I checked back in your build thread, those seats are actually really cool. The headrests remind me of those Recaros with the mesh backing.

 

Yeah, I’ve thought about dying them black to match but I’m afraid it won’t look right.

 

i definitely burned all mine out. found out the hard way the larger rear diff mounts on the S are fluid filled. the log press is just a piston, should work if you can rig up the tooling lol. my lazy *** bought a pneumatic bottle jack and installed it on my cheap press.

 

I don't know about fluid filled bushings but, those old rubber ones can be drilled out (any old rubber bushing). I get the pistol drill, whatever bit seems good for the job and start drilling holes in the rubber. The old rubber comes out in a powder, you can angle the drill around to force it to side cut, get the center out, and then cut through the shell with a sawsall. It's an alternative method to the fire method, but hey, if you're into fire use that method, I hate the smell of burning rubber.

 

for my case, some of the urethane replacements require the shell to remain and some don't.

 

Awhile back I stumbled upon a good deal for some factory Mazda comp control arm bushings. I wasn't really looking for them, but the price was too good to pass up at about $100 for complete front and rear.

Turns out I didn't look at the pictures carefully enough, and I ended up getting a better deal than I had expected. It was a complete front control arm bushing set, but there were no rear control arm bushings. Instead, there was a set of Mazda comp differential mounts. An especially good deal since mine are 100% trashed.

I wasn't going to install them because I will be swapping to the Turbo II diff anyways, but then I did some thinking recently and realized I'd been neglecting some parts of the car and prioritizing getting all the parts I need to complete the swap. And sure, I want to complete the swap sooner than later. But until then I still want to enjoy driving the car. So I decided it was time to swap out my tired original diff mounts for the new set.

I had to evict my mum's Miata from the garage temporarily, since it's been raining for about a week here:





I guess that picture is a bit of a spoiler for the hood update, but I still haven't actually gotten around to doing the write-up yet. It took several months of putting in a couple hours at a time. My god, the sanding...

Anyways, I was going to just remove the diff, but then it became apparent that access was really tight. Trying to avoid removing the subframe would be a false economy, so I just spent the extra hour now and dropped the whole thing:





The motorcycle jack makes this a much easier job, although I should have put a couple planks under the diff to take up some space. The bottom of the diff sits higher when installed than the bottom of the subframe, so to get it to align properly for reassembly the diff needs to be slightly elevated.

But where's the diff in that photo you ask? Right here:



I drained the fluid and then flipped it over so I could remove the old mounts. Speaking of fluid, this is what came out:



It looked pretty good. Still clear like honey, and only a hint of metal dust in it. I was tempted to reuse it, but even though this diff is temporary I decided it deserved some fresh fluid. They don't grow on trees anymore.

The mounts are pressed in from the upper side of the diff, so to remove them you need to push from the bottom side. Hence why I flipped the differential upside down:



It doesn't look so bad in this picture, but if you look closely you can see a lot of cracking on the rubber. That isn't terribly unusual (minor cracks form within a few years, in my experience) but when you look at the center sleeve you can see the rubber has started to separate from it. When I put a screwdriver in the center sleeve and pushed it around, it was also very very stiff. That's likely part of my road noise problem.

Unlike J9FD3S' diff mounts, mine did not want to come out easily. An air hammer didn't even budge them a little. I ended up using the drill method that TonyD89 mentioned above, and that worked really well. Punch a few holes in the rubber until the center sleeve falls out, then sawzall along one of the two seams in the bushing sleeve. Once you are most of the way through, use a chisel to hammer the sleeve inward until it loses tension and falls out:



The old bushings were so old it was like drilling plastic for the first 1/2" depth of the rubber. At the center it was kind of pliable, but the outside had basically no give.

I thought I remembered to take pictures of the new bushings before install, but I guess I forgot. Anyways, they look like the old except they have a slightly oblong shape. If you look at the old one in the above photo, you can see the outer sleeve is two-parts that form a whole cylinder. When not installed, these bushings have a 1-2mm gap between the sleeve halves. As you press them in this gap compresses and then the tension helps hold them in the diff housing.

Speaking of presses, I don't have one. But what I do have access to is a very poorly-built log splitter:



It broke from the mere stress of me pushing it up a hill. I swear, this thing was originally welded together with a soldering iron...



Fixed. After that brief diversion I had to make some space. My brother's GS500 recently turned itself into a GS250, so I moved it aside and pulled the log splitter in to prevent working in the rain. The log splitter makes more torque now anyways...





