Author Topic: more dump valves?  (Read 5556 times)

jonnyshaw49

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more dump valves?
« on: 19:28, Tue 02 December 2008 »
hi just wondering why people have 2 or  3 dumpvalves, do they go off at diff times like one after another or louder?? they look impressive just wondering if they actually benefit you? also whats the best  dumpvalve to get for a t25 turbo recirculating??

James5

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« Reply #1 on: 21:20, Tue 02 December 2008 »
To be honest matey a dump valve isn't really needed on the r5 it's a chav thing really.

jonnyshaw49

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« Reply #2 on: 09:42, Wed 03 December 2008 »
lol ktec recon it helps if you are running high boost, they say it gets rid of twice the amount of boost in the gear change to prevent back pressure, whats the difference with a recirculating dv  and are they any advantage on the r5!

turbodave

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« Reply #3 on: 10:21, Wed 03 December 2008 »
a recirculating dv will put dumped boost back into the boost system whereas a normal dv will just dump it into the atmosphere.

Billiam

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« Reply #4 on: 13:36, Wed 03 December 2008 »
Quote from: "jonnyshaw49"
lol ktec recon it helps....


Why do you think they say that?  Could it have anything to do with the fact that they sell (and therefore make money) them  :wink:

What happens when you remove all the "unused" boost from the system?  When you put your foot back down you have to wait for the system to fill up again before the engine can get any boost, thus increasing turbo lag.

As has been said, gtt's don't require dump valves.  They were not designed to be used with them, and run better without them.

Here's a little story about how dump valves came about:

Back in the 80's, Audi were producing turbocharged cars that gave off that "fluttering" sound whenever the throttle was closed.  It wasn't loud, but it was noticeable.  Now not every member of Joe Public wants their car to be making funny noises all the time, and not many of them knew what it was.  So a lot of customers were taking their nice new cars back to Audi with this "problem".  

Audi were getting a bit bored of trying to explain that everything was fine every five minutes, so they came up with this valve that prevented the unused boost going back through the turbo when the throttle was closed, and therefore stopped the fluttering noise.  Ta da, happy customers once again  8)
Been around these cars for too damn long!

jonnyshaw49

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« Reply #5 on: 09:44, Thu 04 December 2008 »
lol if they run better without im going to take mine off . which dv would suit the r5 most recirculating does it stop lag.

Billiam

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« Reply #6 on: 13:12, Thu 04 December 2008 »
Quote from: "jonnyshaw49"
. which dv would suit the r5 most recirculating does it stop lag.


Re-read my previous post, neither dv suit the gtt imo.  If anything, they increase, not decrease lag, despite what the likes of K-Tec tell you.

They're a marketing gimmick designed to make people money.  If you like the sound then go for it, it's the only "benefit" you'll get from fitting a dv to a gtt.  And of course, if you want the sound, then you need a vent to atmos' dv, not a re-circ'.
Been around these cars for too damn long!

Theros

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« Reply #7 on: 13:19, Thu 04 December 2008 »
I have heard a lot of things about DV, but certainly 90% of the comments are positive.

DV decreases turbo lag and in long run it will save your turbo.

AaronGT

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« Reply #8 on: 14:40, Thu 04 December 2008 »
lol..

Look at turbocharged race cars and high performance turbocharged cars. Do they come with Dump valves as standard? No, Turbos are not designed to need them.. like said before they are just a marketing gimik..

If they reduced turbo lag every car maker would install them to their cars as standard.. Hence the reason they install re-circ valves from standard which recirulates the unused boost pressure back through so that the system is effectivly 'full' of boost again, so when you put your foot back on the throttle you have instant boost..

Or so the idea is..

If you really want to get rid of ununsed boost pressure fit an external waste gate..  8)

Ash-Lee

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« Reply #9 on: 15:27, Thu 04 December 2008 »
I've never noticed any difference with them fitted or removed, that goes for the normal and re-circ types.

Billiam

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« Reply #10 on: 15:48, Thu 04 December 2008 »
Quote from: "AaronGT"

If you really want to get rid of ununsed boost pressure fit an external waste gate..  8)


A wastegate has nothing to do with unused boost as it's on the opposite side of the turbo.  Wastegate's are for exhaust gas.

