Thank you! An OEM duckbill would have been my first choice if they were a bit more common. In retrospect the fiberglass part (crappy as the fitment may have been) has the advantage of lasting longer, all things being equal. I've heard many accounts like yours of the rubbery stock piece deforming due to age and heat. The corner I repaired on the fiberglass piece is beginning to fail, but I'm confident I can do better repairing it next time with what I've learned about bodywork. That's a problem for this summer.

 

Not an update per se, but I did get a chance to try reconnecting the OEM manifold temp sensor. I got most of the way there before finding out that my OEM sensor was dead despite the fact that it worked perfectly fine when I unplugged it to use a GM sensor at the MAF. I don't really want to drill / tap the manifold for a GM sensor when I'll be swapping them out with the engine anyways and the lean condition only presents for a few minutes, so I'll probably just ignore it.

On the CAS front the new trigger wheel should arrive Monday. I probably won't have the time to actually weld it up and install for a few days later since this is exam week. I've also pulled apart the water pump assembly to fix a small leak so all of that needs to go back together before I can test the new wheel on the engine.

 

The trigger wheel arrived, and at first glance it looked pretty good:



But when I actually placed it against the pulley, it wouldn't sit flat. Turns out it's significantly warped:



It would be fixable, but I'd really rather start with a part that is straight. PCBWay has pretty good customer service so I don't anticipate any issues getting a replacement. It does push the timeline out a couple weeks unfortunately.

 

since your CAS is on the Periphery of the wheel it might work, but i can tell you if you had it on the side like the FD/Rx8 it wouldn't run at all
the FD is PICKY

 

Have you tried clamping up to the AC pulley yet? It's thin enough that I'd think you could force it flat again while welding. My preference for these types of parts are to oversize the trigger wheel thickness and post machine to the desired thickness after welding because you'll get some warp from welding as well.

Offer still stands

 

I think it would work if I were to clamp it firmly before welding. The Chevy sensor is really forgiving, and the warping isn't pushing the teeth sideways or anything. But I paid PCBWay under the (reasonable) assumption that the part would be flat, so I'm seeing what kind of resolution they're willing to offer before I do anything.

 

When I restored the air pump, the main goal was to restore proper aux port actuation. I also said I thought there would be a way to gain some area under the curve. This is the post where that all comes together (sort of).

The first thing I needed to do was add in some solenoids, and connect them to my MS3X through a sub-harness. There's one MAC valve on the shock tower:



One stock S5 boost solenoid (borrowed from my Turbo II engine) on the manifold, where the sub-zero cold start assist system used to live (obscured by this hose I probably should've removed for the sake of the photograph):



And a big mess o' vacuum hoses:



So what is going on here? I'll explain:

- One source of vacuum (uppermost blue hose) runs to the MAC valve inlet. Then from the MAC valve outlet, that vacuum is split to the two nipples above the ACV.

- The nipple I added to the air pump outlet connects to the S5 boost solenoid inlet, and the outlet of the solenoid connects to the aux port air supply tube. There's a small hole in the hose on the aux port side to allow air to flow back when the ports return to their home position, otherwise they can get stuck open.

This should in effect give me complete software control of the ACV, but also (in theory) allow for continuous control of the Aux ports rather than the discrete on/off behaviour of the stock system (since I can control the pressure at the outlet by varying the duty cycle on the solenoid). Now, the last part really didn't pan out and I'll explain why in a minute. But it's worth talking about how the stock system works before I move on to my findings.

In the stock system, puttering around at low rpm / low load the ports remain closed. Once you reach a certain amount of load (the training manual says "4500 rpm" although it is in-fact a load based system, not rpm) the ports open and you get the additional intake timing. The way the manual specifies an engine speed is a bit incomplete (6000 rpm at 10% throttle probably won't cause enough back-pressure to open the ports, but 4000 rpm at 100% throttle might).

