Need a Dumpvalve?

[Legnum Boy]

Correct me if I'm being dumb (before I damage my car... :$ )
There is a standard DV in the piping near the Intercooler, yes?
Can it be removed, without installing an aftermarket BOV?
I read somewhere that DV's aren't needed on low pressure turbo systems.

Will removing the DV increase the turbo flutter/wastegate chatter (I know what I mean... :$ ), or just break something expensive? :rolleyes5

[Kenneth]

Im no expert, but ill relay what I have read on the subject...

When you let off the gas, the throttly butterfly closes, causing pressure buildup in the pipework. This pressure is made because the turbo is still spinning, and if you have been WOT at high load, the chances are its spinning very damn fast.

just think about it really... your car is sucking in all this air, and your turbo is pumping enough air to not only supply all the air your engine needs, but enough extra to keep your intake at positive pressure. thats a lot of air. when you stop the engine demanding air, the turbo is still pumping at the same rate.

The pressure buildup will cause back pressure on the turbine, causing it to slow down. if you dont have a dump valve, the turbine can slow very quickly, which isnt good for it.

I have heard that the back pressure causes the turbine to cut the air thats built up in the piping, making a cool sound. even if true, I wouldnt consider it worth possible turbo failure.

So basically, BOVs are good for increasing the life of your turbo and for reducing turbo lag. downsides? i dont know of any... someone might though.

[Legnum Boy]

Thats the same stuff that I have read too, with the exception to the 'reduces turbo lag' bit. I was of the understanding that DV's rapidly reduce the pressure built up, which means that when you get back on the throttle, the turbo's have to re-pressurise the system again, therefore creating more lag. :|

I had an old nissan 200sx before :$ which had no DV in its system, (...and made that cool chopping noise. :-D ) The turbo was 125,000 miles old, and still going strong when I sold it.

I might give it a try on the old girl, just to see what it sounds like.

And on that note.... Wanted (UK) Two new turbo's please.... :laugh: :laugh: :rolleyes:

[Kenneth]

Tell me how it goes, if its cool enough i might try it ;)

As far as turbo lag goes, my understanding is that while the DV does reduce the pressure in the system, the turbo is still spinning fast enough to create bost, so the system presurises again reasonably quickly.
If you dont use a dump valve, the back pressure slows the turbo down considerably, which means when you get back on the gas, there is not enough air flow to keep the system ressurised, so you loose your boost. you then have to wait for the turbo to spool again, AND pressurise the system.

Eithier way you loose pressure, but with the DV your turbo doesnt slow down.

[Legnum Boy]

If you dont use a dump valve, the back pressure slows the turbo down considerably

Thought about this, ten minutes after posting my reply, and what you say makes sense.
The pressure build up bounces back off the closed throttle causing a mini shockwave that powers straight into the spinning turbine blades, causing them to stall. (The wicked sound... :D )
When the pressure is dumped, no reverse shock wave, so the turbine blades slow down under their own steam, prehaps not even stopping before you are back building the pressure again.... :rolleyes5 :rolleyes5

Still going to give the choppy sound a go..... just out of curiousity... ;)

[Kenneth]

Tell me how it goes.

Just a word of caution, I vaugely remember some mention of some turbos being more suited to use without a DV... something about the compressor material maybe? cant remember. Might be worth looking up though!

[Legnum Boy]

Been surfing for info...

Found alot of pro-DV stuff, all stating longevity of turbo, reduction of lag etc etc... :(

Then I found this in the *cough* Performance Ford Forum..



as long as you dont run a T4 turbo then you should be ok to run without a dumpvalve without the turbo shattering itself. 30+psi T4 cars need em tho coz without the turbo will **** a brick when you close the throttle

This advise was being given to a T34 owner running 21 psi boost.
My 200sx had a T25 turbo running 15 psi.
What turbos do we have again? TD03??
Are our turbos mitsu's own make or Garrett units?

Just a little bit more probing before the messy bit, me thinks..

[Legnum Boy]

Really should go look before posting.... :rolleyes:

The Mitsubishi TC03-06A is designed to withstand 210,000 rpm with a turbine diameter of only 39mm.

Fitted to production motorbikes? :$

Surely this is not what is fitted to our beasties... :laugh:

[strangebat]

just found this, if it's any use :-D
MLR (http://www.lancerregister.com/showthread.php?threadid=39038&perpage=15&pagenumber=1)

[Legnum Boy]

Seems that there's mixed feeling about DV's everywhere.

Still no closer to finding out whether running no DV really does have an adverse affect on the turbo. The physic's behind it suggest it 'could', the general opinion of those running no DV suggests it 'hasn't'
I do also wonder if there maybe comfort reasons behind the install of DV's.
Can't really test it though, as I would need the standard airbox to see if noise levels were increased significantly. Another possible theory though...

Next available chance, I will be blocking up the DV, and for those who are interested, I will get some recordings of the neat 'flutter' sound.
Only time will tell whether its detrimental to the turbo and even then, at 70,000 miles old, if they do give up who's to say it wasn't just old age anyway... :rolleyes5

[Kenneth]

um... hehe, I blocked the stock dump valve vac line from the manifold, just to see what it does. It kinda works...

did you download the recording from that dude? It sounds a bit like that, but not as loud. also only get it when accelerating from stopped.

Probably need to block off the DV properly, but I wanted to make sure I could get it all back to stock if it all turned to poos and wees :rolleyes:

[Legnum Boy]

Just listened to that Evo.... damn it sounds cool. :-b :-b
Much better than the sound of my recirc....
Might turn the boost down when I try it though. :-D