A friend of mine has a Mazda Miata with a 2.0L turbo charged FE 16 valve motor.
He is running an external tial wastegate and electronic boost control with a 3way mac valve.

He is having trouble making or maintaining steady boost at 20psi with a 10psi spring.
I am sure it's the duty cycle pulsing of the mac valve bleed port that doesn't deliver steady flow to the top port (Dome) of the waste gate to control exhaust pressure against the spring. I run an external tial wastegate on one car and an internal garrett adjustable on another, both set to 15psi base and have no problems doubling that with a manual boost controller and get a perfect 30psi at all times.

I have been trying to come up with ideas to solve his boost control issues.
Most where to elaborate, complicated or involved multi port valves.
All ideas revolve around delivering steady even pressure to the upper port (Dome) of the wastegate, how to stabilize or correct the mac valve bleed port going to the top port of the wastegate .

I have read many threads on The Turbo Forum and the different ways people control upper port wastegate pressure to control boost.

Today I had a different idea, I am sure someone already though of this and I just haven't found the thread.

I should really draw a diagram and I will latter.

How to stabilized the mac valve bleed port signal going to the upper port of the wastegate, just eliminate it.

The first step in understanding my insanity, is my idea of the best set-up for a manual boost controller:

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Woks better than any other boost control set-up I have tried over the years. Delivers constant boost no matter the ambient temperature and barometric pressure, the principle is that air will chose the path of least resistance so if the boost control bleed valve is set to 5 psi at 6psi manifold boost 1psi if pushing against the waste gate spring, if bleed is set to 5 psi it will always remain 5psi.

The idea is:
-Eliminate the hose between the bleed port on the mac valve to upper port on the wastegate, run the mac valve to atmosphere or to inlet air source before the turbo (depending on air metering used).
-Run a second port/nipple on the charge pipe before the throttle body or carburetor straight to the upper port of the wastegate (cringe "dome or hat", still cringing).
-Install a T just before the wastegate and install a bleed style manual boost controller off the T.
-Bench set the manual bleed controller to the spring pressure you plan to run.
-For the how to I will use a 10psi wastegate and 20psi goal for the example, this required two pressure gauges and a compressor, connect the pressure hose to a T, one side to a pressure gauge and one to another T (T2) connect one side of T2 to a pressure gauge and the other to a manual bleed valve, with the valve manual bleed valve shut adjust the compressor regulator to deliver 20psi to the first gauge (should read 20 on both gauges) open the bleed valve until the second gauge reads 10 psi and the first gauge reads 20psi. Adjusting (turning up) the compressor regulator will be necessary once the bleed valve is opened will be necessary depending on compressor systems.

With the bleed valve set to 10 psi bleed the charge pipe boost signal going to the upper wastegate port will only start to apply pressure above 10 psi, so at 12 psi boost control setting the lower wastegate port will get a 10 psi signal because of the mac valve and the upper port will get a 2psi signal because of the bleed valve hose. The cool thing about this is that if the wastegate spring pressure is set to bleed off the upper port manual boost control valve the above spring pressure setting will be directly applied to the top port of the wastegate at 15psi pressure would be 5psi, because Tial's instructions call for a bleed T between the boost controller and the upper wastegate port this set up would yield more accurate pressure to the top port of the wastegate because the bleed controller would double as a controlled pressure vent between shifts/off boost. If the wastegate is to small, badly positioned or the valve is overwhelmed by exhaust gas pressure simply dial in the manual bleed controller on the upper port until desired set electronic control pressure match the gauge.

Tial directions:
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Controlling boost only with the upper port and mac valves, I don't think this is the "best" way to control boost, nor do I think running boost control as a bypass on the compressor side without a wastegate on the exhaust is an efficient way to regulate boost (spool the turbine to it's maximum rpm all the time and only use what you need for air, or spool it to the rpm you need and only move the air you want. :
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I think mechanical boost control kicks the shit out of electronic boost control when it comes to accuracy, reliability and durability but electronic boost has more versatility. Combining the two my way could improve both of their performance.

 

Have you guys checked drive pressure?
How's the wastegate mounted?
Have you checked the gate for smooth operation? no binding/ sticking ect

Why not install heavier springs so it doesn't take so much pressure to control boost?

 

Co2 to apply pressure to top of wastegate? Doesn’t get much more steady than that.

 

I've read that once boost requirements are about twice the spring pressure then boost may fluctuate.
As mentioned you may try a stiffer spring and see of that helps.

ks

 

I never understood the stiffer spring helping the electronic boost controller being required for 1 bar plus if boost. I use to run a 8psi spring and turn it to 21psi perfectly with my electronic boost controller on a journal T7675 with no issues what so ever. However through I switched to a 14psi spring from the 8psi spring due to the tuners preferences. I do believe in respecting preference so I didn’t mind.

