I'm curious about the effects of fitting a dump valve to a turbo motor.  I'm 
particularly interested in how it may effect the longevity of the turbo it's 
self - or any other components for that matter.

TIA.

"Kevin Scott"  wrote in
news:JCMJe.137668$Pf3.57315@fe2.news.blueyonder.co.uk: 


> I'm curious about the effects of fitting a dump valve to a turbo
> motor.  I'm particularly interested in how it may effect the longevity
> of the turbo it's self - or any other components for that matter.
> 
> TIA. 
> 
> 

Usually fitted by boy racers with small TD engines (eg 1.5 corsa). Makes a 
nice noise but not sure if there's any other significant gain.

-- 
Stuart Sharp

Yes, I know what you mean about the burberry-baseball-cap-corsa brigade but 
they are also huge on the modified import scene and often on big power units 
like Supras', Scoobys', Evos', RX7s', Skylines etc
My understanding (and I couild be wrong about this!) is the valve opens and 
allows the turbo spin freely with the result of reduced turbo lag but I 
can't think of a instance where a manufacturer fits one as standard and I 
suspect this is because they reduce the lifespan of the turbo.

Am I right or am I talking bollocks?


"Stu"  wrote in message 
news:Xns96ACBE632B7FEnobodyhomecom@216.196.109.144...

> "Kevin Scott"  wrote in
> news:JCMJe.137668$Pf3.57315@fe2.news.blueyonder.co.uk:
>
>> I'm curious about the effects of fitting a dump valve to a turbo
>> motor.  I'm particularly interested in how it may effect the longevity
>> of the turbo it's self - or any other components for that matter.
>>
>> TIA.
>>
>>
> Usually fitted by boy racers with small TD engines (eg 1.5 corsa). Makes a
> nice noise but not sure if there's any other significant gain.
>
> -- 
> Stuart Sharp 

> Yes, I know what you mean about the burberry-baseball-cap-corsa brigade 
> but they are also huge on the modified import scene and often on big power 
> units like Supras', Scoobys', Evos', RX7s', Skylines etc
> My understanding (and I couild be wrong about this!) is the valve opens 
> and allows the turbo spin freely with the result of reduced turbo lag but 
> I can't think of a instance where a manufacturer fits one as standard and 
> I suspect this is because they reduce the lifespan of the turbo.
>
> Am I right or am I talking bollocks?


No, I'm fairly certain you're talking bollocks.  I think they're there to 
release pressure or something.

-- 
Peter

"You're not a real UKRCMer until you've had your big end bearings go."

On Mon, 08 Aug 2005 12:40:15 -0500, Stu wrote:


> "Kevin Scott"  wrote in
> news:JCMJe.137668$Pf3.57315@fe2.news.blueyonder.co.uk: 
> 
>> I'm curious about the effects of fitting a dump valve to a turbo
>> motor.  I'm particularly interested in how it may effect the longevity
>> of the turbo it's self - or any other components for that matter.
>> 
>> TIA. 
>> 
>> 
> Usually fitted by boy racers with small TD engines (eg 1.5 corsa). Makes a 
> nice noise but not sure if there's any other significant gain.


On a non-throttled turbo diesel no gain at all.

"Stu"  wrote in message 
news:Xns96ACBE632B7FEnobodyhomecom@216.196.109.144...

> Usually fitted by boy racers with small TD engines (eg 1.5 corsa). Makes a
> nice noise but not sure if there's any other significant gain.


To make a nice noise it'd need to "dump" something, there's nothing to dump 
on a Diesel.

"I think they're there to release pressure or something"
Good answer - and pretty much what I meant when I said - "the valve opens
and allows the turbo spin freely with the result of reduced turbo lag"

Yet somehow I'm talking bollocks. Pots and kettles mate.  lol.  ;-)

No, but seriously I'm interested in starting a flame war or trolling - just 
an answer to a legitimate question.


"AstraVanMan"  wrote in message 
news:HiNJe.3649$jq6.3086@newsfe2-win.ntli.net...

>> Yes, I know what you mean about the burberry-baseball-cap-corsa brigade 
>> but they are also huge on the modified import scene and often on big 
>> power units like Supras', Scoobys', Evos', RX7s', Skylines etc
>> My understanding (and I couild be wrong about this!) is the valve opens 
>> and allows the turbo spin freely with the result of reduced turbo lag but 
>> I can't think of a instance where a manufacturer fits one as standard and 
>> I suspect this is because they reduce the lifespan of the turbo.
>>
>> Am I right or am I talking bollocks?
>
> No, I'm fairly certain you're talking bollocks.  I think they're there to 
> release pressure or something.
>
> -- 
> Peter
>
> "You're not a real UKRCMer until you've had your big end bearings go."
> 

Stu wrote:

> "Kevin Scott"  wrote in
> news:JCMJe.137668$Pf3.57315@fe2.news.blueyonder.co.uk: 
> 
> 
>>I'm curious about the effects of fitting a dump valve to a turbo
>>motor.  I'm particularly interested in how it may effect the longevity
>>of the turbo it's self - or any other components for that matter.
>>
>>TIA. 
>>
>>
> 
> Usually fitted by boy racers with small TD engines (eg 1.5 corsa). Makes a 
> nice noise but not sure if there's any other significant gain.


No gain whatsoever on pretty much any Turbo Diesel.  In fact I think you 
have to be quite clever to get a dump valve to make a noise at all on a TD.

Douglas

> "I think they're there to release pressure or something"
> Good answer - and pretty much what I meant when I said - "the valve opens
> and allows the turbo spin freely with the result of reduced turbo lag"
>
> Yet somehow I'm talking bollocks. Pots and kettles mate.  lol.  ;-)


Heh!  Hang around a bit more in here and you'll find that me talking 
bollocks isn't exactly a break from the norm!


> No, but seriously I'm interested in starting a flame war or trolling - 
> just an answer to a legitimate question.


