With everything tacked I was ready to “finish weld” it.

I put that in quotes because I feel bad calling my work on this project “welding”. In short, it’s a combination of lack of skill and poor tools. My welder is a $300 special from Canadian Tire. It has four voltage settings (so you have to choose between “too hot” and “not hot enough”), the wire-speed varies audibly as I’m welding, and the settings required change drastically depending on temperature.

All that is to say that I was already starting from a poor foundation, and my lack of skill didn’t help. I’d actually made a small repair on the y-pipe in the past and found stainless quite easy to weld, but this time I ended up using too little current in an effort to not punch through the pipe.

This resulted in welds that looked like this:


The "Evil Energy" v-band came from Amazon. The logo is kind of ugly, but then it's hard to argue with $35 for all stainless bands and clamps compared to $100 from Vibrant. They work really well.

Predictably it looked terrible and leaked a lot when I did my first startup. So much so that I ended up grinding down all my welds for several hours and then rewelding everything a second time. I had to turn the welder to maximum power before I ended up getting a decent arc, and then after that the problem was mostly down to my method. The second pass didn't make it look much better, but it was gas-tight.

The back side of the weld was not protected by the shielding gas. Normally these parts should be back-purged with argon to prevent the back of the weld sucking in carbon, but without the equipment to do so I decided to compromise.

There are also two other factors that anyone considering a similar project should consider, which I failed to think about:

- Welding stainless too hot can compromise it’s anti-corrosion properties. Because I had to choose between too hot and too cold, I had to err on the side of too hot, and this has likely impacted the longevity of my exhaust.

- Stainless should be welded with pure argon, and I used 75% Argon 25% CO2. The stainless WILL weld fine with it, but the CO2 in the gas can allow carbon to get sucked into the weld and this will (again) compromise the anti-corrosion properties. I've used it for repairs on stainless before that seem to have lasted fine

Overall I doubt it will seriously matter. I might only get 10-15 years out of this exhaust rather than 30. By that time hopefully my skills will have grown and I can make an even better one.

With everything welded (again), the exhaust looks like this. Starting from the back is the small curved section, that rotates the resonator towards the passenger side, then the resonator itself:



After that, there is a small curved section rotating the catalyst back towards the driver's side (now running under / to the side of the transmission crossmember), and the catalyst itself with heat-shield:



And from there it’s just the original pipe.

Unfortunately I still have a slight leak from the flange where the manifold meets the downpipe (which might actually be the only original part of the car at this point). One or both of the flanges are warped. I did sand them down some, but frankly I just don’t want to fix this part. I have another manifold that might be better, but has bolts snapped off in all of the heat-shield mounts. I don’t really want to chase down another manifold or spend on a set of headers that will be replaced when I swap the engine, so for now I used some of the orange exhaust goo to mitigate the problem and will be ignoring the sound.

Speaking of ignoring the sound, a new set of shifter boots will help with that. I drove with the wrench shifter and no boots at all most of this autumn, and the rushing of the incoming air was lots of fun. Plus some leaves flew in, which added to the whole experience.

Honestly I could live with just having a gaping hole where the shifter comes through, except that the driveshaft is reachable through the hole at the right angle. I don’t want myself or a friend to lose some digits by absent-mindedly putting a hand in the wrong place, so I put the old boot back in while awaiting the new one.

The old boot is pretty crusty:



I found the cheapest source for these was Amayama, although it did end up taking about three weeks to reach my door. A perfectly valid trade-off when I’m not concerned about speed. The set comes with a new lower boot, middle boot, and upper boot. The middle and upper are identical, which made install a bit clumsy. I’m not sure whether it’s supposed to be that way or whether I received two identical parts by accident.

The lower boot was easy to remove because it was in such poor shape. Four bolts hold the little retaining plate in, and then the boot can be twisted inward until it pops free of the plate.

Here’s a comparison:







It was a bit tricky to wrestle the new one in, especially without removing the dash. The best way to do this would be to disassemble the shifter entirely and remove all the dash fasteners so it can be lifted up a bit, but it is possible to install without removing anything else.

Then I installed the middle and upper boots. The upper doesn’t sit very neatly since it’s identical to the middle, leading me to believe that maybe I wasn’t supposed to get two identical ones:



But it does seal, and it does dramatically reduce the noise while driving. So overall I’m happy with it. The wrench shifter started out as 50% joke, 50% not having a shift **** in the correct thread. I usually put the wrench shifter back in whenever the car is in a state of disrepair, but over the autumn months it's kind of grown on me. I'm still not sure how to integrate it with an interior that I try to keep mostly stock-appearing. I kind of want to put the 626 **** back in, but then the wrench feels super "clicky" and it's a lot of fun. Plus all my friends like it. I'm not sure where I'll land on this.