Re-circ' dv's put the unused boost back into the system pre-turbo inlet, so the turbo still has to suck it back into the system before it can be used again.
Been around these cars for too damn long!

Billiam

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« Reply #11 on: 15:59, Thu 04 December 2008 »
Quote from: "Theros"

DV decreases turbo lag and in long run it will save your turbo.


Who told you that, the people who make/sell them by any chance?

Over the years, i've seen plenty of gtt's out there with well over 100k on the clock, still on the factory fit turbo's, with no dv's.  Now are they all lucky?

In the ten odd years i've owned my gtt (ouch!), i've only ever used a dv on it for about 2k miles.  I've used three different turbos on the car over the years, with different boost pressures, and i've never blown a turbo.  My other 5, that i've owned and run for three years at increased boost with no dv has had no turbo problems either. Again, is that down to luck?
Been around these cars for too damn long!

jox

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« Reply #12 on: 14:46, Fri 05 December 2008 »
Quote from: "Billiam"
Quote from: "jonnyshaw49"
lol ktec recon it helps....

Why do you think they say that?  Could it have anything to do with the fact that they sell (and therefore make money) them  :wink:

What happens when you remove all the "unused" boost from the system?  When you put your foot back down you have to wait for the system to fill up again before the engine can get any boost, thus increasing turbo lag.

As has been said, gtt's don't require dump valves.  They were not designed to be used with them, and run better without them.

Here's a little story about how dump valves came about:

Back in the 80's, Audi were producing turbocharged cars that gave off that "fluttering" sound whenever the throttle was closed.  It wasn't loud, but it was noticeable.  Now not every member of Joe Public wants their car to be making funny noises all the time, and not many of them knew what it was.  So a lot of customers were taking their nice new cars back to Audi with this "problem".  

Audi were getting a bit bored of trying to explain that everything was fine every five minutes, so they came up with this valve that prevented the unused boost going back through the turbo when the throttle was closed, and therefore stopped the fluttering noise.  Ta the, happy customers once again  8)


lol what a load of bs audi did not desgin the dump valve lmao if what you just said was correct the customers would be flutter free BUT now they have to hear pshhhhhhhhhh! instead?

Dump valves DO benifit engines, on a standard 5 running low boost it wont have much if any benifit due to such low boost but on higher boost it will have benifits depending on boost

basicaly when the turbo is blowing and throttle is open its pumping  air  into the carb nice and easily, now when you come off the throttle and the throttle closes the air has nowhere to go and will build up pressure between the carb top and the turbo, this back pressure has NOWHERE to go, the turbo cant keep pumping more air into a dead end or the boost pipes will blow out! the only place it can  go is back threw the turbo (making the flutter) whlie this is happening the turbo is still wanting to spin normaly the other way but this back pressure is slowing it down and putting strain on it. with a dump valve when you come off the throttle as soon as the back pressure builds up the dump valves dumps the air out enabling the turbo to KEEP spinning thuss reducing anylagg as when you put you foot back down the turbos still spinning nicely.

If dump valves had no benifit why do new cars have them? vw seat audi volvo all have rdump valves.

Theros

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« Reply #13 on: 15:14, Fri 05 December 2008 »
To be precise...I have got information from the Sport2000 class race car driver...and keep in mind that with high boost DV is good...

How DV works:
When transitioning from a boosted state to a closed throttle state (as in between shifts), due to inertia, the turbo continues to pressurize air, but the closed throttle prevents the compressed air from entering the engine. In this case the pressure exceeds the preset spring pressure in the dump valve and the excess pressure is bled off to atmosphere.

Effects:
Even with a dump valve the compressed air acts as a brake on the turbo (slowing it down), because the pressure on the backside of the turbo is at a higher pressure than on the front side (and the air actually wants to flow through the turbo backwards).

Gtturbo2008

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« Reply #14 on: 15:33, Fri 05 December 2008 »
Who ever is claming dump valves are useless and a gimick needs to stop giving out false information.

As already stated in the last 2 posts d/v's  increase throttle responce,reduce lag and stop the backpressure  hitting the turbo blades causing slow and painful death.

Evern on  a standard gt  a dump valves will increase the life of the turbo, at such low boost it may only increase life by a few days but it will take pressure of the tubo during gear changing.

All modern turbo cars have recirculating dump valves which dose exatly the same thing just silently! except the air gose back into the intake BEFORE the turbo.