Wow! Very impressive project! That's a wild intake setup on there. My impression is that it will be very peaky, but I'd love to see the dyno graph when you get to that point. (lower intake velocity from shorter runners)
Sorry I didn't catch djSL's tag (I haven't been logging on very often) sooner.

Here's something that should be a little helpful: https://www.rx7club.com/2nd-generati...am-uim-946462/
Look at the 2nd picture I posted there, and the item marked "?", that's the Air Bypass Solenoid Valve (didn't bother looking up the name at the time).
It's also related to your idle control system and should be attached attached to the same vacuum line as the BACV, that's pulling a post-AFM vacuum source (note how it's attached to the T hardline).
Unfortunately it looks like someone has blocked that plug on your Dynamic Chamber (intake plenum), it's the large one directly below the BACV port.

Not sure how vital it is, as djSL's mentioned I had been retaining everything except the ACV on my S4 (recently swapped to an S5 intake system, so I'm pretty familiar with most of the bits involved).

Looking at the engine bay pictures, it looks like it's sourcing the BACV vacuum pre-AFM (unmetered air), which could well cause a problem as the computer won't be compensating whenever the valves actuate.
So that's probably the first thing I'd try to address. You can block both of them off (countless people have), but IMO there's really no downside to retaining them as they're only quality of driving improvements.

Similarly, where's the Pressure Sensor vacuum line connected? It would normally be on the Upper Intake Manifold (the piece that your spacer is replacing - see the final picture on the linked post, it's the vacuum line that snakes off toward the bottom right corner). If that's connected somewhere odd that could be causing issues as well.

Keep it up! Excited for you!

 

Ayfkm? Honestly, I've been scratching my head trying to figure out why the BACV is drawing air before the AFM and how that is supposed to help the idle by leaning it out. The FSM and Haines manual have lots of good diagrams and photos but it's not the same as seeing it in person, or with really good photos. Thank you for the link. I've searched and searched for good photos but couldn't find that many that were as detailed.

The pressure sensor, thermo wax and brake booster all draw from the same port located near the fire wall on the exhaust side. Perhaps it's too much vacuum? The photo is looking up under the van.



Put everything back together and no change. Need to check the CAS again and definitely move the port for the BACV. Hope this gets me closer. If not, I'll test the ECU and it that fails, a shop in town said they would be willing to take a look at it but couldn't promise anything. Let's hope it doesn't come to that. It's way more satisfying resolving issues on your own.

 

Yuuuuup.. The diagrams are great - if you're already familiar with the layout, but a bit too busy when you're first learning the system.
No problem! I realized relatively shortly into my RX-Life that such a guide didn't exist (and it would've saved me a LOT of time the first couple times I removed the intake). Also leaving that whole assembly as a single piece is just the right way to go about it.

Hmmm, maybe! You could try checking the pressure sensor by swapping its vacuum source to the lower of the two nipples on the Dynamic Chamber and capping the other hose (assuming it exists because you have the full solenoid rack still - if it's routed correctly this should be one the emissions related solenoids, see: https://www.rx7club.com/attachments/...nes-s4-vac.jpg - if you're not worried about keeping full emissions systems on this, you can eliminate 3/4 of the solenoids and leave just the fuel pressure solenoid+vac lines). Double check that you can suck/blow through that port (at least on the S5 turbo DC there's an apparent vacuum nipple that... Isn't. Can't remember if they did that on any of the the S4 NA DC's nipples as well).
IMO, it's preferable to have the Pressure Sensor's vacuum line be a dedicated port, so that nothing can disrupt the reading (brake booster might well, probably less likely for the thermowax to interfere since it's only going to change once while the engine's running). If that helps, maybe drill and tap a vacuum nipple into your intake adapter/spacer? I would say the Lower Intake Manifold, but it's much more of a PITA to remove.

Stabbing the CAS is always a bit of a PITA. Are you removing the cover when you stab it? Makes it at least a little easier to make sure you got it right (though it'll still move a tiny bit from the nature of the cyclical gear).

The S4 electronics are usually pretty resilient, but this thread also has some good troubleshooting info:
https://www.rx7club.com/2nd-gen-arch...oblems-334730/

You can do it!

 

That color vacuum hose diagram is so helpful!
Thanks again for the links.

To clarify, when you say "pressure sensor", are you referring to the boost or the fuel pressure regulator vacuum? I was referring to the small black box that says "pressure sensor" being connected to the what I think is the vacuum port for a brake booster. According the diagram, the vacuum source for the fuel pressure switch and regulator should come from under the BACV, but due to the modifications of the intake, the main fuel rail gets in the way so it was plugged. I'll have to find where the fuel pressure is sourcing its vacuum from later when I get home.