But seriously, I don't really know the ins and outs of them, but I do know 
that they generally dump whatever they dump when the turbo isn't boosting as 
much, hence why you hear the "pssst" sound when the clutch is depressed just 
prior to changing gear.  So I doubt it reduces turbo lag.  If it was 
reducing turbo lag it'd happen when the throttle's on full.  I could be 
wrong though - it could, as you say, allow the turbo to spin freely, and not 
slow down quite so much, doing exactly what you're saying - reducing turbo 
lag.

-- 
Peter

"You're not a real UKRCMer until you've had your big end bearings go."

Kevin Scott wrote:

> Yes, I know what you mean about the burberry-baseball-cap-corsa brigade but 
> they are also huge on the modified import scene and often on big power units 
> like Supras', Scoobys', Evos', RX7s', Skylines etc
> My understanding (and I couild be wrong about this!) is the valve opens and 
> allows the turbo spin freely with the result of reduced turbo lag but I 
> can't think of a instance where a manufacturer fits one as standard and I 
> suspect this is because they reduce the lifespan of the turbo.
> 
> Am I right or am I talking bollocks?


I think you'll find that pretty much every modern car manufacturer 
making turbo'd petrol engines fits dump valves as standard.  This 
probably means that they are a good idea and I very much doubt that they 
affect the life of the turbo detrimentally.

Car manufacturers tend not to fit the sneezy/squeaky noisy Dump Valves. 
  Dump valves that dump into the atmosphere can, depending on the method 
of air/fuel management, be bad.  Car manufacturers generally fit ones 
that dump the air back into the induction system, this doesn't knacker 
air/fuel metering and it doesn't make a noise like something is wrong.

Douglas

AstraVanMan wrote:

>>"I think they're there to release pressure or something"
>>Good answer - and pretty much what I meant when I said - "the valve opens
>>and allows the turbo spin freely with the result of reduced turbo lag"
>>
>>Yet somehow I'm talking bollocks. Pots and kettles mate.  lol.  ;-)
> 
> 
> Heh!  Hang around a bit more in here and you'll find that me talking 
> bollocks isn't exactly a break from the norm!
> 
> 
>>No, but seriously I'm interested in starting a flame war or trolling - 
>>just an answer to a legitimate question.
> 
> 
> But seriously, I don't really know the ins and outs of them, but I do know 
> that they generally dump whatever they dump when the turbo isn't boosting as 
> much, hence why you hear the "pssst" sound when the clutch is depressed just 
> prior to changing gear.  So I doubt it reduces turbo lag.  If it was 
> reducing turbo lag it'd happen when the throttle's on full.  I could be 
> wrong though - it could, as you say, allow the turbo to spin freely, and not 
> slow down quite so much, doing exactly what you're saying - reducing turbo 
> lag.


I could also be spouting bollocks but here goes:

When the turbo is on full boost under hard acceleration and you close 
the throttle (to change gear or whatever) the high pressure air being 
thrown out of the turbo has nowhere to go.  This air gets all rowdy, 
tries to burst things and ends up stalling the turbo.  When you go back 
onto the gas in the next gear, the turbo has to spin up to boost speed 
again (this is lag).

In a Dump Valve equipped car, the throttle butterfly closes but the dump 
valve opens uatomagically and gives all the rowdy high pressure air 
somewhere to go (be it into the atmosphere with a sneeze noise or back 
into the inlet tract).  The turbo can keep spinning and be closer to 
boost speeds during the gear change, and is ready for some hardcore 
acceleration sooner after you let up the clutch as it doesn't have to 
spend so much time spinning up.

HTH

Douglas

Douglas Payne  wrote:


> > But seriously, I don't really know the ins and outs of them, but I do know
> > that they generally dump whatever they dump when the turbo isn't boosting as
> > much, hence why you hear the "pssst" sound when the clutch is depressed just
> > prior to changing gear.  So I doubt it reduces turbo lag.  If it was
> > reducing turbo lag it'd happen when the throttle's on full.  I could be
> > wrong though - it could, as you say, allow the turbo to spin freely, and not
> > slow down quite so much, doing exactly what you're saying - reducing turbo
> > lag.
> 
> I could also be spouting bollocks but here goes:
> 
> When the turbo is on full boost under hard acceleration and you close
> the throttle (to change gear or whatever) the high pressure air being
> thrown out of the turbo has nowhere to go.  This air gets all rowdy, 
> tries to burst things and ends up stalling the turbo.  When you go back
> onto the gas in the next gear, the turbo has to spin up to boost speed
> again (this is lag).
> 
> In a Dump Valve equipped car, the throttle butterfly closes but the dump
> valve opens uatomagically and gives all the rowdy high pressure air 
> somewhere to go (be it into the atmosphere with a sneeze noise or back
> into the inlet tract).  The turbo can keep spinning and be closer to 
> boost speeds during the gear change, and is ready for some hardcore 
> acceleration sooner after you let up the clutch as it doesn't have to
> spend so much time spinning up.


Sounds about right.

The first example certainly catches me out in the Passat far too often.
I'm getting used to driving around it now, but it's a bit of a surprise
after years of n/a cars delivering the same sort of power output.

-- 
Steve H 'You're not a real petrolhead unless you've owned an Alfa Romeo'
http://www.italiancar.co.uk - Honda VFR800 - MZ ETZ300 - Alfa 75 TSpark
Alfa 156 2.0 TSpark Lusso - Passat 1.8 Turbo SE -  COSOC KOTL
BoTAFOT #87 - BoTAFOF #18 - MRO # - UKRMSBC #7 - Apostle #2 - YTC #

"AstraVanMan"  wrote in message 
news:zBNJe.1296$Y04.874@newsfe4-win.ntli.net...