 

He has the wastegate mounted to the number 4 exhaust runner I believe.

The wastegate is functioning properly it just spikes and dips boost when trying to run 2X the spring rate.

This is a street car and he wants to run it on some road course tracks, the engine is Japanese Mx6 GT 2.0l naturally aspirated, 10:1 compression factory 160 hp 160 torque.

My first suggestion was to run a stronger gate spring but the miata weighs nothing and he is running the 5speed transmission that isn't very strong so for traction reasons and the life of the transmission he wants to keep base boost at 10psi.

On top of that he lives in northern Ontario, the highest pump gas available is 91 octane, no there is no E85 gas stations (I think the whole country has less than ten locations selling it).
So he can't even run 20psi on 91 octane, he took the car to Toronto to have it tuned and the set it up to run 10 to 14.5psi (I believe) then they put in 95 octane and turned the boost up to 20psi, boost would spike to 21psi and fall to 18.5psi near redline.
And then the transmission died.

He is however taking wastegate boost reference from the compressor housing and not the charge pipe before the throttle body, I have asked him to take it from the charge pipe instead and eliminate any pressure loses from the intercooling and piping from the boost controllers requirements. More accurate boost and less early and unnecessary wastegate travel.
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Myself I want to figure out a better way to run Mac valve electronic boost control, maintain steady boost and run 2X the wastegate rating, right now I run manual boost controllers, the external wastegate has a 1bar spring and the internal gate is set to 15psi, my cars are front wheel drive and make lots of early torque in the powerband so they already spin at 15psi (something I am working on), I have decided to run speeduino on the 2door instead of 50 different piggy back systems like the 4door.

Speeduino will give me the ability to tune and monitor the water/meth system and run boost by RPM or by gear and potentially manage to run the 1/4 mile with out spinning the tires 1/8th.
To do this I will have to run a 3way mac valve and will probably have the same issue holding steady boost at 2X the wastegate rating.
The two door runs the external wastegate, I run it off the internal wastegate hole in the turbine housing and never had any boost control issues.
The 4door runs the junkyard single port internal adjustable wastegate, it is better than the Tial because it's adjustable vs buying expensive springs (everything is expensive in Canada after exchange, shipping, customs, tax...).

I don't want to have to run 20psi spring pressure to make 30psi intake pressure .

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What I am trying to come up with is a way of making electronic boost control using a 3way solenoid valve as steady as running manual boost control when doubling the wastegate spring rate boost.

This set-up would give the waste gate the accurate "dome" upper port pressure of a manual boost controller and the versatility of electronic boost management. The upper port pressure would be completely adjustable allowing the proper amount of dome pressure to be set to achieve and maintain peak desired boost everything else can be dialed in with the electronic boost control settings.

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The PSI chart is based on the behavior of a manual boost control bleed valve set-up, manual boost controllers control boost before it's reached, electronic boost control chases a voltage value from the map sensor.

You are correct but not really practical for a street car and adds another solenoid valve to the build (added fail point).
Out of curiosity what Co2 pressure do you run to the upper port to achieve desired boost, what spring is the wastegate on and what is set boost.
If the required Co2 pressure is never greater than intake manifold/charge pipe pressure than you can replace it with this set-up unless you require advanced top port pressure to achieve that boost.

I read the same thing when I purchased the Tial in 2003 but managed to maintain steady boost on a manual set-up and figure that "superior" electronic boost control should do the same thing.

Remember these are street cars, I cant stuff anything wider than 225/50 r16 on the car without going to coil overs (not street legal here), rolling the fenders or sacrificing handling.
I doubt the Miata has much room in the rear factory tub for fat tires, increasing base boost would be impractical.

I think the placement and size of the wastegate plays a big part in regulating boost, personally I would never run a wastegate off one exhaust manifold runner, it will mess with flow and add to reversion on that cylinder.
Size is deceptive, diameter and circumference are linear but area grows exponentially.
Take a 38mm wategate (1.5") vs a 66mm wastegate (2.6") the 66 mm has less than 2x extra diameter and circumference of the 38mm but the 1.5" has an area of 1.767 square inches and the 2.6" has an area of 5.3 square inches so it has 3 times the area of the 1.5" valve/port, theoretically should flow 3 times as much exhaust and have 3 times more resistance to the effects of exhaust pressure overwhelming the valve.

