Well i have been told different things,

people say and i have been lead to believe DV's help your turbo by stopping it from spinning back.

yet others say that DV's dont really make a difference unless the car has very big power,

is this right ! i have taken it off the car now as i have the wastegate chatter...

What are they for what do they do ?

 

dont listen to what all these guys are saying. ford didnt placed a dv without a reason in the first place. when you rise the boost pressure you want to loose this boost pressure when you get of the trottle. without a dv the boost pressure try's tpo stop the compressor wheel from spinning (rough). this is because the pressure cant go anywhere then going back trough the turbo. and that chatter sound is nothing more then the compressor wheel is chopping air which is forced to go back trough the turbo. well that a healty situation (NOT). dont get me wrong it is a great sound. a dv will take of the strain of the turbo a lot more.

most guys who are saying "i'm driving 3000miles without a dv, no problem"
i say......WTF is 3000miles. its nothing. i'll drive 90000km without problem.
guys who are saying "you only need a dv with a t-4 on high boost" come on guys thats bull shit.

a t-34 on 30psi is spinning also real hard. why putting more stress on a turbo which has a lot of stress allready with 30psi.

wim

 

As per wimwerf, most turbo charged cars have dump valves fitted as standard, but they simply bypass into the air intake rather than to atmosphere. They are an anti stall device and driver aid. The poor old dump valve has been so abused by people, most only think it's there to make a nice noise. It's up to you but I would advise some sort of bleed off arrangement to protect your turbo!

Regards

 

it is also there to help it meet noise regs, at the sort of boost running out the facotry there is no need and it not a driver aid by any means bung it off though even with the std airbox and filter and you will get the chirping which , out form the facotry simply was not accepable.

 

Also re-circ valves are NOT dump valves.

 

So a device which goes towards less lag ain't a driver aid!!!! so should I take the ALS off my rally car...I don't think so!!!

 

i always thought recirculating valves does the same thing as a dump valve but instead of going to atmosphere the released charge air goes back into the intake system

 

recirculating DVs are there to reduce noise, nowt else

 

if it DID actually reduce lag then yes - but ive tried recirc, VTA and none and the throttle response with none at all is noticably the crisper and comes back on boost quicker. this ive tried with 4x4 saph, evo 6 (GSR turbo and TME turbo) and now T34 escos.

i'm not saying it may not on other cars, but on the ones i've had it doesnt.

 

I find throttle response a lot better and quicker without a dumpvalve.

 

well i'll drove mine today with and without. the only thing i've noticed is without it chatters and with it sissed. if your dv is not leaking you'll get no better performance. all the blokes who keep saying that is total bullshit. its only between the ears your car is going faster.

if your dv is leaking.....well yeah its going faster without it. i'll say.....buy a proper dv then and keep the turbo a little while longer.

 

My one has a lot better response with out

 

Chatter all the way!

 

sounds like a strangled turkey

wicked

 

The dump valve issue is age old goes back years.....the actual question at the top refers to reliablility and performance rather than JUST performance or thats how I read it. In my opinion and its just my opinion if I was building something like a mint sierra saph which was to be standardish I would fit the standard re-circ dump valve. Theoretically the dump valve should improve turbo lag and defo does prolong the life of your turbo, I was personally only trying to advise in a positive manner not fuel an age old debate....

 

Lee - keep the dump valve in the bin!

Chatter all the way

 

My small turbo Escos used to stop for a half of a second after every gearchange before I put a dump valve on it. NOw I got Bailey one from Cossymad and it's MUCH MUCH better

 

give it to me

 

For all those who think it makes the turbo last longer, Consider this:

When you are running 30Psi, the compressor has a 30psi restriction against it and is being forced to spin via the airflow at the Turbine which it is connected to.

When we back of, there is no longer any airflow at the turbine and thus, the turbo begins to slow down.

If we have a dump valve the pressure escapes through it with a "hisssssss" if we dont, the air escapes back through the compressor housing with a "Warble" as it rushes through the spinning compressor...

The max compressor load in each case is still 30psi

What the atmospheric dump valve was initially designed for was to stop the system dumping HOT air back into teh turbo and thus artificially increasing ACT's.. every little helps in motorsport.

The original recirc valve on most cars is there to silence the "warble" that Joe Bloggs would soon complain about.

On an airflow meter equipped car it is a NECESSITY as Air mass meters cannot deal with air that flows the wrong way and often stall

On very large turbos with excessive mass wheels (T4 + ) The valve will in fact save damage as the compressor torque reversal on a huge compressor like these can cause damage to them if running high boost and processing very large volumes of air at pressures above 1bar.

Thats odd because the T28 has one as std and its FAR better than any aftermarket dump valve that has ever been on the market to date...


All the above is my honest opinion of the situation. Hope its of use.

 

As far as I studied the construction of the stock valve bulid into compressor wheel it lets the air out in front of the turbo - maybe it backs off through the MAF and that's why the car stals? I only know it runs much much smoother now, when on ligh throttle I can shift gears just like in any other car. It used to behave wird when changing gears or lifting of. It simply runs great IMO (exept that I have other problems with it all the time :-((( )

 

Your std valve may have been leaky and required overhaul.

 

May be - but it did hold boost all right.

By the way - I have just put blocking ring spplyied by the Bailey with DV - it is a good way to get rid of standard one?

 

Yes, they work ok

 

I'd like to add to that . Over the last few seasons of racing ive sen 3 T3 Turbo failures and a T4 with all the same symptom , they smash the exhaust housing around the ring of bolts that secure the 3 sections together, none of these cars,An Escort Cos, 2 sierras and a Mk 1 escort turbo were using dump valves . I reckon a dump valve may have no performance advantages but safeguards the build up of stress behind the compressor. I now always use one , its not for the noise, i cant hear anything over the row the rest of the car makes anyway !!

 

I GET WASTE GATE CHATTER WITH STANDARD SET UP, ONLY DIFFERENCE -31, STAGE 3 CHIP, DRILLED AIR BOX

 

then i suggest that you check your dump valve system (including the pressure/vaccum supply pipe) for leakage

 

In my experience running with a Cossie + T4 the dump valve fitted to the car siezed and we ran the car without it, it only took two runs on the strip before the turbo main shaft twisted and broke off :-( so I would say for reliablilty you defo need one. On the other hand an external wastegate can also aid in getting that chatter sound

 

Full boost, max rpm, then suddenly back off and stop the airflow... Does anyone got the equipment to measure how high the boost peaks before it slams backwards and out of the compressor...?

 

why not buy a cheap second hand old DV and put that on...thats what i did and i get a comination of both hiss and chatter! eveyone is happy!

 

Theres no expensive equiptment required. Put the boost gauge on teh compressor outlet to the actuator.

 

So anyway, I just binned my dumpvalve and am now rejoicing in CHATTER, wherever the fuck it comes from and whatever it's SUPPOSED to be called, it sounds WELL 'ARD

 

chatter,chatter,chatter...................throw the dumpvalve in the bin and leave it there,and yes i believe if it didnt have one in the first place why bother!

 

If you want a dv to reduce turbo damage but dont want that pssst sound im sure you can get silent dump valves somewhere

 

yep,a recirc one as fitted as std on all cossies