I don't know what was more dangerous, my improvised log-splitter hydraulic press or the abysmal state of my garage.

To be continued

 

I had to spend a long time getting the spacing right. Actually, it wasn't that long a time, more like 5-10 minutes per side.

Basically the issue is that the diff needs to be tipped a little to fit the mount down into the valley of the log splitter, and then it also needs to be kept concentric to the nub in the middle of the moving side of the press. If the bushing isn't pushed in perfectly straight, it will want to skew sideways instead of pressing in. I just took it slow until I got it pressed most of the way in.

Fun fact, that big socket is the absurdly large 54mm flywheel socket. It's the perfect size to press the top of the bushing in, and then once it's 80% of the way installed the center sleeve will want to collide with the plank on the other side. Then flip the socket over and place it on the other side, and it will provide a pocket to let the diff mount push all the way home.





Other than the actual pressing of the mount, the other challenge is to make a flat surface for the splitter to press against. Turns out that's easily solved - if you put a plank in but oriented so it's cutting against the grain, the splitter won't want to cut through it. Conveniently the splitter bit (or whatever it's called) that I am using here is also pretty dull.

Once I got the first side installed, the other probably only took about 5 minutes. I was working alone, so the most challenging part was stretching my left thumb to start the motor while my left pinky was holding the dead-man switch, since my other hand was helping to hold the diff straight. Conveniently the people who designed the guard to prevent me from doing so were as lazy as the people who actually built the splitter, and I was able to do it without to much fuss.

The new bushings installed:



It's weird, old bushings are somehow firmer than new but also allow more slop. I don't know how both are possible, but if these mounts are anything like the front mount I replaced last year, it will both improve ride quality and decrease slop.

Speaking of slop:



I thought the diff felt a bit weird lately. At some point the rear nut backed off and vanished, and the front one wasn't super tight either. Apparently new ones are $17 per from Mazda (!) and no parts stores around me have any in this size for some reason (M12 x 1.5, 10.9). So I'll need to see if I have a spare. I know a guy who sells all sorts of fasteners at really low prices, but he's about 40 minutes away. Conveniently he's near the Mazda dealership that I'll be returning to next week to pick up some other parts:



Yup, those are my subframe bushings. They're also pretty stiff, and the rubber is separated all around from the sleeves. I don't know how much of a difference this makes to ride quality, but I intend to keep this car for a long time. I also don't feel like dropping the subframe again if I find the diff mounts didn't completely resolve the noise issue. So I sold a few more of my organs and went to the dealership to order two brand-new ones.

You may notice rust on the subframe and control arms despite my restoring them a few years ago. Nothing structural, but a few winters outside seem to have caused it to return. I'm on the fence about whether I want to spend the hours stripping the rust and repainting just for it to return again (since I don't have access to a blaster or a way to chemically dip a subframe), or just leave it. It doesn't hurt anything functionally, and I have medium to long term plans that don't involve keeping this suspension or rear-end at all. I'm leaning towards ignoring it for now.

ETA on the parts is Tuesday, possibly a bit later. I have a few days after that before classes pick up again, so I should hopefully have the car back on 4 wheels by the end of next week.

 

POR15 that ****.

also, white countach is best countach.

 

I do have some POR-15 left over from the Miatas floor, so I might just do that.

Agreed, Countach always look best in white. That picture is one of my favourites. It isn't even a poster, it's actually the front of a puzzle box that we no longer have, but I like the picture so I keep it up there.

A Countach seems like a nightmare to own, but I'd like to drive one someday.

 

ive mentioned before how bad my subframe mounts were, but changing them was a night and day difference in ride, which i did not expect

 

It's iconic, but if you get too close the magic will die a little. I vaguely remember being in one at work a million years ago.

 

i can't find a pic of my lego countach (i went for a Wolf of Wall Street, so the guy is lying next to it )

but i do have this,


arrow is pointing at the diff, but the trans is at the other end

 

showoff!

 

That makes me feel a bit better about spending on new ones. I wasn't sure it would make a difference, since all it does is absorb some of the impact from the control arms.

I went out to start removing the old ones, but then I thought I might be better off waiting until the new ones are in hand. I don't want to destroy the old ones and then find new ones aren't available. My local dealership actually had an ETA on these parts, which implies they exist, but I have ordered before only to find that the parts are nonexistent but not actually marked NLA yet.

 

Amazing way to spend the start of the new year! Reading my favorite FC forum 😁

 

Happy New Year, everyone!

Today the new subframe mounts came in from Mazda, so I went to pick them up. Pleasantly surprised that these were available next-day (in fact, it's less than 24 business hours since I ordered). I had disassembled the entire rear suspension a few days ago in preparation:





Everything was in pretty good shape, surface rust aside. My homemade camber links are still smooth. I ended up swapping in another set of toe rods that I had around, purely because I felt like the joints were a bit smoother. It's unlikely to make a noticeable difference, but hey, I'm already here. Then it came time to remove the old bushings.

I started by drilling out the rubber like last time, but these mounts also have an additional inner sleeve that makes this difficult. So after drilling many holes (and snapping several bits, because titanium bits don't like to be pulled sideways), I put it in the log splitter and pressed the innermost sleeve out:



I then used a chisel to force the outer sleeve away from the subframe opening, and then worked my way around until it fell out. This was much more difficult than the diff mounts, and took over an hour per side:



Boy, my arms are tired from hammering.

Once again, they were in terrible shape. Not only was the rubber really stiff, but the outer sleeve was so rusty it had the consistency of one of those wafer cookies:



And it left a lot of crust inside the subframe:



I got all of it out by chipping away at it with a claw-hammer. Once I chipped it away, the inner surface was actually fairly smooth. Most of what you're seeing in there is mount remnants, not subframe.

I wire-wheeled everything clean, and then hit it with some black spray-paint. I expect it to rust again in the future, but I figured a thin coat of paint would mitigate the issue without interfering with the fit of the new mount.



You can see my alignment marks here. I'm not sure that it matters, but the mounts aren't actually pressed in straight. They have a slight outward angle. The differential mounts are installed with the split oriented longitudinally to the car, and I think in that application it would matter because the outer and inner sleeves have rubber between them in four locations, in an across-pattern. If the mount is rotated differently, it might absorb force differently. Or maybe I'm overthinking this whole thing.

The new mounts:





You can see what I meant in the previous post about the split. When the mount is pressed in, that split closes:



I picked up some fresh hardware from my usual guy:



We'll talk about those big washers shortly.

To be continued

 

I thought about installing some DTSS deletes that I have had in a box for years, but first I thought I'd check the state of my current bushings. To my surprise, I already have DTSS delete bushings installed:



I don't recall ever deleting my DTSS, but then I did swap these hubs in when I did the 5-lug swap. So it's likely that they came with the hubs. I remember liking how DTSS felt when I first bought the car, and then being a bit less clear on whether I liked it the past few years after the 5-lug swap. I guess I have been driving without it for awhile and not noticing.

I reassembled the rear suspension on the jack:



No, I didn't end up painting anything. I would like to make excuses as to why, but the truth is I just don't care that much how it looks anymore. It's under the car and it functions well, and I have some ideas that involve replacing the entire thing anyways. While the FC handles pretty well (even by modern standards), the rear suspension is kind of crude. Especially without the DTSS.

Without DTSS the spindle and trailing arm are basically acting as one unit. Like most trailing arm suspensions, it isn't terrible. It's just that it squats when you accelerate, and the toe and camber curves aren't ideal. In addition to that, I really don't like the front differential mount design:



Those are brand new nuts and lock washers. I only needed one, but decided to just get both.



Mounting the differential from the side like this is a really poor choice. First off, the mount is constantly in shear. Either the diff is shearing it downwards when at rest (admittedly not a lot, but it adds up) or when you accelerate the nose wants to move up and it shears upwards. This leads to shortened life, and allows a good amount of movement. I have a pinion snubber installed to mitigate this, but it's still a pretty lame design. Then as if that wasn't bad enough, the entire force of the differential moving up (ignoring the snubber for a moment) is placed on that tiny tab above the wide washer. If the differential moves too much (and you are making too much power) it can rip that tab, or rip the entire mounting flange off the subframe.

I don't think this will be an issue due to the snubber. I also don't make that much power (yet) or launch the car very frequently. But overall, the entire design of the diff mount and rear suspension in general kind of irks me.

I had an opportunity at my last job to see a lot of different Honda suspensions (none with diff installed though) and most of them use round bushings for all three mounts, and in orientations that place the mounts in tension / compression and not shear. I'd like to implement something similar.

At this point in reassembly, I encountered a bit of a mystery. For some reason, I had an inkling that there should be a washer on top of the differential mount, like this:



The service manual makes no mention of this, though. I also can't find mention of it anywhere else. But still, I had a strange feeling that there needed to be a washer there. I dug and dug and dug, until I found the reason I thought that:





Aha! In the parts fiche:



18-2782 doesn't actually return any results on it's own. I didn't find it in the fiche, nor on Amayama. But after googling around awhile, I found this on another site:



EDIT: Even more interesting, I just now this part on Amayama, but only in the diagram. Not searchable. The part number is also in a totally different font from the rest of the diagram, not listed on the right hand side, and hovering over the part / number does not pop up with the part info as it normally does for other parts.

"Thrust" also implies it's there for spacing and not to spread out the load. So that confirms it, there should be a washer there. Right?

Well, I'm not sure. I reinstalled everything and this is what I discovered:



Apologies for the poor photography, this was taken under the car with a flash.

The nut doesn't seem to get a lot of engagement with the additional washer. And this is without any sort of lock-washer either. The cup thing also has a wide gap between the rubber crown and the differential ear, so it seems like the washer isn't supposed to be there. Maybe the parts fiche was created before the part was removed from the design and not updated?

As if that wasn't weird enough:



The subframe mounts install fine, but the rubber contacts the subframe pretty firmly. I think they're supposed to contact, but this seems like a lot and doesn't allow even the slightest movement of the subframe mounts. This picture is without a lock-washer, so with a lock-washer the nut should end up right at the end of the threads.

This requires some more thinking before I proceed, and I'm all out of thinking for the day, so I'll return to this once I have had time to ruminate on the issue. Any advice or feedback is appreciated, as always.

Until next time

 

I did some more research, and I realized that not only does the FSM not list those two washers I added to the diff mounts, but it doesn't show any lock washers on the diff or subframe mounts either. Which makes sense, since I didn't remove any on disassembly.

So, I dropped the subframe assembly again and removed those two washers, then reinstalled to see what would happen. Turns out that without the extra washers, all four mounts align perfectly. What doesn't align perfectly is the camber link:



This link is necessary when you've installed lowering springs. The lowering springs end up causing negative camber, and you need this link to help pull that camber out. Shortening the link lifts the rear of the subframe closer to the body, and that tilt removes the camber. While looking at this link I realized that this heim joint probably doesn't do a great job of isolating vibrations, so I've made note of that and will need to find and modify my original link.

In my case, it won't align anymore. This photo was taken with the rear of the subframe jacked up as far as it would go, and there is a good 1" of gap still. This begs the question how it aligned in the first place.

To add to this, take a look at this photo:



You can see that the subframe has clearly been colliding with the body at the spot above the inner camber link. That's why there is exposed steel visible there.

Speaking of the inner camber link, I already have a set that are slightly shortened from stock. These are the second iteration. If you remember, I made these awhile back after my first attempt snapped when I went over a pothole.

So I can think of a few options forward, and I don't really like any of them:

1. Modify the body of the car. Take a big mallet and hammer in some clearance at the locations where the subframe is colliding.

2. Modify the subframe. Cut out a rectangular section of the part that interferes, then put a lip on it and weld it back in. Basically drop it 0.5" or so.

3. Put those extra washers on top of the subframe bushings. I have enough thread on the shaft for this option to be done safely. This will lower the subframe by a little bit at the front, which will translate to a bit more clearance between subframe and body.

4. Modify the inner camber links. Measure to make them as short as mechanically possible without the trailing arm hitting the subframe. Then wind out the rear adjuster so everything fits and take it for an alignment.

Option 1 is distasteful because I don't like modifying the car when it's avoidable. Option 2 would work, and I can always get another subframe.

Both options 1 and 2 (and 3, to an extent) have the same issue, which is that it puts the subframe mounts under stress. It pushes them into a slightly twisted position when they would normally be untwisted, and holds them there 24/7. It also makes the bottom of the subframe contact the stopper-cup, which might send more vibration through the body.

Option 4 wouldn't stress the subframe mounts any. It would actually allow me to remove some stress. It would however put stress on the trailing arm bushings, twisting them the in the exact same way that I don't want to twist the subframe mounts.

Once again I'm going to have to do some thinking. Did I mention that I don't like this suspension design?

 

how much camber are you trying to take out? on my old 20B car i just cranked the camber link as far as it would go, but the diff hits the floor, etc, not good
my car now, i have the same camber link as you (which maybe is louder than i want), i put the suspension together and put it on the ground and set the bar to its neutral, the bolt can go in and out with no tension, and then i'll shorten it.
i don't go very far though, as it is one of the limits of the suspension design.

my car also isn't that low, it is kind of a battle between how it looks, the limits of the suspension, and how it drives. i'd rather have it drive better, so its just not that low.
the funny bit is that i lowered it a turn in the rear, in anticipation of Sevenstock, and it looks much better, but it added enough rear toe in that if you're on the gas the car doesn't turn!

and B if you want less camber putting the pivot point of the suspension arms helps, although you can't go very far. so adding a washer on top is the wrong direction.

 

Well that's the strange part, I don't really need to take that much camber out.

My car sits on Tanabe GF-210 springs. I don't have any means to adjust ride-height. They're definitely a drop from stock, but nothing too crazy.

Clearly it aligned before I replaced all the mounts, even if the subframe did hit the body, so something must be different. Maybe the subframe sits higher in the chassis than before because the old mounts had sagged? Now it's not even close.

What I could do is just wind out the adjuster and install it at neutral height. Then with the car on ramps get it as close as I can before deciding what to do. Or go get the camber measured and see what's up.

There's nothing to prevent me shortening the inner two links later on. It's not a difficult task. My main reluctance is that welding those links shorter might cause my poly trailing-arm bushings to bind.

 

I looked at the subframe a bit more this afternoon, and realized the camber problem wasn't as bad as I had thought. The plank I was using to jack up the rear of the subframe was also contacting the diff, so what I had thought was the subframe hitting the body was actually the diff hitting the body.

Once I repositioned the plank I was able to get it much closer, although I still had to wind the adjuster out about 1/2" to get it to line up. It also occurred to me that the new subframe mounts might be causing it to sit at a slightly different height. This is actually almost certain to be the case considering how bad my old mounts were. So it might be that the camber link won't need to be wound out as far to achieve the same effect. Pure conjecture, but that's all I've got at this point.

Anyways, I reassembled everything and put the car back on it's wheels:



The camber doesn't seem to be that negative, if at all. Before I last got it aligned it was so bad I was getting obvious tread-wear issues and I could see the camber with the naked eye. Now when viewed from the side-profile, it looks pretty straight to me. I'll know more when I get it aligned.

The other thing I noticed is that for some reason the exhaust tips hang straight now. I've always followed the same method for installing the exhaust (hang everything, slip gaskets and fasteners in finger-tight, tighten in sequence front to back). It's unclear why it's hanging straight now when it didn't before, but it's a happy accident.

With snow on the ground and summer tires I didn't want to take a long drive. But it's insured year-round and the road was clean and salt-free, so I took a quick drive to the end of the road and back. The NVH from the rear is dramatically improved, and the car also launches much more smoothly. It's still too loud (exhaust drone), but this has gone a long way to improving some of the more fatiguing factors in driving the car for long periods.

 

its interesting the exhaust lines up now, i wonder if its got something to do with the hangers on the subframe?

my thinking with the camber link is like this: basically the two limits are that the diff eventually hits the floor (or subframe), which is bad. also it seems like the camber link pulls asymmetrically, so camber might be even with the thing loose but the more you tighten it, the more camber varies side to side.

i think (key word there), that the best way is to do the camber adjusting last, and your limit is kind of where it starts going asymmetrical. what the final number is depends, mostly on ride height (our cars are pretty similar)
and then it kind of is what it is. IMO part of the fun of a vintage car is the quirks the vintage car has

 

I had one more project I wanted to try out before classes pick up again. There were a few times this fall when I drove my Rx7 to work. Conveniently I was only working 2 minutes from my house, so normally I would start the car and let it warm up while making coffee.

I noticed that in the morning, when idling with all the accessories on, the voltage was pretty low. Sometimes around 12V. Granted this was with headlights on, fan at maximum, defroster, stereo, etc. But still, it should never be below about 13V in normal operation.

I've known what this issue is for a long time, but it was easier to ignore when it was summer because I rarely use any accessories other than the radio. My alternator is too big for it's own good, and shaft speed at idle is too low to get any real charge out of it. As a refresher, I swapped to the Ford Taurus alternator a long time ago to support the Taurus e-fan:


I really need to redo the wrinkle-paint on the water-pump housing and thermostat neck. Or just go for powder-coat.

This alternator normally makes 130A, but mine is a blend of at least three separate alts at this point, and the current guts in that casing are tested at 170A. Clearly it's been rewound at some point.

Now I don't need 170A. I probably don't even need 100A. But the headroom is nice, so going back to an FC or FD alternator wasn't really something I wanted to do. So I started by doing some math. I found a webpage from PA Performance with some useful information about the shaft speeds required for a 3G alternator. Working from their estimates, I would want about 1900 RPM alternator shaft speed at idle. 2000-2100 would probably be better. So what do I currently get?

The diameter of the crank pulley is about 120mm (measured with it installed, so that's a rough estimate). The diameter of the silver pulley in this photo is 72mm. 120/72 = 1.67. This means that for every rotation of the crank, the alternator rotates 1.67 times. Since my idle is currently set at 900rpm (partially due to the idle voltage issue), the alternator shaft speed at idle is 900 * 1.67, or ~ 1500rpm. Not nearly enough. This means I need a smaller pulley.

I spent a long time looking for a dual v pulley in a smaller size, but it turns out mine is already on the smaller side. I couldn't really find a pulley that would work for my application. I need a dual pulley because my air pump has been relocated, and without the air pump the water pump doesn't get a lot of pulley contact:



Having too little contact here could cause the water pump to slip at high rpm. Well, in theory. I'll get to that. In theory I've also heard that the water pump cavitates at high rpm anyways, so maybe slippage here would actually result in better cooling? Hard to say.

I ended up finding this pulley:



It's a single, but it has a 54mm outer diameter. This gives us a ratio of 120/54, or 2.23. Multiplying 900 * 2.23 = ~2000 rpm shaft speed at idle. Even if I want to restore the stock idle speed of 750rpm, that gives ~1700rpm at idle. Not amazing, but better than before.

Here's a comparison:



This pulley is really small. So small, in fact, that high rpm operation has me a bit concerned. 7000rpm isn't crazy these days, but it's still higher than the 6000rpm redline that the Taurus engine was meant to reach. I've also been known to rev past 7k on occasion. So using 7.5k as an estimate, 2.23 * 7500 = 16,725 alternator RPM. I've seen some estimates that 15,000 RPM is the safe limit for these alternators, but I've also seen reports from people that they can be wound much higher without issues. I'll just have to see what happens.

Since they were cheap, I bought two of these pulleys. I have an idea of how to make it into a dual:



I was thinking I could just have the inner part of one pulley machined off, and then weld them together in the position shown above. This won't work because the diameter of the nut is greater than the innermost part of the V, so it would end up destroying the pulley when the center is bored out. Instead, I'm thinking I could bolt it together on the bench with a spare nut, then weld the nut on. Basically, the inner pulley would now be one with the mounting nut. Then bevel both edges (center in this photo) to create a channel and lay a weld around the circumference. Lastly, put another nut on the outer side of the outermost pulley and weld that on. This sounds complicated, but basically I would be putting internal threads on the pulleys to install onto the alternator, and an outer hex on the pulley so it could be tightened.

The other option (and probably easier) is to build a simple idler pulley. It wouldn't be that difficult, but then it needs to be tensioned so I would need to find some sort of solution for that.

It turns out all of that might be moot, because I installed the single pulley and the water pump grips up really well:





This pulley is almost comically small, but in my testing today it works great. At hot idle, with all accessories on, I still get about 12.9V. With minimal accessories (running lights, fan) I get a solid 14.2V. Meanwhile I tested and I can't turn the water pump by hand without turning the entire belt drive with it. It sure seems like there is plenty of contact. One weird thing I noticed is that the car seems to run noticeably richer at low RPM, both with my MAF tune and an old Speed-Density tune I loaded up for comparison. Maybe the better voltage at idle is causing a hotter spark, and therefore better combustion? The car is also happier idling near 13:1 instead of the usual 12.5, so I'll need to do further testing in the spring and see what I can do there.

I also went for a slightly longer test drive since the weather today was nice, and despite my complaints about the rear suspension it actually drives really well. Wherever the alignment has landed, the car seems fairly happy with it. The car actually feels much faster now that the mounts are replaced, because I'm no longer as afraid to push it.

One thing I notice back-to-back with my Celica is that there are some situations where the Celica feels faster. One of the things that contributes to this is how solid and quiet it feels compared to my Rx7. I vastly prefer the Rx7, but with the old mounts the speed was very noticeable. It's perfectly stable at 120km/h, but you wouldn't think so because you can feel each of those km/h in your spine as you accelerate. It makes it feel like I'm going a lot faster than I actually am, and that makes me reluctant.

The new mounts have gone a long way to improving this, and I took it to about 100km/h today and never for a moment felt like it was unstable. I'm curious to see how it feels on the highway. I still feel a bit of humming from the rear, which is probably due to that camber adjuster and it's heim joints. Mazdatrix offers a modified OEM piece that does the same job for $180 USD, but I don't know if I want to spend the money for that. I might get the cost of the OEM part from Mazda and see if I can modify it myself.

 

I think it must have to do with the subframe sitting higher up due to the new mounts. I wouldn't have expected it to make this much of a difference, but between the camber link not aligning anymore and the exhaust sitting straight, that must have been at least partially responsible.

I also don't like the subframe link solution for adjusting camber. I think the correct way (barring major suspension changes) is the way those old Mazdatrix adjustable links worked, where you had a separate inner link for each control arm and could adjust them independently. The only reason I am using the subframe link is that those adjusters are expensive (and NLA), and that I was getting even camber with the subframe link. But those links only work if you have rubber bushings that will comply more easily than poly.

Neither solution is good though. I think the best solution (if one is really determined to keep the stock suspension) is to both notch + reinforce the subframe in those locations where it collides, then clearance the body with a big hammer in the same location. This gives the most play for the subframe adjuster method. Then get / make the inner links, also adjustable in length. Then take it to a really knowledgeable shop (lots of technicians know how to align cars, but not all get the theory behind it) and explain the situation. They should be able to strike a balance between tilting the subframe and shortening the inner links to try and minimize any stress on the bushings.

 

One of the next things I ended up tackling was my exhaust. As a refresher, I was using a stock exhaust manifold, connected to a 2.5” downpipe welded where the pre-catalysts used to be, down to a v-band flange with some sort of stock replacement catalyst, going into a 3” expander through to a Racing Beat REV TII y-pipe and mufflers:


(This is an old picture from before the v-band when I was using a 3 bolt flange that leaked profusely)

The problems with this setup are manifold (Get it? Manifold? I feel like I may have made this joke before…):

- It’s ugly

- It’s rusty

- It drones at highway speeds

- The catalyst hangs low, reducing ground clearance

- The exhaust stinks like you wouldn’t believe

- I get a loud bang every time I shift at high RPM, and also on decel before the fuel cutoff kicks in.

- It will not flow enough once I swap the turbo engine in

I wanted to address all of these with a new center section, replacing that catalyst and adding a resonator to take out some of the drone. The downpipe will still be retained for now, but everything downstream would be ready for the turbo engine.

This was going to be a longer term project but I stumbled onto some good deals for a resonator, catalyst, and flanges. So I moved it up. I started with the following, all in stainless steel:

- 3” Vibrant Ultra-Quiet Resonator x1

- 3” Flowmaster 200 Cell catalyst (metallic core) x1

- 3” 90 degree elbow x1

- 3” V-Band clamps / flanges x3

- 5/16” and ¼” rod

I had the following goals:

- Make everything out of stainless so it would last a long time

- Increase ground clearance

- Eliminate drone

- Reduce the exhaust smell as much as possible

- Retain compatibility with the Racing Beat downpipe (without modifying it) should I want to use it in the future

- Add additional flanges to allow me to swap out the resonator / catalyst for straight pipe sections, in case I want to use it at a track later, or to replace them easily later without having to replicate curves.

First I removed the current catalyst, and the downpipe. Unfortunately the patient did not survive the surgery:



Apparently the all-thread hangers I made years ago were too much stress for the catalyst to handle and the welded on heat-shield was almost broken off. I tore it the rest of the way with my bare hands.

I also put aside the split-air tube and the downpipe. Normally the air pump sends air into the catalyst under certain conditions to improve emissions. This tube also has the nipple to provide pressurized exhaust to the aux port actuators. I have an idea to use the split-air tube with the new exhaust, but I have yet to actually implement it. I’ll talk about the actuators later on.

I do have the Racing Beat resonator that is intended to go in this location, but unfortunately it won’t work for me:



It’s intended to be used without a catalyst, but I want to run one. I like being able to take the car through a drive-thru without feeling bad for the workers, and I also like being nice to the environment when possible.

Using both a catalyst and a resonator requires a lot more planning, which I’ll get to shortly. One goal of mine was to retain compatibility with the rest of the Racing Beat exhaust by keeping my center section overall shorter than the resonator. This further complicates things.

The best way to start fabricating an exhaust would be to start by mocking up everything under the car. Unfortunately I couldn’t find a great way to do this. I don’t have enough jack-stands and jacks to get everything in the right place. So instead, I just started with what I knew would be hard points. I tacked the v-band flanges onto the resonator and the catalyst:



The idea is that the only parts of the pipe that will have curved sections are the parts that adapt between the Racing Beat exhaust and my custom section. I wanted the resonator and catalyst to remain straight with just flanges. This wouldn't end up panning out for the catalyst, but we'll get to that later

The space under the car requires that the pipe makes a bend in front of the y-pipe and the catalyst (now resonator) sits at an angle relative to the rest of the car. Here's the Racing Beat part for reference:



Then the pipe makes a smaller turn back towards the axis parallel to the car as it makes it’s way around the transmission crossmember. This sounds more complicated than it is, so pictures will make it more clear.

The y-pipe uses a 2 bolt flange. Fortunately I have this cut-off piece of the original pipe. I added a curved section and then the v-band flange was tacked onto the end of that:



I got the angle right on the second attempt. Basically found it was quicker to eyeball the measurements and tack it together for a test fit rather than to fumble around mocking everything up below the car.

I also had to address the hanger situation. One thing I observed from the Racing Beat resonator is that they used really sturdy hangers. They also had the hanger mount in two places creating a triangulated shape in the direction the exhaust wants to rotate. Meanwhile the crude hangers I welded onto the catalyst heat-shield years ago were not nearly as well thought-out. Even over a short length the hanger being welded in one place causes it to act as a lever and flex the weld. That could cause it to fatigue and snap, and also adds some flex to the whole hanger that might allow it to resonate weirdly. I’m no expert in physics (I was particularly poor at waves) but I imagine the vibrations transmitting through the exhaust at one frequency, and then bouncing unpredictably back because of flex in the hangers acting sort of like a double-pendulum and allowing it to interfere.

I’m probably overthinking this as usual. Point is, I wanted the hangers to be sturdy. So I measured carefully under the car and made some cuts in the rod to make one “main” hanger, and then added a support rod for the front to back axis and a support rod for the side to side. This left me with a pyramidal shape:



This should provide ample support, and the length of the “lever” part of the hanger is down to a couple of inches.

I tested and this setup is really sturdy. I can’t flex the hangers any noticeable amount by hand, which was not true of the previous ones.

Then I had to deal with the catalyst. I was hoping to keep it further back, but it became apparent early on that this wouldn’t be achievable without significantly modifying the y-pipe. So I had to push it a bit forward, which meant it no longer sat entirely under the heat-shielding that Mazda put in the transmission tunnel.

Would it cause an issue? No idea. But the transmission tunnel of the car already gets hot, so I didn’t want to aggravate the situation. I decided the best thing to do would be to add a heat-shield to the catalyst itself. Enter some 304 plate, two 304 M6 nuts, and aluminum sheet:



Even with just the two mounting points, it’s fairly sturdy and doesn’t rattle around. I also added an additional O2 bung here. That’s to allow a place for me to reinstall the split-air tube at a later date by welding on an M18 O2 spacer.

When selecting the catalyst I put a lot of thought into which one would serve my needs. I contacted a couple vendors and more than one told me they did not recommend a ceramic catalyst at all for rotary applications. Maybe it would be fine but I’d be reluctant to test it behind a turbocharger.

This Flowmaster catalyst has a stainless steel body and a 200 cell metallic core that should be resistant to clogging up or blowing out from the heat.

Mocking it up, I found that with the resonator in the right place the catalyst was at entirely the wrong angle. I kind of expected this, but I realized it was severe enough that modifying the downpipe would not be a good solution:



It is pointed right into the frame rail. So I ended up having to add some more of the curved pipe to the catalyst to achieve the angle I needed. Before:



After:



Then I mocked up the v-band flange, a 2.5” to 3” expander, and a cut section of the original pipe with the O2 bung to mate the two:



A bit ugly, but that entire forward section of the exhaust will be discarded soon anyways when I swap the engine.

To be continued.