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This is almost a non-update, but it's kind of neat so I thought I'd share. I recently re-soldered the CPU (again) to try and fix a brake light issue, which turned out to be the switch. A bit of silicone spray on the plunger inside the switch has fixed the issue nicely.
Anyways, tonight I went out to get something from my Rx7 and noticed this:
My factory option back-lit keyhole started working. I spent some time on that last year installing an LED bulb when I had the handle out for unrelated reasons, and was a bit bummed that I put it all back together and the back-light never came on. I guess the CPU cold-solder joints strike again.
At some point I am going to put all the bulbs back in the warning lights and see if it fixed that too. I got tired of the seat-belt light (and others) blinking in and out for no reason, but maybe now they work.
It's been a month since I posted, and not a lot has happened on the Rx7 front. Despite the sync-loss issue returning, it continues to run perfectly fine and be fun to drive. A hall wheel conversion is in the works.
Here's a couple pictures I took this evening after driving back from class:
I have a few irons in the fire, and hopefully I'll have at least one wrapped-up in a few weeks that I can post about.
Oh, and if you're a fan of long, drawn out, elaborate solutions to problems that most people don't care about, I have a big one for you soon.
I'm working on a custom hall wheel setup that should achieve the same thing without interfering with stock components.
I did ask about the FFE kit and people have modified it to work with PS/AC. Trouble is the cost. The kit is expensive on its own, then finding someone local to do machine-work on the accessory bracket is going to cost as well. I'd be looking at something like $500 Canadian total.
Meanwhile a custom wheel + an S10 sensor I found costs <$100 Canadian.
I'm working on a custom hall wheel setup that should achieve the same thing without interfering with stock components.
I did ask about the FFE kit and people have modified it to work with PS/AC. Trouble is the cost. The kit is expensive on its own, then finding someone local to do machine-work on the accessory bracket is going to cost as well. I'd be looking at something like $500 Canadian total.
Meanwhile a custom wheel + an S10 sensor I found costs <$100 Canadian.
welp im interested if you come up with something that works better than oem, is relatively pretty and keeps my AC. im stripping this car down to damn near nothing but ill be damned if it wont have AC.
I'm working on a custom hall wheel setup that should achieve the same thing without interfering with stock components.
I did ask about the FFE kit and people have modified it to work with PS/AC. Trouble is the cost. The kit is expensive on its own, then finding someone local to do machine-work on the accessory bracket is going to cost as well. I'd be looking at something like $500 Canadian total.
Meanwhile a custom wheel + an S10 sensor I found costs <$100 Canadian.
You have piqued my interest. I'm happy with my FC at the moment, but putting in a Haltech has constantly been in the back of my mind. It would be nice to do so and ditch the CAS and keep AC.
When we left off I discussed a hall wheel conversion that would let you retain the PS and AC. Well, the parts arrived today. And while I probably should have spent the time on something else, it was still above zero here so I decided to make hay while the sun was shining (figuratively - there was no sun). The photos will get grainier as the light disappears and the camera ISO gets cranked up, so apologies in advance.
Starting out, I got this custom 36-1 wheel from an eBay seller called Elenel (I wish I had thought of asking need-a-t2 before I ordered, but oh well). The price was fair and the quality is great.
These are the dimensions:
ID 113mm
OD 153mm
Thickness 4mm
These dimensions need to be fairly exact, although 112mm ID would probably be better for reasons I'll explain later.
The sensor is a simple late 90s GM sensor. I believe it's an S10, although it's probably used on multiple cars (hence why it's available for less than $30):
Then I thought for awhile about the location of the sensor. The location that FFE uses with their kit is good, but mounting it is a challenge (which is part of the impetus for this entire project), so it's basically out. There are no practical mounting locations near the bottom of the engine, so mounting it underneath is not an option either. This leaves two possibilities:
- Mount using a custom bracket and the bottom alternator adjuster bracket bolt
- Mount using the air-pump adjuster bracket hole.
Mounting from above would be my preferred option since it keeps the sensor as far as possible from rain and dirt, but unfortunately it gets very close to the belts. I have also misplaced my AC compressor bolts (the really long ones) which means any mount I made may need to be altered once the AC goes back in. For those reasons I chose the air pump location instead.
My air pump is "remote mounted" as j9fd3s so eloquently put it, so this makes it easy:
It may work with the air pump in the stock location, but otherwise an Rx8 electric air pump conversion would also free up the space. The first thing I did was to take the front stack apart and measure to make sure the pulleys still fit:
Perfect. There is one place that is very, very close, which I'll show later. But nothing interferes, so we're ready to proceed. You can see in the above photo that I made a red mark equivalent to the first timing mark on the power-steering drive pulley. This is because that's the pulley to which I am going to mate the hall-wheel.
