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Originally Posted by JasonC SBB
You should ask:
- what is the best setup for (insert hp target here) for a 1.8L gasoline engine that makes 140 hp when stock / naturally aspirated for a (street/track) application ?
Originally Posted by Godless Commie
I understand you completely, because you make sense.
Me, **** sense.
I want the challenge. I want to play. I want to think about this till steam comes out of my ears.
I do not want to be sensible. Uncharted waters are excite.
I was talking about the sizing of the two turbos, not the control method.
The above talks about the black region in your last post. It's about fuel economy at cruise.
The red area is crucial for response and performance. I would like to see a more realistic breakdown of the red area, for each of the 2 wastegates, for a gas engine.
The first PDF file you linked (post #16) does have them, but it contradicts 2 statements. Albeit this is for a diesel, not a gasoline engine.
Remember 10 bar of BMEP is approximately 100 kPa of MAP.
The first statement is that the wastegates are open in vacuum (below 10 bar BMEP). This is a minor point as you can implement this if you want to.
The second contradiction is that the below map shows that the LP wastegate is completely closed until 3000-3500 RPM. There is no "blending" where both wastegates are partially open below 3000 RPM.
Ergo, the HP wastegate appears to be doing all the boost controlling below 3000-3500 RPM. This is different than the strategy you typed wherein the HP wastegate opens at 3 psi of boost.
What would be very useful is a typical map of the pressure between the 2 compressors as a function of BMEP and RPM for a gas engine. If resembles a simple function of MAP and/or RPM, then perhaps you can build a simple, separate controller for the HP wastegate. It can be done with a pressure sensor and a microcontroller like an Arduino or perhaps a small analog circuit.
The second file (https://www.miataturbo.net/attachmen...ry_532_626.pdf) seems to offer clues. See below graphs.
The issues are it only shows what happens at full boost, and it doesn't show what the wastegates are doing.
Based on the curves:
- full boost is reached at 1400 RPM
- the engine "comes on cam" from 2500-3000 RPM, which is why the target MAP drops; looks like they're trying to maintain a flat torque curve from 1400-4000 RPM.
- the 2 curves suggest to me that from 1400-3000 RPM the LP wastegate is completely shut and boost regulation is done by the HP wastegate. This is consistent with the wastegate maps above, and inconsistent with the statement "HP wastegate opens at 3 psi, regardless of RPM". It looks like it operates at all boost targets at <2500 RPM
- there is no blending of the 2 wastegates.
- above 3000 RPM the HP turbo is completely bypassed, and the compressor bypass is also opened
I would think at part-boost operation the strategy would be the same, but the HP wastegate would fully open (and LP wastegate start opening) at a higher RPM (based on the diesel wastegate maps - first 2 maps of this post).
The entire discussion above is about steady-state operation. No talk of transients, i.e. spoolup (WOT but not yet at full boost).
When spooling generally you keep both wastegates shut for maximum shaft acceleration. But, for high RPM spoolup I suspect you would need to begin opening the HP wastegate at some point to prevent the HP turbo from operating outside its most efficient region (else spool might be slowed) and to prevent shaft overspeeding. This is why I'd like to see the wastegate maps and a map of the pressure between the compressors, with BMEP or MAP on the Y axis, and RPM on the X axis.
-----------
Compressor pressure ratios at full boost:
Turbine pressure ratios, full boost:
Sorry for not responding sooner, I just did not have the time.
I really think there is a misunderstanding here. (I'm not saying it's you, could just as well be me)
To make things clear, let's not call all these valves or bypasses wastegates.
The system has one WG, and that's the IWG just before the DP connection.
There's a HP-LP baypass,
And a LP bypass to free up the flow into the IC, than IM.
Let's call HP-LP bypass A
LP bypass, B, and
IWG C.
This will simplify things.
On this setup, all three are operated by vacuum.
During below 100 kPa conditions such as cruise and whatnot:
C is open,
A and B are closed.
B opens after a certain RPM threshold to help with flow into the IC
Above the 100 kPa threshold:
C is closed (till max system boost is reached, then acts as a traditional WG)
A opens depending on manifold pressure (preset level) OR RPM (because LP spools easily at elevated RPM levels)
B acts pretty much the same as A, with different values, to allow compound boost briefly to bring manifold pressure levels up.