Now when I say that they only have a discrete "on/off" behaviour I don't mean that in the literal sense - the manual lists 1.2 psi as the point where the actuator should start to move, and 2.1 psi as the point where it's done). But in my testing the actuators have basically three positions: "Closed", "Open slowly", and "Open quickly". I can't find any duty-cycle that causes the actuators to hang at 1/2 way for example. So while I can smooth the transition a bit by setting say 50% duty, I can't actually hold a specified intake timing. At least with my current setup.

So with that knowledge I decided it was time to try and find the best transition point for the ports. I started by setting the duty on that solenoid to 0, and then started a second gear run from idle to redline. Then I changed the duty on the solenoid to 100, and did an identical run. Once I got home I cut out the remainder of the log to end up with the following:



You can kind of see the trend there, but it isn't very clear because there's a lot of other things going on. Conveniently the histogram tool in MLV makes it easy to cut out the noise and visualize the data, and also lets me specify the y-axis units:



If that still seems confusing then here's what's going on:

- The left hand side shows the engine RPM.

- The middle column shows the MAF reading at a given RPM value with the Aux ports closed.

- The right hand side shows the MAF reading at a given RPM value with the Aux ports open.

Most of the alternative Aux pump actuation methods I've seen either just tap off the air pump (tying the aux port actuation to engine speed, although the exact RPM at which it changes over is unclear), or sometimes use an RPM based switch to allow the user to select the engine-speed for the changeover. Either of these works fine, but from experience the Aux ports being open too early (say 2000 - 2500 rpm) is noticeable when driving.

So I really wanted to be a bit more scientific about it. The rationale for the aux port is that at low load the smaller secondary ports are more efficient. In my (admittedly amateur) understanding of the engineering concepts behind this, this is because a port being too large causes a decrease in flow. I'm assuming that (like an exhaust system with too great a diameter) this is due to the turbulence in the large port causing a decrease in overall flow. The aux ports only become efficient at high load because at that point we are exceeding the limitations of the primary + secondary ports in terms of flow.

With that in mind, my intuition is that MAF is actually the best measure of where to configure the changeover (since we want to pick the point where we are outflowing the primaries + secondaries, not some rpm value). Someone running speed-density could use the calculated air flow as a proxy and it would work just as well. We don't actually care about the number so much as the comparison, since the MAF flow curve was not changed between those two runs and we know it will be consistent. So with all of this in mind, here's a PowerBI graph visualizing the above data:



There are a couple of really interesting things about it (keeping in mind that both of the above runs are at WOT so throttle doesn't enter the equation here and we can speak in terms of rpm):

- There is surprisingly little difference from 1500 to 2000 rpm. This might just be due to the poor low rpm chamber filling of the rotary engine itself, but that's just me speculating.

- There is a surprisingly large difference from 2500 to 4500 rpm. This is definitely noticeable when driving. At 3500 rpm it's around 15% more flow with the ports closed.

- The aux ports only become efficient at 5200 rpm. About 1200 higher than the commonly accepted online 4000 rpm number for when the ports are "supposed" to open, and still 700 rpm higher than the training manual's 4500 rpm figure.

- Something's going on to cause that dip at 6250. I think it's tune related. My AFR table still references map for the load which might be causing some weirdness (MAP by 6000rpm shows as 90, which is actually less than the 95-98 I see earlier in the run), and I also noticed AFRs started to get really rich nearer to 7000. In fact, AFR was actually out from target quite a bit during this entire run, so I'll need to revisit my flow curve to see what's up.

Now there are some mitigating factors. For one, I only did one test run. A proper test would involve many back-to-back tests. Two, my car is not stock. The engine itself should be a stock port S4, but I have a different MAF from factory and my exhaust is probably flowing more than stock with it's 3" diameter from the catalyst back. It's not clear to me whether the behaviour I observed would be the same for a stock car (although admittedly I would've expected a modified car to outflow the primaries earlier, but then air flow is a complicated thing). And lastly the intake temp drops a few degrees between runs.

