Dump Valve, BOV, or Wastegates???

[d19yda]

so mant people have sat me down and tried to explain these to me and im slowly getting my head around it.

first of all what one does my car have?? its a 1999 uk turbo wagon (think its called a turbo 2000)???

I like a nice loud, sharp sounding D.V but as im fairly new to subaru whats the  opinion on them? Cool or Not Cool?

If it turns out that i wont get laughed at for liking to take a noisy dump now and again, anyone have one that will fit my car and might sell?

Davie

[jamie_wood]

You have a re circulating Dump valve. Its factory fit.

Leave it as it is.

Fit an after market "Dump to Atmosphere" valve and you run the chance of causing engine damage.

Just leave it be.

[RS Grant]

Kartman was selling an HKS Dump Valve from his P1 for £150 recently... that would bolt straight onto your wagon and IMO, the HKS gives the sharpest and cleanest sound you can get.

Cheers,

Grant

[corsa]

You have a re circulating Dump valve. Its factory fit.

Leave it as it is.

Fit an after market "Dump to Atmosphere" valve and you run the chance of causing engine damage.

Just leave it be.

 

What sort of damage Jamie and what are the reasons?

 

I have just fitted a Turbosmart supersonic and would like to know more about the possible damage that may/may not occur.

 

[the squiggle]

Righto

The Impreza runs off the MAF sensor when in open loop fuelling, when you are giving it some stick. The Mass Air Flow will meter the amount af air being drawn into the engine and inject the corrosponding amount of fuel amount to achieve a rich enough Air to Fuel Ratio when on boost/load conditions.

When you release the throttle, to change gear or slow, on a std recirc dump valve, the pressurised air will be dumped back into the inlet tract between the MAF and turbo inlet. When the throttle is closed on gear change on slow down the ecu will inject a corresponding amount of fuel to achieve a satisfactory AFR to compensate for the extra volume being drawn in. When you fit a Vent to Atmos dump valve, the pressurised air will be released to the atmosphere when the throttle is closed but the ECU will still dump extra fuel in trying to achieve a satisfactory AFR. The ECU thinks there is an extra volume of air being drawn in the engine and will inject the right amount of fuel to compensate, this metered volume of air has now been dumped into the atmosphere instead of the inlet tract. A std ECU has no way of knowing that the Air volume that has passed the MAF , which has been metered for and compensted for accordingly has been released outside the inlet tract instead of being drawn into the engine. This will in turn make the AFR be very RICH due to the air part of the AFR being expelled through a valve the ECU has no knowledge of 

The extra fuel that is being drawn into the engine, minus the volume of air the ECU was expecting will do 1 of 2 things.

1. It will explode when the rich mixture hits the piston crown, giving a flash of lift off DET. At full boost and at the point of ignition the temp of the exhaust gases can average 800 and hit 900 - 1000 degrees centigrade after a spirited drive, the crowns of the piston at the point of ignition can be as high as 700 - 800c. This tempreture is more than enough to ignite the fuel mixture before the spark can do the job and be a cause of lift off det and lift off dat can be damaging as DET under load 

2. It will not expolde but as the mixture has ignited by the spark from the plugs and the flame front travels across the piston, by the time the exhaust valve has opened on the exhaust stoke the overrly rich mixture has not fully burnt by the inappropriate igntion level . Sometimes the rich fuel vapours not burnt from the time alloted in the combustion process will pop in the exhaust housing of the turbo when the gases exit the combustion chamber. Sometimes these pops will be sufficient to produce a a flame strong enough to travel the length of the exhaust syatem resulting a nice wee flame for everyone to go aaaaaawwwwww at but every time you do not get a flame the unburt fuel will be lingering somewhere in the exhaust tract, headers, hot side of turbo or even the chamber walls

