Juat fitted Forge VTA Dump Valve!
12 November 2004, 06:27 PM
#2
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Total waste of time you boy racer !!!!!!!!!!
Well, you did ask
Edited to say,
This was tongue in cheek, he did ask
Don't like them myself though.
Well, you did ask
Edited to say,
This was tongue in cheek, he did ask
Don't like them myself though.
Last edited by Gary C; 13 November 2004 at 09:00 PM.
12 November 2004, 07:36 PM
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I don't know why I bought it as I agree it is a definate boy racer item!
My 3 1/2 year old thinks it's great, so that says it all! LOL
I saw it on Ebay and it was only going for £50.00 so I bid for it, then I got carried away as I had had a few beers and ended up paying £95.00 as someone was bidding against me. Still a good price though.
What is this bore wash? I have read that there a mixed views on turbo life with these fitted but, to be honest I'm not going to have the car forever so I can't see a real problem.
Matt
My 3 1/2 year old thinks it's great, so that says it all! LOL
I saw it on Ebay and it was only going for £50.00 so I bid for it, then I got carried away as I had had a few beers and ended up paying £95.00 as someone was bidding against me. Still a good price though.
What is this bore wash? I have read that there a mixed views on turbo life with these fitted but, to be honest I'm not going to have the car forever so I can't see a real problem.
Matt
12 November 2004, 10:49 PM
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Bore wash is where excessive amounts of petrol (very rich mixture for example) wash the oil of the cylinder bore so that the piston rings don't have a nice film of oil to slide up and down on and you get premature bore wear.
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13 November 2004, 12:26 PM
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Basically, (i think) the volume and density of air going into the engine is measured by your air flow meter. This then matches the air with the correct amount of fuel. With the standard recirculating dv, all the air is kept in the system. With vta dv's, air is let out of the system and hense your engine runs rich with fuel. Only for a split second though.
Stand to be corrected!
Stand to be corrected!
13 November 2004, 12:36 PM
#10
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Mate i run the same one on my ra and it works fine, if anything it makes it a wee bit rich which is fine cos i get more pops and bangs from the exhaust! hehe. I got mine for £100 inc. fitting. (mate had one in his shop window gathering dust!)
Enjoy!
P.s dv's are hardly boy racer material, I can think of things that are far worse - neons led washer jets, etc.
Enjoy!
P.s dv's are hardly boy racer material, I can think of things that are far worse - neons led washer jets, etc.
13 November 2004, 12:36 PM
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Well I ran a forge VTA for several months and had no problems and really enjoyed it. It isn't intursively loud and gives the car a nice mean sound and a brilliant chatter at half-boost lift off. Good on you I say
13 November 2004, 06:52 PM
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If you have the car mapped to run a vta its ok, if not id advise against it.
People say that it gives you a rich mixture, and this is correct, but they forget or dont know about the opposite effect that it gives, ie it leans out as the ecu tries and over corrects the lack of air by adding more, unfortunately the car is back to normal by then and it over endulges on air (not good).
Some people have run vta's for years and not had problems though, but there is a possibility of damage, though slight.
There is also one point id like to make for those none believers
If a subaru was meant to run a vta it would have one fitted as standard from the factory, the reason it doesnt is that the re-circ is better on our car (and quieter).
If you want noise, add an exhaust
Tony
People say that it gives you a rich mixture, and this is correct, but they forget or dont know about the opposite effect that it gives, ie it leans out as the ecu tries and over corrects the lack of air by adding more, unfortunately the car is back to normal by then and it over endulges on air (not good).
Some people have run vta's for years and not had problems though, but there is a possibility of damage, though slight.
There is also one point id like to make for those none believers
If a subaru was meant to run a vta it would have one fitted as standard from the factory, the reason it doesnt is that the re-circ is better on our car (and quieter).
