whats the craic on the "chatter" sounding dumpvalve mostly associated with rally cars?
can be got for a road goin impreza?

 

prob a stupid question by the amount of replies *cough* , is it the wastegate makin that noise or whats the storee

 

rally cars don't use a dump valve, the noise comes from the air rushing back through the turbo when backing off the throttle. The more boost you have when backing off and the larger the turbo the louder and more sustained it is.

 

was thinkin thatd be more like it, just wonderin cos theres a chap sellin a WR1 here and says it has a "chatter" sound dumpvalve,hks ssqv is the closest to that sound

 

Put a strong spring in any dumpvalve and you'll get the wastegate chattering

 

il bare that in mind, i put a forge piston type dumpvalve on a starlet turbo 2 weeks ago, the spring in it was v.stiff, had to hit high revs just to give a little "psst", changed to a soft one and she gave a nice woosh..jaysus this thread sux man.
chattering dumpvalve me ****! lol

 

and the turbine stalling?

 

I think you'll find this thread blows LOL


rich...heard of anti-lag????

 

nice username i run without a DV, chatters like a good one

 

No that is a misconception, the turbine doesn't stall. The air that's going over the blades of the compressor is what stalls, as the compressor and turbine keep rotating but the air has no where to go against a closed throttle.

If using a big turbo with a MAF sensor this causes problems, as it can happen when you go from large to small throttle opening as well as just closing the throttle. If it does happen, the MAF sensor measures the air going in and back out again and thinks there is much more airflow than there is, resulting in overfuelling, jerkiness and generally feeling not great to drive. But unless you are looking at a turbo at least as big as a TD05/06 20g this will not be a problem.

Paul

 

Apparently the Turbo X/S BOV makes a sound like a rattlesnake so that maybe the 'chatter' you hear??

 

Rattles like a good one you mean

 

How does that work then?

Is it something we can all do?

 

if you don't mind your turbo disintegrating and the bits being sucked into your engine then this a good mod (disregarding the fact that you'll get more lag). i think you'll find a wrc turbo is built to a somewhat higher spec than a road car.

 

And isnt meant to last as long

 

Do you not reduce lag by running without a DV (the whole point in doing it)?

 

Lol,
Dont you lot get bored of typing the same thing 1000's of times

Dave

 

your turbo weighs something therefore has inertia and therefore takes energy and time to get spinning.

so to keep it spinning when the throttle closes momentarily (ie gearchange) the air is vented either to atmosphere or to before the turbo (recirculated). removing the dv entirely causes the air to back up between turbo and throttle plate on gearchanges, and eventually go backwards over the blades - so called compressor stall. it's a bad thing generally because the air is trying to force the blades back the opposite way they're going. eventually, they will shatter and the resultant mess will end up in your valves - nasty.

 

not worried TD05's last forever and i have no lag with my setup

 

*Titter* Back off to muppets then

 

Removing a dump valve will generally reduce lag between gearchanges. However fitting a "performance" dump valve will often reduce lag between changes when compared to a soft OE setup. It usually manages this by reducing the amount of air that's bled off and how fast it bleeds off.

Many people run without dump valves of any sort, and for the most part it will not harm the turbo, although the more boost you run, the more severe the effects of not running a DV will be. I don't know anyone that has removed the dump valve and had the turbo fail, certainly not within a year, and beyond that it's difficult to say whether the DV was a factor at all.

Paul

 

Ahh, a proper, knowledgeable answer

 

So why didn't anyone believe me! I bloody knew it reduced lag running without a DV!

Also, Wasn't it stated that it is the air that stalls and not the compressor?

 

ner ner ner ner nyeeeer!

 

Mind you - I dont think I'll risk it with the VF28 that is fitted to my motor!

 

hmmm, I was going to say that early VF turbos might benefit from a DV of some sort.

But remove/block dump valve for drag racing!

Paul

 

i fail to see anyway in which removal of a dv would decrease spool up speed - could someone explain why this is the case? manufacturers are increasingly fitting recirc dvs to modern cars, to the point where i don't know of one that hasn't got one, but if it is increasing lag and not lengthening turbo life the question of why arises?

 

It doesn't change the spool up point of the turbo. Lag is NOT the RPM at which the turbo spools up, Lag is a time measurement of how long the turbo takes to spin up. When you change gear you let all the pressurise air between the turbo and the manifold out, and you have to wait for the turbo to make all that back up again. With no dump valve you will maintain some pressure, such that it's there when you put your foot back on the throttle.

A top mount intercooler will be less sensiive to this, but an FMIC with all it's long pipes will show a noticable difference in lag on gearchanges with a stiffer DV or no DV at all.

There can be problems with it though, it will make driveability suffer in some situations, but probably not that a performance nut would notice, while the manufacturer will have strict quality controls on such things. The TD04 has rather small bearings too, so perhaps over the life of the car, say 140,000 miles, the DV will make a difference.

Paul

 

What is the inherent weakness in the VF series turbo that will not allow it to run without DV?

 

Compressor wheels seem to in the past be less than fantastic. But there is no hard evidence linking failure with DV specifically, but there isn't much evidence in generall.

Paul