But this does tell me where to configure the changeover:



The reason I picked 112 g/sec and not 118 (where the lines cross in the graph) is that it takes a moment for the ports to open. So I want the ports to start opening slightly in advance of then. The hysteresis value was just something I picked somewhat arbitrarily to prevent the solenoid bouncing around. I'll only know whether 15 is a good number with testing.

So for now that's where I'll leave it. As soon as I get the chance I'll do another back to back to back test with the ports always open, always closed, and opening at my configured set point. Then I can overlay the three lines and see what happens. Until next time

 

On my lunch break at work, and I wanted to take a second to expand on why I originally wanted continuous control of the port timing:



(Forgive my editing, I did that on my phone)

The difference in port closing time from the secondary port only to the aux port fully opened is pretty significant. I think it goes from 40 degrees to 80 degrees, or something like that. So even though the opening of the ports is smoothed somewhat by the actuator, it's a pretty dramatic change in intake timing.

The challenge here is that I can't pick and hold an arbitrary port closing time. So I can choose between 40 or 80, but I can't choose 50. This leaves some power on the table. If we look at the first red mark I made on the graph, we know that 40 degrees is unambiguously flowing more than 80 degrees would at that RPM.

But to the right of the first mark, we can see the gap starts to narrow. So while 40 is still definitely closer to ideal than 80, 50 might actually maximize the power output.

What I'm going to do is try to fine-tune my current setup (the vacuum hoses certainly need to be neatened) and see if I can find a duty-cycle on that solenoid that gives me the fine control I'm looking for.

 

interesting, i hadn't thought of that. maybe you should find a half way point, and make a run and see what that is like?
so one run at 40 degrees, one at 80 and one at 60?

 

rotary VTEC just kicked in yo! as always great stuff, my poor car hasnt been touched...im still fiddling with her s2000 and i bought my first subaru so im learning about EJ engines the hard way.

 

That's a good idea. What I could do is another set of two runs with full open and full closed, followed by a run with the actuators zip-tied in the 1/2 way open position. If my theory is correct (which I suspect it is, because that's how VVT works on traditional engines) I should see the 60 degree line land right in-between the 40 and 80 degree lines.

That won't fix the issue with my being unable to hold an arbitrary port position. But it will show me if the theory stands. My original goal was to move to entirely electronic actuation using stepper motors or possibly solenoids, but either one will be unhappy with the heat in that area of the engine. I'd have to make some sort of elaborate bracketry with cams and cables (sort of like a throttle cable but with two ends going opposite directions) and mount the solenoid far away from the heat.

I'm thinking I should swap around the MAC valve and the stock boost solenoid because it seems like a bit of pressure wants to sneak past the stock solenoid even in the closed position. Maybe the internal seals are gone. Then tee a PCV valve or similar into the line to the actuators so I can get rid of the small hole I added to the hose (to allow the actuators to return back to their home positions). This should make the relationship between the duty cycle of the solenoid and the amount of pressure on the outlet side more precise and hopefully let me vary the duty to hold a desired intake closing time.

If that works then what I would probably do is figure out what duty equated to what intake timing (I'm measuring the rotation of the point on the outer circumference of the rotating sleeve in terms of linear shaft movement at the actuators, so I'd have to learn the math behind that). Then do runs at closed (40), 50, 60, 70, and finally full open (80) and overlay all the lines in Power BI. Draw a line through the intersection points of each subsequent line (where 50 crosses 40, where 60 crosses 50, etc) and that line would be the theoretical maximum. Then use the 3D table for generic PWM on that solenoid as a 2D curve (I want it agnostic of RPM since I'm purely concerned with MAF) by making all bins in a row identical. So knowing the maximum MAF at 40 degrees and knowing the maximum MAF at 50 degrees, the ECU will do the job of interpolating the duty between those bins so it moves smoothly through 41, 42, etc like it would on a piston engine.

Or maybe it doesn't work like this and I'm getting ahead of myself

There's no easy way to earn about EJs. I once talked with a guy who told me his 2017 STI was on it's third engine and had under 100,000km. I'm willing to bet none of them were stock, but damn. My Rx7 is on engine 3 (supposedly, the previous owner wasn't super clear on that) and it's going to hit 400k km soon. And people say rotary engines are unreliable.

