Wastegate Actuator Vacuum/Boost Source Options

[dirtysouth_msp]

I've noticed that, on our cars, it seems like the wastegate actuator vacuum/boost line is extremely long compared to many other setups. It seems to me that this increases the potential for our cars to have boost spike.
Many applications on other vehicles have a nipple on the turbo's outlet (where the hot-side cahrge pipe is attached) or on the hot-side charge pipe itself with an extremely short vacuum hose leading to the wastegate actuator. I may be mistaken, but I am guessing that this type of setup would produce a more accurate boost signal, therefore reducing the potential for boost spike. Any supported opinions on this would be appreciated...
If that type of setup would not be beneficial, what would be the best source?

 

[jmv]

sounds like an interesting idea, although i wouldn't know where the best source would be.

Do you have boost spike?? i know when i put on the ATP wga i had absolutely none.

 

[dirtysouth_msp]

My car has always had some, with and without the ATP actuator (more when not running stock boost). I have just seen a lot of other turbo systems with the setup I was talking about and wondered if it might help.

Here is an example of what I'm talking about. However, this one has the nipple on the turbo, a little futher down the outlet.

 

[Yellow MSP]

I've noticed that, on our cars, it seems like the wastegate actuator vacuum/boost line is extremely long compared to many other setups. It seems to me that this increases the potential for our cars to have boost spike.
Many applications on other vehicles have a nipple on the turbo's outlet (where the hot-side cahrge pipe is attached) or on the hot-side charge pipe itself with an extremely short vacuum hose leading to the wastegate actuator. I may be mistaken, but I am guessing that this type of setup would produce a more accurate boost signal, therefore reducing the potential for boost spike. Any supported opinions on this would be appreciated...
If that type of setup would not be beneficial, what would be the best source?

One small correction is that the outlet is on the compressor housing, or the charge pipe as you said, but that is the cold side, not the hot. As far as the spike issue, on my GSX I have it setup where a line from the top nipple on my BOV (crushed 1g) T'd off with a line running to the intake manifold provides the boost source leading to my mbc which then goes to the actuator. Completely different turbo and actuator (Evo III 16G with an internal wastegate) but boost held steady for me at 21 psi on the street. I would think it would be more of an issue with the actuator itself as JMV mentioned. If you think about it, the hose itself has a relatively small diameter. It does not take too much air to fill it, and if you are set for 6 psi, then it will fill to 6 psi pretty much instantly. Unless you had a line that wrapped around the car 6 times I can't see the line being at fault here (unless it was cracked or not on tightly of course).

Edit: I just read your post again and saw that you say hot pipe, not hot side. But the charge pipe will always be post turbo ('hot') so I guess that is a little redundant.

 

[dirtysouth_msp]

One small correction is that the outlet is on the compressor housing, or the charge pipe as you said, but that is the cold side, not the hot. As far as the spike issue, on my GSX I have it setup where a line from the top nipple on my BOV (crushed 1g) T'd off with a line running to the intake manifold provides the boost source leading to my mbc which then goes to the actuator. Completely different turbo and actuator (Evo III 16G with an internal wastegate) but boost held steady for me at 21 psi on the street. I would think it would be more of an issue with the actuator itself as JMV mentioned. If you think about it, the hose itself has a relatively small diameter. It does not take too much air to fill it, and if you are set for 6 psi, then it will fill to 6 psi pretty much instantly. Unless you had a line that wrapped around the car 6 times I can't see the line being at fault here (unless it was cracked or not on tightly of course).

Edit: I just read your post again and saw that you say hot pipe, not hot side. But the charge pipe will always be post turbo ('hot') so I guess that is a little redundant.

Huh?

Hot-side charge pipe = before intercooler

Cold-side charge pipe = after intercooler

The vacuum routing setup you refer to is the same as that used in the stock mazdaspeed. You are right it does not take much air to fill the vac hose, but I've always heard shortest is best when it comes to the WGA line and what could be shorter than the setup in the picture? I wonder what kind of effect it would have on vacuum to the wga?

 

[Yellow MSP]

Huh?

Hot-side charge pipe = before intercooler

Cold-side charge pipe = after intercooler

See my edit...I thought you were refering to the hot or cold side of the turbo itself, not the pipes. My mistake.

The vacuum routing setup you refer to is the same as that used in the stock mazdaspeed. You are right it does not take much air to fill the vac hose, but I've always heard shortest is best when it comes to the WGA line and what could be shorter than the setup in the picture? I wonder what kind of effect it would have on vacuum to the wga?

I agree that the shortest routing should theoretically be the best, I just have not seen a case where a longer line will affect the wastegate actuation. As far as vacuum, I would think it should be the same anywhere inbetween the turbo and manifold, so it should not make a difference. You could easily find this out if you had a nipple off your housing or charge pipe as you said and hooked it up directly to a boost/vacuum gauge. I don't have one on any of my cars, so I can't help you out there. Then again, a wastgate still should not open until the desired boost level is reached, and therefore should remained closed whether there is -20 in vac, 0 psi, or anything below what the bc is set to. So the level of vacuum would not matter. A bov needs vacuum to help it open once the throttle plate is closed, but this is just how I understand the wga to work. You can correct me if I am wrong.

 

[Kansei]

So do you want it on the hot side or the cold side? If there's like 2psi of pressure loss across the intercooler, wouldn't you want everything on the cold side so that your boost gauge and wastegate are reading the actual boost level that is entering the combustion chamber?

I'm new to the bewst thing. Building my kit right now

 

[terbow]

they are talking about using this as a source for the WG, so right off the turbo is best since thats what the WG affects directly. i wouldnt use it for a boost gauge cause u want to see whats going into the mani for that

So do you want it on the hot side or the cold side? If there's like 2psi of pressure loss across the intercooler, wouldn't you want everything on the cold side so that your boost gauge and wastegate are reading the actual boost level that is entering the combustion chamber?

I'm new to the bewst thing. Building my kit right now

 

[dirtysouth_msp]

they are talking about using this as a source for the WG, so right off the turbo is best since thats what the WG affects directly. i wouldnt use it for a boost gauge cause u want to see whats going into the mani for that

Yeah, talking about source for the wastegate. It seems like this setup would be better at preventing spikes and keeping the turbo from over boosting due to leaks after the intercooler, at the manifold and in other vac lines.

I agree, I would not use that source for a boost guage either.