The front hub and main pulley on Rx7s are matched sets. This means that mixing and matching pulleys and hubs can lead to minor variations in timing marks, and while it probably isn't an issue, I just don't like it. But since the mount holes are offset, the pulleys can only ever be bolted on in one orientation. So, mounting the hall wheel to the power steering pulley lets me use this wheel now & also easily swap it onto my Turbo II engine later on, without worrying about the mismatched pulley and hub.
The factory timing mark on the main pulley will always be used to set base timing, so the new mark on the power steering pulley is only for reference. I flipped the power steering pulley over and sanded away a few spots. I don't think I'll be adding enough weight to matter, but I chose spots opposite one another anyways. A 112mm ID would probably make this step self-aligning, but since I had measured 113 instead I had to carefully try and use feeler gauges of a known thickness to get the alignment as close as possible. It will never be perfect, but it should be close.
One thing I would do differently is to drill holes in the hall wheel and use plug welds. I had to spend quite awhile with a carbide burr grinding a channel into my (ugly) welds, or else the brim of the main-pulley wouldn't clear since it fits into that channel. At the end of the day, it works.
Turning our attention to the sensor, it needed very little modification. The first thing I did was bend the mounting tab in so that it was parallel to the sensor (visible in the following photos). Then I got some wire and a Metri-pack connector:
The wiring is very simple. Black is ground, red is power, yellow is signal. When the sensor is in the presence of ferrous metal, it closes the circuit and sends voltage down the signal wire. The ECU reads these pulses as a square wave and there you have your crank signal. Conveniently because rotary engines fire once per rotation, we can also run full sequential fuel using only one wheel.
One thing I don't like about this sensor is the slack where the metal mounting tab grips the body of the sensor. On an S10 this probably won't matter since that o-ring seals the sensor into a bore and the outer tab only holds the sensor more securely. In my case that slack is a problem. However, for now I will leave it until I can play with the gap. Once I have the gap set, I'll probably 3D print a small shim and JB weld it in.
Before we install it on the engine, here's the one place that the hall-wheel is tight:
I measured around 10mm clearance between the outer edge of the power steering pulley and the water pump pulley before ordering the wheel, hence the 153mm OD. Tooth height is about 8mm past the brim of the power steering pulley. There is also about 5mm of clearance between the flat of the rear of the power steering pulley and the flat of the front of the water pump pulley, which is why I chose a 4mm thick wheel. This leaves enough space in both of those dimensions for the water-pump pulley to clear, although it is very tight.
To locate the sensor in the appropriate spot, I first cut a small piece of steel into a tab and drilled an 8mm hole. Then I bolted the tab onto the mounting hole and measured a bit before adding a tack to put the sensor in place:
I'll come back and finish welding this properly after I've tested the whole setup. Until then, one tack is more reversible. Then I bolted it up:
The sensor can be re-gapped by rotating it around and then tightening down the bolt. This will work for setup and testing, although I may add a second piece of steel that goes from one of the air pump bracket mounts down to that second hole on the sensor bracket, for extra support. We'll see how much wobble is in it when I have it finish-welded and go from there.
Photographing the gap itself was impossible due to it being dark out and the water pump pulley obstructing the flash, so here's the closest I could get:
And that's it for now. I'm at the point in the process where proceeding means doing some rewiring in both the engine bay and at the ECU, so that will have to wait until I have more free time. Everything is shaping up well, and if it doesn't work I can still start and run the car as the factory VR setup is untouched.
is the crank assembly in the 13b going to be pissed about the welds? as in having them like that going to cause any vibration issues?
I doubt it, but frankly I'm not certain.
On the one hand, I welded about the same amount of material on opposite sides. And it also isn't really that much material. I've also found other pictures of welded crank pulleys online and plenty of people who say they've had no issues.
Eage8 also had a thread where he modified his pulley stack to use the FFE kit with power steering, and he cut some material out of the pulley for clearance. Seemingly it caused no issues.
On the other hand, I've never actually tried this before.
I'll have to see what happens when I actually start it. Conveniently I have a couple spare power steering pulleys if I need them.
It occurred to me that I don't actually need the hall sensor wired up to check whether there are balance issues. I went out and started the car, and after it warmed up I gave it a few revs. No noticeable difference from before at any engine speed up to and including 7000rpm.
I was also curious about what the tolerance is for imbalance in the rotating assembly. Mazda stamps all rotors with a letter A to E, which denotes the approximate weight. Then when rebuilding an engine, the rotors must be within two letters of one another to be balanced. I found some posts online where people had weighed different letter rotors and subtracted to find ~35g of variation between two letter weights apart. I doubt if I added 35g of weight total with the welds, let alone 35g of imbalance. Not exactly scientific, but coupled with my testing I'm confident that it's fine.