Even the local shop that does tons of Subarus has no illusions about it.

 

Have you put any more thought into actuating then with a servo of some sort?

 

A lot. Unfortunately it's a bit of a complicated problem. The first problem is the actual motion of the actuator sleeve. Here's a picture I found online:



The sleeve rotates and the little pawl thing that engages on the actuator is eccentric to the center of the sleeve. So the actuator has that little hinge to allow it to translate linear motion into rotation of the shaft (otherwise pulling straight down on something that is forced to turn in an arc just wouldn't work). That's not that complicated on it's own, and someone has solved it before as this blurry photo shows:



My concern is the "withstand extreme heat" part. One thing I found when searching online is that these solenoids often have a relatively low duty cycle, so if they're on for 30 seconds they need to be off for two minutes to cool off. Let alone being directly above the hot exhaust manifold.

So with that knowledge, I would need to remote-mount them. I thought of a few designs, here's one I just drew quickly in MS Paint to illustrate my point:




The two shafts both need to be pulled inward. So I thought of this design with a wheel mounted on a central spoke placed centered equidistant between the actuators. The two straight black lines from the wheel to the actuators are rods, and the black line going to the blue solenoid would be a cable. There would also have to be a spring somewhere here to make it return to the home position.

When the blue solenoid pulls the cable inward it rotates the wheel counter-clockwise, which in turn pulls each rod in the direction away from it's respective actuator and pulls the ports open. Then a spring would pull it back.

The problem with this (and all other designs I thought of) is the design complexity, manufacturing complexity, and the amount of space it would take up. I put the solenoid pretty close to the wheel in that drawing but it would actually have to be much further away to remain cool. Even then I doubt it would last long. Then it also has to be reasonably strong. Maybe it's possible to make a heatsink and fan but at that point it's a lot of effort when the air pump method just works with minimal effort.

The blue solenoid and it's wheel could also be replaced with a stepper-motor with a wheel on the end of the shaft, so as the wheel on the stepper rotates it causes rotation on the central wheel. I think there would still be heat related challenges though. Plus the engineering complexity of this sort of solution in the first place. If I weren't concerned with heat it would be best to just modify the ends of the sleeve shafts to accept the stepper motor shaft directly and make some sort of mounting solution, linking it 1:1 with minimal complexity. But again, I have my doubts on any of these electronics surviving long directly above the exhaust manifold.

If I can get the boost solenoid I'm using to be a bit more consistent I think I might be able to make continuous control work the way I want it to with the air pump actuation. I think the current problem is that the hole I put in the hose to allow the actuators to return obviously leaks some air constantly, and the solenoid itself seems to leak a little air past even when closed. So if I can fix those two issues then I might be able to control it more precisely by varying duty-cycle on the solenoid to control pressure on the outlet side.

At present it either doesn't open or opens slowly, which puts me in a weird place that I would need some sort of peak-and-hold behaviour on the PWM output (start high to force the actuator open, then taper down to some duty that holds it open at the desired rotation). Obviously that would be complicated to implement properly and is an electronic band-aid to a mechanical problem, which is why I won't be going down that road. I only mention it as a sort of thought-experiment.

 

too bad you cant just slap a 3d printer servo right on to the rod that sticks out of the seal.

 

McMaster Carr lists the insulation maximum temperature for their solenoids and steppers at 266 degrees F. That might be possible to make last with some heat shielding. For 256$ they have 12v solenoids rated at 350 degrees.

 

Look up Watts linkage, it's a suspension thing but I think it might work for actuating the aux ports, your idea is very close to it. basically a vertical bar with a rod coming from the top and going to one side and the bottom to the other side. rotation either moves both rods away from the center or towards it. Maybe fashion a bracket and use longer block off plate screws for mounting, run the actuator to one of the pivot bolts on the vertical bar.

 

If you do go with a linkage style, you could use something like a cruise control motor and mount it wherever you want.