>> "I think they're there to release pressure or something"
>> Good answer - and pretty much what I meant when I said - "the valve opens
>> and allows the turbo spin freely with the result of reduced turbo lag"
>>
>> Yet somehow I'm talking bollocks. Pots and kettles mate.  lol.  ;-)
>
> Heh!  Hang around a bit more in here and you'll find that me talking 
> bollocks isn't exactly a break from the norm!
>
>> No, but seriously I'm interested in starting a flame war or trolling - 
>> just an answer to a legitimate question.
>
> But seriously, I don't really know the ins and outs of them, but I do know 
> that they generally dump whatever they dump when the turbo isn't boosting 
> as much, hence why you hear the "pssst" sound when the clutch is depressed 
> just prior to changing gear.  So I doubt it reduces turbo lag.  If it was 
> reducing turbo lag it'd happen when the throttle's on full.  I could be 
> wrong though - it could, as you say, allow the turbo to spin freely, and 
> not slow down quite so much, doing exactly what you're saying - reducing 
> turbo lag.


The purpose off a dump valve is to reduce lag when changing gear.

On a normal turbo'd engine, when you change gear and lift off the 
accelerator, the throttle valve closes.
This effectively creates a blockage for the air flow from the turbo, which 
leads to a pressure build up before the throttle valve. This pressure build 
up acts as a brake on the turbo, and combined with the reduced exhaust gas 
flow to power the turbo, the turbo slows down considerably. So when you put 
your foot down again, you've got to wait for the turbo to pick up speed 
(turbo lag)

Now fit a dump valve, and when you close the throttle, the dump valve opens, 
venting the air before the throttle (to atmosphere with pleny sound for the 
ultimate boy racer effect), preventing the pressure build up which would 
otherwise slow the turbo. Result being, that when you put your foot back 
down, the turbo is still spinning at a fair speed reducing turbo lag.

On Mon, 08 Aug 2005 19:49:17 +0100, Douglas Payne wrote:


> AstraVanMan wrote:
>>>"I think they're there to release pressure or something"
>>>Good answer - and pretty much what I meant when I said - "the valve opens
>>>and allows the turbo spin freely with the result of reduced turbo lag"
>>>
>>>Yet somehow I'm talking bollocks. Pots and kettles mate.  lol.  ;-)
>> 
>> 
>> Heh!  Hang around a bit more in here and you'll find that me talking 
>> bollocks isn't exactly a break from the norm!
>> 
>> 
>>>No, but seriously I'm interested in starting a flame war or trolling - 
>>>just an answer to a legitimate question.
>> 
>> 
>> But seriously, I don't really know the ins and outs of them, but I do know 
>> that they generally dump whatever they dump when the turbo isn't boosting as 
>> much, hence why you hear the "pssst" sound when the clutch is depressed just 
>> prior to changing gear.  So I doubt it reduces turbo lag.  If it was 
>> reducing turbo lag it'd happen when the throttle's on full.  I could be 
>> wrong though - it could, as you say, allow the turbo to spin freely, and not 
>> slow down quite so much, doing exactly what you're saying - reducing turbo 
>> lag.
> 
> I could also be spouting bollocks but here goes:
> 
> When the turbo is on full boost under hard acceleration and you close 
> the throttle (to change gear or whatever) the high pressure air being 
> thrown out of the turbo has nowhere to go.  This air gets all rowdy, 
> tries to burst things and ends up stalling the turbo.  When you go back 
> onto the gas in the next gear, the turbo has to spin up to boost speed 
> again (this is lag).


Correct. You get compressor stall and you end up going over the surge line
on the compressor map. This wrecks the turbo bearings very quickly.


> 
> In a Dump Valve equipped car, the throttle butterfly closes but the dump 
> valve opens uatomagically and gives all the rowdy high pressure air 
> somewhere to go (be it into the atmosphere with a sneeze noise or back 
> into the inlet tract).  The turbo can keep spinning and be closer to 
> boost speeds during the gear change, and is ready for some hardcore 
> acceleration sooner after you let up the clutch as it doesn't have to 
> spend so much time spinning up.


Guess why turbodiesels don't have dump valves....:-)

Douglas Payne  wrote:


> Stu wrote:
> > "Kevin Scott"  wrote in
> > news:JCMJe.137668$Pf3.57315@fe2.news.blueyonder.co.uk: 
> > 
> > 
> >>I'm curious about the effects of fitting a dump valve to a turbo
> >>motor.  I'm particularly interested in how it may effect the longevity
> >>of the turbo it's self - or any other components for that matter.
> >>
> >>TIA. 
> >>
> >>
> > 
> > Usually fitted by boy racers with small TD engines (eg 1.5 corsa). Makes a
> > nice noise but not sure if there's any other significant gain.
> 
> No gain whatsoever on pretty much any Turbo Diesel.  In fact I think you
> have to be quite clever to get a dump valve to make a noise at all on a TD.
> 
> Douglas


Actually, you can buy a little speaker arrangement to go under the
bonnet that makes all the noise without having to even buy a turbo.

-- 
Andy Hewitt
Using somebody elses computer

Douglas Payne  wrote:


> Kevin Scott wrote:
> > Yes, I know what you mean about the burberry-baseball-cap-corsa brigade but
> > they are also huge on the modified import scene and often on big power units
> > like Supras', Scoobys', Evos', RX7s', Skylines etc
> > My understanding (and I couild be wrong about this!) is the valve opens and
> > allows the turbo spin freely with the result of reduced turbo lag but I
> > can't think of a instance where a manufacturer fits one as standard and I
> > suspect this is because they reduce the lifespan of the turbo.
> > 
> > Am I right or am I talking bollocks?
> 
> I think you'll find that pretty much every modern car manufacturer 
> making turbo'd petrol engines fits dump valves as standard.  This 
> probably means that they are a good idea and I very much doubt that they
> affect the life of the turbo detrimentally.
> 
> Car manufacturers tend not to fit the sneezy/squeaky noisy Dump Valves.
>   Dump valves that dump into the atmosphere can, depending on the method
> of air/fuel management, be bad.  Car manufacturers generally fit ones
> that dump the air back into the induction system, this doesn't knacker
> air/fuel metering and it doesn't make a noise like something is wrong.


