External Wastegates.

[cheekychimp]

I have a twin port actuator on my internally gated turbo. I understand the difference between the internal gate utilizing a flapper and the external gate having a sort of diaphragm but I always believed the concept of using twin ports to better regulate boost was similar in both designs.

But how to you connect these up? In a single port actuator the boost solenoid from the boost controller can only be connected to the one port. When you have two ports how are you guys routing the lines? I had this discussion with Aaron quite some time ago and some of the fancy electronic boost controllers allow you to run two boost solenoids with one for each port. However the more I read the more I am getting concerned about reliability and wondering if I should just use an MBC.

Essentially I just need to know how to connect an MBC up properly to a "twin port actuator".

 

[Diego]

I'm glad you asked because I was just about to write something similar as I need some teachings on this as well.

 

[3rdstrikedsm]

I have just always used the top port to hold boost better on high boost (over 30) and just hooked up a mbc just like normal but try to match the spring as close as you can to your desired boost then use the bc to fine tune it, This is if I understand your question correctly?

 

[4thStroke]

I've always used the bottom port with a MBC. I was spiking 32psi, but it tapered to 30psi out the top. I wonder if it would have help the 32psi out the top if I did plumb the top port to a boost reference.

ECMLink has a nice write up on how to plumb an EBC using one or both ports.

 

[cheekychimp]

Spence,

Is that write up in the forums or in the downloads/wiki section?

 

[broxma]

This will answer your question.

click

Essentially the top port goes unused, as long as the spring is able to hold back the exhaust pressure. If this is not the case, you tee off and use a vented line on the top port with a boost controller. Essentially, the bottom of the diaphragm will be at spring pressure plus boost on the surface area of the diaphragm. Adding the top bleed line adds pressure on the top of the diaphragm helping to keep the spring closed.

I have never understood how this system would work with an MBC, interrupt style boost controller, on the top port. It would seem to me, that in that setup, the bottom would be at full boost, and the top would be at zero WGDC until the spring pressure of the MBC was overcome, at which point, the pressure of both the bottom and the top would rise together. The vent may be the key here honestly, but not a lot of specifics into the size of the vent are mentioned on the Tial site, so I assume the vent is to allow the diaphragm to return to a closed position, relieving the vacuum in the top chamber once the MBC closes. Having a bleed type controller on top makes sense to me though as you could regulate a percentage, more or less, or total boost the top of the diaphragm would see.

I just run it with an MBC on the bottom port and call it a day.

/brox

 

[4thStroke]

I meant to post the link.

click

 

[cheekychimp]

Thanks guys that's very useful. Actually Brox, unless I have misunderstood those diagrams that you posted this all actually makes sense to me. If you are using an MBC which routes air to both ports it stands to reason that by equalizing pressures on both sides you can keep the gate closed maintaining full boost without worrying about the spring pressure which I guess is what really closes the gate after you let off. The problem here would be getting the gate to open at preset boost.

I guess if you say wanted 26 psi you would set the MBC to around 28-30 psi and 'bleed' the top to 26 psi so that at that pressure you have more pressure at the bottom than the top opening the valve.

I can see an EBC and two BCS' achieving the same thing and arguably being more accurate when things are working correctly but it seems more prone to failure.

I have heard those Ingersoll/Rand valves offer very accurate boost control but that setting boost control via ECMLink can be complicated (although extremely reliable once set up correctly) I'm tempted to use the Ingersoll valve with a stand alone boost controller!

 

[broxma]

My only question was, if you had equal pressure top and bottom of the diaphragm, then wouldn't it essentially be back at spring pressure, which is why you would use the top port in the first place...spring pressure isn't enough? And since the MBC effectively stops any boost signal until it's spring pressure opens it, how does the gate open? Boost on the bottom would be fighting the top pressure. It would have to have enough pressure to overcome the pressure coming in on the top and the spring combined.

I think of it like this. Let's set the top MBC to say 15 PSI, and the gate has a 10 PSI spring. At boost pressures above 10 PSI, the gate would open due to pressure going into the bottom port, the top port would be doing nothing because the MBC would still be closed(Until 15 PSI). So at >10 PSI the gate opens. Then at 15 PSI, if it got that far, the top port MBC opens up and does what? I would think it would shut the gate yes?

Unless the gate is specifically designed so that the surface area differential between the top and bottom of the diaphragm allows for such magic. It's all still confusing to me hence the single MBC/bottom port hook up I use. If anyone can really nail the way the two port system works with an MBC on the top port, I'm all ears. I can see how a variable bleed valve might work if you could specify a boost pressure in the top port and all else would vent. That I can see.

/brox

 

[4thStroke]

ECMLink boost control isn't very tough to set up at all, but the wiki makes it seem somewhat confusing. I didn't use the wizard to dial in boost. Once I got the duty cycle dialed in, then I set the target boost table once error correction was turned on. Just take your time when trying to dial duty cycle so you don't way overshoot your target. There are some other nice tricks to try out once the car is at a safe dial in. If you want some help getting it dialed in, PM me and I'll try to point you in the right direction.

Once it is set up, the log looks beautiful.

I did have an issue though, I am one of very few and have not found a solution, nor has anyone else. My waste gate would flutter once the solenoid started working. The car just didn't pull very smooth. I'm back on a MBC /ubbthreads/images/graemlins/frown.gif

 

[cheekychimp]

Spence I appreciate that. I'll need to get that Solenoid and I am also having issues, not with DSMLink so to speak but with the ECU. I know everyone says that a 91 and a 90 ECU only require a change of wires but I am beginning to wonder if JDM wiring means that that is NOT the case. According to the ECU pinouts it shouldn't make a difference but I CANNOT get this car to run with a USDM ECU. I'm currently back running native JDM code in a JDM ECU. I'm going to have to spend another day troubleshooting at some point after which I might be forced to trade up DSMLink for V3 and take Thomas up on his offer of doing a cheap non-EPROM JDM 90 ECU conversion and hope that works.

I'll holla when I've sorted out those issues one way or another.