Manual Boost Controller?

[tschultz]

Guys, I did some looking didn't find any previous threads on this topic... I was wondering if anybody uses a manual boost controller. What are the benefits and the downsides?

I was only considering ball and spring check valves, but wanted to get some opinions. Do they make much of a difference? Do they have any major downsides (from what I have read so far, maybe boost spikes if incorrectly adjusted)?

I read it helps improve boost response by limiting creep of the wastegate. Any first hand experience you'd like to share? For reference, I have Motronic with RRFPR. I was looking at the dawe's-devices boost controller as it seems like the highest quality piece for a fair price.


Thanks!

[offroadkarter]

I'm using a ball/spring style MBC on my 745i. Currently have it set to run 10psi. I was trying to find an adjustable wastegate but after that proved impossible I gave this a shot and it works perfectly fine.

I haven't had any boost spikes, its held 10psi every time in every gear. Is it the perfect solution? Probably not, but it was cheap and gave me adjustable boost. It works fine on my stock system until I'm ready to install my TCD S3 + MS3 setup.


I made a thread with my random thoughts on "that other site" a while back. http://www.bimmerforums.com/forum/showt ... Controller

[tschultz]

Good thread, thanks for sharing!

I think I'm going to try it, but not with the cheapo ebay ones (mainly for reduced boost creep from the wastegate, although I may play with it for getting 2-3 more psi with the same wastegate spring).

[offroadkarter]

Good thread, thanks for sharing!

I think I'm going to try it, but not with the cheapo ebay ones.

The one I bought was like 80 bucks, seems well made and it had good reviews on some of the evo/DSM boards I read. I'll see if I can find the make when I get home, I have the box kicking around somewhere.

[demetk]

I've been using a simple dawes device for years now. It just works.

[marc79euro645]

Just run on the spring. You're going to want all the boost. I've got an MBC can't remember the name ,but it was a nice anodized unit. I installed it in the glove box. I keep it cranked down all the time. It might come in handy if one of my boys wants to borrow the car

[offroadkarter]

this is what I bought, in black. I found it on ebay cheaper

http://www.amazon.com/Hallman-PRO-RX-RD ... B00IFWMQ3O

[Shadow]

From wastegate to mbc I remember noticing getting into boost faster. It'll give you more of a hit.
I connected it to the intake manifold. That gives better response for some reason I can't remember why but it does.

[tschultz]

From wastegate to mbc I remember noticing getting into boost faster. It'll give you more of a hit.
I connected it to the intake manifold. That gives better response for some reason I can't remember why but it does.

Interesting, as I thought about this a little bit today.

The theory behind the ball/spring MBC is that it will not allow the boost pressure to reach the wastegate until the desired threshold value is met. At that threshold, the ball moves against the spring and allows the boost signal to reach the wastegate and open. Since the wastegate needs boost pressure to open, there is no wastegate creep or lost exhaust energy from the system. This amount of exhaust energy is significant when boost pressure is low. In this manner the boost controller can be used to both reduce wasted exhaust energy (reduce spool-up time), along with allowing adjustment of boost pressure to the engine.

On to Shadow's point:

If you run the signal to the wastegate off of the TB (after throttle plate), you are subjecting the wastegate to a vacuum that it is not designed for. Tial and other wastegate manufacturers do not suggest one install a wastegate with this sort of signal. They do it for a reason, but I didn't spend a lot of time researching this.

But anyway, at high RPM when letting off the throttle, the throttle plate shuts, and instead of a boost signal being present, the wastegate would see vacuum and tend to hold closed (as opposed to opening/relieving). This situation may potentially cause an unwanted boost spike to the engine that is otherwise returning to an idle state. Unwanted detonation if tune and AFR are not held in check?

With a Ball/spring MBC in the same situation, the characteristics are a little different by my approximation:
When letting off the throttle, the ball in the MBC actually prevents the vacuum signal from reaching the wastegate. The ball seats fully (in a high quality MBC) when under vacuum, and the wastegate simply sees atmospheric pressure (approximately). Certainly the spring/ball will not allow it to see the full -15 or -18 vacuum. Of course the safer position would be the standard wastegate signal before the TB, as it will send signal to open the wastegate when the throttle plates closes, even with the MBC in place.

Interesting subject, I may try It out both ways and see if there is much of a difference.

[downforce22]

From wastegate to mbc I remember noticing getting into boost faster. It'll give you more of a hit.
I connected it to the intake manifold. That gives better response for some reason I can't remember why but it does.

But anyway, at high RPM when letting off the throttle, the throttle plate shuts, and instead of a boost signal being present, the wastegate would see vacuum and tend to hold closed (as opposed to opening/relieving). This situation may potentially cause an unwanted boost spike to the engine that is otherwise returning to an idle state. Unwanted detonation if tune and AFR are not held in check?

With a Ball/spring MBC in the same situation, the characteristics are a little different by my approximation:
When letting off the throttle, the ball in the MBC actually prevents the vacuum signal from reaching the wastegate. The ball seats fully (in a high quality MBC) when under vacuum, and the wastegate simply sees atmospheric pressure (approximately). Certainly the spring/ball will not allow it to see the full -15 or -18 vacuum. Of course the safer position would be the standard wastegate signal before the TB, as it will send signal to open the wastegate when the throttle plates closes, even with the MBC in place.

Interesting subject, I may try It out both ways and see if there is much of a difference.

I think you have your vacuum lines mixed up. There are 2 ports on the wastegate; one on top and one on bottom of the diaphragm. The line on top of the diaphragm should be either to atmosphere or to an electronic boost controller(EBC). So the EBC opens when programmed and keeps pressure on top of the diaphragm to keep it closed when necessary. When it's set point is reached that boost pressure is removed. Now instead of equal pressure on both sides of the diaphragm and a spring holding it closed, there is a vacuum on the top, and a boost pressure on the bottom that opens the wastegate diaphragm.



With a manual boost controller it is the same idea but the check valve should be used between the boost signal line and the diaphragm on bottom of the wastegate. The top port should be open to atmosphere. That way the spring in the wastegate holds the wastegate closed until boost pressure builds to overcome the ball/spring boost controller set point. Once this happens the boost pressure passes to the bottom side of the wastegate helping overcome the wastegate springs force and and open it, similar to the EBC scenario when the boost pressure from the top of the wastegate goes from equalized (positive PSI) to atmospheric (0 ps or vacuum).

[Pavel]

Great thread. Subscribed. M106 needs some kick.