects of not running a DV will be. I don't know anyone that has removed the dump valve and had the turbo fail, certainly not within a year, and beyond that it's difficult to say whether the DV was a factor at all.
Paul
06 June 2005, 10:19 PM
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Originally Posted by tath
your turbo weighs something therefore has inertia and therefore takes energy and time to get spinning.
so to keep it spinning when the throttle closes momentarily (ie gearchange) the air is vented either to atmosphere or to before the turbo (recirculated). removing the dv entirely causes the air to back up between turbo and throttle plate on gearchanges, and eventually go backwards over the blades - so called compressor stall. it's a bad thing generally because the air is trying to force the blades back the opposite way they're going. eventually, they will shatter and the resultant mess will end up in your valves - nasty.
so to keep it spinning when the throttle closes momentarily (ie gearchange) the air is vented either to atmosphere or to before the turbo (recirculated). removing the dv entirely causes the air to back up between turbo and throttle plate on gearchanges, and eventually go backwards over the blades - so called compressor stall. it's a bad thing generally because the air is trying to force the blades back the opposite way they're going. eventually, they will shatter and the resultant mess will end up in your valves - nasty.
Originally Posted by Pavlo
Removing a dump valve will generally reduce lag between gearchanges. However fitting a "performance" dump valve will often reduce lag between changes when compared to a soft OE setup. It usually manages this by reducing the amount of air that's bled off and how fast it bleeds off.
Many people run without dump valves of any sort, and for the most part it will not harm the turbo, although the more boost you run, the more severe the effects of not running a DV will be. I don't know anyone that has removed the dump valve and had the turbo fail, certainly not within a year, and beyond that it's difficult to say whether the DV was a factor at all.
Paul
Many people run without dump valves of any sort, and for the most part it will not harm the turbo, although the more boost you run, the more severe the effects of not running a DV will be. I don't know anyone that has removed the dump valve and had the turbo fail, certainly not within a year, and beyond that it's difficult to say whether the DV was a factor at all.
Paul
07 June 2005, 12:03 AM
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Originally Posted by TonyFlow
Also, Wasn't it stated that it is the air that stalls and not the compressor?
Originally Posted by tath
removing the dv entirely causes the air to back up... so called compressor stall
07 June 2005, 08:11 AM
#28
It doesn't change the spool up point of the turbo. Lag is NOT the RPM at which the turbo spools up, Lag is a time measurement of how long the turbo takes to spin up. When you change gear you let all the pressurise air between the turbo and the manifold out, and you have to wait for the turbo to make all that back up again. With no dump valve you will maintain some pressure, such that it's there when you put your foot back on the throttle.
A top mount intercooler will be less sensiive to this, but an FMIC with all it's long pipes will show a noticable difference in lag on gearchanges with a stiffer DV or no DV at all.
There can be problems with it though, it will make driveability suffer in some situations, but probably not that a performance nut would notice, while the manufacturer will have strict quality controls on such things. The TD04 has rather small bearings too, so perhaps over the life of the car, say 140,000 miles, the DV will make a difference.
Paul
A top mount intercooler will be less sensiive to this, but an FMIC with all it's long pipes will show a noticable difference in lag on gearchanges with a stiffer DV or no DV at all.
There can be problems with it though, it will make driveability suffer in some situations, but probably not that a performance nut would notice, while the manufacturer will have strict quality controls on such things. The TD04 has rather small bearings too, so perhaps over the life of the car, say 140,000 miles, the DV will make a difference.
Paul
07 June 2005, 10:37 AM
#30
Compressor wheels seem to in the past be less than fantastic. But there is no hard evidence linking failure with DV specifically, but there isn't much evidence in generall.
Paul
Paul