Ok, got loads of things to post on this thread, some very interesting techy views on the use of DVs with regards to turbo life, but lets start with a question...

Who HAS damaged their turbo in a way that has led them to belive it was running with no DV that did it? And that damage was actually done?

Il post some tech views about it all in a bit, but if anyone else with decent experience (like Karl etc, or Maybe Mike could ring Harvey n ask his views ) can put forward their experiences (not theory, we all seem to know that) then thatl be cool too...

 

i dont run a d/v steve but only had car for 2 weeks lol so dont no if im fooking up turbo


DAN

 

What damage would it cause without the DV???

 

bending/shattering the blades when the air comes back at the turbo tiff.. (in theory)

 

BUT have you ever heard of it happening????????????????

 

no.. hence the (in theory) you plonker

 

thinking of taking mine off .mate took his off 6 months ago seems ok at mo

 

I have ONLY heard this happening with a T4 car and some of the smaller (thin)shafted GT series turbos and that is obviously from my association with Harvey and his experience .

In all my 11 years of Cossie ownership, I have never experienced such failures as I have always followed Harvey's advice (as in not running one on anything smaller than a T4 and running one with both T4 equipped cars).

 

I never run a dump valve on my T3 and that was at 28psi for about 5000 mile, rang the knackers out of it,took it off and it was MINT

 

got a big turbo escos would i be ok to take it of mine

 

Yes

 

thans fella

 

I didn't run one on my silly boost T34 either, and the turbo was mint the entire time I had it!

 

I still think that dump valve induced overspeed is potentially as bad as, if not worse than, compressor stall so the jury is out in my mind, although i DO know of GT turbos letting go immediately after a throttle off with both:

Dumper fitted....
Dumper not fitted....

No help whatsoever in that case...roflol

For smaller turbos im happy to recommend no dump valve at all if your not bothered about the sound you will have to endure/enjoy.

 

Arthur,
I have never had a dump valve on any of my TO3/4B cars and have not suffered a failure that I would attribute to the lack of d/v. I have killed plenty due to over-speeding them with 34-36psi peaks though .

 

How many are you talking here? 1 T4 car then? What ACTUALLY happened to the turbo (ie what damage)

 

I ran one on my T34 running 30psi either and was caned to fuck for about 12k miles and was spot bollocks on.

What Stu said about overspeed is a very valid point

 

Steve,
Harvey never quantified it to me, he just said that you must run a d/v on T4, as he has seen them shear the main shaft from the stall (at big psi). HTH?

 

On a T3 car you'd never boost it enuff to worry about!!!!...A T34 hybrid always comes with a 360 bearing which is 100% safe for no dump running.....T4 you need one.

If one T4 breaks thru no dump then thats enuff to say your risking it surely?

 

arthur!!! my mum calls me that when im in trouble.artie please anyway 30 psi bloody hell must be screaming

 

Sorry Artie, I just didn't feel comfortable calling you by your car's registration , and I remembered your name from the mag feature...

 

dunno if this is the case with all, but i know of a 4x4 T4 equiped cossie that chatters then dumps, wtf pmsl

 

its no worries mate been called alot worse in my time

 

The SHAFT snapped from stall?

Another think im kind of getting at is people ASSUME the turbo has broken due to no DV, but have they?

 

I ran my T3/T4 at 28PSI for a full year with no dump valve took it off last winter didn't see any damage at all. I also ran no intercooler and the turbo was still in the factory location less than 12" from the throttle body.

I only run one now to scare old ladies.

 

I would have thought that intercooler size and pipework diameter will play a part in the chance of damage, the bigger the volume of charge between the turbo and the throttle then the larger "buffer" to help absorb the shock being sent back to the blades.

Thats just theory though, so ill get my coat and clear off from this thread now.


Chip

 

Steve,
Yep, that's what the big man has seen on more than one occasion (but I don't know how many times). Some of the GT range that are smaller than the T4 also MUST run them, as the shaft diameter is tiny (so no strength). Apparantly it is all down to this dimension and the amount of airflow the turbo can produce at peak boost. The T4s have sufficient flow and small shaft size for the stall effect to shear the shaft in high boost applications, hence the d/v requirement. The TO3/4Bs don't have the flow capability to do this kind of damage.

 

Phone your local Volkswagen dealer and ask what they call the recirculating "dumpvalve". From swedish it translates to noice surpressor.

 

When ive finished doing stuff il post some tech stuff ive found v.interesting, but hers summat for you.

IF dumpvalves help with reliability of turbos, why was they NEVER (IIRC) used on Turbo F1 and Indy Cars? These cars ran upto 4bar of boost!

LeMans 24hr cars, seen one with a DV fitted? I havent.

Some people use the line of "well its a race car, they rebuild them after every race" to reason why most turbo race cars have no DV. Thats bollocks, if it REALLY snaps shafts and bends wheels thats not really a wear thing, that just happens, and besides, hours and hours of flat out racing at huge boost, 1000s of times on and off the throttle from full boost to full vac, its the equivalent of absolutley fuckloads of road use, so WHY is it of any use to us, but not to road cars?

 

Hmmm, but how will I impress schoolgirls if I take it off

 

Nothing tehnical yet, but i got to post a couple of things as they literally made me nearly fall off the chair laughing...

(Honest to god they both are off 2 totally seperate websites and dated nearly 2years apart)

 

thanks steve! i broke a rib or 2

 

strong point

 

just took my dumpvalve off and went for a blast...car does seems more responsive.
sooo weird with no dump. cant even really hear th chatter cos i still run airbox.
any more info on this subject would be great!

 

Yup, Look in the Mazda RX7 (Twin turbo) workshop manual and it also says...

DECELERATION CONTROL SYSTEM

DESCRIPTION
....
* Air bypass valve: Bypasses compressed air from after the turbocharger to before turbocharger during deceleration to prevent noise.



Il post a load in a bit, some of it is well over my head, but its getting that convincing that im willing to do without...

 

In one season '03 , i saw 2 T3 equipped racecars blow the turbos apart at the join of the core and the exhaust housing .Neither had DV's , read into that what you like ! Ive blown several turbos in a long time of cosworth ownership a few T3's without DV's and a T4 with !
I sit on the fence on this but i now use one , as do some of the quicker cars you will know of !

 

i have snaped 2 shafts on a t2 ihi turbo both with 360 thrust bearings and it was all the stack of boost that was building up on the comprser wheel once fitted the dv never hapend run 1,5 bar

 

i run my car for 4 years now WITH dv...no prob

if your dv is leaking...it will distroy your turbo...

if it is working properly...no problem

 

i can see people getting paranoid now

 

im one of them!