Where should the brake booster get vacuum? From the location in my photo? The line for the booster in the Vanagon is melted because of its location above the cat so right now it's plugged. The fuel return line also goes over the cat so that will need to be rerouted. That big vacuum port goes to a T, splitting off to the booster and the other half going into a fitting with 4 vacuum ports (like for the oil injection). That 4 prong port supplies the thermo wax and pressure sensor

In one if your photos, I can see where the BACV is connected to the fresh air intake. Just up from there is another T going into a metal pipe. What is that for?

 

No problem! Hopefully they prove helpful!

Pressure Sensor has been in reference to the intake air pressure sensor (boost/vacuum sensor), correct the little black box.

Yeah, if the pressure regulator isn't being regulated correctly you'd probably run richer. Not sure how big of a difference it makes though. My impression is that it's more critical on turbo cars.

Correct, that hardline with the banjo bolt on the LIM is normally a direct line to the brake booster (with a one-way check valve in the hose right before the booster).
Oooh that's curious.. Not sure what that would do with the line plugged (or leaking from damage?)

Ahh yeah, definitely better to reroute away from the hot exhaust juuuuust in case.

Hmmm.. I'd probably try to give the Pressure Sensor and thermowax their own dedicated nipples on that intake spacer - or at least the Pressure Sensor.

So on that BACV picture, you can just about see that it is the fresh air source for both the BACV and Air Bypass Solenoid Valve. The metal pipe routes to the far side of the intake - In the picture immediately afterward it's the pipe that does a swerve above the thermowax and has a hose with a white dot on it, scroll down to my final picture and you can see where it attaches to the bottom of the full size intake tube.

 

The funny thing about this swap is that so much of it looks really professional and it's obvious the original owner had skills, but then I run into problems like the BACV port etc. Not only does the return line need rerouted, but I think I need to install a heat deflector to prevent any wires or brake booster hose from melting.

Yesterday, I plugged off the BACV and disconnected the lead then tried several times to start the engine but it still required just a small amount of starting fluid. It revved high for several minutes then came down to a smooth idle, which is hasn't done for a while. I was surprised to find that the BACV was still drawing a lot of air even with the lead off. It must be dual controlled by the coolant and ECU? Once the motor warmed up, there was hardly any vacuum. This van doesn't have A/C or power steering so I imagine the BACV doesn't get used much while driving. Hopefully this is true because I'm trying to imagine the original builder driving this van all around while running lean. Not a good feeling.

I want to dedicate that brake booster line and reroute the thermowax and boost sensor to another source. It looks like I don't have a charcoal canister so I was wondering if I could steal the vacuum going to the purge control valve (or at least share it). I also found that the fuel pressure regulator is getting vacuum by sharing it from the switching solenoid valve. Maybe I should find a different source?

 

Indeed!
It seems like they tried to copy and paste most of the stock systems in place, which is usually a good approach.
I like the secondary injectors and their baby fuel rails, haha.
Probably didn't know about the unusually large heat footprint required for these engines' exhaust.

Ahh nice!
Interesting - TBH, I've never tested it, but I'd always presumed that the BACV was nominally closed, but perhaps it's only supposed to be mostly closed?
Shouldn't be controlled by the coolant running through, I believe that was one or both of: a convenient place to join hoses or to help warm it up quicker.

The stock ECU is pretty conservative on richness, I wouldn't worry about that too much (if it's lean enough to hesitate that's about the only time to be concerned).

PCV and Charcoal should be unrelated? Though, you could disconnect both PCV vacuum lines to the DC, cap one, and have one available for each the pressure sensor and thermowax (again, make sure both nipples have airflow freely into the DC).

I'm still in favor of adding additional vacuum nipples to your intake - maybe one above and to the left of where the BACV bolts up?

 

Thanks to Derekcat (and the rest who chimed in) I was able to take Van Wankel on its first drive since 2006! There is still a lot more work to do before it's completely road worthy (expect more questions) but it sure feels good to drive it. Brap Brap!

 

Awesome! Kudos man!

What was the final trick there?

 

Right now, just plugging off the BACV until I come up with the best way to connect it to the fresh air intake post AFM. I also need to resolve the cold starting issue. Still requires a small squirt of starting fluid but fires right up and runs well after that. Before taking it on a test drive, I checked input 3b on the ECU and it was close to 10v while cranking. The AFM tests good and I replaced the water thermo sensor. Double throttle chokes when cold and the engine fast idles for several minutes. Not sure what else I can check. It seems to start fine when warm.

 

The other day, I went through all of the circuits on the ECU and most were in spec, save for a few.

2I water thermo sensor reads 2.5v cold (60 degreesish) but I think that's normal
2P relief solenoid reads 12v. Should be below 2v
3J battery (not sure what this means) no voltage

On the 1 row, E, G, I, F, L, O, W and R are disconnected.

​​​​​​Then I tested the trailing circuit because I'm not getting any spark. Results are as follows:

1m 10.2v, 1u 2.12 with engine running, 1v 1 volt, 1x 1v cranking and 10 running.