I might worry about it more if I were running this engine past 9000rpm, but on a high rpm engine everything should be sent out for balancing anyways.
It occurred to me that I don't actually need the hall sensor wired up to check whether there are balance issues. I went out and started the car, and after it warmed up I gave it a few revs. No noticeable difference from before at any engine speed up to and including 7000rpm.
I was also curious about what the tolerance is for imbalance in the rotating assembly. Mazda stamps all rotors with a letter A to E, which denotes the approximate weight. Then when rebuilding an engine, the rotors must be within two letters of one another to be balanced. I found some posts online where people had weighed different letter rotors and subtracted to find ~35g of variation between two letter weights apart. I doubt if I added 35g of weight total with the welds, let alone 35g of imbalance. Not exactly scientific, but coupled with my testing I'm confident that it's fine.
I might worry about it more if I were running this engine past 9000rpm, but on a high rpm engine everything should be sent out for balancing anyways.
thats what i was wondering. if minute vibrations were an issue or if the engine was that picky.
I spent some time this morning making the wiring changes necessary for the hall sensor. Conveniently the OEM dual-VR setup already has four conductors, and I only needed three. One for 12V, one for ground, and one for the signal to the crank input on the MS3X.
After adjusting the potentiometers and putting everything back into the car, it started right up:
It ran like garbage until I had the timing dialed in. One thing that makes this easier is that rotary engines will run with the timing way out. When I clocked the hall wheel on the power steering pulley, I thought I had it so that the leading edge of the first tooth after the missing tooth was about 90 degrees BTDC. I figured I would only have to put in minor corrections.
It turns out I had to adjust the tooth 1 trigger angle all the way to 163 degrees before it was agreeing with the timing light, which means I was around 70 degrees off. It doesn't hurt anything since timing can easily be adjusted using the tooth 1 angle setting. I'm just impressed that it ran at all with timing that far out.
After I got it all the way warmed up, I wound the engine out a few times and there was zero sync-loss. None during cranking, none at high rpm, none under decel; none. The only thing I noticed (somewhat predictably) is that I can make the engine die by wobbling the hall-sensor.
Next up is to print that shim to remove slack on the sensor mount, finish weld the little mounting tab, and then most likely add some other mount point to hold it more sturdily. Oh, and also print a cap of some sort to plug the CAS hole.
It won't be a real test until I actually drive the car for an extended period. Unfortunately that won't be for a few months, but the early results are promising.
thats what i was wondering. if minute vibrations were an issue or if the engine was that picky.
well if you think about it the Rotors are ~5000g each, plus ~9000g for the flywheel, that is about 20,000g right there, 44lbs. a couple ounces either way isn't going to matter
When I left off, I needed to make the sensor bracket more rigid. I was considering adding a second mounting point, but that proved unnecessary. Instead I cut a small gusset:
Welded it in, then ground it back a bit:
Then I added a bit of JB weld to stop the sensor moving back and forth in it's mount. It doesn't look quite as clean as I would like, but it has worked great. A new sensor is very cheap, so I may revise this at some point.
Functionally, it works fine.
I noticed a couple of scratches in one place on the brim of the water pump pulley, and wasn't sure if they were from installing the trigger wheel or if the trigger wheel was colliding once the engine was hot and everything had expanded. So as a precaution, I used sandpaper to clearance the brim. The best way to do this would be to find a way to chuck it in a lathe, but I uh... just used sandpaper while the engine was running...
Clearance aplenty!
Next I took some time to sand and clean all the pulleys before painting with Duplicolor flat-black engine enamel.
It seems like they've changed the formulation since last time; this new can laid down more evenly and seems tougher. I'm very happy with it.
And once again it was dark by the time I finished, so here's a flash photo that makes it look much uglier than it really appears.
The hall sensor has been working great so far, and the reinforced mount is very sturdy. The only thing I don't love about this is the JB Weld, and that I now need to either remove the sensor or the accessory pulleys if I want to replace the alternator belts.
After working on it this long, I completely understand why FFE charges what they do for their kit. They also include a CAS plug, hardware, etc. But for <$100 (Canadian $), I'm really happy with the results.
The JB weld is there to fill space and arrest motion front to back. On whatever application this sensor was meant for, the end of the sensor went into a hole and the bracket was just there as a hold-down. Then the trigger wheel was on the other side of the hole. This means no gapping is necessary, because it's pre-set. This is why there is some slack there from the factory.
In my application, not only is the tab the main mounting point, but the forward & back slack between the sensor body and the bracket lets the gap change by about 1.5mm. A zip tie wouldn't really fix the issue unfortunately.
Like I said though, the sensor was quite cheap and the welding didn't take more than an hour total. I could always get another one and modify it a different way. It works, it just looks a bit ugly. For now I'm spending my time on other projects.
