solenoid boost control, simple questions about EBC ect

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I looked into EBC's a few years ago and came to the conclusion that they were just a fancier way of doing the same thing the standard MBC did.

since then some newer more interesting uses of boost control solenoids have come to my attention so I am trying to learn more.

I have heard of some stand alone CPU's using a solenoid to hold the waist-gate closed until the a preset boost is reached. This helping improve spool up time by not showing the waist-gate any boost pressure until it reaches a preset boost. keeping the WG completely closed rather than creeping open as it sees progressively more pressure with a standard BCS.
^ Is this correct?

Does this new breed of EBCs simply hold closed the solenoid until triggered by a hobs-switch and then open? or would that cause waist-gate flutter, if that's the case how is it controlled to hold a pressure using just a solenoid?

Learn me somethin' guys.

 

[the_mork]

In the case of my 3port BCS (modified FPRs) the solenoid remains closed until it is requested to open and allow boost through, then when it closes again it vents all of the air on the wastegate side.

There isn't a ton of increase in spool here because your regular MBC controlled wastegate is closed all the way until approaching the set boost point. The difference will be in the areas close to maximum boost but will be so minimal that you probably would never notice.

The usefulness of a computer controlled bcs is that you can easily set your boost consistently and alter your boost settings based on conditions. I can easily set my car to 22.5psi then quickly change it to 17psi with no guesswork, and if something changes such as a small boost leak or if I change intercoolers my boost will remain at its setting since it is controlled by a feedback loop and is capable of corrections.

The number one cool thing about computer controlled boost is conditional settings. I run no more than 18psi in first gear to reduce wheelspin and then I ramp up boost in 2nd gear after about 3700RPM which helps save the transmission and reduce wheelspin as well. Beyond that if I set it to do so my WGSC is based on TPS position so that half throttle might max out at 14psi instead of 23psi which makes a much more streetable car that doesn't always act like the accelerator is an on/off switch.

All of the stuff I've mentioned is available on an evo8 ecu with Tephra mod v7 and splicing the FPR solenoid that everyone hacks off anyways into the BCs wiring.

 

[Bender]

The AEM EMS uses something similar to what you mentioned. It is a duty table, and it opens the solenoid a certain %. That %, in conjunction with your wastegate spring pressure, determines your boost. There is a feed back as well, which will automatically raise and lower the boost to what you set it at. This comes in handy for saving a pump gas and race gas tune, without messing with your manual boost controller. Also, it allows you to have different boost in different gears / rpm's / speed. This can help eliminate wheel spin.

I have a GM BCS for sale if you need one. I have it on my AEM EMS, and it worked great. I just recently upgraded to new vacuum lines, and had to use an AEM BCS.

Also, it isn't a new breed. This has always been around.

 

[the_mork]

Also for the record 3port BCSs make really weird sounds. People who are unfamiliar with them may think that your car is broken, but as a DSMer people probably already think that many of the unique sounds your car makes are bad.

They make a pftpftpftpftpftpftpftpft sound very rapidly when your hitting full boost.

Although this sound may only be obnoxiously loud when your using a fuel pressure regulator solenoid as a BCS.

 

[Ceddy]

A 3-port solenoid connected to the top port of a external wastegate can help spool, especially if you have a light spring.

Connected to only the lower port the wastegate will start to crack open at 1/4 to 1/2 spring pressure. Adding air pressure to the top port helps keep the wastegate shut.

Not really anything new, two port wastegates have been around forever, most people don't take advantage of them though.

 

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Thanks for the responses guys. some things learned, others reaffirmed.

So it sounds like in order to maintain a set boots level the solenoid has to flutter in order to stay somewhere between the waistgate's two natural positions, open or closed. makes a fair amount of sense.

this also confirms that, for the most part they are just a fancier/easier/more convenient way of controlling boost. For an underpowered Awd the only advantage (other than the convenience factor) would be a very minimally better spool up time when compared to a MBC. although its worth mentioning that 1 person is hardly a scientific servey so if any one else want to chime in on spool up time i would be glad to hear it.

the note about TPS varied boost pressure is a really interesting notion. assuming you have a turbo that could deliver through most of your range it could make for good progressive feel. thats something i may some day look into as i find with my quick spooling little turbo i rarely get about 30-40% throttle even when enjoying a back road. makes ya miss a little Na roadster like the old miata where you really got to rev out the engine and use wot a good bit even when just playing around. (sometime i like wringing out underpowered cars... sue me. ) in the words of the immortal James May' you rev and rev and rev till all the vales come out and dance on the bonnet... and then you change gear!' But I digress..