Going into boost:
A may be open already (if engine has sufficient pressure / RPM) OR opening may be imminent
B is closed if engine below set pressure / RPM threshold
C closes (obviously)
Sudden acceleration:
A opens at set PSI threshold OR set RPM level
B open already if RPM or boost above preset level, or opens at such levels
C closes
Deceleration:
A open or closes depending on rpm and manifold pressure
B open or closes depending on rpm and manifold pressure
C Closed / opens with delay (delay helps retain turbine momentum in the case engine accelerates again - like coming out of a turn and hitting a straight)
In this scenario, A does not control boost at all. It just completes a "handover" between HP and LP, and the process is completed at preset manifold pressure and RPM levels.
Boost controlling is carried out by C, the IWG. It operates as we know wastegates once there is boost.
So, I have come up with a very simple control scheme based on these scenarios.
I will post the details.
I have to bring another player on the stage here.
The reason is, the IWG on this system performs 2 functions, namely, it opens below 100 kPa to help with efficiency and economy, and then acts as a normal WG under boost.
I figured I could retain such functionality if I used an EWG. They would split the tasks; IWG would work below 100 kPa, and the EWG would be installed and hooked up with EBC in the traditional sense.
So, there will be an EWG.
But, we will be discussing the 3 actuators and their respective controls here.
So, there.
First off, we need to understand the default behavior of these actuators...
And, let's keep this control map in mind:
After long and careful deliberations, a necessity for vacuum controls has become quite apparent.
That way, I can keep the original actuators and save myself the trouble of modifying / calibrating unknown push-pull thingies.
Vacuum distribution is fairly simple:
Accordingly, individual actuators will be controlled as follows:
You may have noticed the ? after RPM and kPa values.
They will have to be fine tuned with the engine running to get a smooth boost and torque curve.
It will just be a matter of plugging in new numbers in the MS output values.
Getting the solenoids is easy. So are the checkvalves.
I can have a custom vacuum canister made to fit in a specific area under the hood.
Could be anywhere, like, behind the firewall, in the front bumper, behind the driver side headlight.. Not a concern.
Solenoids will go in a nifty enclosure with a filter for VTA ports.
All I need to is figure out my output ports from the MS at this point.
Gents,
I am researching and learning as much as I can on this thread's subject matter but some things are a bit too much for me.
Such as: You can connect a NPN BJT transistor or a N-channel MOSFET to any of the spare ignition outputs. This will create a low-side output.
and, For the MS2E, since it has CANbus, a CAN I/O would be perfect.
Could anybody please elaborate on these statements, or point me towards some source to accomplish extracting more outputs from my MS2E please?
I also read about an IO Extender for MS2.
Would this be a module I could buy/make and use, or are they talking about the daughterboard already installed in the MS2?
On a completely unrelated note, I ordered an EWG, recirculating BOV setup (so it would be quiet), EBC solenoid, bunch of vacuum solenoids, various checkvalves and misc. hardware..
Manifold, DP and IC intake piping fabrication will commence as soon as I receive the said EWG and BOV.
A bit of quiet before the storm for now.
Apologies for the delayed response, life/work get on the way more often than I would like! As stated, MS2e has CANbus connectivity. You can transmit all sorts of data through a single CANbus channel, so it is ideal to connect an expansion device(s) to it. There are several examples of such modules out there; most of them designed for industrial automation where there's need to communicate with robot controllers via CAN. For mine, I have a friend designing and building CAN sensor "nodes" with 8 total inputs, but there are also market available solutions, for example:
"I have to bring another player on the stage here.
The reason is, the IWG on this system performs 2 functions, namely, it opens below 100 kPa to help with efficiency and economy, and then acts as a normal WG under boost.
I figured I could retain such functionality if I used an EWG. They would split the tasks; IWG would work below 100 kPa, and the EWG would be installed and hooked up with EBC in the traditional sense.
So, there will be an EWG.
But, we will be discussing the 3 actuators and their respective controls here."