I think you're thinking of the Waste Gate. That also reduces lag, but
also limits maximum pressure too, as it will dump boost pressure once it
hits maximum pressure. That is there to help engine life. On Ford
Escorts (and probably a lot of other cars), the ECU will actually cut
the fuel if it reads an over-boost, so fiddling with the Waste Gate
adjustment has no benefit.

-- 
Andy Hewitt
Using somebody elses computer

Douglas Payne  wrote in
news:42f7a477$0$18643$14726298@news.sunsite.dk: 


> Stu wrote:
>> "Kevin Scott"  wrote in
>> news:JCMJe.137668$Pf3.57315@fe2.news.blueyonder.co.uk: 
>> 
>> 
>>>I'm curious about the effects of fitting a dump valve to a turbo
>>>motor.  I'm particularly interested in how it may effect the
>>>longevity of the turbo it's self - or any other components for that
>>>matter. 
>>>
>>>TIA. 
>>>
>>>
>> 
>> Usually fitted by boy racers with small TD engines (eg 1.5 corsa).
>> Makes a nice noise but not sure if there's any other significant
>> gain. 
> 
> No gain whatsoever on pretty much any Turbo Diesel.  In fact I think
> you have to be quite clever to get a dump valve to make a noise at all
> on a TD. 
> 
> Douglas
> 

Oh, you can, believe me. My old apprentice had one fitted to his 306TD 
(besides chav alloys & suspension etc). Made a lovely hissing noise ever 
gearchange, right up till the point where he ran a red light and got 
himself wiped out. Dickhead.



-- 
Stuart Sharp

Andy Hewitt wrote:


>>Car manufacturers tend not to fit the sneezy/squeaky noisy Dump Valves.
>>  Dump valves that dump into the atmosphere can, depending on the method
>>of air/fuel management, be bad.  Car manufacturers generally fit ones
>>that dump the air back into the induction system, this doesn't knacker
>>air/fuel metering and it doesn't make a noise like something is wrong.
> 
> 
> I think you're thinking of the Waste Gate. That also reduces lag, but
> also limits maximum pressure too, as it will dump boost pressure once it
> hits maximum pressure. That is there to help engine life. On Ford
> Escorts (and probably a lot of other cars), the ECU will actually cut
> the fuel if it reads an over-boost, so fiddling with the Waste Gate
> adjustment has no benefit.


I'm pretty sure I'm thinking of a dump valve.  I think you're thinking 
of a waste gate.  (c:

Douglas

Andy Hewitt wrote:


>>>>I'm curious about the effects of fitting a dump valve to a turbo
>>>>motor.  I'm particularly interested in how it may effect the longevity
>>>>of the turbo it's self - or any other components for that matter.

>>>Usually fitted by boy racers with small TD engines (eg 1.5 corsa). Makes a
>>>nice noise but not sure if there's any other significant gain.

>>No gain whatsoever on pretty much any Turbo Diesel.  In fact I think you
>>have to be quite clever to get a dump valve to make a noise at all on a TD.

> Actually, you can buy a little speaker arrangement to go under the
> bonnet that makes all the noise without having to even buy a turbo.


That's not really a dump valve though is it?

Douglas

Stu wrote:

> Douglas Payne  wrote in
> news:42f7a477$0$18643$14726298@news.sunsite.dk: 
> 
> 
>>Stu wrote:
>>
>>>"Kevin Scott"  wrote in
>>>news:JCMJe.137668$Pf3.57315@fe2.news.blueyonder.co.uk: 
>>>
>>>
>>>
>>>>I'm curious about the effects of fitting a dump valve to a turbo
>>>>motor.  I'm particularly interested in how it may effect the
>>>>longevity of the turbo it's self - or any other components for that
>>>>matter. 
>>>>
>>>>TIA. 
>>>>
>>>>
>>>
>>>Usually fitted by boy racers with small TD engines (eg 1.5 corsa).
>>>Makes a nice noise but not sure if there's any other significant
>>>gain. 
>>
>>No gain whatsoever on pretty much any Turbo Diesel.  In fact I think
>>you have to be quite clever to get a dump valve to make a noise at all
>>on a TD. 
>>
>>Douglas
>>
> 
> Oh, you can, believe me. My old apprentice had one fitted to his 306TD 
> (besides chav alloys & suspension etc). Made a lovely hissing noise ever 
> gearchange, right up till the point where he ran a red light and got 
> himself wiped out. Dickhead.


I'm aware that you can get them to make a noise, indeed, I know that at 
least for the 306 you can buy them off the shelf.  I don't think they 
work quite the same way as they do on turbo petrols however.  Diesels 
not having a throttle butterfly to close being one of the main reasons.

Douglas

Kevin Scott wrote:

> I'm curious about the effects of fitting a dump valve to a turbo motor.  I'm
> particularly interested in how it may effect the longevity of the turbo it's
> self - or any other components for that matter.


My understanding is that they relieve the pressure, which increases the
longetivity of the Turbo charger.  I don't know whether it effects the
performance though.

Douglas Payne  wrote:


> Andy Hewitt wrote:
> 
> >>Car manufacturers tend not to fit the sneezy/squeaky noisy Dump Valves.
> >>  Dump valves that dump into the atmosphere can, depending on the method
> >>of air/fuel management, be bad.  Car manufacturers generally fit ones
> >>that dump the air back into the induction system, this doesn't knacker
> >>air/fuel metering and it doesn't make a noise like something is wrong.
> > 
> > 
> > I think you're thinking of the Waste Gate. That also reduces lag, but
> > also limits maximum pressure too, as it will dump boost pressure once it
> > hits maximum pressure. That is there to help engine life. On Ford
> > Escorts (and probably a lot of other cars), the ECU will actually cut
> > the fuel if it reads an over-boost, so fiddling with the Waste Gate
> > adjustment has no benefit.
> 
> I'm pretty sure I'm thinking of a dump valve.  I think you're thinking
> of a waste gate.  (c:


Well, most production cars with turbos don't have a dump valve, they
have a waste gate.

