Which is better for turbo setup: BOV or Dump valve?

[MMamdouh]

which is better to have on a given turbo setup? what are the +ve and -ve side of both valves?

MMamdouh

[klonek78]

which is better to have on a given turbo setup? what are the +ve and -ve side of both valves?

MMamdouh

when you have mapsensor (don't have airflow sensor) you can use BOV (better sound ) or DV - your choice. There isn't any diff. between them for engine to work. when you have airflow sensor you must use DV, becasue if "air" has been already "counted" and must return to intake pipe.

[PrecisionBoost]

I'm a little confused about what you mean by "bypass valve"

You have two choices.... dump air to atmosphere or dump it back into the intake.

Dumping air back into the intake before the turbo makes the system more efficent but it also increases the temperature of the intake air before the turbo.

When you say "bypass valve" I immediatly think of waistgate on the turbine side.... since it allows the exaust to bypass the turbo and reduce the pressure going to the turbine side of the turbo.

[Audacity Racing]

i personally like recirculation valves better than bov's. if your intercooler is designed well enough for the system, you get better returns from a RV than a BOV. a lot of times, if your intercooler is to big and you get a massive pressure drop, you can recirculate to bring the temp up and thus raise the pressure

[MMamdouh]

I'm a little confused about what you mean by "bypass valve"

i was aming at the dump valve with that term.

MMamdouh

[MMamdouh]

when you have airflow sensor you must use DV, becasue if "air" has been already "counted" and must return to intake pipe.

in this case the air return point should be after the sensor to avoid counting the same amount of air twice... right??

MMamdouh

[klonek78]

when you have airflow sensor you must use DV, becasue if "air" has been already "counted" and must return to intake pipe.

in this case the air return point should be after the sensor to avoid counting the same amount of air twice... right??

MMamdouh

of course. DV return point is always after airflow sensor and before turbocharger.

[klonek78]

i personally like recirculation valves better than bov's. if your intercooler is designed well enough for the system, you get better returns from a RV than a BOV. a lot of times, if your intercooler is to big and you get a massive pressure drop, you can recirculate to bring the temp up and thus raise the pressure

but return point is before turbocharger and high temp of intake air won't be good for performance. It won't raise pressure in intake system, only raise temp of intake air.

[PrecisionBoost]

Our airflow is calculated from MAP, IAT, TPS sensors.... which are not affected by the position of the recirculation point.....you do have to worry about the point if you using a MAF (mass air flow) sensor. (like they do in the C20LET, C20XE )

[Stefan]

If there's no MAF before the turbo use an atmospheric dump valve (BOV) as close to the compressor outlet as you can.
If there is it's best to use a recirculating valve.


Stef

[klonek78]

If there's no MAF before the turbo use an atmospheric dump valve (BOV) as close to the compressor outlet as you can.
If there is it's best to use a recirculating valve.


Stef

I won't agree. BOV and DV should be used as close to throttle body (not compressor outlet) as it possible.

[MMamdouh]

what does the difference in valve position affect?

MMamdouh

[Stefan]

If there's no MAF before the turbo use an atmospheric dump valve (BOV) as close to the compressor outlet as you can.
If there is it's best to use a recirculating valve.


Stef

I won't agree. BOV and DV should be used as close to throttle body (not compressor outlet) as it possible.

No.
Think carefully about the function of the valve...
Think about the effects of losses incurred in having the airflow go through all the intercooling pipework and an intercooler...
Just because most people and many "tuners" do place them near the throttle does not mean it's the right way... Many engineers at professional levels of motorsport don't.
Placing the valve near the throttle rather than near the compressor outlet will cause a greater drop in boost/compressor speed between gearshifts and higher loads on the turbos thrust bearing.
If anyone says "what about response!" well an extra 2 ft of vacuum hose won't make a difference that you can tell...


Another benefit of mounting it near the compressor outlet is that the valve will be louder If you like that kinda thing

Stef

[klonek78]

If there's no MAF before the turbo use an atmospheric dump valve (BOV) as close to the compressor outlet as you can.
If there is it's best to use a recirculating valve.


Stef

I won't agree. BOV and DV should be used as close to throttle body (not compressor outlet) as it possible.

No.
Think carefully about the function of the valve...
Think about the effects of losses incurred in having the airflow go through all the intercooling pipework and an intercooler...
Just because most people and many "tuners" do place them near the throttle does not mean it's the right way... Many engineers at professional levels of motorsport don't.
Placing the valve near the throttle rather than near the compressor outlet will cause a greater drop in boost/compressor speed between gearshifts and higher loads on the turbos thrust bearing.
If anyone says "what about response!" well an extra 2 ft of vacuum hose won't make a difference that you can tell...


Another benefit of mounting it near the compressor outlet is that the valve will be louder If you like that kinda thing

Stef

but returning "airwave" will be dumped earlier before reach compressor.... don't you think so?

[Stefan]

The returning "air wave" in the days when turbo kits had no intercooler would have an adverse effect on the compressor.
However, these days where most people now use intercoolers, most of the waves energy is dissipated as it expands into the intercooler end tank and then into the intercooler core.
If no intercooler is used it is still advisable to mount it near the compressor outlet. The energy of the wave will be reduced by the effects of the "T" junction where the BOV is fitted.
The main point of installing the BOV after the compressor outlet is so the compressor does not have to pump air through all the piping and the intercooler. All these cause flow losses and the compressor requires hp from the turbine to overcome them. With no power supplied by the turbine because the throttle is closed the compressor will "coast down" quickly as it tries to overcome those losses. If the compressor can pump air direct to atmosphere after the outlet there's minimal losses to overcome, so the compressor requires less hp to overcome them and will "coast down" slower.
In translation it means there is less boost drop between shifts.

Stef