Badass or Badness, Rate or hate, Love or Loathe ?

 

Poll is anonymous.

Edited June 19, 201015 yr by Yowser

taken from another forum :)

 

The "Pigeon" mod is to remove any dump valve and just let the compressor surge when you close the throttle.

 

You can run like this but the damage is cumulative and I shall try to expalin why.

 

When you spec a turbo (and by spec here I don't mean select one froma website I mean have meetings with the turbo manufacturer who is about to commit a production line to your specific turbo application for the OEM you are developing the engine for) you do a number of tests to develop the application.

 

From basic power curve work to develop the appropriate turbine/compressor spec to altitude and high temperature work. When I talk about testing a turbo, I'm also talking about a fully instrumented unit and that means a minimum of mass flow, pressure and temperature in and out for both the compressor and turbine as well as a slew of other parameters including turbo speed.

 

All of the above are analysed and among other things all the pressures across the device are analysed. This allows the overall thrust on the turbo shaft to be calculated which will determine the design and life of the turbocharger thrust bearing. This is why the aftermarket does hybrids (big comps on small turbines while the OEMs do not, at least in volume production at any rate) as the imbalance in the sizes of both items causes excessive thrust bearing loads.

 

So now you're sitting there saying why the hells he going on about thrust bearings???

 

Well, when a turbo is at full boost and spinning the pressure is as balanced (exhaust side to inlet side) as we can get it at the design stage so that the load on the thrust bearing is kept to the design amount. Now hen you take your foot off, two things happen:

 

1) the pressure in the inlet rises very sharply indeed.

 

2) the exhaust pressure rapidly fall to nothing.

 

You can see where I'm going with this now can't you? SO TRANSIENTLY, we have a very high thrust bearing load spike. Now this won't kill your turbo immediately but IT WILL shorten the life of the turbo.

 

Your man two posts up whose turbo died very shortly after he did this mod is right: that extra movement in the shaft caused by the additional shock thrust loads will have caused the piston ring seal in the turbine to run on parts of the shaft it hadn't run before and that will have hastened it's demise.

 

But surely Dump valves prevent comp blades falling off?

 

Old wives tale!!

Seen any rally cars with a dump valve? No.

F1 engines? No.

 

The reason most comp wheels fail is foreign object damage or overspeeding.

 

A recirculation valve (proper name) is there to add durability to the turbo thrust bearing in much the same way that a water jacket aids the life of the bearings by preventing oil coking.

 

If you stop the water flow by removing the pipework or remove the RV to add noises, the turbo won't die. But You WILL shorten it's life.

 

On and while I'm on a hobby horse:

 

Externally venting DVs:

 

1) They make your car drive like crap

2) You sound like a tw*t

3) You will kill your cat

 

and 4) I can guarantee you that a car making funny noises does not loosen the knicker elastic of the girl you are trying to impress....... :rolleyes:

_____________

They seem to be mandatory for rev-happy boyos in RSturbos down Maccys and other such dis-respective establishments. :rofl: :)

 

so do aftermarket exhausts and aftermarket alloys but that doesn't stop a large proportion of Z owners (and owners of other 'respectable' imports) fitting them.

i think it's a matter of it's not what you've got it's what you do with it that counts (!). donutting in McD's carpark and dumping your valves will make you a ricer forever, but installing them just because that's what you want to do doesn't make you a chav.

as for the drop in performance/poor running, yes i understand the momentary over-fuelling, yes i understand the lost pressure, but have I physically noticed poor running or drop in performance over the past few years? hell no :hyper: do i care that if i was to do 100 runs with BOVs and 100 runs without BOVs under exactly the same circumstances and the 100 runs without BOVs were a tiny bit quicker would I care? hell no :hyper:

 

just my opinion of course! :bow:

when i was young and foolish i fitted dumpvalves! then i realised i had nothing to prove so i took them off!:lol:

 

dan.:whistling:

Thought they were cool.......... Bought and fitted some........... Took them off and now think they're sh1te

It comes down to wether you like the noise or not; They neither improve or reduce performance, reliablity or the general running of the Engine compared to stock Recircs.

Personally I preffer chatter (compressor stall), I have hks bov's fitted but they are only loud on high boost so it's never really crossed my mind to remove them, they don't bother me in the slightest and if I heard one I certainly wouldn't turn my nose up

They neither improve or reduce performance, reliablity or the general running of the Engine compared to stock Recircs.

 

Rubbish. Sorry, but BOVs are and always have been detrimental to the running of an engine running OEM management. As to how much you notice it is another thing, but certainly good recircs are far better for the engine than dump valves for the reasons I've explained countless numbers of times. :)

Would rather hand in my turbos than fit something that messed up the running of the engine.

 

i wish you would

I might do. I can shove them up your arse then. :rofl:

i wish you would

 

You after a second set of turbo's like? :whistling:

You after a second set of turbo's like? :whistling:

 

might well be ;)

Rubbish. Sorry, but BOVs are and always have been detrimental to the running of an engine running OEM management. As to how much you notice it is another thing, but certainly good recircs are far better for the engine than dump valves for the reasons I've explained countless numbers of times. :)

 

No , the affect of a couple of milliseconds of slight richness after gearchange is neglidgeble to the point of irrelevent.

 

It's all about the noise; for or against.

Edited June 20, 201015 yr by Yowser

More than that. I've known plenty of people who've fitted them and since ditched them as they said they ran better without. I've even seen it mentioned on here.

More than that. I've known plenty of people who've fitted them and since ditched them as they said they ran better without. I've even seen it mentioned on here.

Well having fitted and tested plenty of them to Z's, Supra's and other Jap cars, thats simply not the case.

 

I know people have had problems with improperly fitted and adjusted BoV's, but Fitted correctly and adjusted properly there is absolutely no noticeable difference at all.

btw - Im not speaking up for or against them...just trying to keep this to the actual real life facts - Psshh/Whoosh/Tish/Shoo or Silence.

Well having fitted and tested plenty of them to Z's, Supra's and other Jap cars, thats simply not the case.

 

I know people have had problems with improperly fitted and adjusted BoV's, but Fitted correctly and adjusted properly there is absolutely no noticeable difference at all.

 

It's the case I've experienced. The best, logical and simplest way is to keep recirc valves to which the ECU was designed to work with.

Every time I hear a dump valve, a little voice in my head says "oh dear" !

 

:duffer: