'93 Mazda RX-7 FD "mostly street car"

Heh.  Yeah, mine has both cats still in it, and that pretty much prevents the flames. :)

I was looking for one of these for a long time for an occasional track car and just couldn't find one I liked for a reasonable price.  

Got something else for now but I will have one one day. 

You're in southern cal, are you not??

jfryjfry said:

You're in southern cal, are you not??

I'm in the SF Bay Area -- Santa Clara to be specific.

Prices on FDs seem to be heading upwards, people seem to be asking $35K+ for low mile ones especially the R1/R2 packages.  When I was looking for this one about 18 months ago, 60K mile unmodified cars were going for around $20K.

Washed the car and then noticed I had an hour of "golden light" available, so grabbed the camera and ran off to a parking lot to do some shooting...

Gallery:  http://photos.codrus.com/Cars/FD/

codrus said:

So I took the FD to a local rotary shop to get formal compression test numbers with a Mazda tool to compare to my DIY tester numbers.

rotor 1: 6.7/6.7/6.9 at 264 RPM

rotor 2: 6.1/6.3/6.4 at 265 RPM

So it looks like my #2 rotor is only marginally in spec -- I guess that's sort of expected for the 58K miles that are on the car.

I need to sit down and crunch some numbers to work out conversion factors for my DIY tester to the factory one.

I missed this the first time around. There's an Arduino based diy solution which was open sourced by TwistedRotors that does the math for you. Instructions.

Yeah, the issue with my solution is that I used a board-mount pressure sensor and a vacuum hose adapter.  This means that I've added all of the volume of the hose/etc to the combustion chamber, throwing off the pressure ratio.  Theoretically I could compensate for that if I could accurately measure how much volume I've added and recompute the ratio based on the new total volume, but in practice it's really hard to do that accurately.  In the twistedrotors one they're using a threaded transducer that threads directly into the spark plug socket, so the volume change is minimal, that's the right solution.

In other news, I took it autoxing again today.  A few photos:

And a video.  I remembered the external mic this time, so no more boomy audio:

This was my last run -- also my best, despite going through the finish sideways.  Oops. :)  No cones, and I didn't hit the timing lights!  With the Ohlins the car is a bit more tail-happy than it was before, I toned it down a bit on the later runs by adjusting the shocks and tire pressures, but I think it may be time to look at the swaybars.  Despite that tendency towards oversteer, it's much faster and more confidence-inspiring than it was with the tired stock springs and sloppy FUCA bushings.

So I was driving the car yesterday and noticed that on fast 1-2 shifts it no longer chirps the tires, but it slipping the clutch instead -- sounds like for replacement.  The previous owner must have not been very good with a manual, this car only has 61K on it, and AFAIK the clutch is one of the few things on the FD that isn't well-known to fail in a short period of time. :)

As the title says, this is mostly a street car, so I'm not going to do anything nutso with the clutch, thinking about the Exedy stage 1 that Racing Beat sells.  The question is the flywheel -- the stock one feels overly heavy to me and something more responsive would be nice.  Racing Beat has an 8 lb aluminum one and a 12 pound Exedy steel one (vs 19 pound stock), but cautions against the 8 lb one for street cars.  Has anyone driven one and can comment?  I've got a 9.5 pound aluminum flywheel in the Miata and it doesn't bother me for street driving at all, is the 13b significantly less forgiving of lightweight flywheels than a BP?

Any useful input on rx7club?  I'd go lighter, you're not commuting in this thing.

Beautiful car, I'd love one of these.  Always held off since I need a daily that can do winter, and I can barely keep my S13 track car working, much less a rotary... but man does one of these with a nice suspension and diff, some aero, and a big EFR turbo sound delicious.  If I had the space for another car this would be high on the list along with NSX and GT-R. You've already got the daily and track cars covered with the S6 and Miata, right?

Yeah, the S6 is the daily & family car, the Miata is the track car.  A truck for hauling it there and a CX-9 for my wife.  The FD is just a fun street car that occasionally goes autocrossing -- gotta qualify for the Mazdaspeed Motorsports discount on it! :)

Based on recommendations here, threads on rx7club, and chatting with the folks at Racing Beat on the phone, I went with the 8 lb flywheel.  Pulled the trigger on the parts and tools this week, they're all here, and I think I'm good to go.

Clutch, flywheel, pressure plate, pilot & throwout bearings, clutch tool, flywheel puller, counterweight, transmission seals, and 54mm socket:

Rear seal & O-ring, new master/slave cylinder and flex line, a couple exhaust gaskets, pilot bearing remover & installer tools, flywheel lock tool:

Hopefully one of my impact wrenches will get the flywheel off, if not I'll need to find a 3/4" breaker bar somewhere.  Oh, and I need to find a friend who can loan me a bigger torque wrench too.

I do wonder if I should be replacing the downpipe as well.  This is more for heat mitigation, I'm not really looking for more power.  I mean, I wouldn't turn it down, but I'm not sure if the stock ECU will keep up with the fuel if I do that, and I don't want to go down the aftermarket ECU road on this car.  Hmm.

One part I did not buy was the turbo-to-downpipe gasket, Mazda wanted $170 for it!!!

WHAT??

Seriously?

I got my 3/4" ratchet at harbor freight for a decent price.   It's one of only a few things I've got from them

turtl631 said:

Seriously?

Yes, seriously.  That's with the discount that the Mazda dealer gives me (the parts dept manager is a local Miata club member and arranged it), normal price is over $200.

I was looking at it because I was thinking that I needed to take the downpipe off to get the transmission off to do the clutch, and as long as that was going to happen it would make sense to put an aftermarket downpipe on at the same time.  That's a metal gasket, supposedly they're usually reusable but I'd prefer not to have to try to find one at 5PM on a weekend afternoon if it turned out that mine wasn't.  After doing some more research, though, it sounds like the downpipe can stay on for the clutch so I've decided to defer that part.

Last week on the way to lunch one day the clutch went from slipping on 1-2 shifts to slipping at 20% throttle.  Limped it home, parked it in the garage and it hasn't moved since.  Going to try to get the clutch/flywheel done this weekend.

Started on the clutch today with help from a friend:

Various covers & exhaust came off easily:

The FD PPF looks really weird compared to a Miata one.  Fortunately, mine does not appear to be cracked.

Transmission came off pretty easily, no drama.

OEM clutch assembly:

The clutch disc is down to the rivets on one side.  This one gave its all.

Now for the infamous flywheel nut.

Mr Ingersoll got it off no problem.

Racing Beat flywheel puller and Mazdatrix flywheel stop tool:

And it's off, easy peasy.  Rear main seal is definitely leaking.

The Mazda pilot bearing removal tool made short work of it.

And that's pretty much where we stopped for the day.

A strange thing we noticed though, is that the tension bolts all seem to have a surface crack on the head.

Anyone know what's up with that?

Heat possibly? Or maybe too many heat/cool cycles would be my guess.

Bill Mesker said:

Heat possibly? Or maybe too many heat/cool cycles would be my guess.

Knurled replied to my question about it in the general GRM section and said it's totally normal and they all look like that, so I proceeded onwards with the job.

After much cleaning of the back of the motor:

Assembling the Racing Beat flywheel to the counterweight:

Counterweight is on the back:

It goes on the eccentric shaft:

Time to torque that flywheel nut -- this calls for a big wrench.

More assembly:

Then it came to reassemble the pivot & throwout bearing onto the transmission.  Apparently the pivot arms like to crack, so it's recommended to replace them when you're doing the clutch, so I bought a new one from Mazda.  After installing it, though, the throwout bearing's travel was very limited, much more so than with the old one.  Some investigation showed that the new one had a bunch of casting flash that interfered with the bearing.  Alas I didn't take a "before" photo, just one after some quality time with the die grinder and carbide tip.

After that everything else went in pretty well until I got to the cat.  One of the nuts had been stubborn coming off, and I knew the stud was damaged.  I hadn't looked at it all that closely until the end, though.  It's mangled, the last 3 threads are missing (stuck in the nut) and it's bent somehow.  So it's not going to run tonight, I'll have to figure out a solution later in the week.