The atomised fuel droplets that cling to the wall in the combustion chamber will clean the oil off the walls of the piston bore every time the overly rich Air/Fuel mixture is being drawn into cylinders. The unburnt fuel mixture will get past the compression and oil control rings due to petrol mixture being a lot finer than oil and the excess mixture that has not been ignited will stick to the cylinder walls due to the condensation effect of the AFR that is being pumped into the engine every time the inlet valves open, mixture being around 10-30c and the walls of the cylinder being around 200 - 400c, the retaining temp from the previous combustion cycle which at 6000 rpm (avg gearchange rpm) would have happened millisecs beforehand . This fine petrol mixture will be transferred to the oil in the sump, getting past the oil control rings as atomised fuel is a lot finer than thick engine oil. The classics lubricated the piston bores and under the piston crown with the end of the crank scooping oil up and throwing the oil up the bores, apart from STI RA's which had under crown oil cooling jets to cool the underside of the piston.  The oil that has been thrown up by the crank to lubricate the bore is prevented from entering the combustion chamber by the rings on the piston but atomised fuel can easily get past these rings assisted by the pressurised gases in the combustion chamber above helping it on its way and once past the rings the tiny droplets of fuel will soon find its way to the sump abley assisted by the laws of gravity.  Over time these droplets of fuel will be sufficient to start to thin the oil down to a dangerous level and increase the chance of picking up a big end bearing

My advice for the peeps running a Vent to Atmoshere is to, apart from dump them in the bin, is to increase the regularity of oil changes.

Hope this helps

All my own work

[corsa]

you could have just used the bottom bit instead of the encyclopedia Granty!!

 

My advice for the peeps running a Vent to Atmoshere is to, apart from dump them in the bin, is to increase the regularity of oil changes.

 

Keep things simple, it doesnt confuse.

[_jac_]

Will a car that has been mapped with a vent to atmoshere be a safe ?

[d19yda]

thanks for the breakdown TheSquirrel555  it was very interesting and by your extensive knowledge i believe that your more mechanically educated than me so im going trust you 100% and bin the dump valve idea.

That was a lot of effort you put into my reply. Appriciated.

Davie

[the squiggle]

Will a car that has been mapped with a vent to atmoshere be a safe ?

Yes because the mapper can switch the fuel off on the over run

[the squiggle]

you could have just used the bottom bit instead of the encyclopedia Granty!!

 

My advice for the peeps running a Vent to Atmoshere is to, apart from dump them in the bin, is to increase the regularity of oil changes.

 

Keep things simple, it doesnt confuse.

That may well be Davie but you did ask and i quote

You have a re circulating Dump valve. Its factory fit.

Leave it as it is.

Fit an after market "Dump to Atmosphere" valve and you run the chance of causing engine damage.

Just leave it be.

 

What sort of damage Jamie and what are the reasons?

 

I have just fitted a Turbosmart supersonic and would like to know more about the possible damage that may/may not occur.

 

 If you did not want to know then why did you ask?

You could have asked, i have have fitted a VTA dump valve to my car anyone have some advise to best look after the engine with one of these valves fitted?

Best advise is to remove the valve, fit the std recirc and also  fit a Soda Stream maker to the pax seat, this will give the noise to scare the grannies  and provide a refreshing soda drink as well

That fecking reply took 3 hours to write

[RA Dunk]

 fit the std recirc and also  fit a Soda Stream maker to the pax seat, this will give the noise to scare the grannies  and provide a refreshing soda drink as well

 

LoLoLoL!!! []

next question, what is the best way to remove soda stream stains from the passenger seat

[]

[corsa]

[H] cool reply Grant, thanks for your valued reply.

[the squiggle]

[H] cool reply Grant, thanks for your valued reply.

No problem Davie

Pleasure to help

[jamie_wood]

All these posts and the second post said it all ![:|]

[_jac_]

good post Grant its good to see how it all works... that way we can have a better understanding of the workings

of a scooby engine rather than a no don't do it...

cheers

JAC 

[kloon]

Righto

The Impreza runs off the MAF sensor when in open loop fuelling, when you are giving it some stick. The Mass Air Flow will meter the amount af air being drawn into the engine and inject the corrosponding amount of fuel amount to achieve a rich enough Air to Fuel Ratio when on boost/load conditions.