So what does the exhaust sound like? I took a short video to demonstrate:


Unfortunately it clipped the mic when I revved it, and it isn’t quite as bassy as real life, but it is a fairly good representation. The resonator made it a little quieter and removed some of the higher frequencies. It’s still quite loud when I wind it out, but idle and cruise are a lot better. I do still have a loud pop when I rev it high, but I think that’s something I’m going to have to live with. I might be able to tune out the popping on decel by playing with the DFCO transition point.

I was able to take a few test drives before the snow returned and the car is much more enjoyable to drive now. Not nearly as loud, and no exhaust stink rising through the shifter hole into the car. The only thing I have yet to test is whether the drone on the highway is gone.

Even from behind the car the stink of the exhaust is significantly, significantly reduced. I still need an air pump solution to help the catalyst survive longer but for now I’m quite pleased with the improvement. The catalyst sits much higher than before and only the heat-shield dips down below the frame rails, so I’ve also regained some clearance.

Lastly, the car feels like it makes more power at the top end. I’m thinking the original catalyst was clogged. Here’s an interesting picture I took:



I’d noticed this in the past and always chalked it up to being part of how the split-air tube works. I figured maybe the reason it goes all the way though the catalyst at an angle is that it has perforations to deposit the air evenly throughout the core, but then I don’t see any light coming through it even when I shine a flashlight. This leads me to wonder if the split-air tube is clogged (or mostly clogged). I know my auxiliary ports were working before. This means that there was at least some flow coming through that tube to drive the actuators.

Speaking of which, I am running with the aux ports zip-tied open for now (basically keeping the intake ports open 40 degrees later than normal at low RPM). I don’t love this solution (idle is noticeably worse and the car is a bit unhappy cruising below 3k now) but it will remain that way until I add in a better solution. Once I have the parts in-hand I should have a solution that improves the idle / emissions, and adds in improved aux-port functionality without a belt-driven pump or ACV. I think I also have a way to add some area under the curve in the 2500-4500 region too, but no promises until I can test it.

Until next time

 

I love it when this gets updated also that new exhaust *****

 

if i might share what i've learned about turbo rotary exhausts, its pretty simple.

Metal cat vs Ceramic. the metallic cat has two advantages over ceramic. the first is that the metal substrate is thinner, so it flows better. the Japanese tuners claim the metal cats (SARD/Metallit) flow the same as a straight pipe, which is nice. you get to have your cake and eat it too
the second thing, is that it can handle higher temperatures. ceramic works at like 450-650c, over that and they get melty. the metal cats can run hotter, the SARD/Knighsports ones claim 1100c. the stock ECU runs really rich to keep cat temps under control, if you remove that, you can tune for power instead.

the other is just size. i read a book by David Vizard, and he wants 2.2cfm of exhaust flow per hp. he then says pipe is 115cfm per square inch. he didn't go further, but its easy to do the math.
Mazda's stock exhaust pretty much fall in line with this formula, 60mm id is about right for 200hp.

the aftermarket and/or rotary people use something closer to 3cfm per hp. which puts you at more like 70mm. the problem is that the flanges for the FC are 60mm, which is the problem.
the Japanese tuners go a step further, and since the stock turbo is a limitation, you put an even bigger exhaust on, which sort of maximizes the stock turbo. the next thing that pops up though is the boost creep, and you just need to either put your big boy pants on and run 13psi, or not have that exhaust, lol

 

Yeah, that was part of my thinking when selecting the metal core. I've basically been tuning it with complete disregard for the catalyst, and that's what I intend to continue doing. If the catalyst needs to be replaced after a few years then so be it, but if possible I want to get as much life from it as possible while not compromising at all on the tuning side. I can't do much about when I'm running lean (I'm not going to waste fuel and reduce power to save the catalyst) but the air pump should help minimize the impact from the rich idle.

Vizard is an interesting guy, and he seems super knowledgeable. I've watched a handful of his YouTube videos but have yet to read his book. Those numbers agree with my intuition which is that 3" is a bit too big for an NA rotary, but then I'm not really building it with NA performance in mind so I'm okay with that.

There's an interesting discussion to be had around how the diameter of the pipe being too large can be a detriment as well. There is a lot of internet myth about how you need "back-pressure" for low-end torque, which I think is a misunderstanding, but it makes sense that too large a pipe can cause turbulence on the exhaust side whereas an appropriately sized pipe will basically use the momentum of the exiting exhaust to pull a vacuum on the exhaust ports and help suck out any remaining exhaust.

Then if I were building to keep it NA, I would also have to sit down and learn the math about how to determine the correct header length to maximize horsepower at redline too. Basically doing what Mazda did with the dynamic chamber "dynamic supercharging effect intake" but on the exhaust side.