-- 
Andy Hewitt
Using somebody elses computer

Douglas Payne  wrote:


> Andy Hewitt wrote:
> 
> >>>>I'm curious about the effects of fitting a dump valve to a turbo
> >>>>motor.  I'm particularly interested in how it may effect the longevity
> >>>>of the turbo it's self - or any other components for that matter.
> 
> >>>Usually fitted by boy racers with small TD engines (eg 1.5 corsa). Makes a
> >>>nice noise but not sure if there's any other significant gain.
> 
> >>No gain whatsoever on pretty much any Turbo Diesel.  In fact I think you
> >>have to be quite clever to get a dump valve to make a noise at all on a TD.
> 
> > Actually, you can buy a little speaker arrangement to go under the
> > bonnet that makes all the noise without having to even buy a turbo.
> 
> That's not really a dump valve though is it?


No, but it might explain how you've heard on on a diesel!

No need to be a smartarse now! :-)

-- 
Andy Hewitt
Using somebody elses computer

"Stu"  wrote in message 
news:Xns96ACBE632B7FEnobodyhomecom@216.196.109.144...

> "Kevin Scott"  wrote in
> news:JCMJe.137668$Pf3.57315@fe2.news.blueyonder.co.uk:
>
>> I'm curious about the effects of fitting a dump valve to a turbo
>> motor.  I'm particularly interested in how it may effect the longevity
>> of the turbo it's self - or any other components for that matter.
>>
>> TIA.
>>
>>
> Usually fitted by boy racers with small TD engines (eg 1.5 corsa). Makes a
> nice noise but not sure if there's any other significant gain.
>

i'm sorry, but you are talking bollcoks
even though you CAN fit a dump valve to a diesel engine, it's very expensive 
and not a lot of people bother
a dump valve dumps the boost pressure when you lift off the throttle by way 
of using the vacuum produced by your engine to open the valve
this releases any boost which could, in some cases, case the turbo to slow 
down it's spin rate due to the amount of air in the system "backing up"
think of it as the release valve in a dam, too much pressure breaks things 
so releving a little when it's not needed helps

if you don't want the noise you can always go with a recirculating valve, 
but that just defeats the object in releasing the vented up air in the 
system, where does it go?


> -- 
> Stuart Sharp 

"Douglas Payne"  wrote in message 
news:42f7c124$0$18650$14726298@news.sunsite.dk...

> Stu wrote:
>> Douglas Payne  wrote in
>> news:42f7a477$0$18643$14726298@news.sunsite.dk:
>>>Stu wrote:
>>>
>>>>"Kevin Scott"  wrote in
>>>>news:JCMJe.137668$Pf3.57315@fe2.news.blueyonder.co.uk:
>>>>
>>>>
>>>>>I'm curious about the effects of fitting a dump valve to a turbo
>>>>>motor.  I'm particularly interested in how it may effect the
>>>>>longevity of the turbo it's self - or any other components for that
>>>>>matter.
>>>>>TIA.
>>>>>
>>>>
>>>>Usually fitted by boy racers with small TD engines (eg 1.5 corsa).
>>>>Makes a nice noise but not sure if there's any other significant
>>>>gain.
>>>
>>>No gain whatsoever on pretty much any Turbo Diesel.  In fact I think
>>>you have to be quite clever to get a dump valve to make a noise at all
>>>on a TD.
>>>Douglas
>>>
>>
>> Oh, you can, believe me. My old apprentice had one fitted to his 306TD 
>> (besides chav alloys & suspension etc). Made a lovely hissing noise ever 
>> gearchange, right up till the point where he ran a red light and got 
>> himself wiped out. Dickhead.
>
> I'm aware that you can get them to make a noise, indeed, I know that at 
> least for the 306 you can buy them off the shelf.  I don't think they work 
> quite the same way as they do on turbo petrols however.  Diesels not 
> having a throttle butterfly to close being one of the main reasons.
>

electronic, and they use the vacuum for the rbeaks to open the dump valve
perhaps this is why he ran the red light when he found he couldn't stop?



> Douglas 

Andy Hewitt wrote:

> Douglas Payne  wrote:
> 
> 
>>Andy Hewitt wrote:
>>
>>
>>>>>>I'm curious about the effects of fitting a dump valve to a turbo
>>>>>>motor.  I'm particularly interested in how it may effect the longevity
>>>>>>of the turbo it's self - or any other components for that matter.
>>
>>>>>Usually fitted by boy racers with small TD engines (eg 1.5 corsa). Makes a
>>>>>nice noise but not sure if there's any other significant gain.
>>
>>>>No gain whatsoever on pretty much any Turbo Diesel.  In fact I think you
>>>>have to be quite clever to get a dump valve to make a noise at all on a TD.
>>
>>>Actually, you can buy a little speaker arrangement to go under the
>>>bonnet that makes all the noise without having to even buy a turbo.
>>
>>That's not really a dump valve though is it?
> 
> 
> No, but it might explain how you've heard on on a diesel!


Personally, I haven't actually heard a TD with a dump valve (electronic 
sound effect or actual dump valve wise) .  However, I've mildly looked 
into TD tuning in the past and I know that such devices exist.


