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skyline69_uk said:
It's there for a reason
Purely noise suppresion reasons on 99% of standard cars fitted with em ;)

IMO they not ANYWHERE near as vital as most people think.
But most people who know that still fit them in a "better safe than sorry" manor.

Can usually find a lot more people with proof its had no noticable effect than people who can prove running with one has helped them.

Lot of AFM equipped cars NEED them as airflow going backwards past the AFM messes the fueling up tho.

Performance reasons are generally laughable and despite a lot of searching, seems to have never been proven. Just tons of internet/book/tv rumour and myth, like "wastegate chatter" and other such bollocks.

Turbo reliablility reasons are genuine depending on boost level and turbo strength.

Some turbos are fine without one, I ran 30psi held boost for over 12k miles with no DV at all with no ill effects, hell, I ran agressive ALS at the same time just to make it worse, lol.
Did the same at 23psi on another car, and know countless people doing the same.

Theory has it that they do something, reality is what they do is far more often than not not even slightly noticable.
 

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I doubt anyone in the UK skyline world has tried with none, its not the most daring scene ever!

I dunno how well the ceramic turbos will take it, but otherwise id have a go personally as never done me anything but good in the past.

But id never advise someone tho, as tried it on tons of cars, just never a GTR.
 

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tyndago said:
The Super Taikyu N1 race cars didn't have them. Not the 2 cars we have.

I am not that much of a fan of them. Most of my old experiences of them have been leaking under high boost. The leak does more damage by over spinning the turbo.
Careful mate, someone on the internet might call you a mug cause of stuff theyve heard but never tried :p

Glad someone else can back me up here, as id tried it many many maaaany times, but as ever on here, I expected the internet backlash, lol...
 

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skyline69_uk said:
I'm only going by what half a dozen professional auto engineering books and a friend who spent 3 months with the Renault F1 team say but maybe they're all mistaken.
Yeah, cause TURBOS are such a top subject on a modern F1 car :p

And for what its worth, when F1 cars were turbod in the 80s, did they run dumpvalves? Not on any ive seen, and I know someone who builds historic turbo F1 engines for a living...
Neither do any LeMans/GT cars ive seen actually...

Must be mugs
 

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If they did ANYTHING worthwhile in performance reasons, why wouldnt they run them in 80s F1 and current GT/LM?
10th of seconds count in them races, so im sure theyd fit one if they did anything at all... ;)
They didnt have ALS systems in 80s F1, and you cant imagine instant response when you got a 1.5litre engine running 1400bhp turbos...
Granted, they run dog boxes so gearchanges are almost instant, but a 10th of a second is an instant...

The damage running a full F1 or GT or LM race at anything up to 4bar boost with no dumpvalve will be more than youd ever give a turbo car in a lifetime of ownership...
 

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No, i TOTALLY understand the theory behind it, if you look at it purely from books etc, they are vital.

But NOTHING beats practical testing.

And testing proved to me they not half as vital as they seem on paper.

Paper and reality are two different things, regardless of how complex the books are.

Like said from the start, id never reccomend it as never tried it on GTRs, but tried it on plenty other cars at far higher boost than most GTRs to know that personally id take the risk to see what it was like, but if there no reason to on your car, then dont bother.

From a performance side, many dumpvalves that vent a lot of air can often make throttle response worse rather than better...
 

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IMO i dont think there an advantage recirc or vent to atmo with regard to performance. Both do nothing. As recircs vent back to the non pressure end theyd not do anything of use really anyhow, not enough air to spin up the turbo or anything, esp as its never angled to shoot direct into the turbo inlet.
Recirc/Atmo is purely a noise/ECU issue in my opinion.

Only failures ive EVER seen that can be associated with no DV are pure shaft failures.

Never seen blades damage barring foriegn object damage, or a dead bearing or shaft snapping causing the wheel to hit the housing.

GT series turbos seem to generally have thinner shafts than T series ones and ive seen shaft fails when running very high boost with no DV.

T series ive only ever seen it on T4 sized turbos, and even then only at 25psi+ sorta boost.

I ran a T34 with no DV at 30psi for 12k very hard miles and it was fine when taken off the car and checked, and thats totally common as most people with T34 cossies dont run DVs these days, as they never seem to do anything of use.
 

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I dont see, despite all these words, how recirc valves can help (ignoring AFM issues) anything at all over VTA ones.

A partially leaking DV, which is common and v.hard to spot, will overspeed the turbo and kill it far quicker than not running one.

As far as I can see, the only two people here who have actually had a lot of experience with this tested on a good few cars at decently high boost levels to see the effects of not running one is me and Tyndago (Sean), and funnily enough we both say they a waste of space.

Books say lots of things.
If books were always bob on tuning would be easy, all cars would be as good as the next one with the same money spent, and anyone who has read these books will be the best tuner ever.
How many of those statments are true in reality? None.
 

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They leak often tho, thats our point, its been mentioned every time Sean posts. Most the time its a tiny amount that you could never detect with the naked eye/ear, but they still do.
So turbo overspeeds trying to make the same boost pressure as its leaking half of it, so loses efficency at least, overspeeds and dies sooner at worst.

The only plausible reason for recirc ones is to "re-use" the boosted air, which is total bollocks as it wont be enough air to be pressurised on the pre-turbo side, will go back to atmo pressure before anyone could ever re-open the throttle, so will be no different in regard to response etc.

And recirc valves will just be putting hotter than ambient inlet air into the turbo, losing efficiency!

Dont see how atmo ones can be any more harmful than recirc, and deffo seen no differences in the all important... reality.
 
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