Power differential between exhaust valve open and closed

[Daveop]

Was wondering if anyone cared to guess what the power difference, if any, between closed and open valve modes on the exhaust.

For example if you had one of the tools on the market which allows you to force the valves open or closed, would you notice any acceleration differences between having valves open and closed?

[Ian1973]

I'm sure it's nothing more than sound leading peoples brains in believing there is a slight improvement

You don't need a tool to force it open, it can be done by simply unplugging the solenoid, or whatever they use down there.

[Daveop]

Originally Posted by Ian1973

I'm sure it's nothing more than sound leading peoples brains in believing there is a slight improvement

You don't need a tool to force it open, it can be done by simply unplugging the solenoid, or whatever they use down there.

So no perceptible difference in back pressure (and resulting power) between the two then. Just sound basically. Good to know.

[gtrsam]

I highly doubt it is just sound. Oem mode opens the valves at wot so why would you ever run it closed with the valve mod

[BMWJ]

Originally Posted by Ian1973

I'm sure it's nothing more than sound leading peoples brains in believing there is a slight improvement

You don't need a tool to force it open, it can be done by simply unplugging the solenoid, or whatever they use down there.

You would actually need to force it closed, since it's always open at WOT

[Ian1973]

Originally Posted by BMWJ

You would actually need to force it closed, since it's always open at WOT

I mean force it open all the time. That is simply unplugging the solenoid when it's already open.

I do not know if there is any power added with the valve open, just was saying the sound itself would probably make people think there is more power. I'm sure if there are gains, it's like 1-2hp, which of course you could loose 5lbs to get.

[pikkagtr]

Originally Posted by BMWJ

You would actually need to force it closed, since it's always open at WOT

If you unplug the solenoid when valves are closed, they will stay closed no matter what throttle position is
This can also be done for opened at all times.
The sound is better but I doubt there is a performance difference

[YasM3]

There may be a slight backpressure difference but as far as power, I bet its very minimal.

Anyhow the car does not run the valve closed @ WOT ever so there really is no comparison to be made. Unless you are trying to go for some super sleeper WOT pulls lol

[mc3456]

According to my ear dyno, it measures about 80hp, which translates to 10hp due to reality loss.

[CanAutM3]

I am pretty sure there is not much power difference at low RPM with the valves either open or closed.

I am not so certain at higher RPM though. BMW do mention a reduction of back pressure with the valves open at higher RPM. I will try to find the quote.