I ended up disregarding most of that. Turbo is the easy button, just get as little exhaust restriction as possible (or in our case, as our wastegate will allow) and you're set.

 

For our next installment of “parts everyone else throws away but I go to way too much effort to keep”, we need to talk about the air pump.

I left off talking about a solution for the air pump that didn’t involve the belt-drive or the ACV. Unfortunately, my research basically turned up no electric air pumps that were designed for constant duty.

The Rx8 for example only runs it’s pump during warmup. Most of the pumps I have looked up say something to the effect of “90 seconds maximum continuous run time”. They just aren’t designed to do what I want them to do and run all the time.

This left me with the stock pump. It’s reliable, it’s purely mechanical, and it has a built-in clutch so it freewheels past about 3000rpm and doesn’t rob too much power. Unfortunately there’s a glaring issue with that plan which I have yet to figure out, but we’ll come to that later on (bonus if you can figure out what it is).

My stock pump is not in good shape though:





It’s a bit dirty, but the bigger problem is that there is some friction in the bearing. When I spin the pulley I can feel a couple tough spots. It also makes some pretty bad scraping noise as I turn it.

Keep in mind I had no idea how these pumps work or what I was doing. I saw some old pictures of a disassembled pump, but a few old post indicate that the inside of the pump was “not serviceable” or at least not easily. We’ll see about that.

Lastly, there’s the reason I initially removed it:



The bolt that holds the pump to the tensioner arm snapped off. You can see some of the damage I caused trying to remove it years ago, but trust me, this wasn’t me being overly aggressive. That thing is STUCK in there. Extractors didn’t bite, heat did nothing, and I even slotted the bolt with a Dremel to try and use an impact driver. All I managed to do was twist the hardened impact driver bit.

Disassembly is actually fairly simple. I expected it to be a lot worse when I read that the entire front stack is pressed together. To start, the pulley comes off of the hub with three bolts:



Then there are four 12mm bolt that hold the cast-iron back plate to the aluminum housing.



The two locating dowels can make it tough to remove but a hammer will free it. Be sure not to damage either of the machined surfaces or the dowels themselves.



Once it’s free we can see this spindle thing. I don’t know the technical name, but the bottom surface (race?) is concentric to the pulley and the spindle is offset. It’s really neat how this works, I’ll get into that a bit later.

If you’re using this as a guide, make sure to take alignment marks from here on out. Everything inside the pump is balanced, and wears together. I don’t know exactly what happens if they’re out of balance but I’m not eager to find out.

The inside has this plate with balancing marks on it and a central bearing:





It comes out with 6 hex bolts. I put it aside after noting it’s alignment, and now we can see how the pump works inside:



There are three vanes, each made of some sort of plastic (phenolic I think). Then there are these graphite-feeling seals on either side of them, one of them sprung. These vanes ride in a round cutout at the bottom of the aluminum housing (sorry, forgot to photograph the empty housing) concentric with the pulley, but their clearance to the housing is actually dictated by the shaft on the back plate.

The shaft sits offset from the center of the housing so that as the inner rotor spins, the vanes move in and out. They first move outwards on the intake side of the housing until they touch the housing itself, forming an enclosed chamber around the intake air. Then they spin around to the outlet side and pump the pressurized air out, before retracting back into the rotor. They pull all the way back into the rotor to sweep past that little wall dividing the sides of the pump before beginning the cycle again.

I know it’s just a simple rotary vane pump but I still find it neat. The problem with my pump is that it's full of crap:







Most of it looks like soot, which likely means the ACV I had on the car before wasn’t sealing very well internally and exhaust was somehow backfeeding into the pump outlet. Maybe the catalyst being clogged caused the pressure in the exhaust to exceed the pump outlet pressure? Who knows.

The pump also sat in the shed for a couple years in a box, which likely didn’t help it any.

To be continued

 

On disassembly I was careful to note down the position of every part and put it back where it came from. I also noted the orientation of all the seals and kept them as matched sets.



Not dissimilar from the apex seals and springs actually. I guess it’s more like two apex seals, one unsprung, sealing laterally against a third apex seal driven directly by an e-shaft? The analogy kind of breaks down here, but it’s kind of fascinating that the inside of the air pump uses many of the same principles as the rotary engine itself.

With all of the insides removed other than the rotor, I first turned my attention to removing the hub. It’s pressed on, but some heat and some careful levering with a chisel freed it without too much difficulty.





Then I gently tapped the rotor on it’s end to remove it from the housing and set it aside.





Lastly I removed the big circlip and then tapped the bearing out. For anyone considering a similar rebuild:

- The front bearing is a common one, NTK 6204. I was able to get two replacements from Timken for about $12 each.

- The rear bearing is unobtanium. NSK DB-36227. I was not able to find any replacement options, but luckily this one is a non-sealed design and mine was serviceable.

- The small bearings in the vanes (six total) are NTK J-25. I read that these are available but mine were in good condition, so again, I chose to just service my existing ones.

Servicing them starts by removing all dirt. Brake cleaner would do it, but mineral spirits and the ultrasonic bath makes it much simpler:



Then I finished with brake cleaner to remove any remnants. The vanes and seals all got the same treatment, cleaning only one or two parts at a time to avoid confusing where they are supposed to go for reassembly.

Removing the broken bolt was a nightmare. That one task probably took longer than the rest of this project combined. My first thought was to weld a nut on top, but after multiple attempts the weld would always break before the bolt would start to spin.

Then I thought I would use an extractor. I drilled through the bolt and got the extractor started, only to thread it in really far and then snap it off. Now I had a hardened extractor stuck inside the shaft. Great!

I decided the next step would be to just drill through the remains of the shaft until there was almost nothing left and then tap for a larger size. Unfortunately the drill bit also got most of the way through before hitting the extractor and breaking off. Now there was an extractor and a drill bit stuck in it…

So I ended up going medieval on it. I basically started drilling away at the bolt, and then once I had drilled away all I could get the bits to bite into I started drilling away the aluminum around the bolt.

Eventually I welded another nut on, and I could feel it starting to snap my welds when the broken bolt finally cracked loose:





To be continued

 

As you can tell there was not a lot of meat left on the mounting ear after this. So I cleaned everything with brake cleaner a few times and decided to fill it with JB Weld (bear with me, it’s not as crazy as it sounds):



The epoxy won’t actually be taking much stress, because I’m going to use this steel insert:



M12x1.75 outer, M8x1.25 inner.

You might ask whether it would be smarter to just use an unthreaded hole with a nut on the back, and the answer is “probably”. But I don’t like that solution because you need three hands to tension the belt with it. So I was determined to add threads back in for OEM functionality. Down to the correct M8x1.25 thread pitch.

I drilled out the mounting ear to 11mm through, and then tapped it to M12x1.75 most of the way:


I've officially used the 54mm flywheel socket for clamping / pressing more often than I've actually used it on a flywheel





I didn’t tap it all the way because I wanted to insert the sleeve from the rear, so that the tightening action of the fastener pulls the insert forward and there is a bit of a ridge to help retain it without adding stress to the threads.

Speaking of the threads:



You can see what I meant with the JB Weld. It’s only filling some of the smaller voids where there was damage from the drill bit, and most of the threads are still aluminum.

Then I coated the inner threads with more JB Weld, threaded in the insert, tightened it, and used a bit of JB on the back side to help retain it.

After running an M8 tap quickly through the insert to clear any epoxy that found it’s way in:



Nice clean threads. I’m confident this repair is going to be sturdy and long-lasting, and the problem is unlikely to reoccur since it’s now a steel fastener threading into steel threads. No galvanic reaction here. Plus I am compulsive about anti-seize.

After that the inside of the housing, the rotor, and the back plate all got a good cleaning to remove the soot. I painted the back plate, pulley, and tensioner arm. I also lightly sanded the back plate and the inside of the housing where the vanes contact. Photos to come later.

Reassembly of the pump is the reverse of removal, but reinstalling the rotating assembly was a bit of a chore. Nothing crazy, and I forgot to photograph it, but I’ll explain.

The first 6204 bearing I tried installing in the housing was damaged because it required too much force and I foolishly used the wrong side of a socket to tap it in. Fortunately I purchased a set of two, so I put the second one in the freezer for an hour before reinstalling. Meanwhile I heated up the housing for an hour as well to expand it:



That copper ring inside is a sort of clutch. Together with the bearing I guess it qualifies as a viscous clutch? The outside of the bearing doesn’t really contact the housing, it contacts that copper ring and the ring contacts the housing. At idle and low rpm it behaves like a normal bearing, but then above 3000rpm the copper ring starts to spin in the housing (presumably due to the viscosity of the grease inside the bearing).

At least I think that’s how it works.

With the shrunk bearing and expanded housing, I was able to tap it home. Then I reinstalled the circlip.

After that I had to put the rotor in the freezer for an hour to shrink it and heat the housing + bearing back up to expand them, and then I tapped the rotor from the back side of the housing inward to seat it in the bearing. It also has a little mylar plate and shim that go between it and the bearing, so I made sure to put those back in first.

Then I had to put the entire assembly in the freezer while I heated up the front hub, and tap the front hub home (being careful to put the flywheel socket under the rotor so I was not tapping it out of the bearing while doing so).

Altogether it was a bit time-consuming, but it all went back without fuss.

Then I started reassembling the seals and vanes, again, careful to put them back where they came from:



I had marked the alignment of the rotor and used a marker to remind myself where everything went. I first put the seals back in:



The seal that has a spring behind it sits in the deeper groove. For now I treated it like an apex seal and didn’t put the spring in yet. Then I put the vanes in:



Each of the vanes has two small bearings, so after cleaning them in the ultrasonic cleaner I thoroughly regreased them. I wasn’t sure exactly what grease was best so I went with silicone brake grease. I figured it has the high heat tolerance required, while also having enough staying power not to creep out of the bearings into the housing.

The bearings won’t stay concentric without the back plate, which is to come after the springs. I inserted the springs and pushed them all the way home. They make a tactile “click” when they are all the way home.

To be continued

 

Then I pushed the vanes roughly into position. I managed to get this nice picture that shows the vane, the bore it sits in, and the nice fresh housing surface it seals against:



It didn’t take a lot of sanding. All I was doing was removing a bit of oxidation and whatever crap had stuck to the housing, but the surface itself was relatively unmarred.

Then the rear bearing and retainer plate go on, again, careful to keep the alignment correct:



You can see the nice fresh grease in the bearing. I’m glad the bearing was still smooth, as I would not have been able to source a new one.

One thing to note is that there is some sort of babbit type material on that aluminum divider that separates the sides of the pump. Much of mine had flaked off, so I scraped away anything loose and then sanded it a bit to smooth it. I’m assuming this is there to reduce pressurized air slipping back to the inlet side and decreasing the pump’s efficiency, but I don’t have a good way of repairing it and the clearance is small as-is. I’m not worried about it.

With that the rear housing goes on. The shaft engages in the bearings for all of the vanes, so I had to fiddle with it a bit to get everything to align. But once it slides home, the bearings are concentric to one another. Then the bearing surface at the back of the rear plate engages in the rear bearing and it maintains the vanes at the correct eccentricity from the center of the pulley to keep everything in the right place.

Lastly I tightened down the 4 12mm bolts in an across pattern:



And reinstalled the pulley:





And there we go. One fully rebuilt air pump. Well, not fully, because I didn’t replace the vanes and have no idea how to measure their wear. But it now spins smoothly and absolutely moves air, so I’m calling it good.

Did you guess the problem I mentioned earlier that makes the air pump difficult to use? That’s right, I put a crank sensor where the adjuster arm normally goes. At the time I was happy because my S10 crank sensor setup didn't interfere with any stock components, but I had forgotten about this one stock component... I could install the arm on top of the sensor mount but then the belt will want to occupy the same place as the sensor anyways, so I still have some thinking to do.

Probably a bit underwhelming since I doubt anyone cares about this part, but it lays the foundation for some more interesting work to come. And if nothing else, I learned something.

Until next time

 

neat! ive thought about putting the air pump where the AC compressor would/could/should live on my car, for me it makes room for more turbos
but you probably have AC..

 

At present I don't have AC, but I plan to restore the system at some point.

I can think of a few places to relocate the sensor (using increasingly convoluted brackets to do so) but it might make the most sense to design and print a mount to locate it where FFE puts it and have the accessory bracket machined to accommodate. I don't know how much I would trust a plastic bracket so I would probably need to get it printed in aluminum like fidelity101 did with his intake manifold.

 

Getting rid of the CAS, while keeping A/C, PS, and the air pump is the riddle no vendor has provided an answer for yet. We must DIY this solution.

 

I (tentatively) think I have a plan. Waiting for another S10 crank sensor to show up. Conveniently my spare engine and accessory bracket lets me do a lot of mockup without taking my car apart.

 

I always wondered if you blocked off your OMP, could you replace the CAS drive gear with a wheel for a newer sensor and just put the sensor in the old hole for the CAS?

 

I don't see why not, although I tried something similar with a spare CAS and ran into the issue of wheel diameter.

I was able to fit a small trigger wheel (36-1 I think?) inside of the stock CAS where the gears normally go, and drill the side to fit a sensor. The problem is that once the wheel is super small the teeth are so close together that even between two teeth it's triggering the sensor.

It might be possible with the optimal wheel size and sensor though. The second issue is that I think hall sensors don't like oil, so you might need a VR sensor. But it would improve on one issue with the stock CAS which is that gear lash affects the reading.

In my case it's a no-go because I like the OMP. I also want a solution that will transfer neatly to my S5 engine later on. But I think it certainly could be done that way with enough testing, and it would be a really clean & compact install once all was said and done.

 

I thought of a few mounting locations that might be possible candidates for the hall sensor. In counter-clockwise order

- Current location, installed on the mount for the air pump adjuster (9:00)
- Down where the OMP lives below the air pump with a bracket to pick up the OMP bolts (7:30)
- Right side where accessory bracket mounts (3:00)
- Picking up on stock CAS mount (1:30)

9:00 is a no-go because there's no good way to keep it there. The air pump adjuster is one thing, but the belt will want to run right through the back of the sensor which means changing the air pump mount as well.
7:30 would work, except that the OMP lives there and it would be extremely difficult to keep it while also mounting the hall sensor on it.
1:30 would put the sensor directly in the place the AC belt runs. All that does is kick the can down the road until I want to put the AC back.

So that left me with 3:00, which is exactly where FFE locates their sensor. It's obvious why they chose that location, but what wasn't obvious to me was why they didn't offer a kit that was compatible with the stock accessory bracket. I figured that all that was required was a simple bracket for the sensor and some spacers for the accessory bracket.

Here's what I came up with:



Test bracket printed and installed:



As you can see based on the 1/4" gap, I will need some spacers for the remaining three fasteners on the accessory bracket.

From above:


Sensor gap is a bit too wide, but it's close



Here's one of two probable reasons that FFE doesn't offer a kit that works with the stock accessories. With the bracket spaced out even 1/4" the two outermost mounting studs are too short. I can get longer ones, but I'll have to be careful about the length (or else they'll collide with the AC compressor when I reinstall it. I'll have to do some more measuring on other studs and bolt to see if they're long enough to use safely.

Secondly they would need to create a custom AC pulley with the trigger wheel built into it, otherwise the belt spacing for the accessories would be off by the width of the trigger wheel. Mine avoids this issue since it's welded to the back of the AC pulley but has a larger inner diameter than the main pulley behind it.

Looking at why this location works so well in comparison to some of the other possibilities I mentioned:



The alternator and air pump pulleys are inboard of the sensor, and don't interfere with it. The AC pulley looks like it does, but it doesn't (see next photo) and the PS pulley lives outboard of the sensor. One other thing I wanted to achieve with this bracket was to make it simple to replace belts. With this bracket the sensor still needs to come out to slip the alternator / air pump belts through that gap, but the sensor clearance is set. At present I need to remove the sensor entirely and re-gap it every time I want to remove the belts.



This shows the direction of travel of the AC and PS belts. The AC belt is the outermost pulley photographed here (PS pulley is actually outermost, but not installed) and it completely runs around the sensor and bracket. Meanwhile the PS runs right through it, except it's outboard enough that it will run in front of the sensor with no interference.

It seems like this is a go. I'm currently printing a heavier-duty version out of the bracket (polycarbonate filament, 100% infill) and we'll see if that's sturdy enough. I'm currently using polycarbonate for my Z32 MAF adapter (still need to write about that) and my CAS plug. I've found it to be super strong and resistant to deforming in the heat of the engine bay, whereas PETG and Nylon both tend to deform a bit. CF Nylon might do it but I have the polycarbonate already.

The other consideration is whether this pushes the AC compressor too far out, and might make it hit the power steering cooling loop or the frame rail. I took some measurements in the car with the AC compressor in place for mock-up and it looks like it will clear. If not, I've at least improved on my current set up and will now have a way to reinstall the air pump.

Hopefully I'll have another update soon, and if I can get working I'll share the STL file for the bracket.

 

i think we've seen people trim the PS/AC bracket, i'm not its got 1/4" worth of meat but certainly its got 1/8"

actually you could have your CAS bracket bolt to the AC/PS bracket directly, but its just a ton more work, lol

 

I could get the bracket machined, but if I can't make that part of the sensor bracket 1/4" thick then I need to get it made in a stronger material (maybe aluminum). Both of those increase the cost of this project. I don't mind paying to get it done right, but since the only goal here is to restore the air pump, it would push this little project back in terms of priority. That would definitely be the cleanest and most compact solution though.

Bolting it directly to the accessory bracket is an interesting idea. I kind of toyed with it before realizing just how tight the clearance was between the AC compressor and the bracket. The round body of the compressor actually gets super close to the bracket on the inner side. I had trouble even installing the compressor for mockup because the power-steering pressure switch (no longer in use since I have a standalone) wants to interfere with the compressor until it's all the way home in the bracket.

I'm going to take another look at the accessory bracket and see if I could find a place to drill some mount holes. I have some spare brackets so I'm not worried about experimenting with one.

 

I looked at the engine for awhile longer and realized I was a fool.

What's the one thing in the accessory-drive / crank area that I can safely delete to make space for the hall sensor, without having to relocate anything else?

The stock CAS, of course:



I already modeled a plug awhile back that blocks off the opening for the stock CAS. I realized that by taking the hall sensor mount I designed and instead adding a vertical up from it to the CAS plug, I could avoid having to pick up the accessory bracket mounts in the first place.

The rendering above is actually not the final version, but an attempt I was making to increase stiffness. The only place it flexes is at the top where it meets the CAS plug, but then this model is already a bit clunky because I've edited it so many times and the mesh is starting to become pretty sketchy. I will probably be remodeling it shortly.

