The Off Topic Thread.

[k31th]

If you connect the "bottom" port to your wastegate control solenoid, it'll be the same scenario as in with a stock internal gate, e.g. the amount of pressure referenced holds the WG closed longer or will open at "minimum" boost pressure rating of the diaphragm+spring combination. If you connect the "top" port also then if you supply vacuum here you'll have the WG open earlier and if you supply boost, it'll hold the WG closed longer. Only really "smart" boost controllers can do both the bottom port (bleeding small incremental amounts of pressure off so that the WG opens slower or faster depending on changes the WCS supplies) and the top port (which supplies pressure to help the bottom port to keep the wastegate closed strongly in the process of reaching the desired boost level above the minimum).

 

Basically the bottom port minimum pressure is diaphragm+spring and the boost controller allows you to go higher but to a limit. Adding pressure to the top port will allow you to run as much boost as you can supply to the top port and it'll get to maximum desired boost as fast as possible and then it'll bleed everything once it opens; e.g. wheelspin city on the street  

 

Just vent the top to atmosphere and have a stiff enough spring for your desired minimum boost and let the factory boost control run the boost control on the "bottom" port up until you get your desired maximum boost level if it happens to be higher than the spring-rated-boost.

[biddie_fiddler]

Cheers for some clarification @Slowxr6t @k31th  

 

This method appears to be extremely popular because its so simple, interesting to see other methods too though!

[Puffwagon]

1 hour ago, biddie_fiddler said:

Falcons are fitted with a very basic 2 port solenoid. It can either be open to let the high pressure gas flow, or closed to prevent the gas flow. I'm assuming this is also done via some form of modulation technique too. Am I right so far?? Hope so.

 

Yeah nah, they have a 3 port solenoid that works exactly how a 3 port solenoid works. Below are ways you can hook it up.

 

The spring in your gate will make roughly double it's rating as boost, if it has no boost reference to the gate.

If you run a hose from the compressor housing to the bottom of the gate, you will get roughly the spring pressure as boost.

If you run a hose from the compressor housing to the top of the gate, you will get a minimum of double the spring pressure plus whatever the turbo can provide until the exhaust manifold pressure can push the gate open. Simply put, sh*tloads of boost.

If you run a hose from the compressor housing to the solenoid and from the solenoid to the bottom of the gate, you will get anywhere from the spring pressure up to roughly double the spring pressure, depending on solenoid duty cycle.

If you run a hose from the compressor housing to the solenoid and from the solenoid to the top of the gate, you will get anywhere from roughly double the spring pressure, up to as much as the turbo can make until the exhaust manifold pressure can push the gate open, depending on the solenoid duty cycle.

 

Worth noting sometimes using the top of the gate will max out a turbo and sometimes it will open the gate before the turbo is maxed out.

[k31th]

The funny thing is, with the "3 port solenoid" in our OEM solenoids, the "return the bled air" is never returned to the intake, it's just vented to atmosphere. Just the two ports are used, "input/output".

 

In Puff's examples above, only Option 3 is what you should do to your car... unless you either want to run bad boost control with your minimum as your actual maximum (Option 1) or you'll make engine-destroying overboost (Option 2 or 4).

[biddie_fiddler]

Just always thought of the factory solenoid as a basic 2 port, because there are only 2 ports on it 🤣

 

I guess it'd make sense that there is in fact a 3rd, but its not a barb and instead probably just a hole somewhere on the thing

[k31th]

As you can see, on the left side is the electrical connector on the top part and the "boost pressure input" on the bottom part. On the top-right is the "wastegate control output" and the bottom-right black part is the 3rd unused port which just vents to atmosphere.

 

On another note for external wastegates; I wonder how hard boost would be to control if you used the bottom-right port and put that to the top of the wastegate and used the top-right to go to the bottom of the wastegate. The ratio of bled/used air may not match up to a reasonable boost control... hmm

[biddie_fiddler]

I'm learning so much today 😄

[Puffwagon]

This is the proper way of doing what you're thinking of @k31th  Here is the link, I was gonna post about it earlier but was still half asleep lol.

 

[k31th]

With that picture you'd be setting it up so the pressure outcome is reversed... e.g. the more you bleed off, the earlier your wastegate will open (but the wastegate will be strongly held closed). Normal single-bottom-port connections will increase boost as you bleed off (wastegate won't be as strongly held closed as the pictured example, I would surmise)

 

What I was thinking is have no t-piece and have the turbo go into the 'input' of the solenoid (as it does on the OEM falcon one), have the "output" of the solenoid go into the "bottom wastegate port" (as it does for the OEM wastegate) and have the 3rd output (where the 'bled' solenoid air goes to) connected to the "top wastegate port" (e.g set it up like a 4-port solenoid in your link, but instead of it having an "exhaust/bleed" port as the 4th port, use the 3rd port on a 3-port and instead of venting it to atmosphere connect it to the top of an external wastegate). Would this sort of setup make boost control too much of a juggling act of pressure received at the bottom port versus the top port?

[Puffwagon]

The air needs to bleed off cos the wastegate is a sealed system. I think it would equalise after a second or two and you'd be back at the equivalent of no boost reference.