I think you're over complicating the WG control, it's pretty easy to scale the initial value and target values so the chart starts at 100kpa and goes to whatever your max boost. So you would simply fill the 100kpa column with 0 values if you want the WG open or 100 if you want it closed. Once you go above 100kpa you can tune the tables as normal. Most people setup the WG control to keep it closed till target boost to improve spool.
"I have to bring another player on the stage here.
The reason is, the IWG on this system performs 2 functions, namely, it opens below 100 kPa to help with efficiency and economy, and then acts as a normal WG under boost.
I figured I could retain such functionality if I used an EWG. They would split the tasks; IWG would work below 100 kPa, and the EWG would be installed and hooked up with EBC in the traditional sense.
So, there will be an EWG.
But, we will be discussing the 3 actuators and their respective controls here."
I think you're over complicating the WG control, it's pretty easy to scale the initial value and target values so the chart starts at 100kpa and goes to whatever your max boost. So you would simply fill the 100kpa column with 0 values if you want the WG open or 100 if you want it closed. Once you go above 100kpa you can tune the tables as normal. Most people setup the WG control to keep it closed till target boost to improve spool.
I understand. Your suggestion would indeed make life less complicated.
But, given the fact that the IWG has a vacuum actuator, I am afraid it simply will not be fast enough to respond in time.
For example, there are times when you come off boost and stay in vacuum (for an extended time, or briefly)
I just did not want a case where the turbo would be freewheeling in vain due to a still closing IWG, or delayed opening to relieve backpressure and EGT..
Also, (you may chalk this one up to my ignorance) programmable outputs of the MS does not allow for complex conditions.
In other words, I can have a vacuum solenoid active above a certain threshold. Period.
I can not have the same output turn off again above another, higher threshold.
For example, I can tell it to be active (meaning, close the internal wastegate) at 90 kPa manifold pressure. But, I can not tell the same solenoid on the same programmable output to open it again at 190 kPa. (made up values for the sake of an example here)
What I mean is, I can't have this:
IWG open all the way from 0 to 90 kPa, closes at 90. Then, it opens again at 190. The parameters set in MS only allow for one condition.
Actually you can....scale your tables to cover the functional range you need and just populate the table to match your plans. Not only can you do what you want based on map values but also by RPM. The MS3 firmware also has provision for dual wastegate tables and I believe you can use different values for each specifically for a dual turbo setup that's in series vs. a conventional parallel arrangement.
I'm not sure I follow your logic on the IWG being vacuum actuated, external gates are vacuum actuated as well. Hell I think only a few OEM setups (BMW) use electronic actuators.
You can download the software to play with, you should probably familiarize yourself with what the MS3 is capable of before you waste time trying to come up with an overly complicated mechanical system.
Gents,
I am researching and learning as much as I can on this thread's subject matter but some things are a bit too much for me.
Such as: You can connect a NPN BJT transistor or a N-channel MOSFET to any of the spare ignition outputs. This will create a low-side output.
and, For the MS2E, since it has CANbus, a CAN I/O would be perfect.
Could anybody please elaborate on these statements, or point me towards some source to accomplish extracting more outputs from my MS2E please?
I also read about an IO Extender for MS2.
Would this be a module I could buy/make and use, or are they talking about the daughterboard already installed in the MS2?
Please help.
Npn transistors on The spark outputs will convert the 5v pwm signal to 0v pwm.
Npn transistors on The spark outputs will convert the 5v pwm signal to 0v pwm.
Actually, I just found out a pretty cool way to incorporate the said transistors to the outputs.
A friend suggested I could use a VW/Audi ignition control module, and just hook up the outputs from MS to it.
The module has very sturdy transistors in it, and I would get lowside outputs to run pretty much whatever I need within reason then.
In other words, I would not have to worry about the load a solenoid would impart on the output.
Neat.
Here's the ignition control module:
9 pins; 4 in, 5 out..
4 inputs, 4 outputs plus one ground...
Easy.
This is far from simplistic, now you have this huge modules to mount somewhere and extra connections to manage. Adding the transistors to the proto area of the MS is the cleanest simplistic approach you can take.
I still think you're doing yourself a huge disservice by trying to use a MS2 to control this thing. The boost control methods in that firmware is barely adequate to control a simple single turbo let alone what you're trying to do.
01-13-2018, 09:33 PM
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