I stopped by the Mazda dealer this morning, but they don't sell that stud, so I guess I'm cutting/drilling it out and putting in a bolt instead.  Both rubber shifts boots were ripped, so I wanted new ones of those too.  The 3-bolt one at the bottom (that connects shifter to transmission) is the same as a Miata, so they had that one in stock, but everything else I had to order.

So we applied more heat to the stud, got a really good grip on it, put a lot of torque on it, budged it half a turn and then it snapped.   So time to drill.  The idea was to try to drill near the edge, then peel the threads inwards so it would come loose.

Didn't work, so out came the carbide tip for the dremel and I basically ground it out to a small sliver, then drilled out the hole.

The edge is a little ragged but the gasket will seal fine.  Ordered a 12x1.75 50mm bolts from McMaster, no stainless available alas.  Picked up new gaskets, new nuts, and new shifter boots from the Mazda dealer.  The FD turns out to use the same inner 3-bolt shifter boot (the one between the shifter and the transmission itself) as the Miata, so they had that one in stock, the others took a day.

Put it all in this evening and the car runs again!  The flywheel definitely spins up more quickly, and the Exedy is much grabbier than the worn-out stock one.  Put together it's like i'm 16 all over again and not in a good way, lots of stalling. :)  I need to learn to drive this car again!

Been driving it around a bit since swapping the clutch.  As I expected it didn't take long to get used to the lighter flywheel, very pleased with it now.

One other thing I've noticed is that it's shifting a whole lot more smoothly.  I'd never put much stock in the "changing fliud to improve shifting" thing before, but it's a night-and-day difference on this car.  It still makes noise if I bypass 4th and go straight from 3rd to 5th (5th gear synchro is a known weak point), but the issues I used to have with it being reluctant to go into reverse or 1st are all gone.

The fluid that came out of it was suspiciously clean, so I wonder if the previous owner had it changed at some point and they put crap in it.

Took it up in the hills last week:

Did you replace the rear main seal while you were in there?

I did, yes.  The previous one was leaking badly.

I thought about replacing the O-ring on the rear stationary gear (the guy at the Mazda parts dept suggested it and sold me one), but after reading writeups on rx7club about damage resulting from misaligning things, and without any clear evidence of a leak, I decided not to.

A few random other things.  I picked up a SakeBomb Garage master cylinder brace -- it's a similar concept to the Miata one, basically it braces the front of the master cylinder to the shock tower so that you don't wind up flexing the firewall when pushing on the brake pedal.  This gives a noticeable improvement to the brake feel.  Kinda hard to take a good picture, but:

I'd done a "Bose-ectomy" on it early on, replacing the Bose head unit and the door speakers with some normal config aftermarket stuff.  It had always been a bit lacking in bass, though.  The Bose system included an "anaconda" subwoofer in the trunk, which I hadn't taken out because to avoid it looking ugly you need to source the trunk carpet and rear deck lid from a base model car.  So I decided to open it up, bypass the Bose amps, and connect the drivers (there are two, sealed face-to-face) to a spare channel on my normal amp.  The drivers are about 1.5 ohms each and my amp doesn't go that low, so I wired them on one channel in series to get about 3 ohms.  I went back and forth on the correct polarity a couple of times, but setting them up reverse to each other turns out to be correct.

It also got used as a cargo vehicle.  Can you fit the a box of Miata coilovers into an FD and still use both seats?  Yes, but only just.

I'll join the chorus of "thanks yous" for generally leaving the car alone. I find as I get older I'm appreciating the look of a stock FD, and cars in general, more.

I also love how you managed to fit a HD-9ST in the garage in your first post. I've been measuring and calculating and humming and hawwing about stuffing one in my garage for about 2 years now and I always seem to conclude it's too small. It doesn't look like you had a lot of room to work with but it fits.

I looked into an HD-9W, but it's too long for my garage.  Well, it'd barely fit, but I'd only have 3" between it and the door and that doesn't work.

What I ended up ordering was the HD-7W, which is still a high rise lift, but is 2 feet shorter than the HD9.  Fits in my garage perfectly and the lift rep told me that the HD7 and HD9 both use the same motor...

Which motor did you get?  The 220v one is MUCH faster than the 110, BTW.

Opportunistic photo from the parking lot at work this evening: