here ya go

 

Tasca never responded when I asked where my moldings were, but then they arrived on Thursday so I guess that answers my question. As I mentioned in my previous post the originals have no openings for the roof rack mounting studs:



Yesterday morning they were still frozen in place, but this morning it had warmed up a bit and I was able to remove them easily. I used a plastic spudger tool to pop the front free, and then just lifting and wiggling the molding was enough to free the other clips. With it out, I found there were a fair amount of leaves and pine-needles stuck underneath. Here's the front mount point:



There are these little rubber clip things stuck to the roof as well:



The little valley at the top seems to catch water and let it pool, and on all four of them I noticed a tiny bit of surface rust. I think this part was assembled with adhesive before paint, and then over the years the adhesive has cracked as it contracted and then allowed moisture to get to the metal.

These are the actual rack mount threads (as well as a little black spacer that fell off of the original moldings:



I gave everything a good scrub and then a little bit of rust paint around the rubber clips. Then I popped the new moldings on and removed the little black covers:



Which let me pop in the studs:



I wasn't sure if there was a torque-spec for these, and if there is it's likely in inch-pounds for which I don't have a torque-wrench. So I just put a little anti-seize on the threads and then installed them snugly. After installing the four studs I dropped the front bar on:





The little red plastic thumb-screw (or whatever it's called) is larger than the gap between the stud and the rack when installed, so you actually need to start threading it on before seating the bar all the way. Then the plastic cover goes on:



On both the roof and pillar side the rubber base extends onto the paint a bit. The previous owner kindly included some 3M clear film that would protect the paint but I found it was very noticeable when installed, so I decided not to put it on. Instead I'm going to ceramic-coat the car in a few days. I doubt the rubber will cause any issues anyways.

And with that, they're installed:





I took a drive and didn't notice any increase in wind-noise, so I'm going to test it out for a bit and if I don't hear anything I'll probably leave them on there semi-permanently. Will I actually put anything on them? Well, I don't know. I already have a bike-rack for the trailer hitch so I don't need another for the roof. On the other hand I've been considering buying a set of skiis lately instead of continuing to rent, so maybe they'll find some use soon.

Until next time

 

I've finally found what I hope will be an acceptable solution for the aux port actuation.

Most of you will be familiar with the aux ports and the challenges with actuating them on a modified FC, but for new readers and since I cross-post this on GRM, I'm going to recap from the beginning. It also helps explain what my goals were with this project.

On a rotary engine the port timing is controlled by the footprint of the intake and exhaust ports. Smaller intake ports with an earlier closing time promote better idle, and larger intake ports with a later closing time improve performance (to a point, of course). In a piston engine this is normally controlled with a VVT actuator, but since there are no cams in a rotary engine, Mazda's answer to this problem are the auxiliary ports:



These ports have sleeves inside of them. Normally the sleeve is closed, which means that the engine runs only on the smaller port (closing at 40 degrees). This is helpful for idle and midrange, where the extra port area kills air velocity. Then at higher load, a set of actuators rotate the sleeves, opening the port:



The actuator looks like this (on S4 models):



The little tube to the left is a pickup that connects to the exhaust. As you cross about 4000rpm, the back-pressure in the exhaust drives these actuators and the ports start to open up. This presents an obvious problem with an aftermarket exhaust - where do you get this pressure from? Most exhausts don't have the pickup for the tube, and even if you wanted to add a tube the aftermarket exhaust probably won't have as much back-pressure. There are a few solutions I've heard of (and tried):

- Use air from the air pump (with or without an RPM switch)
- Use an electric air pump and an RPM switch
- I've read of at least one person saying they used cable actuation connected to the throttle (for which I can no longer find the post)

There are problems with all of the above:

- The air pump builds pressure way too early (2000rpm) which means the ports are opening about 2500rpm earlier than they should
- Most electric air pumps are an impeller style. After testing, I was not able to find any that build enough pressure at the outlet to budge the actuators at all. I've read of people using an aquarium pump, but I have my doubts about that pump surviving a long time under the hood of a car
- Even if you did get either of the above to work, an RPM switch is the wrong approach. We want to actuate the ports based on load (in my case MAF), not RPM. At light load above 4000 rpm the ports being open is worse than them being closed. Now I know that light load above 4k is not a common situation, but my point stands.
- A throttle cable has a similar problem, which is that now it's tied to throttle-position instead of MAF. If you floor the throttle from idle, even before you leave idle the ports are already all the way open.

I experimented awhile ago (page 20 of this thread) with using air pumps, MAC valves driven via PWM, etc to try and have the ECU control the ports based on MAF. But there wasn't any solution that I was happy with.

Recently I decided to pick this project back up. Here were my goals:

1. The ports should open at the appropriate time, consistently (I could never get this to happen with the air pump options).
2. I should be able to control them with the ECU, and adjust the opening time.
3. They should be controllable based on MAF
4. The solution should be reliable
5. (Nice to have, but not 100% required) I should have infinite control over the port position, not just simple open / closed control.

Why did I want number 5? Well, one thing I noticed when testing with the air pump and a MAC valve is that it's not difficult to get the ports to open, but it's difficult to get them to stay part of the way open. I wanted a way to have the ports not just be open or closed (40 degrees vs. 80 degrees closing time) but to be able to hold them at say 60 degrees closing time. This would maximize the area under the curve in the powerband. Speaking of which, here is some data I took from a log:




It's a bit crude since I'm using MAF as a proxy for power, but since I don't have a dyno this will have to do. The first thing to notice is that the closed ports flow a lot more until about 4250 rpm, and then the gap starts to narrow. At about 5250 rpm the open ports surpass the closed ports in terms of airflow, and after that there's no contest. I think the weird dip at 6250rpm was tune related, but this was several months ago so I don't recall the exact cause.

Anyways, this begs the question - if 80 degrees close time is flowing more at 5250 rpm than 40 degrees close time, is 50 degrees close-time outflowing both 40 and 80 at 5250 rpm? Ideally, I should be able to start opening the ports at around 4250 rpm and open them smoothly until they reach full open at say 5750 or 6000 rpm. More testing would be required to determine the exact transition points.

I'd seen a photo online of someone using solenoids to pull the ports open, but I originally scrapped that idea for a few reasons. Mostly that it required mounting some return springs (with no good OEM location to mount them to) and also that I was concerned with reliability because of the short duty cycle and the fact that the solenoids would sit above the exhaust manifold.

But then I saw these on Amazon and I did some more thinking:



They have an integrated return spring, so that simplifies the bracketry. They have 60N of force which should be much more than required to open the ports. They fit in the available space, and they also had a clevis that looked like it might fit the stock linkages. And at 3A each, they could hypothetically be PWM driven by my Megasquirt. So I ordered a set for about $40 and did some testing:



The first thing I tried was powering it for awhile and seeing how hot it got. The answer is "not very". It has more than enough strength to pull the ports open, and the "3 seconds 80 degrees temperature rise" in the description didn't seem to occur. It definitely got warm, but not that hot (even after 10 seconds). I didn't end up pushing it because at some point I would burn out the solenoid. Even with the added exhaust heat I'm confident that these will last a good long while. Besides, how often am I above 6000 rpm with the pedal flat-out for more than a few seconds? Every time I shift it will drop back down below the threshold anyways.

Worst case scenario, these are pretty cheap. I can always replace it if I burn one out.

You can also see the mounting plate and linkage. That linkage is for testing only, since I was in the middle of fixing my 3D printer at the time. The linkage is required not only because of the fact the sleeve is rotating, but also because the actuator is positioned somewhere in the center of this rotation. So when the actuator starts moving the linkage ends up pivoting from one side to the other. I'm probably not describing that well, but suffice it to say the linkage is required. Here is a mock-up with a drill bit since I didn't have an appropriately sized screw and some M8 nuts used as washers:





I tested it and confirmed that it absolutely had enough power to pull the ports open. The return spring was a bit too weak, so I removed the circlip and stretched it taller before putting it back and that fixed the issue.