Seems your tuner wanted to increase boost accuracy weather or not it was required.
I have a question, if your build required an 8 psi base boost and you where asked to run a 14psi spring would you have swapped, it is cool to respect preferences but more important to respect requirements.

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I appreciate and thank you all for your replies but am trying to pick your brains about a better way to control electronic boost.

 

I have a Holley Terminator X. I am currently using a 4 port Mac Valve. I have a very light WG spring. I built tables that compare a target boost vs RMP to actual MAP. Depending on the difference it's out puts a duty cycle to the Mac Valve. I started with a duty cycle I was running when open loop, have not tweeted it much at all but so far it seems to work well (until the poor placement of the wastegate shows up and it runs away) and this setup only requires one output. It sure if you can do something like that or not.

 

It seems like what you're trying to do is like, trying to find a better way to get more air in your tire, when the tire has a hole in it...

I'm not saying what your trying to do won't work, or shouldn't be done, etc. Just sounds like you're putting a band aid over a problem too cover it up.

That's why I asked about drive pressure. There's a point where the boost isn't enough to fight against drive. Doesn't matter if you've gone 2x spring pressure before, what sort of drive was you fighting against there? Is the current system more or less?

Your completely right on the placement of the wastegate, that's a shitty ass spot, but when your upping the boost, your closing the gate down and sending less flow through there anyways, so I don't think that's the problem.

Need to check drive pressure, check the gate, valve, ect. If all is good and it's a weird phenomenon, by all means make it better if you can.

 

That's easy, take a tire puncture kit and scuff the hole, prepare the plug on the installation tool, insert an air wand in the hole and fill the tire from the hole and valve stem at the same time, pull the air wand and install the plug. Tire filled twice as fast and repaired.

Perspective.
I think I am trying to reduce the problem, in my mind electronic solenoid duty cycle boost control is the problem.
I also think that if the wastegate reference signal on the miata is taken from the charge pipe instead of the compressor housing it will improve accuracy at higher boosts.
I don't see how adding consistent, durable and reliable mechanical to improve the performance of delicate, temperamental and unreliable electronics is a band aid (if the idea actually improves performance of course).

Maybe I am jumping to conclusions, the old piggy back electronic boost controllers sucked at controlling boost and in many threads I have read here people had trouble regulating and stabilizing boost with mac valves and electronic boost control.
I ran an HKS controller in the early 2000's, it would bounce boost between 14.5psi and 15.5psi on the autometer gauge while the hks screen displayed 15psi (not only could it not regulate boost, it lied to me), the bouncing boost drove me nuts, you could feel the power fluctuating and I went back to manual boost control.

How much boost are you running and how many PSI is you spring?
How accurate is your boost?
And how is your mac valve set up?

I have found many different hose configurations and set up when searching.

 

Seems like you have already convinced yourself that your method is better than what everyone else uses.

Don't forget that the "delicate, temperamental and unreliable electronics" also run the motor so maybe you want to go back to a carb..?

Those MAC solenoids that you are referring too are extremely high precision made by a company that specializes in high precision air control systems.

https://www.macvalves.com/industries/

If you have a problem with it then it's probably the users fault not the valve.

For reference: I have 18psi WG springs and run 39psi of boost with the signal coming off of the turbo and the data logs shows that boost fluctuates between 0.1 and 0.5 psi.

Here's how I have mine plumbed:

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ks

 

I do not think that, but I do think what everyone else uses can be improved upon and I am trying to figure that out.

The car is fuel injected from factory, so I won't be swapping it to carb, I do carry a spare factory ECU in the car, have had 2 fail in 26years, cars are 1988's (2 too many), also carry a spare alternator, timing belt, alternator belt, axles...
The only reason I am planing stand alone is because Arduino controllers seem more reliable than mega squirt and are cheap enough to purchase and burn a spare to carry in the car.

I have a bunch of Mac valves in my basement, worked 22 years as a licensed industrial millwright, in H/Vac, controls, electricity, pipe fitting, certified in advanced pneumatics ...
These are pneumatic control valves used in pressurized controls and automation. Before all the building yanked the mechanical pneumatic systems that lasted for ever to install electronic controls many where "upgraded" to running duty cycle controlled pneumatic pressure, this gave the systems the ability to ramp down and save energy when possible but the mechanical pneumatic valves and devices did not function as well, some required calibration or inline reducers or manual pressure control valves to get them to operate within acceptable range (mechanical solutions to electronic problems) there was a trade off of accuracy for function.

That is a good reference point, and that is better accuracy than I though for 116% boost over spring rating controlled by a single duty cycled solenoid valve, the fact it is that close to set point controlling two wastegates / turbo's on two banks is impressive.