 

Ohhh, those are linear too. You could have finite control of open positions. Tie a linkage between them like windshield wipers and actuate the linkage with the cruise cable.

 

the Turbo 2 and FD actuators are stepper motors, with a cable!

 

well nevermind then! back to the Baja!

 

Okay, so I have some new findings. This evening after work I swapped around the vacuum lines a bit to use the MAC valve for AUX port control instead of the S5 boost solenoid, and I made a few observations:

- Boy, the MAC valve is super loud!

- I did not need to put a hole in the outlet side hose to let the ports return to their home position, so there's definitely something wrong with the S5 boost solenoid I'm using. Glad I found that out before I tried to, you know, control boost with it...

- I did actually gain some control of the AUX port opening.

But there's a caveat that throws another wrench into things - it's still dependent on RPM. Most of my plan was based around the understanding that the air pump free-wheels above 3000rpm. I even noticed a sort of slip-ring clutch type thing inside the front hub of the air pump while rebuilding it.

My initial theory went something like this: The air pump flows some maximum amount of air when it starts to freewheel. By testing with various hole sizes drilled into the little plug I 3D printed, I was able to find the right size so that the pressure is sufficient around 2500rpm to open the AUX ports. By using the solenoid to control the on/off of that vacuum hose I am able to control when the ports open. By using the solenoid with PWM instead of a simple on/off, I can control the pressure on the outlet side and open the ports part-way to a position of my choosing (above 2500rpm of course).

The air pump continuing to build pressure above the point where I thought it was at maximum adds some challenge to this. In my testing I was able to find a duty value that made the ports open later (full open at 6k) which presumably means that if I were to hold at some RPM below that they would hold at a given point (say halfway). This means that it is theoretically possible.

The challenge is that now RPM is an extra variable that needs to be accounted for. I could potentially wire in another MAP sensor (I have one around), test to see the PSI required to hold the ports at various positions (the factory gives some values but I'd want to be sure), note it down, see what PWM duty provides said values at what RPM, put that into the table, do some runs, etc. Since PWM is a 3D table I can make a map for it that has various PWM duty values for various RPM and MAF points. But frankly that's extra wiring and a lot of time for something probably best solved with a proper linkage. And while this has been a really fascinating experiment it's hard to justify the time and expense to fabricate said linkage for maybe 5-10hp gain when I could just put that money towards dropping in the Turbo II engine sitting in my garage and make an immediate ~70hp gain.

For now I think the AUX port project is on the back burner. I'm working full-time again for my summer contract and the car drives great as-is. I'm probably going to just use the MAC valve in the on/off arrangement I was using the boost solenoid and leave it at that for the time being.

 

as much as the cutting edge of port actuation is a stepper motor to a watts type linkage, perhaps i have another idea.

the FD has a vacuum and a pressure tank, and it stores these so it can slam the turbo actuators open (or closed), so maybe that would be the way to go
use the air pump to fill a little pressure tank (you need a check valve) and then you can open the valves whenever you want. it doesn't fix the pressure vs rpm problem, but it probably makes it better more complicated

 

You could use a vacuum pot too, just make sure it's pulling in the right direction. Use a vacuum tank to store vacuum if you think it's necessary, but I think controlled engine vacuum would be sufficient.

You just need a way to apply and kill vacuum to the actuator.

 

Actually using vacuum would have made this a much easier proposition. Then I could ditch the belt-driven air pump entirely in favour of a small vacuum pump and just use the solenoid from there (since the output is set).

Unfortunately the actuators work using pressurized air, so vacuum won't do it.

EDIT: Actually, come to think of it, I've never tried using vacuum. I can't see how the actuator would work on both positive and negative pressure, but maybe I'll test it just to see.

 

I meant to operate the mechanism I described, I offered up the linkage idea because it allows you ditch the exhaust pressure actuators, seems that's a sticking point in every thread on doing this. You might need a double acting mechanism to generate enough force to close them, the vacuum pot return spring may not be strong enough. Adding a simple spring might be enough, those vacuum pots have a lot of force in the one direction.