If you want noise, add an exhaust
Tony
13 November 2004, 07:45 PM
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Bore wash shouldn't cause you pistons to melt, that'll be down to detonation or pre ignition. (normally caused by running very lean or too much boost, both leading to high temps then det/pre ignition)
13 November 2004, 10:17 PM
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Hmmmmmmmmmm .. No thanks .
My 2p ..
I put one of these on my WRX Wagon ..
It did sound good .. for a while .. then eventually began to bug the t*ts off me when ur going on and off the power every 10 / 15 seconds on a twisty run !
BUT ..
WITH Forge VTA ......... 20 mpg .. 210 to a tank !!
.. Rich !! U bet !!
WITHOUT ................. 28 mpg .. 300 to a tank !!
I put one of these on my WRX Wagon ..
It did sound good .. for a while .. then eventually began to bug the t*ts off me when ur going on and off the power every 10 / 15 seconds on a twisty run !
BUT ..
WITH Forge VTA ......... 20 mpg .. 210 to a tank !!
.. Rich !! U bet !!WITHOUT ................. 28 mpg .. 300 to a tank !!
14 November 2004, 12:41 PM
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just use standard dv, aparently there as good as baileys etc
mind you still got my old baileys dv from my old my00 uk classic
must get round to flogging it some time !
mind you still got my old baileys dv from my old my00 uk classic
must get round to flogging it some time !
14 November 2004, 01:44 PM
#24
The magical properties of dump valves is something that has entered Scooby Net mythology.
Why change the O/E dump valve?
In a high proportion of cases the OE dump valve will perform more than adequately. An aftermarket dump valve does not add power or result in a quicker gear changes etc. etc. etc.. On cars where the dump valve is flange mounted on the top mount intercooler it is often necessary to change the dump valve when going to a front mount intercooler so that the DV can be mounted in the pipe work without the need for a flange adaptor. A satisfactory flange to pipe adaptor can be bought/made to utilise the OE DV.
Good reasons to change the DV are :
Appearance.
Noise.
Placebo effect.
Regardless of how the car is mapped, if it still has a MAF sensor then with a VTA Dump Valve there will be momentarily over fuelling every time the dump valve operates. Ie. on lift off. This is unavoidable. Air has been lost from the system through the VTA but the ECU has provided fuel for the original amount of air that flowed past. Obviously when mapping it will be preferable to work on a car with a recirc dump valve.
I have no idea if the momentary over fuelling is a bad thing but if you are a perfectionist or a mapper it is certainly undesirable.
Another piece of useless knowledge. Many people hold a mistaken belief that because of the boost they are running, or for some other reason they need a very strong dump valve spring. This is usually a misconception and many cars I have driven judder on lift off simply because the DV spring is too strong and air is going back through the turbo. This is the cause of the judder and it will obviously shorten turbo life.
Forge dump valves for instance are available in any of four spring settings, red being the strongest the other colours being blue, green and yellow so if you are suffering this judder think about a weaker DV spring.
It is obviously simpler to fit a VTA because there is no need to make a return pipe entry to the induction system somewhere between the MAF and turbo.
Why change the O/E dump valve?
In a high proportion of cases the OE dump valve will perform more than adequately. An aftermarket dump valve does not add power or result in a quicker gear changes etc. etc. etc.. On cars where the dump valve is flange mounted on the top mount intercooler it is often necessary to change the dump valve when going to a front mount intercooler so that the DV can be mounted in the pipe work without the need for a flange adaptor. A satisfactory flange to pipe adaptor can be bought/made to utilise the OE DV.
Good reasons to change the DV are :
Appearance.
Noise.
Placebo effect.
Regardless of how the car is mapped, if it still has a MAF sensor then with a VTA Dump Valve there will be momentarily over fuelling every time the dump valve operates. Ie. on lift off. This is unavoidable. Air has been lost from the system through the VTA but the ECU has provided fuel for the original amount of air that flowed past. Obviously when mapping it will be preferable to work on a car with a recirc dump valve.