Is the 0.1 to 0.5 psi linear? Like boost gets to 39 and gradually drops to 38.5 or climbs to 39.5 or does it ramp up and down along the rpm band?
I doubt it takes very long for the transmission to shift and would be hard to notice.
The engines I run are inline 4 12v with 7.8:1 (or lower) compression ratio, making about 115 wheel hp and 139 ft-lb without boost (shit that sounds lame on this forum), all the power they make comes from boost and for some reason you can feel it if boost fluctuates, a 5th gear pull from 50 to 157mph takes under 8 seconds if boost drops or climbs it's okay (it doesn't) but when it's ramps up and down it's noticeable and makes the time feel long.

Why do I think what everyone else runs can be improved upon, because the last guy who did posted the set-up and we have even more information than he did available.
As a millwright the company I worked for took any contract they could get, I had to perform a lot of skilled trades and do a lot of thinks without experience, that gave me the advantage of not being an apprentice and not being tough only one way of doing things, I would look at all the other companies work and combine the best ideas or use them to come up with my own.
Isn't that what this forum is all about? Not a bunch of followers copying other peoples recipes but a bunch of individuals writing their own.

I appreciate your post and reference point.
What would be so wrong about trying to get accuracy fluctuations down from 0.5psi to under 0.1psi when it comes to boost control if it can be simple, reliable and affordable.

 

When traction control is pulling timing it pulls timing to 20*ATDC in order to get traction and during this time the boost wiggles between 38.8 and 39.1 but may vary an additional .2psi.

Along with the traction control bouncing the timing from 11* BTDC to 20*ATDC and my WG boost lines being long at around 8ft in length I contribute the boost fluctuation to both of these parameters,.

My system is all custom and I understand exactly how each part works and what is needed for those parts to function to the precision I need them too. Some people simply toss parts on and have no idea what the parts require in order to function at high precision.

I'm changing from the 2V heads (require 39psi to make 950RWHP) to 4V heads and expect boost to drop to around 26-28psi and make 1200RWHP so the boost may be a bit more stable but I'm happy with the precision it currently has.

You can do whatever you want...You can stuff the head of a rooster up the WG I don't care but you proposed some non-normal solenoid plumbing for an issue that you are blaming on the solenoid valve, which I suspect is not the issue. If the WG position is designed correctly for the air flow it needs to control and the plumbing for the solenoid valve is correct (lines aren't too small, exhaust of the solenoid not plugged, etc), then it will maintain "consistent" boost pressure. Naturally "consistent boost" is in the eye of the user.

I'm all for building custom parts based on ideas that are different. I rarely buy aftermarket parts b/c they rarely "perform/function" the way they need them to for my builds. My car makes 950RWHP through dual 2 1/2" exhaust and three mufflers, so please build and test what you want then post the before/after results.

ks

 

I will build what I want but what I want to build is what works and I am trying to find out what works for my build or in general, you claim you don't buy aftermarket because custom performs better for you, yet everyone say think within the box. You have all suggested do what I do because it works, solutions not pro, cons or alternatives to my idea.
The more info I gather the better, small details can save on huge amounts of of R&D enough info can eliminate R&D all together. You can make 9500 rwhp and run 130 mufflers who cares, if your happy with the boost control set-up you run cool, you don't want to help improve boost control cool, thank you for the information you posted.

Why take it so personally that I don't want to follow the set-up you used that you copied from someone else, I make minimal power, my priority is steady boost, traction and good 1/4 mile times aren't concerns because they will never matter for these cars.
But improved boost control is good for everyone.
I would rather spend 90% of my time planning and 10% executing, execution must be executed at 100% but if planing is flawed everything fails.

 

I run 4 1/2lb wg springs. Using one 3 port mac valve, I have run 30lbs with more DC left on the Mac valve just running boost pressure on the top of the gate.

My ecu logger probably fluctuates 1lb. I only run duty cycle on the valve. I don't let the computer try to hold the boost. The boost gauge will read steady boost. The ecu takes snap shots, that's why the boost will fluctuate depending on the pulses in the intake where the ecu gets the map signal from.

 

It appears that you're reading negativity in my reply. I'm not taking anything you write personal and posted info that I thought you would find encouraging by giving examples of my mindset which is similar to yours....

ks

 

That was wrong of me to be defensive, I did find the info useful, just felt at the end you sorta said: "you do what you want put it together, test it and get back to us".
Before ever attempting to build, assemble or modify something, I want to understand it completely and be 100% positive it will work, I am way to lazy to want to do things twice, that's why I wrote this post.