This use of solenoid boost control by various EMS for the purpose of quicker spool time is whats new to me. i understand their use by traditional two (or however many) staged boost controllers either for traction advantages or street/ strip setting.. ect. I will probably end up using the BCS i have laying around to switch between stock boost and the mbc preset soon for just that convenience.

I do still want to hear more about the function of these solenoids and how they maintain a preset boost level.. is it merely by fluttering constantly as per the repose of a hobs-switch or is the control more finite.

Keep up the good discussion guys

A 3-port solenoid connected to the top port of a external wastegate can help spool, especially if you have a light spring.

Connected to only the lower port the wastegate will start to crack open at 1/4 to 1/2 spring pressure. Adding air pressure to the top port helps keep the wastegate shut.

ahhh see this is what i was getting at. the advantage of the solenoid controlled WG because of its partial opening before full boost. I will have to think about the 3 port setup though. I am having a hard time picturing that this late at night. maybe ill get it in the am, that or have more research to do

 

[Bender]

You pretty much got the grasp of it. I personally do the 3port BCS on a 2port wastegate in both my cars, and spool is a lot better. Well.. on the bigger turbos. There is a negligible difference in 16gs and the like.

I can get pictures if you are still having trouble visualizing it.. or even a screenshot of the duty map in the AEM software..

 

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i have a pretty good understanding of it now.

But i would love to see your maps if your offering.

thanks bender

 

[Bender]

Follow the link to a screenshot I took of my old tune. This kept 30 psi pretty steady on my old setup, and you can see how I have the solenoid disabled up to around 22 psi, then it opens half way, then it opens to where it needs to be. If it starts creeping past 30 psi, you can see I have the load really low to bring it back to 30.

Also look at the toolbar, where in the expanded menu you can see the logic it can use to determine what boost you want. Each option just brings up another table, only one axis will be Vehicle speed, or TPS %, etc.

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[the_mork]

FWIW this is how it is done with an evo8 ecu.

The first table is your desired settings and the second table is your base settings. The computer uses your base settings then corrects them to get to your desired settings if something changes that causes the base settings to not cause the desired settings. Personally I've just left error correction off because my base settings are dialed in where I want them and I no longer tend to think of boost in terms of PSI but instead as kpa or load (SD load is based off of manifold pressure).

The top axis is gear, this is set in another table based on RPM/speed and the left axis is RPM. It has more gears available than I have in my transmission but some evos have 6spds. Also the table on the right is wastegate duty cycle, how much of the time a wastegate is either closed or open. A higher number causes higher boost.

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[Bender]

Interesting, but I think you have it a little backwards.. Did you mean the higher the number, the closest it is it wastegate spring pressure, meaning the lower the boost.

I know it can be inverted depending on how you have your solenoid wired/plumbed in, but on your particular setup.. i doubt you want the most boost on the bottom of first gear..

 

[the_mork]

No, I stated it correctly. That section of the map is actually irrelevant because I'm below 190load which is the point at which wastegate control stops simply being 100%.

I saw that when I looked at my map and wondered why I did that but it works and it isn't an issue. When I pull the car out in spring I will clean it up. I think part of it was that I had a friend driving who doesn't know how to launch when I was tuning so I was just cutting down values until I stopped getting wheelspin from a dead stop just by mashing the pedal. Like I mentioned though that part of the map doesn't do much.

 

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verry interesting. THANK YOU for taking the time to post up your maps and give me a little extra to go on. honestly until i change engine-management to something this capable i will probably will be unable to play around with this sort of setup. But i am glad to have learned something and i will definitely put it to use some day.

Cheers guys!