When you release the throttle, to change gear or slow, on a std recirc dump valve, the pressurised air will be dumped back into the inlet tract between the MAF and turbo inlet. When the throttle is closed on gear change on slow down the ecu will inject a corresponding amount of fuel to achieve a satisfactory AFR to compensate for the extra volume being drawn in. When you fit a Vent to Atmos dump valve, the pressurised air will be released to the atmosphere when the throttle is closed but the ECU will still dump extra fuel in trying to achieve a satisfactory AFR. The ECU thinks there is an extra volume of air being drawn in the engine and will inject the right amount of fuel to compensate, this metered volume of air has now been dumped into the atmosphere instead of the inlet tract. A std ECU has no way of knowing that the Air volume that has passed the MAF , which has been metered for and compensted for accordingly has been released outside the inlet tract instead of being drawn into the engine. This will in turn make the AFR be very RICH due to the air part of the AFR being expelled through a valve the ECU has no knowledge of 

The extra fuel that is being drawn into the engine, minus the volume of air the ECU was expecting will do 1 of 2 things.

1. It will explode when the rich mixture hits the piston crown, giving a flash of lift off DET. At full boost and at the point of ignition the temp of the exhaust gases can average 800 and hit 900 - 1000 degrees centigrade after a spirited drive, the crowns of the piston at the point of ignition can be as high as 700 - 800c. This tempreture is more than enough to ignite the fuel mixture before the spark can do the job and be a cause of lift off det and lift off dat can be damaging as DET under load 

2. It will not expolde but as the mixture has ignited by the spark from the plugs and the flame front travels across the piston, by the time the exhaust valve has opened on the exhaust stoke the overrly rich mixture has not fully burnt by the inappropriate igntion level . Sometimes the rich fuel vapours not burnt from the time alloted in the combustion process will pop in the exhaust housing of the turbo when the gases exit the combustion chamber. Sometimes these pops will be sufficient to produce a a flame strong enough to travel the length of the exhaust syatem resulting a nice wee flame for everyone to go aaaaaawwwwww at but every time you do not get a flame the unburt fuel will be lingering somewhere in the exhaust tract, headers, hot side of turbo or even the chamber walls

The atomised fuel droplets that cling to the wall in the combustion chamber will clean the oil off the walls of the piston bore every time the overly rich Air/Fuel mixture is being drawn into cylinders. The unburnt fuel mixture will get past the compression and oil control rings due to petrol mixture being a lot finer than oil and the excess mixture that has not been ignited will stick to the cylinder walls due to the condensation effect of the AFR that is being pumped into the engine every time the inlet valves open, mixture being around 10-30c and the walls of the cylinder being around 200 - 400c, the retaining temp from the previous combustion cycle which at 6000 rpm (avg gearchange rpm) would have happened millisecs beforehand . This fine petrol mixture will be transferred to the oil in the sump, getting past the oil control rings as atomised fuel is a lot finer than thick engine oil. The classics lubricated the piston bores and under the piston crown with the end of the crank scooping oil up and throwing the oil up the bores, apart from STI RA's which had under crown oil cooling jets to cool the underside of the piston.  The oil that has been thrown up by the crank to lubricate the bore is prevented from entering the combustion chamber by the rings on the piston but atomised fuel can easily get past these rings assisted by the pressurised gases in the combustion chamber above helping it on its way and once past the rings the tiny droplets of fuel will soon find its way to the sump abley assisted by the laws of gravity.  Over time these droplets of fuel will be sufficient to start to thin the oil down to a dangerous level and increase the chance of picking up a big end bearing

My advice for the peeps running a Vent to Atmoshere is to, apart from dump them in the bin, is to increase the regularity of oil changes.

Hope this helps

All my own work

 

Grant, would you like that read back to you in an Aberdonian accent on Friday night ? [] 

[jamie_wood]

good post Grant its good to see how it all works... that way we can have a better understanding of the workings

of a scooby engine rather than a no don't do it...

cheers

JAC 

 

Will get my coat [:|]

[scoobaroo]

Grant, could you repeat that, as i missed it first time round []

Marty. ptttcccchhhhhhhhhh.

[kassam]

alright grant so what about the "Turbosmart Dual Port dump valve, for Subaru Impreza" 

A high

performance re-circulating and atmospheric dump valve in one.

would this cause the same problem or is i just the same as all and u

wouldnt recommend it?

u can check it out in www.scoobyworld.co.uk

   

[insane clown]

this is what the clubs about!!!....detailed answers. .......i prefer long detailed answers!...it's good to talk. []

every reply is important isn't it!!??........good stuff.

mark