Trying to resolve no cold start issue and no trailing spark.

 

Any advice on not starting while cold? AFM tests good, water thermo sensor seems to be with-in spec, pin 3B on ECU reads 9+ volts during cranking, I have good compression (95-100 cold on both rotors), injectors were cleaned and tested with new seals and battery is charged. Motor will start pretty quickly with starting fluid and starts ok when warm. There's a possibility it's burning coolant but the plugs don't seem wet when I check them.

 

Hey sorry!
Been super busy moving and working to death (Never do the full deal on a first gen IS300 timing belt/waterpump/seals kit.. freakn nightmare).

Hmmm.. How fast does it sound when it cranks over? Generally trouble cold starting would be an indication that your compression or cranking speed is too low.
That it starts with a hit of fluid is weird though.. What about if you squirt a little 2-stroke oil into the combustion chamber via the Leading spark plug hole (simulates increased compression) while cold and try starting?

I don't think BACV should affect start up.. Though no Trailing spark may be an issue as well (once warm most people say the only help emissions, but I imagine it helps with cold start). IIRC there was a test for the trailing coil packs in the FSM? Checked wiring continuity to them?

 

Thought I'd post a quick update on Van Wankel. Finally found a shop willing to look at it as my wife was becoming increasingly annoyed at how much time I was spending on it. They sent me a link with the results if anyone is interested.

https://reports.autovitals.com/Inspe...0BynXFaT9ewagA

I have bad plug wires. That's on me for not replacing them. Found a low voltage issue with the trailing coils. I'll need to get more info when I pick it up and he is concerned about the TPS. If I read it correctly, it's maxing out too quickly (1/4 throttle compared to WOT). I'm more concerned about that more than anything.

Good news is, no hydrocarbons in coolant but I need to find out why it keeps going low. Decent compression on motor and otherwise seems to be in good running order

Can anyone look at the ECU results I posted earlier and let me know if they see anything that sticks out?

 

The TPS reading is normal for an S4. No need to replace it based on the travel. It might need adjustment based on the "surging while cruise" noted.
Replace the plug wires.
Didn't see anything about timing check. Did you re-stab the crank angle sensor?
"Underpowered Engine" - That chopped manifold is going to perform poorly at low RPM. Does it still have the 6-port actuators on the lower intake manifold?
In their compression test picture, the fuel supply line looks tiny compared to the hardline. Could that be restricting fuel flow?
Not getting 12v at the 1J ecu pin seems like an issue.Might be worth getting that connected. Don't think the dash light is worth worrying about right now.

For cold start, maybe the fuel pressure isn't building fast enough. Possibly a cracked o-ring or leaky in-tank connection. But then it's fine when there's already pressure in the system. You could try adding a manual switch to prime the system.

I don't think the other ECU pins should change how it cold starts or performs.

 

Red

 

Finally got a chance to speak with the mechanic yesterday. I walked away with mixed feelings about spending money at this shop. Though I don't doubt he knows how to work on cars, I think his experience with rotaries is limited. He said the motor had good compression but he did the test using a standard compression tester with the check valve in. He's pretty adamant that the TPS is bad because it maxes out at 1/4 throttle. He didn't check the timing or the water thermosensor. And when it comes to the trailing coil issue, he says it's a voltage drop problem because the 1M BL/R wire is reading 10v. FSM says it should be below 2v so I'm not sure where he is getting that info from.

In regards to the trailing coil, anyone have any insight on whether it's a CPU or coil problem? I've taken it off and wire wheeled the mounting bracket and cleaned up all of the mounting screws and bolts. Then I added two additional ground wires to the harness just to make sure it has a good ground source.

Ground- .2 ohms
T1 & T2 resistance .7 ohms on both with negative battery disconnected

Key on
BL/R 1M approx 10v (should be below 2)
BL/Y 1X 5v then 0v while hand cranking engine
Br/Y 1U 5v then 0v while hand cranking engine
2 wire connector B/Y 12v+ (matches battery)

Running
Bl/R 10v approx
Bl/Y 1v cranking/Ov running
Br/Y 2.1v

I'm going to double check the above values because this was before I cleaned the grounds.

 

Updated DMM numbers.

Bl/R 1M 12v running
Bl/Y 1X .7v running

I adjusted the TPS via the 1v method this time. Was using the ohm method before. Started at 1.35v but now correct. Seems to pop less now after revving.

When I do rev the motor up, a small puff of water vapor shoots out of the tail pipe and there is a steady drop of rusty looking water as well. The exhaust also smells a little sweet so I'm pretty sure I'm losing coolant in the combustion.

Lastly, I discovered something new about starting it cold. If I crank it several times then let it sit for about 2 minutes or more, it will fire up instantly on the next try. Not sure what the motor is trying to tell me but I thought the information could be useful.