Understanding boost management.

[Steiner]

I installed an aftermarket wastegate actuator and manual boost controller last night. Per the WGA manufacturers instructions, I lowered the boost controller to the lowest possible setting and then began adjusting the boost at the wastegate. Once I got to 13psi I began increasing the setting on the MBC. I'm still getting it dialed it in (eventually I want to spike to 18psi and then hold 16psi through the power range), but I really don't fully understand the raw physics of what I'm doing. I hate being a results whore. I wanna understand what's going on.

This is the setup I'm running: Turbo to MBC > MBC to WGA.

[Polygon]

Did you forget about the Forced Induction forum?

I think you will find more input there.

[Steiner]

I didn't even know there was one. Thanks for the heads up.

Can I ask a mod to move this?

[LjasonL]

What are you trying to understand, how the boost controller and wastegate control boost? The wastegate has a hose that runs to the outlet of the compressor housing for "signal", if you set it to 13 psi for example, once there is 13 psi on the outlet of the compressor (the part of the turbo that goes to the intercooler and eventually the throttle body), there is also 13 psi going through the signal hose (signal hose being the green turbo to wga line in your pic). This opens a flapper valve in the wastegate, and now the exhaust flow from the engine leaves through the now open flapper valve and bypasses the turbine, instead of going into the turbine and continuing to spool the turbo. A boost controller goes in the signal hose and limits the amount of air that can flow through, so even though you have your 13 psi coming out of the compressor, 13 psi doesn't actually make it to the wastegate yet so it won't open and the turbo will keep spooling. By adjusting the boost controller you can control how much air can pass through it, when less air can pass through it takes longer for the 13 psi to build at the wastegate and you end up with more boost, with the boost controller fully open the wastegate will open at 13 psi, you can't turn the boost below what the wastegate is set at, only above.

I don't always make complete sense, so if you don't understand any of that ask and I'll try to reword it.

[Steiner]

OK, I think I'm getting it a little now.

So if the WGA has been set to boost to 15psi can turning down the MBC drop that to say 13psi...or does a boost controller just limit the spike/speed at which the turbo spools up. I guess what I don't understand is what the MBC does since I have an adjustable WGA to regulate boost levels?

[LjasonL]

You can't use the boost controller to turn below what the wastegate is set at, only above. One advantage you'll get by having a boost controller is faster spool up. When just using the wastegate only, the flapper valve will open slowly as you get close to the set boost level, and as it starts to open early you will lose some exhaust through the partially open valve instead of having it all to spool the turbo. With a boost controller the pressure doesn't get to the wastegate till later and it hits all at once, so there is no early opening and lost exhaust.

[LjasonL]

Hmm... if you wanted to get creative, you could set the wastegate at a "low boost" setting for daily driving and the boost controller at a "high boost" setting for racing. Put "Y" connectors on both ends of the signal hose so you can run one line through the boost controller and one bypassing it. Have the 1st Y connector with some kind of switch you can turn where only one path is open at a time, and now you can go from low boost to high boost at the flip of a switch! Not to mention the high boost race setting would also be the fast spool up setting, and the low boost one wouldn't have the part throttle boosting issues of the MBC.

This actually sounds like a really nifty cost effective setup.

[Steiner]

Originally Posted by ldelaysionl

Hmm... if you wanted to get creative, you could set the wastegate at a "low boost" setting for daily driving and the boost controller at a "high boost" setting for racing. Put "Y" connectors on both ends of the signal hose so you can run one line through the boost controller and one bypassing it. Have the 1st Y connector with some kind of switch you can turn where only one path is open at a time, and now you can go from low boost to high boost at the flip of a switch! Not to mention the high boost race setting would also be the fast spool up setting, and the low boost one wouldn't have the part throttle boosting issues of the MBC.

This actually sounds like a really nifty cost effective setup.

Good idea...but lemme get this thing tuned first...lol.

So how would you recommend tuning this setup for maximum perfomance...when tuning the WGA should I start with the boost controller all the way open (lowest boost) or all the way closed (highest boost)?

[LjasonL]

All the way open. With it all the way closed, the signal will never get to the wastegate, it will not open, and the turbo will keep spooling till something blows up

[Steiner]

So once I get the WGA dialed in to 16psi I'll begin turning up the boost on the boost controller. How will I know when the boost controller is dialed in properly...i.e. set to the same psi as the WGA...it's not an EBC.

[LjasonL]

Once the wastegate is set to 16psi, start tweaking the boost controller till your get more than 16 psi, then go back down to 16. It will probably take a little time. If you're going for 16psi you might have an easier time setting the wastegate to like 14psi then raising it 2 more with the boost controller.

[Steiner]

OK. I think I'm seeing the light now. Thanks for the knowledge. This helps me a lot!

[Steiner]

After some trial and error I've finally got the WGA set to hold 14psi through redline. I've been slowly cranking up the boost with the MBC but it doesn't seem to be doing anything...or at least I haven't noticed anything yet. What are the symptoms of the MBC catching up to the WGA? What am I looking for?

[LjasonL]

The boost controller won't change anything till it's closed enough to slow down the air flow to the wastegate. There's not really a way to tell other than turning it a little and testing it. Told you it would take some time

[Steiner]

Ah ok. I'm enjoying the trial and error. The beauty of F/I is that 1/2 turn on the MBC or WGA is good for about 10hp. The NA guys would guve their left arm for that kind of tune-a-bility. I can't see myself ever owning another naturally aspirated car.