That didn't stop me from printing one though:



Printed in polycarbonate. I really like this stuff. It's a bit pickier than some of the more common materials as far as printing environment, but it's super sturdy when printed properly.

Installed on my car:



I've already confirmed it doesn't interfere with the AC tensioner pulley or the accessory bracket. It actually has a decent amount of room to spare on the right side too. There's a little play in the hole for the bolt so it allows some adjustment.

The only thing I haven't actually done is plug in the sensor and test it out. Unfortunately the doctor tells me I have tendonitis in my left knee which means I can't work a clutch pedal. So I won't be able to do a proper extended test for around 6-8 weeks while I heal up.

This also means I can't drive my daily car either, so when I do leave the house I'll have to borrow an automatic car from my family. Fortunately there are a couple options that should keep me from getting too bored:



And well, that's that. I probably won't have any updates for awhile since I'm supposed to stay off my feet whenever possible, so here's some pictures I took recently instead:





Until next time

 

Well now you're on to something. That looks very promising. Stiffness will be key, since there is only the one bolt, so having it nestle down in the CAS hole like that should also help. I think you've got an extremely promising solution on your hands there. I can't wait to see how it plays out.

I'm really itching to go aftermarket ECU on my FC, but "settling" for CAS makes me not want to do it.

 

Can't believe I never thought of this myself! Great execution too. One thing I see is the opportunity to make the bracket a bit more concise by shifting the sensor upward a bit.

 

Fingers-crossed, it looks like everything is going to work. The only area where stiffness is an issue seems to be at the top, where the downward section from the CAS plug meets the plug itself. The sensor mount and the vertical are pretty stiff, but the weak link at the CAS plug allows some flex. And since it's so long it forms a lever and allows a decent bit of forward-back movement at the CAS mount.

I am working on a revised design right now that should mitigate the issue. Otherwise I'm just making sure that the clearance for the sensor is good, because there will always be a bit of slack in the CAS plug itself. This sensor is pretty forgiving but I still want to get it as close as possible.

I did consider that, but unfortunately that breaks compatibility with the AC system. I installed the AC compressor and tensioner pulley to demonstrate:


This is how the OEMs do it, right?



This picture is with the tensioner at it's maximum, assuming the longest belt size possible. Next is the shortest belt size possible:



So there might be a position in that area that would work, but it would limit the adjustment of the AC pulley and generally complicate things. It would definitely help make a more rigid bracket though.

To keep track of what is required (so far) for this setup:

- One S10 crank sensor. I've been using a $25 Amazon one for a couple years now. The bracket on the sensor needs to be trimmed down slightly with an angle grinder, but it's a very simple cut. I'll provide pictures when everything else is done.
- One trigger wheel welded to the back of the AC pulley. I have the exact dimensions someplace. I'm using an 8mm tooth height because I thought I would need a bit of extra clearance, but a 10mm height would be better. It would also make the design of the bracket a bit easier clearance-wise (at present the bolt for the sensor comes very close to the front cover), so I'm investigating getting another wheel.
- Front brim of water pump pulley needs to be clearanced slightly so it doesn't collide with the trigger wheel. On my car I just used some sandpaper while the engine was running, but this isn't exactly a safe way to do it. I'll provide clearer direction as to exactly where it needs to be clearanced.

Obviously I'll give some more details once everything is hammered out, but it looks like this solution will work. I'm also working on making the above installation steps simpler where possible.

 

With some assistance from need-a-t2 (thanks again), a newer trigger wheel design is on the way from Sendcutsend. The current one works, but the new one should simplify install a lot and be a slightly improved design.

Since I can't actually drive the car I turned my attention back to the air pump for awhile. I was hoping to not need the air control valve but when I did some searching it looks like it's hard to find valves that do what I need. The ACV incorporates several different functions:

- Direct fresh air into the exhaust ports to mitigate intake charge dilution.
- Direct fresh air into the catalyst to help emissions and temperatures.
- Direct fresh air into the manifold on decel to prevent afterburn

I only care about function one. Function three would be nice but isn't critical. I also wanted to add a nipple for pressure to drive the auxiliary ports, which I'll get to in a minute.

I did not intend to restore the split air system simply due to the logistics. I added provisions for the split air tube in the form of an extra O2 port when I made the exhaust, I'd just prefer not to have to use it. The port air system already injects air into the exhaust at idle where the mixture is rich.

As a refresher, on S4 models the aux ports are driven by the exhaust. I no longer have enough back-pressure in the exhaust to perform that function, so I need the pressurized air from someplace. This inlet tube from the air pump looks like as good a place as any to drill and tap for M6x1.0.