Now I mentioned wanting to have infinite control of the position of the ports, so I rigged up a simple system to PWM the solenoids with a microcontroller and see what PWM duty corresponded to what port position. But I noticed something interesting which is that any duty sufficient to move the solenoid would open the ports all the way. I could slow the opening a bit but I couldn't halt it at say 50% open. I realized there was something I hadn't considered with the solenoids, which is that the power required to pull them inwards decreases as the rod enters the coil. This makes perfect sense and I'm not sure why I didn't think of it before. It's possible there is some sort of solution involving a progressive spring for the shaft that increases spring tension as the shaft moves inwards, but for now I'll have to shelve that particular goal.

I also noticed something interesting, which is that the stock actuators don't open the ports all the way. Before the actuator rod hits the inner stop, the actuator itself runs out of travel. You can see how far they open in the second photo of this post. Meanwhile the solenoids have travel to spare, so the actuator rod hits the inner stop and the sleeve opens further:



This is about 2-3mm more open than stock. I could probably get it to open further by filing down the inner stop. That will be a project for another day.

With my 3D printer fixed I made a replacement for the linkage:



In testing I found that flat linkages tended to try and slip off the actuator rod pawl if the solenoid shaft rotated a bit in either direction. So this design fits neatly into the solenoid clevis and has about 10mm of sleeve engagement on the actuator shaft. With some silicone grease everything is nice and smooth.

Since PWM won't help me on this project, I elected to run a relay so there is less load on the Megasquirt. It mounts to the passenger shock tower. Here's some night photography of the solenoids installed:



I still need to loom up the wiring, but otherwise it's done.

And the results? Well, it works. I can use the Megasquirt to open and close the ports when I want, and there is a way to reference it to MAF so it will do what I need. They also open slowly enough that I think if I start opening them at 100 g/sec of airflow they will take enough time to open that it smooths the transition and (mostly) achieves the effect I was looking for regarding infinite control. It's not as good as real infinite control, but it's what I have for now.

Idle and off-idle is also noticeably better with these ports open. Once the weather warms up enough for me to actually drive the car, I'll report back with the results vis-a-vis power and in the summer I'll have to test them on a hot day to see what reliability is like. Fingers-crossed that this pans out and I don't need to go back to the drawing board, because at some point it just makes more sense to focus that effort on swapping in the Turbo II engine I've been sitting on for three years.

Until next time

 

i started reading and was waiting for you to say you stole the stepper motors off the printer so you could literally control the exact positions lol. i'm sure you'll try it eventually!

 

We've been receiving lots of snow recently, so I went looking for a project I could work on inside. Recently JP3 motorsports has made their AC retrofit kit available, and while I won't be purchasing it anytime soon due to the current exchange rate, it is something I'd like to pick up in the future. They released a very helpful video showing how to remove the evaporator assembly and replace the expansion valve. I figured that this was a good idea, since the air in my car has never blown very strong and there was more than likely some obstruction in the system from leaves and dirt. The lack of fresh-air filter on these cars has always frustrated me a bit, so while I was in there I went looking for a way to add a filter to the system.

It starts with removing the clamps that hold the inlet and outlet of the evaporator assembly:



And immediately I noticed that the evaporator outlet wasn't even clamped on. I wonder why the air has never blown properly in this car...

I have had the dash out before and didn't notice this, but then I didn't really pay any attention to the HVAC system at the time. Oh well.

The inlet side (coming from the blower assembly) has a screw clamp instead of a flip handle:



Then there are two nuts on top:



One on bottom:



And then the box comes out. I actually forgot to take a picture before I disassembled it. It's just a grey box with two openings and the fittings for the evaporator core extending out the front.

These little spring clamps hold the box together, so they just pop off:



From there the box comes apart into two halves:



With styrofoam inside both halves surrounding the core:



As you can see, there was quite a bit of yard waste in there. The core itself was not that dirty, but it did have a lot of old tape decomposing on it:



After vacuuming and cleaning everything in the sink, I dried it with a heater:



And then with the evaporator as hot as I could possibly get it, I propped it over the garbage bin for awhile to get any remaining oil to drain out:



To be continued

 

That clamp should have foam on it. If yours is the way mine was, every bit of foam in the air vent, flappers etc is toast.

I bought a spare assembly from Yahoo Japan for around $100 and rebuilt it. It's in a box somewhere...

 

Now one thing that I realized immediately when starting this project was that all the foam in this system needed to be replaced. It had long since turned to dust. I started with removing the blower motor, since it makes the whole blower assembly a bit lighter and easier to maneuver out from under the car:



Yikes. It's been pretty squeaky since I purchased the car, and now I know why. I thought that servicing the bearing might have been an option, but then the carriage bolts started spinning when I tried to disassemble it. Add to that the state of the brushes visible through the vent hole, and I decided to just order a replacement.

This is the blower assembly itself:



That flapper door controls whether the air is in recirc mode or fresh air mode. As you can see, the foam is dusty and the door is covered in rust. The inner door is also rusted in the open position:



At least the wiring is still decent. For an idea of how crusty the foam is, look at what happens when I touch it:



It just turns into a fine dust and falls right off. This project won't be done until spring purely because I now realize I need to replace ALL of the foam, including the heater box and all of the vents. That can't happen easily with the dash installed, and the dash can't safely come out when it's this cold or half the fasteners will break.



The box is held together with the same spring clips as the evaporator box, so with those released we find another rusty plate and some large electronic component with an aluminum heatsink:



This rusty packing plate is on the other side of the blower resistor:



And then the aluminum thing is held on with two fasteners on the back of the box. This side faces the firewall, so if you're thinking of tackling this project yourself then remember to plug this back in before reinstalling the box:



This actuator on the side handles the flapper door:



From the inside you can see how rusty the door was, and the little flapper door on the larger flapper door (flapper door ^2) is rusted in the open position:



This means even on recirc there would have been outside air entering the cabin.

To be continued

 

I was able to get the flapper doors out:



The rusty fasteners presented a bit of a challenge, but they all came out except for one on the smaller door hinge. The head snapped off, so I had to heat it and oil it several times before welding on a new head:



Fortunately that was enough to free it and I went and cleaned all the rust off:



I used gel rust remover, followed by POR Metal Ready to etch the metal. I think the Metal Ready leaves some sort of protective coating so it might actually have been fine to leave it at that, but I decided to paint it just to be safe.

After shooting some VHT Chassis / Roll bar paint, I began adding new foam:









It took some experimentation to find the right foam height, but I got it pretty close. I found there was quite a bit of slack in the door, probably caused by this plastic piece being worn out:



It wouldn't be hard to print another one, but I'm going to test with the original piece first and see what happens. This part is easily accessible with the box installed, so I can always replace it in the future. At its current resting position the door doesn't sit all the way closed:



Once I reinstall the box in the car I'll cycle the controls and see if it still rests here.

Then I reassembled the rest of the box:



To be continued

 

Oh also, is your heater valve bad? It's this piece of copper pipe with a flapper to divert the coolant. Mine was corroded and toast.

 

That was by far the rustiest piece, so I'm glad it turned out okay without too much missing material.

I took the rubber boots off of the relays to clean them:





It doesn't really matter, but everything was grimy from almost 40 years worth of foam dust and dirt from the lack of filter. Plus me always having the windows down and sunroof open due to the heat in the summer certainly doesn't help the matter. A little bit of extra time cleaning everything is well worth it.

The blower motor resistor seems to have melted long ago:



I've always thought the fan was weak on settings other than high. Also on high. Speaking of which, here's the new blower motor:



This is the Four Seasons aftermarket part. I've heard that it's a pretty good fit but blows harder than the original, and with it in-hand it feels like a quality part. I cleaned the fan itself and installed it:



Then the motor and fan fit into the assembly. The Four Seasons part is a bit taller than OEM, and the plastic cover is a bit too short to fit properly:



But at the end of the day, it does bolt on. You can also see I removed the old harness tape and replaced with the fabric anti-rattle stuff I've become a fan of in recent years. It's a small thing, but it helps. The connector for the fan was cut by the previous owner, not me, so when I'm done testing I'll replace it with the correct OEM connector.

Speaking of testing, I've been playing around with a solution for the cabin filter which I'll go into in my next post.

 

I'm sure every other Rx7 owner has had the same irritating experience - you're behind a truck on a dusty day, you enter their dust cloud, and the dust shoots out all of the vents into your eyes, nose, and mouth. It only has to happen once before you learn to quickly hit recirc and close the fresh air vents the moment there is dust in the air.

The solution is a cabin-air filter, but the challenge is finding a place to put one. I had some ideas about installing one under the wiper cowl, but then I really need to worry about it getting soaked with water. Inside the cabin is a better option, but there obviously isn't a convenient place for it. So I found the least inconvenient place for it - the inlet of the blower assembly. Replacement would be about an hour's work, but for the amount of mileage I put on my Rx7 that would still only be every few years.

I started by designing a simple filter basket and printing it out of flexible TPU:





I purchased a cheap cabin-air filter and drew some measurements on it, then took it apart to start constructing a custom one:







I wasn't sure what the correct adhesive was, but the filter was originally assembled with hot-glue so I went with that. It's a bit ugly and the seal isn't perfect, but it's good enough to test and see if this concept will work.

I hooked it up to this jump pack and tested to see how much restriction it added:



For my first (non-scientific) test I simply ran the blower motor with my hand in front of the outlet, then installed the filter to feel the difference. Unfortunately, it seems to be a pretty significant restriction. Then I used an anemometer to measure the actual airflow; without a filter it's about 7.2 and with the filter it's under 5. I don't recall the units offhand but for this comparison the units are arbitrary. Clearly the filter means there will be a pretty big compromise for airflow.

For additional evidence, installing the filter makes the little bypass door open as well:



So I'm going to have to do more thinking on this one. There is no extra vertical space to utilize because it will start to interfere with the flapper door on the bottom and the fresh-air vent inlet on the top. For anyone without a similarly equipped car, Canadian cars came with a slider on either side of the dash that pulls a flapper door inside the dash. This door will cut off the door vents from the HVAC system and instead just direct air from the cowl straight through the vents, so it provides ventilation with no noise or electricity required. It's a pretty cool feature, but it does mean I need to find a way to work a second filter into the system as it uses it's own air supply.

That's where I'm leaving it for now. The heater box is next, but that will have to wait for warmer weather. Until next time

 

My heater valve is actually working well, but I still want to take the heater box apart to replace the foam and the rubber hoses for the core. I didn't realize the core had additional joiners in the car - 40 year old coolant hose makes me nervous.

 

Nice work on the rebuild. When I bought mine and drove it home the first thing I noticed was there was ZERO air coming out of the vents. It was largely in part to that clamp rotting between the blower box and evap. Couldn't find a replacement evap core either.

 

I always thought that's just how old cars were. The blower in my car has always felt weak, and it was my first car so it kind of set the bar for me.

I'm curious to see how much better the air is once the system is all restored and reassembled. Not to mention the defrosters...

 

Don't forget the foam where the ducting joints and grilles are.

 

There are a few updates that have happened (lots of pictures, not a ton of material progress). I'll be dividing it into a few posts.

I wanted to redo my ECU mounting bracket. My MS3X was previously mounted using this plate:


It's not blurry in real life, I swear!



The zip-ties were a temporary mounting solution while I was testing something - the ECU was securely mounted using those screw holes for the last several years. You might also notice the 3D printed Megasquirt case. This was an effort to address my main problem with this bracket; the Megasquirt is significantly taller than the stock ECU, and the kick plate that goes between the ECU and the carpet wouldn't fit properly.

This plate mounts to the stock ECU bracket, and I'd read that the MS3X would fit under the stock kick plate if mounted towards the top of the bracket. However, in my testing I was never able to get it to clear with the stock case. I did however realize that there was space underneath the stock bracket that couldn't be properly utilized with a simple flat plate, so I was determined to change that.

Step one was to snap the spot welds holding this vertical bar to top and bottom bracket pieces:



Step two was to get an appropriate piece of steel:



And bend it up:



I'd like to provide progress pictures of the bending, but I didn't take them. Essentially I took the end length of the bracket, added in about 10mm (*2) for the extra length of the walls of the inset, and then bent it in a metal brake. Unfortunately the brake I have was only able to do 2 of the 4 bends since the walls of the inset are so short that they don't reach the edge of the brake. I made the remaining bends carefully by hand, which is why they look a little wonky:



But they serve the purpose:



I wanted to keep the bottom piece of the bracket, even though not strictly necessary. It has a 10mm stud on one side that may prove useful as a hold-down later on. However, these spot-welded cable guide have to go since they interfere with the mounting plate:





I removed the rust via electrolysis, and then hit it with VHT chassis paint. Speaking of which, that's what I also used for the bracket:



To be continued

 

Now regarding the custom MS3X case, I didn't actually end up using it. I got pretty close to a final design:







It works, and I even used aluminum tape on the inside to make sure it was still RF shielded. But the extra clearance gained with the new bracket is enough that I no longer need the slim case, so I just ended up using the stock case instead. The kick plate fits flush though:





I also decided I didn't like the USB cable I was using for tuning. It was very long which contributed to the messy wiring near the ECU, and I had it run under the dash coming out near the passenger seat belt. It worked fine, but I wanted to tuck it somewhere that is entirely invisible when not being actively used. So I bought a 1ft bulkhead-mount USB B cable online and mounted it to the top of the kick plate:



This sits way up against the firewall. I have another 1.5ft extension (for some reason they only came in packs of two?) which will plug into this one and mount to the bottom of the dash plate where the stock alarm lives. This way I can just plug a USB B cable into the connector when I want to tune, and then when I don't want to tune the car appears completely stock.

Now the next step was going to be replacing the EFI harness with a new custom one, but I wanted to deal with the heater control box so I didn't have too many projects on the go at once. I'll write about that shortly

 

The last part of the HVAC system to need resealing was the heater box. It lives directly behind the center vents and radio in the dashboard. It might technically be possible to remove it without removing the dash, but I think it would be cumbersome enough that removing the dash is an easier proposition:



It really only takes like an hour once you know where all the fasteners are. Ignore the messy wiring for now - we'll deal with that later on. Here's the item of interest:



Those vents to either side just pop out with those little push fasteners removed. Then the entire thing is held in by four 10mm nuts.

I took the box to the basement and started inspecting it. It's neat how this works:



There is a little valve to cut off coolant flow to the heater core when you have the air on cold. I think some cars only have the flapper door, so it's neat that Mazda added this valve to prevent heat excess heat entering the cabin on a hot day even if the core isn't receiving airflow. Not that the cabin doesn't still get super hot the moment the sun is out, but hey, any improvement is appreciated.

As you can tell the vent foam is pretty crumbly:



I gave all of the doors the same treatment as the ones in the blower motor box - strip to bare metal, paint (more VHT chassis paint), new foam:





I had been using double thickness closed-cell foam to try and get a better seal, but I realized it wasn't compressible enough and was leaving a gap at the edge of the door furthest from the hinge. So I stripped off one layer of the foam and added a softer open-cell foam instead:



That resulted in a good seal.

Speaking of good seals, I had a persistent leak from the driver's side heater hose whenever I drove the car hard. I think it was a combination of the extra heat and pressure from high RPM operation, plus deformation of the soft brass tube. I had an idea to strengthen it using an inner sleeve made out of a tougher material. Enter some 5/8" OD stainless steel tube:



I sanded down the OD of the tube just enough for it to fit into the brass heater tube, then rammed it in (being careful not to bend the brass tube any further). Once I felt like I had enough length in the steel tube, I measured how far it fit inside the brass tube and cut out that section:



Then tapped it home:



Now when I tighten the clamp, it should apply pressure against the inner tube rather than deforming the outer one. It might restrict flow by a little bit, but I'm not too worried about that in practice.

I also cleaned every part of the heater box before reassembling of course. I added grease on any moving part. This is more important on the sliding linkages, but I also felt like adding some on the rotating bushings couldn't hurt:



I actually ended up re-using the stock hoses and clamps that connect the heater core to the tubes that go through the firewall. I had purchased some new tubing and clamps, but the old ones still felt quite soft and looked to be sealing perfectly. Also, the new one wasn't as tight a fit and I was concerned that I would have to tighten the clamps extra hard to compensate.



At that point the heater box was ready to go back in the car, but bigger concerns have arisen. To be continued shortly.

 

I resumed taking apart the rest of the parts on the firewall that aren't normally accessible. These small tubes for the fresh-air intake aren't normally accessible with the dash in place, so they're a good candidate for cleaning while I'm in here:



I also removed all of the little brackets for cleaning, as well as the wiring. One of the three stock ECU connectors is for the body harness, and my plans include keeping this particular harness. So I removed any loose electrical tape that had gotten greasy and then wound it in Tesa interior tape:





There was also the matter of this thick insulator mat that sits against the firewall:



It's a jute type padding with a rubber backing. Unfortunately the jute material was so old and deteriorated that just touching it made it turn into dust and blow away, so I figured I would remove the mat and replace the jute with something else. I also noticed that someone has been in here before, since the mat was folded and pinned under this harness:



Is there even one part of this car the previous owner didn't mess with?

Anyways, the pedal box had to come out and the steering column had to drop:




Sorry it's underexposed - my camera has a thumb adjustment for exposure and when taking photos outside it's very easy to bump the adjustment and not notice since it's so bright out.

And then I found this:



Yikes. No holes, but still, pretty bad. At this point I decided to do some investigating (which is never a good idea)

 

It didn't take long to figure out where the water was getting in:



This is the upper left corner underneath the wiper cowl. Water was leaking in there and just soaking the back of the mat. It was most likely sitting against the firewall in that jute for weeks without drying.

It was also leaking down onto the floor:



Some of it in behind the fusebox area:





This was enough to tell me I should remove the carpet and find out just how far the water had crept:





It was pooling in a couple of places, but it seems to have made it's way all the way to the hatch release lever.



I also started thinking that it would be a good idea to inspect all the prior repairs. Particularly since some of them were from before I bought the car, some by my dad, and some from me. And I can guarantee that no one who has worked on this car in the past (including myself in several instances) did body repair correctly.

 

With my Rx7 about to turn 40 this October, it's now an old enough car to just go big or go home. Ignoring floor rust now just means more work later, and clean shells are no longer common or cheap. When I first restored the car a few years back, I inspected all the repairs and found no rust. Then I made sure everything was painted and added some sound-deadening. My standards for what constitutes an acceptable repair have shifted since then.

I first peeled up the CLD that I added myself, as well as some of the closed-cell foam padding I was using under the front of the carpets. Then I took a dead-blow hammer and a chisel and started going medieval on the OEM stuff underneath:



After about 6-8 hours of chipping:



Interestingly, there were several places where I found water under the OEM insulation. I think this stuff is a bit porous and/or has separated a bit from the substrate and allowed water to seep underneath. It also might be a cyclical problem - rust causes insulation to lift a bit, creating a small gap, allowing water to seep in, promoting more rust.

I've heard people use dry ice for this, but actually getting dry ice would have required a drive to the city as well as taking a day off work. So I did it the old fashioned way. The remnants still need to be cleaned up, but it's now clean enough to see what we're dealing with.

Starting at the front of the driver's side, there's rust in the top left of this photo. Not sure whether it's penetrated the metal, but it looks deep enough that cutting is the only correct repair. I also see rust on the floor that the frame rail butts up against, and rust inside the frame rail itself through this access panel:



My frame rails aren't crumbling or anything, but it will get bad soon if not addressed. I already have bolt-in rail reinforcements (the bolts in this photos) but that is no excuse to let the rail itself rot away. You can also see how wet the floor was - those fasteners used to be gold, and now they look like they belong on the titanic.