> No need to be a smartarse now! :-)


Heh, smartarse is my middle name.  (c:

Douglas

"  dojj"  wrote in
news:dd8i5i$gdp$1@newsg1.svr.pol.co.uk: 


> 
> "Stu"  wrote in message 
> news:Xns96ACBE632B7FEnobodyhomecom@216.196.109.144...
>> "Kevin Scott"  wrote in
>> news:JCMJe.137668$Pf3.57315@fe2.news.blueyonder.co.uk:
>>
>>> I'm curious about the effects of fitting a dump valve to a turbo
>>> motor.  I'm particularly interested in how it may effect the
>>> longevity of the turbo it's self - or any other components for that
>>> matter. 
>>>
>>> TIA.
>>>
>>>
>> Usually fitted by boy racers with small TD engines (eg 1.5 corsa).
>> Makes a nice noise but not sure if there's any other significant
>> gain. 
>>
> i'm sorry, but you are talking bollcoks
> even though you CAN fit a dump valve to a diesel engine, it's very
> expensive and not a lot of people bother
> a dump valve dumps the boost pressure when you lift off the throttle
> by way of using the vacuum produced by your engine to open the valve
> this releases any boost which could, in some cases, case the turbo to
> slow down it's spin rate due to the amount of air in the system
> "backing up" think of it as the release valve in a dam, too much
> pressure breaks things so releving a little when it's not needed helps
> 
> if you don't want the noise you can always go with a recirculating
> valve, but that just defeats the object in releasing the vented up air
> in the system, where does it go?
> 

Whoa! Hang on - I never said they were any good for diesels, was just 
pointing out that I worked with a lad, who was a boy racer, and he and 
all his mates with turbo diesels went through a trend of having dump 
valves fitted. Didn't do anything, as I'm well aware, they just thought 
the noise was cool. 



-- 
Stuart Sharp

"  dojj"  wrote in
news:dd8i86$bfh$1@newsg2.svr.pol.co.uk: 


> 
> "Douglas Payne"  wrote in message 
> news:42f7c124$0$18650$14726298@news.sunsite.dk...
>> Stu wrote:
>>> Douglas Payne  wrote in
>>> news:42f7a477$0$18643$14726298@news.sunsite.dk:
>>>>Stu wrote:
>>>>
>>>>>"Kevin Scott"  wrote in
>>>>>news:JCMJe.137668$Pf3.57315@fe2.news.blueyonder.co.uk:
>>>>>
>>>>>
>>>>>>I'm curious about the effects of fitting a dump valve to a turbo
>>>>>>motor.  I'm particularly interested in how it may effect the
>>>>>>longevity of the turbo it's self - or any other components for
>>>>>>that matter.
>>>>>>TIA.
>>>>>>
>>>>>
>>>>>Usually fitted by boy racers with small TD engines (eg 1.5 corsa).
>>>>>Makes a nice noise but not sure if there's any other significant
>>>>>gain.
>>>>
>>>>No gain whatsoever on pretty much any Turbo Diesel.  In fact I think
>>>>you have to be quite clever to get a dump valve to make a noise at
>>>>all on a TD.
>>>>Douglas
>>>>
>>>
>>> Oh, you can, believe me. My old apprentice had one fitted to his
>>> 306TD (besides chav alloys & suspension etc). Made a lovely hissing
>>> noise ever gearchange, right up till the point where he ran a red
>>> light and got himself wiped out. Dickhead.
>>
>> I'm aware that you can get them to make a noise, indeed, I know that
>> at least for the 306 you can buy them off the shelf.  I don't think
>> they work quite the same way as they do on turbo petrols however. 
>> Diesels not having a throttle butterfly to close being one of the
>> main reasons. 
>>
> electronic, and they use the vacuum for the rbeaks to open the dump
> valve perhaps this is why he ran the red light when he found he
> couldn't stop? 
> 
> 

Nah, he'll have just run it because he's an idiot.


-- 
Stuart Sharp

Andy Hewitt wrote:

> Douglas Payne  wrote:
> 
> 
>>Andy Hewitt wrote:
>>
>>
>>>>Car manufacturers tend not to fit the sneezy/squeaky noisy Dump Valves.
>>>> Dump valves that dump into the atmosphere can, depending on the method
>>>>of air/fuel management, be bad.  Car manufacturers generally fit ones
>>>>that dump the air back into the induction system, this doesn't knacker
>>>>air/fuel metering and it doesn't make a noise like something is wrong.
>>>
>>>
>>>I think you're thinking of the Waste Gate. That also reduces lag, but
>>>also limits maximum pressure too, as it will dump boost pressure once it
>>>hits maximum pressure. That is there to help engine life. On Ford
>>>Escorts (and probably a lot of other cars), the ECU will actually cut
>>>the fuel if it reads an over-boost, so fiddling with the Waste Gate
>>>adjustment has no benefit.
>>
>>I'm pretty sure I'm thinking of a dump valve.  I think you're thinking
>>of a waste gate.  (c:
> 
> 
> Well, most production cars with turbos don't have a dump valve, they
> have a waste gate.


Are you sure?  I was fairly confident that they do different things.

I thought waste gates are controlled by +ve pressure from the turbo, 
opening when boost reaches a certain level, and dump valves are 
controlled essentially by vacuum, created by the closing of the throttle?

Douglas

"Kevin Scott"  wrote in message
news:JCMJe.137668$Pf3.57315@fe2.news.blueyonder.co.uk...

> I'm curious about the effects of fitting a dump valve to a turbo motor.
I'm
> particularly interested in how it may effect the longevity of the turbo
it's
> self - or any other components for that matter.



You will find most recentish Turbo's have a dump valve already
fitted.Stalling the turbo when the throttle is snapped shut under boost
doesnt do it much good, which is why it is there.

The reason you dont hear it, is cos they dump back to the airfilter or a pre
turbo hose.

That said 99% of the nasty plastic Bosch type DV's are either already
knackered and dont seal properly anyhow, and should be replaced asap.

The Bailey twin piston DV is about the only one that works properly with all
management systems and can be ducted internally, should you wish.

Tim..

"Chris Street"  wrote in message
news:bchz3vudkho6$.ezjvmugd33a7.dlg@40tude.net...