A little JB Weld seals the threads:



If you're wondering about the creative wiring above, it was something I did to account for damage on the harness-side when I got the car. Luckily I left the spade connector intact on that wire so I just put it back into the housing and it's as good as new.

Then I removed the block-off plate I had installed and put the ACV back in it's home on the engine:



The tube visible in this photo is the outlet side, and normally goes to the silencer under the headlight. I do still have all of that tubing around.

Next it was time to remove my current CAS. I already have the newer CAS bracket installed on the other side, so even if it isn't the final version I can remove the old one for testing.



Then the adjuster bracket arm goes in it's place:



This three-bolt bracket thing goes in:



And then the air pump fits onto it:


This belt is really old. I'm 99% certain it came with the car, and it was old then. But it's the only belt I had around in the right size. so it's fine for testing.

While on the topic, I hate this tensioner system. The way you tension it is to use your left arm at a weird angle to pull the air pump out as hard as you can, and then your right arm to tighten the adjuster nut. And then the belt is still loose. Meanwhile the PS and AC have these excellent tensioner pulleys that let you get the belt tension perfect.

Lastly I popped this thing onto the outlet:



It's part of the stock relief tubing that normally goes down under the headlight to a silencer. I didn't want to install the whole thing for a test, so this little tube and mini-silencer is enough for now. The little blue tube is going directly from the ACV inlet to the aux port actuators. I'll need a solenoid there but for now I could see if the aux ports moved.

With all of that put together I started the car, and I learned a few troubling things:

- The air pump still makes a slight tapping / ticking noise. Unclear where from since everything in it is rebuilt and it turns smoothly.
- Something is causing what I suspect to be a vacuum leak. The idle is a bit less stable even though none of the air pump air should be getting to the manifold, so I think the ACV gasket I reused might be a bit leaky.

Those sound manageable, but then the air pump doesn't provide enough air to actuate the aux ports unless the relief tube is entirely blocked. I didn't test extensively above 1500rpm but this doesn't bode well. If the air pump won't actuate the ports then the main goal of restoring it won't be achievable, and it makes me question whether I want the air pump at all. If all it's good for is port air then I don't really need it.

Otherwise I could block the air pump outlet entirely other than the aux port nipple, but I don't know enough about rotary vane pumps to know if it's healthy to run them with the outlet entirely obstructed 99.9% of the time. Nothing happened when I tested it but my gut says it's a bad idea to run it that way for a long time.

So here's what I'm thinking of as a possible solution:

- Nix the stock ACV entirely
- Add a tube to the block-off plate that goes only to the exhaust port air inlet on the intake manifold
- Put an off the shelf solenoid between the air pump and the above tube
- Configure my ECU to keep that solenoid normally open except above some RPM where I want the aux ports to open, call it 3500 rpm, where the valve closes entirely.
- Add a second solenoid to control the aux ports

The problem is that this prevents me using closed-loop anywhere. Once the aux ports are open I don't care about closed-loop because that's high power time anyways, but when cruising at 2500 rpm I can't have air going into the exhaust ports or else it interferes with the O2 reading. Meanwhile if I drive around at 2500 rpm with the solenoid closed, the air pump is restricted and I don't know what the long term results of that are. Plus it probably robs power for the pump to be spinning constantly and have no place to pump the air. Then again I'm not an engineer.

Any suggestions are appreciated. This whole thing will require more thought than I had expected.

 

The s5 vacum diagram shows the air to actuate the aux ports directly feeding from the air pump inlet to the acv. The fsm says the s5 actuators need 1.4psi to fully open. The s4 fsm says that the s4 actuators take 2.1 psi to open. If you can swap for s5 actuators that might make using the air pump and stock acv an option.

 

That's a good idea. I'll have to look into whether the S5 actuators work on the S4 manifold though, otherwise it's a big headache to swap all of it.

I'm also thinking about it and I don't see how the air pump would be damaged exactly by having the outlet plugged. Obviously they aren't intended to be used that way, but I'm thinking maybe I could keep the ACV but plug the relief outlet. Then have port air at idle, dump air out the back where it normally goes to the catalyst when I don't want port injection, and then close the outlets entirely when I want the aux ports to be able to operate. Then fine-tune the changeover with a solenoid for the aux ports.

Worst case scenario I break the air pump. I don't think there's any scenario where the engine gets damaged by this.

 

If the aux ports are the main reason for keeping the air pump, I remember reading somewhere on here about somebody trying to actuate them with solenoids.

EDIT
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/electronic-5th-6th-ports-no-air-needed-351918/

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/ultimate-fully-electric-aux-vdi-solution-294539/

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/activating-aux-ports-vdi-rpm-switches-907824/

I thought about doing the solenoid approach a while but I didn’t think it was worth it for an s5 with a working air pump