its the clatter when the wrc cars change gear on tv ,so how do i make my dump valve sound like the one in the vid

 

Strange.
Just go on you tube and search 'impreza with chatter'. My username is stints1983.
The vid is of my old car running dv'less.

I got the flutter noise but also got a large whoosh of air when at full boost.

 

Fascinating (the wiki article that is). I already feel that I can be much more comprehensively argumentative now.

 

There's a bit of an irony there then.

A lot of people say that a DV can cause problems, yet in your experience there's no difference with or without.

 

Alot of people report that vent to atmosphere dump valve cause problems

 

When I got my hawk the dump valve was set so strong that it would only open on max boost... And so at lower revs when I let off because the air had no where to go it physically made the entire car judder, it was absolutely horrible!
Now I've had it set up (by Big D, and a bloody brilliant job too) so it retains a bit of the 'pressure' in the system so I still get a fair bit of flutter but no physical judder... Just wondering you guys who blank the dv off do you get that issue?? I'm running 400bhp @ 1.4 bar by the way.


Oh and I did post it the other day but this gives you some idea what the car now sounds like (sorry the camera work is shocking!)...

 

i get no judder...nice and smooth..my evo was fine also..but my GT4 hated dumpvalves...would get judder real bad on motorway driving..i tryed different makes..was crap.

evo didnt like em much either..which is why i looked into caping off...

the WRX is smooth as you like.

 

hold on a minute most people hate them because of the stupid fart noise everytime you change gear making you look like a ****

nothing to do if you can get them to run right or not.

 

To be fair due to the size of my front mount the single dump valve isn't actually getting rid of enough air so it's going out the air filter which makes the loudest noise ever... Thinking about going for a twin VTA set up at some point just to see what that does. But currently it's running sweet as a nut.
And yes I'm a complete c**t... Nothing puts a bigger grin on my face then changing gear next to snotty nose kids and watching them hit the deck Lol

If I want to be 'sensible' however (or town driving) then I simple change gear at low revs and just get a very faint flutter, job's a good un

 

now what we all need is one of these...

 

haha lol

 

Quackers, absolutely quackers.

 

I give up

 

If you start to notice when someone is using fallacies it will really help you determine who to trust. Once you are aware of them you will see it a lot, near constantly from the mouths of politicians.

This is a great resource: http://www.nizkor.org/features/fallacies/


As for dump valves...
Blanking it of and inducing compressor stall is bound to make it take longer to spool up on gear change and will increase stress on the turbo. Some big boy turbos have anti-stall compressor housings that redirect air to atmosphere and i guess the wrc cars have something like this?

So i would think vta or recirc is gonna allow the turbo to keep spinning and make for quicker spool up.

As for vta causing rich running by taking out metered air. Surely the throttle is closed and the injectors are off when it dumps so how much can it affect that?

 

what if you do flat foot shifts ? with a vta unsetup (not that i do this )

 

when you fit a vta dump valve you will notice you blank of a pipe.
this pipe is the one where the air goes back into the inlet on a normal recirc dump valve.

the car is expecting this air to be put back into the inlet and fuels for it.

on a vta valve the pssssst is the air escaping to the atmosphere so is not there in the inlet but the fuel is hence the pop you get as the car has overfueled.

this is one down side the other being you look a bellend as your car farts on every gear change

 

PMSL!!

 

So I'm presuming then when you fit a VTA and then get it mapped the mapper will reduce the fueling at that point to stop it?

But then I also know plenty of people/cars that specifically ask for 'pop and bangs' on the over run, so why doesn't this cause the same so called damage as say running a VTA without mapping?? And if it does then why isn't there more threads (or even a single one) saying about damaging their cars due to over fuelling??

I know the theory is sound I guess but there must be thousands of cars with VTA on standard setups running quite happily?

 

As a complete and utter novice (and hence unaffected by preconceptions) I would have asked 'how can a mapper compensate for that?'.

My reasoning is that you can decide to change gear at any particular revs.
So how can a mapper program in and take account of what revs a gear change will be effected, and the VTA DV affected???????

 

Same as you mate, I've no idea about mapping, just best guessing... But I would guess the ecu would use point of let off as reference to then calculate what to reduce the fueling by?

Then the mapper at this point could add a little bit more fuel for the 'pops and bangs' that some people ask for on the over run???


But then that's my point (trying to get a bit back onto topic) that plenty of people have requested for the pops and bangs but I've never seen anyone complain that it's killed their engine? So why would a DV cause any harm when you're virtually doing the same thing??

 

I believe the requested pops and bangs are created by retarding ignition timing on over-run meaning there isn't a complete burn and some fuel makes it through to the exhaust. A tickle of the throttle when on over-run opens the injectors and you get pops and bangs on demand.

I could be wrong tho

 

Personally when i re-fitted a recirc i got more pops and bangs.

 

Yeah if you run the spring at high pressure on a recirc it's pretty much the same as running a blanking plate.

 

yep

 

That's not entirely accurate, blanking dumps everything through the compressor, with a DV fitted you and accurately control how much is dumped and how much is retained, finding the right balance is infinitely better than blanking and I am more than happy to prove this.

Cheers Iain

 

I would like to add that finding the correct balance is not easy and will be different for every car, there is a lot to consider - primary and secondary spring ratings, speed and length of piston throw, vacuum chamber size, the DV port and vent size etc.

I have no interest in changing anyone's mind or perspective, but I do know that this works wonders and makes a huge difference to through the gears performance.

Cheers Iain

 

Big D, are you referring to adjustable BOV ie. Turbosmart dual port? if im understanding you correctly, trial and error will result with an operating dump valve as well as partial recirc. Eg. A lower volume 'pssst' along with recirced air to keep turbo spin momentum/stall?

 

I only use forge VTA, however they have recently changed the main piston design which has dramatically reduced the tuning range of the valve, I have been in talks with them to revert back or offer the older piston as an option.

What I aim to achieve is to set the VTA to hold in a set amount of pressure in the charge air system, if this is set correctly when you change gear the turbo is still spooled, you have retained positive pressure in the system so you achieve a greater spool response through the gear change. If you just lift off you will get an initial large dump through the VTA followed by a nice chatter. It is a little more complicated than just setting spring ratings in order to get it just right as you have to consider, port size and piston speed (how fast you can dump the charge air) which is directly relative to the size of your Intercooler and what boost pressure you run, also how strong the primary and secondary springs are in order to retain the exact amount of pressure.

Personally I find the turbosmart VTA setup is far too slow at dumping charge air.

Basically when driving hard through the gears the aim is to maintain turbo spool and retain pressure in the charge air system so that the exact point that you lift the clutch and drop the accelerator after a gear change you have ZERO lag and the turbo has a huge head start on pressure delivery. If set correctly at the point of acceleration post gear change the VTA will be fully shut but not run into compressor surge, hence the balance between air out and air retained.

Proper punchy gear change, ZERO lag or running issues.

Cheers Iain