ludeowner

Hi Everybody,

In an effort to understand how the control system works I read up on the writeups on the Robinette site. I wanted to fully or at least partially understand how the system operates before I install a Hallman MBC. The pics on the RobRobinette.com helped out a lot, and now I just wanted to see if I understand it.

http://robrobinette.com/boost_note.htm

Both the WG control and precontrol are controlled by pills, this much I know. UNtil seeing the Robs diagrams I didn't know exactly how they did their job.

From my understanding the pills limits the amount of boost pressure seen by the WG actuator and precontrol actuator. They do this by causing a restriction between the turbo outlet and actuator inlet. So pretty much by replacing each pill with a hallman device, you are replacing the pills with an adjustable restrictor. So now the amount of boost pressure seen by the WG and pre-control actuator is controlled by the Hallman unit.

So for the WG control, INCREASING the restriction will decrease the amount of boost pressure that gets through to the WG actuator...and this effectively RAISES your peak PSI. And of course DECREASING the restriction with the hallman device will allow more boost pressure to get through from the turbo to the WG actuator, which will LOWER your peak PSI.

The pre-control is the same deal, except an INCREASE in a restriction will mean LESS boost pressure going from the turbo to the pre-control actuator, which equals less exhaust to pre-spool the secondary. The result of that would a low transition number correct (ie 10-5-10)? And on the flip side, a DECREASE in restriction means more boost pressure to the pre-control actuator which equals more exhaust gas to spin the secondary turbo and a higher transition.

Now on to the mechanical/hands-on part...I examined the Hallman controllers on Damians pic and I see two nipples on each Hallman device. Am I correct in assuming that one nipple/vacuum line leads to the compressor outlet while the other nipple leads to the WG actuator? or pre-control for the other Hallman device? Do both the WG and pre-control Hallman device get their boost pressure from the primary (rear-most?) turbo?

So pretty much when I install a Hallman MBC I will be replacing the section of vacuum line between the turbo outlet and actuator inlets with the Hallman unit and vacuum line plumbed to the correct nipples. So nothing from the actuator themselves and the solenoid needs to be replaced?

Anyways, if someone wants to take the time to read all that and tell me if I have the operation correct, then that would be cool.

Thanks

ludeowner

I had read through Damians writeup about 30 minutes ago before I checked out the robinette site and I didn't have a clue what he was talking about. Now that I've been to the robinette site and re-read Damians write-up I can understand what he is talking about, because I now know how the turbo, restrictor, actuator, and selonoid all work to control boost.

With that being said, I just rad that he suggests "bypassing the solenoids, but leaving their electrical connections plugged in or you'll throw a ECU code".

So it looks like I will also have to run a vacuum line from the actuators directly to the pipes (dont know the technical name). And I just leave the solenoids elctronics hooked up and plug up the vacuum nipples that were previously hooked up to the actuators.

https://www.rx7club.com/forum/showth...hlight=hallman

DaleClark

iTrader: (55)

You're getting it. The problem with the factory control solenoids is you can't alter their programming in the ECU, unless you have a PowerFC or the like. By playing with the pills, you have control.

One part that you're partly confused on - the pills don't lower the amount of boost that the actuator sees. They reduce the *rate* they see boost. The boost pressure takes longer to equalize itself through the tiny orifice, which keeps the wastegate or precontrol closed longer before it's fully open. A manual boost controller uses the same principle, but it's a variable orifice - instead of swapping out pills, you just turn a ****.

It takes a little thought and study to wrap your head around the turbo control system, but once you understand the basics of how pressure affects things, how the solenoids affect things, etc. it all makes sense.

Dale

ludeowner

Yah, diagrams help me out a lot...if somebody had tried to describe rob robinettes diagram by typing it out, I dont know if I would have understood it. I kinda have to visualize it.

KevinK2

Not quite true. Pills work with bleed rate from the solenoid valves. a smaller pill will lower the max pressure seen in the actuator. But you are correct in that the smaller pill will also slow down the initial response rate, ie how quickly pressure builds to it's target in the actuator. this can lead to spikes.

Only beef I have with dual hallmans is it prespools the 2nd turbo very early, compared to stock control. This is an exhaust leak for 1st turbo, but not sure of any specific negative effects.

DaleClark

iTrader: (55)

The solenoids bleed pressure off to atmosphere, lowering the amount of pressure seen by the actuators, and the pills slow the response of the actuators for quicker spoolup and response.

I was mainly making a case that the pills, in and of themselves, don't lower boost pressure. Given time, pressure will equalize on either side of the pill. But, that's a good point about the solenoids.

Dale

ludeowner

Hello again guys,

I just found something else out...earlier I had said that the turbo outlet was on the rear-most turbo. After looking at another pic on the robinette site I may have gotten that wrong.

Is the turbo outlet line the ones I circled in blue?

I thinjk that it is, because Damian swapped the WG and pre-control hoses between setsup on the nipples I circled. So that would lead me to believe that the blue circle is the turbo outlet. Also I saw in the other diagram the pills were in the vacuum lin between the actuator (I know where those are) and the nipples I circled.

EDIT: also I have another technical question. What size vacuum line do I need? It looks like 5/16" inner diameter, but I think 5/16 might be a little small.

Thanks

DaleClark

iTrader: (55)

Correct vacuum line size is 6mm . Get it from hosetechniques.com - they have it in proper metric sizes. As well as 3.5mm vacuum line, which is the right size for the vacuum lines.