There's rust under the seat mount, which means I'll need to remove it to replace the sheet metal:



Also a prior repair at the rear seat mount. I remember we had a local guy do these repairs for us when I first purchased the car. The repair itself isn't bad, but it wasn't coated very well and the welds are rusty. So is the floor behind the repaired area. This implies to me it should've been cut further back, but I'm pretty sure the guy only charged me $120 for a few hours of work so I can't really be that upset.



The seat mount itself isn't terrible, although it is bent a bit from repeated use of the frame rail as a jacking point:



Then at the passenger front we have this lovely repair. This is actually one of mine:



I think I was trying to repair the double-walled section of the floor at the front, and for some reason I just replaced the outer panel and not the inner. I mean, it works. But if water were to drain into this area then it would just pool there forever. I don't actually think any water was finding it's way here but the sheet metal started to rust on top nonetheless. Add to that some pinholes near the mounting stud for the ECU panel and this entire area will need to be addressed.

The passenger side rear seat mount has been repaired by seemingly riveting some sheet metal over the holes.



From underneath I don't feel a seam anywhere, so I suspect that removing that plate would reveal several smaller holes that were just plated over. This is one of my dads. I love my dad and he's a talented guy, but neither of us have ever been naturally talented at bodywork. Also, I bought this car for $1600. I'm pretty sure he was more concerned with just making sure it was safe and not particularly worried about what the market for clean Rx7s would look like in 8 years.

Here's all the insulation I chipped out:



If you're wondering how much it weighs, wonder no more! It's 28.5 lbs. That's the entire floor area and firewall. Consider that 15 lbs or so is probably insulation I added myself, and the weight gains from removing insulation are pretty slim. Also consider that if you bang on the floor with a hammer the car now resonates like a drum. Unless you're building a race car, you really should leave the floor insulation in place.

And I fully intend to put fresh insulation down, but first I need to figure out how to deal with the floor. I'm no stranger to cutting and welding, but the rust at some of the seams is my main concern. I'm thinking the correct repair might actually be to drill out the spot welds and remove the entire floor pan. That will give me access to the frame rails as well as the ability to replace any of the metal along the seams not easily done inside the car. That does however mean removal of the transmission. I also need to fix the ol' wide-bondo on the driver's side rear quarter, the bubbles on the passenger side quarter, the little panel at the bottom of the passenger quarter where water collects when the drain tube for the hatch isn't pushed through, etc. At this point I'm seriously considering making a simple rotisserie and just going all in.

I'd really like to drive my car this summer, but that probably isn't in the cards at this rate. I'll still be doing everything in my power to make it so. I can't do any more work until I have some proper garage space, and there's a Miata with a disassembled timing assembly in the way right now.

There's more rust than I'd hoped, but actually less than I expected. Overall I'm not too upset by it. It's still a lot cleaner than most of the FCs I've seen for sale lately.



Until next time

 

OOF. and here i am about to sell my entire project as i haven't touched it in years.

 

that rust is a bummer! rotisserie isn't too hard to do, you could also do something like this https://www.rx7club.com/build-thread.../#post12224191

 

It looks like making a rotisserie out of two engine stands isn't that difficult. With appropriately sized stands (and drivetrain out, of course) plus steel for reinforcements and mounts it's probably a little over $500 CAD.

One thing that does concern me is the question of what happens if I find rust in someplace difficult to fix, like the inside of the rear frame rails or something. That's an area not easily sectioned or replaced. I guess at that point the answer is a chemical dip, but that's obviously an expensive proposition and would require a full coating and repaint of every surface. I really don't want to open that can of worms.

I guess that's neither here nor there. I'll find out either way when I start digging

 

my friend did just that, and it works just fine. the only thing is that he didn't run anything to connect the two, so moving the thing is a little awkward
if you need to work under the car its great.