I have no idea if the momentary over fuelling is a bad thing but if you are a perfectionist or a mapper it is certainly undesirable.
Another piece of useless knowledge. Many people hold a mistaken belief that because of the boost they are running, or for some other reason they need a very strong dump valve spring. This is usually a misconception and many cars I have driven judder on lift off simply because the DV spring is too strong and air is going back through the turbo. This is the cause of the judder and it will obviously shorten turbo life.
Forge dump valves for instance are available in any of four spring settings, red being the strongest the other colours being blue, green and yellow so if you are suffering this judder think about a weaker DV spring.
It is obviously simpler to fit a VTA because there is no need to make a return pipe entry to the induction system somewhere between the MAF and turbo.
14 November 2004, 09:34 PM
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A waste gate allows exhaust gas to bypass the turbine. This allows the speed of the turbine to be controlled and thus control the boost pressure.
Being a centrifugal compressor, the discharge pressure is roughly proportional to the speed (unlike a piston compressor where the flow is proportional to the speed). Using a waste gate allows the compressor to be sized to give a good boost pressure across the engine speed range.
The dump valve is their to prevent back flow from damaging the compressor. When at full boost with the throttle open, their is a large mass of air flowing up the pipes. When the throttle is shut, this mass of air cannot just suddenly stop flowing, so it keeps moving and the pressure at the throttle plate ramps up sharply. The air would then flow back up the pipework to the compressor causing it to stall, the dump valve just vents this excess pressure.
Problem is as I see it, the compressor then continues to vent air out of the DV and is therefore doing work, and if its doing work, its taking energy from the spinning mass (as their is now no exhaust to drive it), therfore the turbo slows down faster and you get more lag. Therfore the dump valve should be designed for the application its used on. Best design as I see it would be one that just snaps open to dump the transient peak pressure and then closes.
Being a centrifugal compressor, the discharge pressure is roughly proportional to the speed (unlike a piston compressor where the flow is proportional to the speed). Using a waste gate allows the compressor to be sized to give a good boost pressure across the engine speed range.
The dump valve is their to prevent back flow from damaging the compressor. When at full boost with the throttle open, their is a large mass of air flowing up the pipes. When the throttle is shut, this mass of air cannot just suddenly stop flowing, so it keeps moving and the pressure at the throttle plate ramps up sharply. The air would then flow back up the pipework to the compressor causing it to stall, the dump valve just vents this excess pressure.
Problem is as I see it, the compressor then continues to vent air out of the DV and is therefore doing work, and if its doing work, its taking energy from the spinning mass (as their is now no exhaust to drive it), therfore the turbo slows down faster and you get more lag. Therfore the dump valve should be designed for the application its used on. Best design as I see it would be one that just snaps open to dump the transient peak pressure and then closes.
Last edited by Gary C; 14 November 2004 at 09:46 PM.
22 November 2004, 06:41 PM
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Originally Posted by Mat Mc
Woosh!,
Fan dabby dozy!
(Ready for slating)
Fan dabby dozy!
(Ready for slating)
I have taken it off now. The reasons are.
1) Seem to have used more fuel, this is more than likely me driving differently to make it woosh! Normally 250 - 275 miles before warning light from full, with VTA 220 miles.
2) Car seemed to feel lumpy when accelerating in first and second. Could be recent colder weather but, not too happy with it. Also the Mrs noticed this without me saying anything so I'm not imagining it.
3) When letting off the throttle the car seemed to lunge a bit. Reading one of the posts on this thread this may be due to the spring pressure being incorrect and boost washing back at the turbo causing it to stall?
4) The other morning I started it and it coughed and farted for a few seconds then stalled. Never done this before so I can only put it down to the VTA. I have read somewhere it is possible to get idling problems.
Shame cause it looks really good and sounds great (IMHO)
Anyone want to buy a Dump Valve!! LOL
Matt