[RUNSOK]

Anybody here ever tested the difference if there is any controller makes on power. For example, anyone ever dynoed a stock car and a stock car with just valve controller to see opening the valves 100% makes any difference on the power curve of the S58. I am really curious to see if any gains can be made with just a controller. Especially on the top end I assume it should make a difference. Stock car never opens the valve 100 percent.

[Diesel power]

Other posts on here have said aftermarket intake and full exhaust add less than 10 HP total. I don't think a valve controller adds much of anything.

[mike@x-ph.com]

it's not a good idea to go wide open throttle with the valves closed.

whether its open 70% (stock) or 100% (with a valve controller), the sound difference is noticeable but don't expect any significant power increase.

[Needsdecaf]

Originally Posted by RUNSOK

Especially on the top end I assume it should make a difference. Stock car never opens the valve 100 percent.

This only matters if it's a restriction. I mean, take the following example. You have a bucket, with a hole in it. That hole is capable of flowing 2 gallons per minute of water. You fill the bucket with a hose capable of flowing 2 gallons per minute of water.

Now, enlarge the hole in the bucket so it's capable of flowing 3 GPM of water. But you're still filling it with a hose capable of flowing only 2 GPM. Is the water going to come out any faster? No.

I would expect literally zero performance gain from a valve controller.

[chris3g]

I’ve looked at the factory calibration regarding valve control and in sport plus with the exhaust button on, the car commands 100% open position when the rpm > 4200 and torque request > 340NM. I’m not sure where the idea that the car never opens the valves 100% comes from but as far as I can tell it’s objectively untrue. The value of a valve controller is to open the valves all of the time, at lower rpm /load when the factory calibration does only open them partially or not at all.

[RUNSOK]

Originally Posted by Needsdecaf

This only matters if it's a restriction. I mean, take the following example. You have a bucket, with a hole in it. That hole is capable of flowing 2 gallons per minute of water. You fill the bucket with a hose capable of flowing 2 gallons per minute of water.

Now, enlarge the hole in the bucket so it's capable of flowing 3 GPM of water. But you're still filling it with a hose capable of flowing only 2 GPM. Is the water going to come out any faster? No.

I would expect literally zero performance gain from a valve controller.

I am not arguing with u so don't take this the wrong way. I am not an engineer or anything. But to me from that example u showed, the bucket will be out of water way before the original situation. (2gpmin/2gpmout) what i am saying is in the 2nd scenario, the 2gpm hose filling the bucket can't keep up with the hole that empties the bucket at a faster rate.(3gpm) there fore bucket will be empty at one point. I don't know. Like I said I am not an engineer. So not arguing with you. Just trying to understand. There is a restriction of flow at the end of the exhaust system. So, why would not we see any improvement. If let's say valves were open 20 percent at full throttle vs 100 percent open how can that be no difference. May be there is a point of diminishing returns where bmw engineers figured out at after a certain percentage of valve open it doesn't make difference in power. But changes the sound mostly and some clients may not like the loud sound so they did not open it fully..

[RUNSOK]

Originally Posted by chris3g

I’ve looked at the factory calibration regarding valve control and in sport plus with the exhaust button on, the car commands 100% open position when the rpm > 4200 and torque request > 340NM. I’m not sure where the idea that the car never opens the valves 100% comes from but as far as I can tell it’s objectively untrue. The value of a valve controller is to open the valves all of the time, at lower rpm /load when the factory calibration does only open them partially or not at all.

That's great to know. From what I saw in the forum and YouTube it sounded like valves don't 100 percent open no matter what.

[Needsdecaf]

Originally Posted by RUNSOK

I am not arguing with u so don't take this the wrong way. I am not an engineer or anything. But to me from that example u showed, the bucket will be out of water way before the original situation. (2gpmin/2gpmout) what i am saying is in the 2nd scenario, the 2gpm hose filling the bucket can't keep up with the hole that empties the bucket at a faster rate.(3gpm) there fore bucket will be empty at one point. I don't know. Like I said I am not an engineer. So not arguing with you. Just trying to understand. There is a restriction of flow at the end of the exhaust system. So, why would not we see any improvement. If let's say valves were open 20 percent at full throttle vs 100 percent open how can that be no difference. May be there is a point of diminishing returns where bmw engineers figured out at after a certain percentage of valve open it doesn't make difference in power. But changes the sound mostly and some clients may not like the loud sound so they did not open it fully..

Well, I am an engineer so I got you covered.

Let’s change my example from a 3 gpm hole and enlarge to a 5 gpm. Either way, the hole flows more gpm than the hose can fill the bucket. So decreasing the “restriction” makes no difference because it was never a restriction to begin with. Make more sense now?

If the valves open at less than 100% has enough capacity to flow as much exhaust gas volume as the engine is capable of WOT, opening them to 100% won’t make a difference.

[SwankPeRFection]

Originally Posted by chris3g

I’ve looked at the factory calibration regarding valve control and in sport plus with the exhaust button on, the car commands 100% open position when the rpm > 4200 and torque request > 340NM. I’m not sure where the idea that the car never opens the valves 100% comes from but as far as I can tell it’s objectively untrue. The value of a valve controller is to open the valves all of the time, at lower rpm /load when the factory calibration does only open them partially or not at all.

In a turbo car, a little bit of back pressure isn’t a bad thing, so it can actually be used to help spool or even control an over boost condition outside of what the stock wastegate can handle (on some cars)… but this is usually seen due to stock power restrictions, etc.

All that said I think people assume it never goes to 100% because they’re not out there hanging off the bumper and looking the exhaust, they just assume base on other standstill conditions or what they’ve “heard”.