> On Mon, 08 Aug 2005 19:49:17 +0100, Douglas Payne wrote:
>
> > AstraVanMan wrote:
> >>>"I think they're there to release pressure or something"
> >>>Good answer - and pretty much what I meant when I said - "the valve
opens
> >>>and allows the turbo spin freely with the result of reduced turbo lag"
> >>>
> >>>Yet somehow I'm talking bollocks. Pots and kettles mate.  lol.  ;-)
> >>
> >>
> >> Heh!  Hang around a bit more in here and you'll find that me talking
> >> bollocks isn't exactly a break from the norm!
> >>
> >>
> >>>No, but seriously I'm interested in starting a flame war or trolling -
> >>>just an answer to a legitimate question.
> >>
> >>
> >> But seriously, I don't really know the ins and outs of them, but I do
know
> >> that they generally dump whatever they dump when the turbo isn't
boosting as
> >> much, hence why you hear the "pssst" sound when the clutch is depressed
just
> >> prior to changing gear.  So I doubt it reduces turbo lag.  If it was
> >> reducing turbo lag it'd happen when the throttle's on full.  I could be
> >> wrong though - it could, as you say, allow the turbo to spin freely,
and not
> >> slow down quite so much, doing exactly what you're saying - reducing
turbo
> >> lag.
> >
> > I could also be spouting bollocks but here goes:
> >
> > When the turbo is on full boost under hard acceleration and you close
> > the throttle (to change gear or whatever) the high pressure air being
> > thrown out of the turbo has nowhere to go.  This air gets all rowdy,
> > tries to burst things and ends up stalling the turbo.  When you go back
> > onto the gas in the next gear, the turbo has to spin up to boost speed
> > again (this is lag).
>
> Correct. You get compressor stall and you end up going over the surge line
> on the compressor map. This wrecks the turbo bearings very quickly.
>
> >
> > In a Dump Valve equipped car, the throttle butterfly closes but the dump
> > valve opens uatomagically and gives all the rowdy high pressure air
> > somewhere to go (be it into the atmosphere with a sneeze noise or back
> > into the inlet tract).  The turbo can keep spinning and be closer to
> > boost speeds during the gear change, and is ready for some hardcore
> > acceleration sooner after you let up the clutch as it doesn't have to
> > spend so much time spinning up.
>
> Guess why turbodiesels don't have dump valves....:-)


Actually some do, and are beginning to feature more and more now. As modern
TD's are running pretty high boosts as standard now (the GM/ Fiat 1.9 150
runs 1.6bar stock, 1.8bar in overboost) stalling the compressor is dangerous
and more so keeping lag down between gearchanges is more important.

Most of the GM 1.9, 2.2's, the Ford 2.2 155 ST, Volvo's D5 (in 185 spec) to
name afew, are fitted with an inlet throttle valve and an integrated DV on
the turbo.

Tim..

"Andy Hewitt"  wrote in message
news:1h0zx4w.1usml5h96gfz6N%hairy.biker@spamcop.net...

> Douglas Payne  wrote:
>
> > Andy Hewitt wrote:
> >
> > >>Car manufacturers tend not to fit the sneezy/squeaky noisy Dump
Valves.
> > >>  Dump valves that dump into the atmosphere can, depending on the
method
> > >>of air/fuel management, be bad.  Car manufacturers generally fit ones
> > >>that dump the air back into the induction system, this doesn't knacker
> > >>air/fuel metering and it doesn't make a noise like something is wrong.
> > >
> > >
> > > I think you're thinking of the Waste Gate. That also reduces lag, but
> > > also limits maximum pressure too, as it will dump boost pressure once
it
> > > hits maximum pressure. That is there to help engine life. On Ford
> > > Escorts (and probably a lot of other cars), the ECU will actually cut
> > > the fuel if it reads an over-boost, so fiddling with the Waste Gate
> > > adjustment has no benefit.
> >
> > I'm pretty sure I'm thinking of a dump valve.  I think you're thinking
> > of a waste gate.  (c:
>
> Well, most production cars with turbos don't have a dump valve, they
> have a waste gate.


All current turbo petrols have a DV, alot of 'last seasons' do too, Saab
were fitting them in the mid 80's! And yes you still need a wastegate or
other means of controlling peak boost.

We do it with VCT turbo's now though.

Tim..

"Douglas Payne"  wrote in message
news:42f7d571$0$18648$14726298@news.sunsite.dk...

> Andy Hewitt wrote:
> > Douglas Payne  wrote:
> >
> >
> >>Andy Hewitt wrote:
> >>
> >>
> >>>>Car manufacturers tend not to fit the sneezy/squeaky noisy Dump
Valves.
> >>>> Dump valves that dump into the atmosphere can, depending on the
method
> >>>>of air/fuel management, be bad.  Car manufacturers generally fit ones
> >>>>that dump the air back into the induction system, this doesn't knacker
> >>>>air/fuel metering and it doesn't make a noise like something is wrong.
> >>>
> >>>
> >>>I think you're thinking of the Waste Gate. That also reduces lag, but
> >>>also limits maximum pressure too, as it will dump boost pressure once
it
> >>>hits maximum pressure. That is there to help engine life. On Ford
> >>>Escorts (and probably a lot of other cars), the ECU will actually cut
> >>>the fuel if it reads an over-boost, so fiddling with the Waste Gate
> >>>adjustment has no benefit.
> >>
> >>I'm pretty sure I'm thinking of a dump valve.  I think you're thinking
> >>of a waste gate.  (c:
> >
> >
> > Well, most production cars with turbos don't have a dump valve, they
> > have a waste gate.
>
> Are you sure?  I was fairly confident that they do different things.
>
> I thought waste gates are controlled by +ve pressure from the turbo,
> opening when boost reaches a certain level, and dump valves are
> controlled essentially by vacuum, created by the closing of the throttle?


That's right. An excellent succinct explaination if I may say so.

Dump valves are fitted to reduce turbo lag. IOW to keep the turbo spinning
as fast as possible, by allowing the boost pressure to escape when the
throttle is closed.

Waste gates open to allow the exhaust gasses to bypass the turbo when the
boost pressure reaches a certain level, to protect the engine.

