Spec me a Dump Valve

Bear · 11 Dec 2006 at 19:59

Bug One said:
This one has been discussed at length on FccUK. How can you be overfuelling when you're not pressing the accelerator? Plus the amount of air thats actually dumpted is tiny compared to the volume of air the engine intakes.

It overfuels because if you have a MAF, the air is metered passing the sensor at the filter end. If you then dump the air to atmosphere the fuel the ECU has worked out for that air that its metered is no longer the correct amount due to the air you have vented. This is why recircs put the air back into the intake after the MAF.

Hawk Tuah · 11 Dec 2006 at 20:06

Bear said:
It overfuels because if you have a MAF, the air is metered passing the sensor at the filter end. If you then dump the air to atmosphere the fuel the ECU has worked out for that air that its metered is no longer the correct amount due to the air you have vented. This is why recircs put the air back into the intake after the MAF.

I understand the that. However you're missing one thing. Its dumping because you've stopped accelerating, so its not going to overfuel.

L0rdMike · 11 Dec 2006 at 20:20

Bug One said:
I understand the that. However you're missing one thing. Its dumping because you've stopped accelerating, so its not going to overfuel.

Its still going to provide fuel for air that isnt there though.

Bear · 11 Dec 2006 at 20:42

Bug One said:
I understand the that. However you're missing one thing. Its dumping because you've stopped accelerating, so its not going to overfuel.

And when you open the throttle plate again and it thinks that air in the intake from the MAF to the throttle plate is going into the engine and it isnt there. Thats where the overfuelling comes from, you got all that fuel metered for the air you have vented plus the fuel for air that is being subsequently metered when you accelerate again.

sigma · 11 Dec 2006 at 21:01

When i took the d/v off my car i actually have better throttle response.

Also d/vs have a habit of suffering from split diaphragms.

I now have the pleasure of listenin to compressor surge

most people expect to heard a d/v when i drive past, usually get a :eek:

and a

when they hear it chirping

Firestar_3x · 11 Dec 2006 at 21:02

Don't get confused thats actually the sound of your bank balance going down.

L0rdMike · 11 Dec 2006 at 21:10

silane said:
When i took the d/v off my car i actually have better throttle response. Also d/vs have a habit of suffering from split diaphragms.

I now have the pleasure of listenin to compressor surge most people expect to heard a d/v when i drive past, usually get a and a when they hear it chirping

They then laugh when you are gone as they know your Turbo wont be lasting long.

Hawk Tuah · 11 Dec 2006 at 21:19

silane said:
When i took the d/v off my car i actually have better throttle response. Also d/vs have a habit of suffering from split diaphragms.

I now have the pleasure of listenin to compressor surge most people expect to heard a d/v when i drive past, usually get a and a when they hear it chirping

So stalling your turbo on every gear change improves throttle response?

panthro · 11 Dec 2006 at 21:22

L0rdMike said:
They then laugh when you are gone as they know your Turbo wont be lasting long.

What does it mean if you have a dv fitted, but still get the chirping noise?

L0rdMike · 11 Dec 2006 at 21:27

panthro said:
What does it mean if you have a dv fitted, but still get the chirping noise?

Depends, but if its air being forced back into the Turbo stalling it then I doubt the blades will last too long.

Giddy · 11 Dec 2006 at 21:27

What percentage of the cars total value is this dump valve costing you?

panthro · 11 Dec 2006 at 21:37

L0rdMike said:
Depends, but if its air being forced back into the Turbo stalling it then I doubt the blades will last too long.

thats not good, my car does that. How the hell do I stop it?

Meridian · 11 Dec 2006 at 22:37

ConfusedTA said:
There are only two types of cars where DVs are acceptable IMO.

Very, very highly modified Japanese cars.

Disagree. No matter how modified. If you look at the real experts running stupid power just about none of them use VTA.

Very old, modified sleepers with a turbo engine. Such as a Ford Anglia 105E with a Nissan 1.8 turbo lump and ~230bhp. So it squats down, ****s off, and goes vrrrrrrmmmm*tish* to give people an idea of what's under the bonnet.

Agree!

M

Psycrow · 11 Dec 2006 at 22:38

vanpeebles said:
heres my hks ssqv in action

http://www.youtube.com/watch?v=ass8V0lo1MA

Yours sounds wussy

sigma · 11 Dec 2006 at 22:43

Bug One said:
So stalling your turbo on every gear change improves throttle response?

I will let you drive my car ( providing you can show me that you have insurance to do so ) with the d/v on and off if you want?

L0rdMike said:
They then laugh when you are gone as they know your Turbo wont be lasting long.

Well the turbo has lasted long enough without it so far.

Most of the owners club ( rtoc.org ) run without d/vs, many have track cars that see a lot of action and many cars as daily drivers which also see a lot of miles, and they all seem to have no issues with consistent turbo faliure due to a lack of d/v.

Also the car didn't come with a d/v so I see no need to add one - surely Renault would have done so if it was needed.

agw_01 · 11 Dec 2006 at 23:10

L0rdMike said:
Depends, but if its air being forced back into the Turbo stalling it then I doubt the blades will last too long.

Exactly.

andi · 11 Dec 2006 at 23:31

Heard reports of turbos running better with no dump valve before.

And the "it'll kill your turboz!!11" thing is a tad exagerrated, lots of manufacturers don't bother fitting them without a problem. It probably shortens the lifespan, but its not exactly going to explode as soon as you take it off

Hate · 11 Dec 2006 at 23:56

ConfusedTA said:
Very old, modified sleepers with a turbo engine. Such as a Ford Anglia 105E with a Nissan 1.8 turbo lump and ~230bhp. So it squats down, ****s off, and goes vrrrrrrmmmm*tish* to give people an idea of what's under the bonnet.

then a a loud rattle as the chocolate big ends lunch themselves

The_Dark_Side · 12 Dec 2006 at 00:01

dump valves/baseball caps/burberry/LED washer jets etc etc.

all different shades of the same colour IMHO.

Entai · 12 Dec 2006 at 07:38

andi said:
Heard reports of turbos running better with no dump valve before.

And the "it'll kill your turboz!!11" thing is a tad exagerrated, lots of manufacturers don't bother fitting them without a problem. It probably shortens the lifespan, but its not exactly going to explode as soon as you take it off

Personally I have never seen a modern factory standard turbo'd car without a recirc valve of some kind or other fitted.

Some older cars just piped up the wastegate control differently so that the excess pressure would be dumped down the exhaust on accelerator lift off, but that just increased turbo lag because the whole unit would slow right down as it had no pressure feed into the impellor housing.

I know from experience even taking the standard recirc off an Audi A3 1.8 turbo, and just piping up straight, resulted in bits of compressor housing and blades being dug out of the bonnet, bulkhead, and surrounding areas after about half an hour of hard driving.
The whole housing and turbine grenaded itself due to compressor stall. because of the increased back pressure on accelerator lift off.