I did not expect everyone to have such a small window of boost fluctuation or to be regulating boost only through upper port pressure with full boost pressure on the diaphragm.

So you run 2lbs of wastegate spring and have ran up to 15X spring rating.
You don't use closed loop to have the ecu chase boost instead you program you own fixed duty cycles and they give you steady boost. So your boost control is acting and controlling boost not reacting and chasing boost.

"My ecu logger probably fluctuates 1lb. The boost gauge will read steady boost. The ecu takes snap shots, that's why the boost will fluctuate depending on the pulses in the intake where the ecu gets the map signal from."

So the boost gauge reads steady boost after the butterflies, but the ECU map sensor picks up variations due to the engine doing it's thing. So you do hold steady boost.
Do you run a carb style intake or a large chamber throttle body style intake manifold? I would guess that a carb style intake manifold with it's small "collector" volume and the flow of a large displacement V8, flow of the heads, big valves and large lift and duration cam ... it's simply a matter of volumes.
If your boost gauge takes it's signal from a spot that gets steady boost pressure wouldn't it be better to take your Map sensor pressure reading from the same spot or is it just more sensitive / accurate than the boost gauge. (I really am asking, not making a suggestion).

This has really made me think.
Understand my mind is still thinking around controlling the diaphragm pressure and using the output to assist control of top pressure.

You will probably all hate me for this idea but it's just an idea.

"Duty Cycle" is what echoed in my mind.
On the old primitive set-up regulating diaphragm pressure what if 100% duty cycle on the mac valve was limited to peak desired boost set with a manual bleed valve, so basically a manual boost control system with a mac valve installed before the bleed controller.
90% of the time at peak boost the manual controller will be maintaining boost and the mac valve just stays opened, when electronic boost control is called for (in 1st gear and 2nd gear progressive through the rpm to match traction limits) mac valve duty cycles are programed and the mac valve controls the boost, if boost fluctuates it wouldn't matter because it's progressive boost anyway.

This could be used as a failsafe to limit peak boost using a 3way mac valve to regulate pressure to the lower port of a wastegate, if the wrong duty cycle is ran or the mac valve fails opened boost can't spike beyond the manual set bleed valve. Can also limit fluctuating boosts highest point, if 30psi duty cycle is called for and the bleed valve is set at 30psi and the mac valve's boost control varies between 29 and 31psi boost would still never pass 30psi.

Although these types of set ups are a bad idea
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Both of these set ups are bad ideas but people still use them, if the solenoid valve fails with the NC port opened or reaches 100% duty cycle the wastegate gets no boost signal and unless the ecu is set-up to cut fuel or timing during boost spikes something breaks.
At least if the solenoid valve gets no control signal it just gets wastegate spring boost.

These layouts all come from the same website.

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And the final layout almost looks right but it's not.

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Am I wrong, if his port layout is the same as the first to pics in the normally opened de-energized position the mac valve will bleed off it's maximum air flow and at 100 % duty cycle will run spring only boost.
If this solenoid fails in its natural position boost spikes to valve flow limit.
If a Bleed valve was added to the middle C to intake hose and set to maximum safe boost limit .


I am thinking something like this would better :
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I see why you guys regulate boost with dome pressure only or with set ups like Kevins, if the solenoid fails to normal state you get spring boost.

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If a bleed valve was added to Port 3 of solenoid vent to atmosphere and set to a failsafe limit, the solenoid valve could fail to the energized position or hit 100% duty cycle without causing uncontrolled boost spikes.

 

Reading all this really makes me want to go look at how I hooked mine up haha

 

I'm running 4 1/2lb wg springs. Not sure where you got the 2lb from.

I'm running a single plane carb style intake with 90* adapter.

I just use DC for my boost control. If I run say 40-45% DC, it will give me a pretty steady 15lb boost across the rpm. Basically I am running DC vs mph vs gear vs traction. It has been working well for me.

 

Haha, and I read it and though about it several times before getting it wrong. But that's why I wanted to confirm.

1st possibility was you ran a combination of springs that added to 4 1/2lb wastegate spring pressure.
2nd possibility was you ran 4 x 1/2lb waste gate springs.

It never dawned on me until now that you're running dual wastegates with 4.5 lb springs.

Duty Cycle is what I've been looking into, it is proving to be difficult to figure out the SCFH to boost ratio.

 

Pay attn the operating frequency for the solenoid you are using
http://www.circuitse7en.net/page26.php

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Speeduino have closed loop boost control
You've got to know or control the exhaust gas pressure
and you'd better know how to read a compressor map and understand what it means to run off the right side of one