I see no reason why dump valves should influence the life of a turbo either
way. In a sense they don't affect affect it's normal operation.
Mike.

"Stu"  wrote in message 
news:Xns96ACE42EEFE49nobodyhomecom@216.196.109.144...

>"  dojj"  wrote in
> news:dd8i5i$gdp$1@newsg1.svr.pol.co.uk:
>
>>
>> "Stu"  wrote in message
>> news:Xns96ACBE632B7FEnobodyhomecom@216.196.109.144...
>>> "Kevin Scott"  wrote in
>>> news:JCMJe.137668$Pf3.57315@fe2.news.blueyonder.co.uk:
>>>
>>>> I'm curious about the effects of fitting a dump valve to a turbo
>>>> motor.  I'm particularly interested in how it may effect the
>>>> longevity of the turbo it's self - or any other components for that
>>>> matter.
>>>>
>>>> TIA.
>>>>
>>>>
>>> Usually fitted by boy racers with small TD engines (eg 1.5 corsa).
>>> Makes a nice noise but not sure if there's any other significant
>>> gain.
>>>
>> i'm sorry, but you are talking bollcoks
>> even though you CAN fit a dump valve to a diesel engine, it's very
>> expensive and not a lot of people bother
>> a dump valve dumps the boost pressure when you lift off the throttle
>> by way of using the vacuum produced by your engine to open the valve
>> this releases any boost which could, in some cases, case the turbo to
>> slow down it's spin rate due to the amount of air in the system
>> "backing up" think of it as the release valve in a dam, too much
>> pressure breaks things so releving a little when it's not needed helps
>>
>> if you don't want the noise you can always go with a recirculating
>> valve, but that just defeats the object in releasing the vented up air
>> in the system, where does it go?
>>
> Whoa! Hang on - I never said they were any good for diesels, was just
> pointing out that I worked with a lad, who was a boy racer, and he and
> all his mates with turbo diesels went through a trend of having dump
> valves fitted. Didn't do anything, as I'm well aware, they just thought
> the noise was cool.
>

my original post may have been a bit harsh :)
sorry :)
but they do the same thing for either engine so it's not as if it's going to 
not help
but the speeds at which the turbos can stall is very high and i don't think 
a diesel will reach them sort of speeds for air flow and stuff


>
>
> -- 
> Stuart Sharp 

The boost doesn't make any difference - TDs don't have a throttle
butterfly, so there is absolutely no need for a DV...

wrote in message
news:1123587821.559049.265860@g49g2000cwa.googlegroups.com...

> The boost doesn't make any difference - TDs don't have a throttle
> butterfly, so there is absolutely no need for a DV...
>


Some do, some dont, the increasing trend now is to *have* a throttle valve.

Tim..

"Douglas Payne"  wrote in message 
news:42f7d571$0$18648$14726298@news.sunsite.dk...

> Andy Hewitt wrote:
>> Douglas Payne  wrote:
>>
>>
>>>Andy Hewitt wrote:
>>>
>>>
>>>>>Car manufacturers tend not to fit the sneezy/squeaky noisy Dump Valves.
>>>>> Dump valves that dump into the atmosphere can, depending on the method
>>>>>of air/fuel management, be bad.  Car manufacturers generally fit ones
>>>>>that dump the air back into the induction system, this doesn't knacker
>>>>>air/fuel metering and it doesn't make a noise like something is wrong.
>>>>
>>>>
>>>>I think you're thinking of the Waste Gate. That also reduces lag, but
>>>>also limits maximum pressure too, as it will dump boost pressure once it
>>>>hits maximum pressure. That is there to help engine life. On Ford
>>>>Escorts (and probably a lot of other cars), the ECU will actually cut
>>>>the fuel if it reads an over-boost, so fiddling with the Waste Gate
>>>>adjustment has no benefit.
>>>
>>>I'm pretty sure I'm thinking of a dump valve.  I think you're thinking
>>>of a waste gate.  (c:
>>
>>
>> Well, most production cars with turbos don't have a dump valve, they
>> have a waste gate.
>
> Are you sure?  I was fairly confident that they do different things.
>
> I thought waste gates are controlled by +ve pressure from the turbo, 
> opening when boost reaches a certain level, and dump valves are controlled 
> essentially by vacuum, created by the closing of the throttle?


Traditionally (before ecu's and such nonsense), the turbo wastegate purpose 
was to limit boost pressure (all turbos have them fitted in one form or 
another), and was controlled directly by the boost pressure.
A dump valve was an additional valve, for performance reasons.

On modern cars, the turbo wastegate is often controlled by the ecu, and can 
be operated by either boost pressure or vacuum (vacuum being the most 
common). This has the benefit that with a little bit extra programming in 
the ecu, the wastegate can also serve the purpose off a dump valve.

"Douglas Payne"  wrote in message 
news:42f7a477$0$18643$14726298@news.sunsite.dk...

> Stu wrote:
>> "Kevin Scott"  wrote in
>> news:JCMJe.137668$Pf3.57315@fe2.news.blueyonder.co.uk:
>>>I'm curious about the effects of fitting a dump valve to a turbo
>>>motor.  I'm particularly interested in how it may effect the longevity
>>>of the turbo it's self - or any other components for that matter.
>>>
>>>TIA.
>>>
>>
>> Usually fitted by boy racers with small TD engines (eg 1.5 corsa). Makes 
>> a nice noise but not sure if there's any other significant gain.
>
> No gain whatsoever on pretty much any Turbo Diesel.  In fact I think you 
> have to be quite clever to get a dump valve to make a noise at all on a 
> TD.


They do have a slight gain, but not as much as a petrol engine.
Although you don't have any throttle valve, when you do lift your foot off 
the accelrator, there is still pressure built up in the intake system, so 
fitting a dump valve will let the turbo spin for longer.
On most modern diesels fitted with ECU controlled wastegates, they are quite 
often programmed to open the wastegate during deceleration, effectively 
acting as a dump valve.