Dale

ludeowner

errr....which vacuum lines are you referring to? it sounds like you are talking about two different kinds. Did you mean to say 6mm for the turbo outlet to actuator lines? and 3.5mm for all others like BOV lines and stuff like that?

TIA

KevinK2

OEM boost control is based on controlling air flow though the pill and the related pressure drop, by way of the solenoid bleed. The wg solenoind is about 10% open before transition, and varies from about 40-70% open after. Always flow, always reduced pressure in actuator vs boost.

Proof? Knowing an M2 ecu can raise boost to 12-13 psi, and wg actuator cracks wg open at 8 psi and wg is fully open at 10 psi (static test), it would be impossible to sustain 12-13 psi (5th gear highway climb) if pressure equalized across the wg pill .... the max boost would be limited to 10 psi.

DaleClark

iTrader: (55)

You got it - the "small" vacuum lines like in the majority of the rat's nest, lines to the BOV, etc. are 3.5 mm. The larger lines that go to the turbo actuators and the like are 6mm.

Dale

DaleClark

iTrader: (55)

Pressure does equalize across the pill, but the solenoid continues to bleed boost pressure off to vacuum at the inlet to the first turbo. It works exactly like a boost controller, because it truly is a boost controller. The ECU has a map to control the solenoid - the map was designed to cycle the solenoid so the turbo gets up to the desired speed, then maintained at that speed. You keep the wastegate closed until you approach the speed you want, then start bleeding off exhaust pressure to maintain that turbine speed.

If you took the solenoids out of the equation and just had the pills, you would see boost ramp up, then plateau at 8psi. If you took the pills out in the same situation, boost would take longer to get to 8psi, but it would still do so. BTW, this is a theoretical example to point out the role of the pills and solenoids, not necessarily a real-world explanation on what would happen to your FD if you tried this .

Dale

twinturboteddy

Personally I think you shouldn't mess with the pills. I you want to up the boost get a boost controller or use a Power FC to do it.

The reason almost everyone has problems is because they are always fiddling with the pills. If you are missing them perhaps a good idea is just get them replaced by ordering those two vacuum lines from the dealer (pills are included inside) and not go the route of the home depot bleeder valve.

If you want to up the boost chances are you should have already a Power FC anyway.

I have a perect boost pattern and my DYNO shows absolutely no power drop during turbo transition. All I use is the Power FC to control boost. Turbos are stock and I have no cats and run anywhere between 12~14psi.

ludeowner

For now I will be using my M2 stg III ECU with the mods listed in my sig. I want to use the Hallman MBC and copy Damians setup. I had read about adjusting boost with pills and I didn't like that idea, I also heard bad things about the neddle valve type MBCs so that idea was out.

So far I've only heard good things about ball and spring type MBCs like the Hallman. I have also heard about good results with people controlling spiking with a MP and stock ECU. I have been thinking about adding a MP and Greddy 2-row with my unported WG and seeing if the Hallman can control boost.

Later on I will eventually upgrade to a Apexi PFC, but I dont want to rush myself into getting that ECU. I want to learn as much as I can about it before getting it. For now I want to add a Greddy 2-row to my mods list and maybe a MP. 12-13 PSI on 91 with all those mods should yield some good HP numbers if I can control spiking with the MP.

KevinK2

First, correction to my last post ... before transition the wg solenoid (vent) is about 90% open, not 10%.

Your last statement describes a hallman type or profec-b type controller. Based on my measured values of wg duty cycle (and datalogit output for the PFC from other posts) the stock FD boost control is a lesser system, and does not do this. Sequentional operation negates the need to fully close wg until just prior to target boost is aproached. Go single or non-seq, and those controllers are recommended.

Your first statement is in conflict with basic fluid dynamics ... flow thru an orifice/pill results in a pressure drop. With stock fd ecu, there is always flow through the wg pill, and less than boost pressure in the actuator.

We can agree to disagree

ludeowner

n/m

DamonB

Yeah, Dale's right. If you look at the system the pills control the volume of boost making its way TO the actuators and therefore the rate at which the actuators respond. At the same time the solenoids function on set duty cycles from the ecu and actually vent the pressure FROM the acuators to control the actual amount of opening and closing of the wastegate and precontrol doors.

The pills regulate boost into the actuators while at the same time the solenoids are venting pressure from the actuators. The solenoids are on the backside of the actuators so to speak. This is why when I had a nipple on my precontrol solenoid break off while on course I would hit boost cut on the primary turbo. Since the solenoid was unable to bleed pressure off the precontrol, the door would stay shut and the primary would overboost.

bureau_c

Be careful here. Read the later updates to Damian's thread that you referenced. You should cap the exit side of the wastegate and precontrol actuators, don't leave them connected to the pipe coming down from the solenoids (not sure if that's what you referred to below but it seemed like it was). The old way (where the actuator outlets were connected to the solenoids) seemed to work OK for Damian, but it definitely did not work for me....in that configuration I was getting horrible spiking on initial onset of boost. It makes sense too...the ball-and-spring controllers were opening, but there was too much volume aft of the actuators for the pressure to build up enough to open the wastegate. Once I capped those off, it worked great.

jds

cover8

I have the PFC and the Greddy Profec B spec II for boost control and have just removed the stock line for the pre-spool controller and replaced with the Hallman device. I have not bypassed the precontrol solenoid and did not cap the precontrol actuator. Boost seems to be the same with some unpredictability in spiking.

I am excitied to simply cap off the actuator (If I do this, shouldn't have to bypass at the solenoid right?) Seems with the Hallman the way I am set up, spools boost noticeably quicker.