'90 Mazdaspeed Miata Rallycross Project

paranoid_android said:

MR was a close one!  .211 seconds :-)

That's just how we roll in Ohio.

There was one event where we tied.  The win was decided by who hit the fewest cones.

So I bought some nice wheels with sticky tires from EastsideTim this weekend. I thought I would throw them on and drive the Miata to work sometime this week. Unfortunately something broke again. 

A while ago after I was in an accident with the Miata I found that one of the ears had broken off the rear diff cover (actually Knurled found it). I figured it was from the accident and replaced it with another Miata cover. Today when I was changing wheels the diff went up quite a bit further than normal while I was jacking the rear up. Turns out the same ear broke again. 

So time to find another cover or have it welded and reinforced. 

Also, pictures of the Miata with all the stickers to remember what it looked like since I decided to strip them all off. 

Very cool project man! 

good luck with the diff issues.

also, I think this is one of if not the oldest active build thread. 

The last time this happened (way back on page 23), I had it up on the lift where I work to check something or other and noticed that it was broken, and with like one day to go before having to take it up to Michigan, I wrapped a chain around the PPF and the rear subframe to hold things up.

It worked out okay.

I was just at a guy's place in Youngstown who was parting out a bunch of FCs, the time to know you needed another brace would have been about a week ago.

spacecadet said:

also, I think this is one of if not the oldest active build thread. 

I was going to gloat and say i finally beat Josh at something but then i noticed his e30 thread was started 2 months before this one.

But i did have a rallycross miata thread for this car before that until i abandoned it for this one .

In reply to Knurled. :

Yea i messaged my miata parts friend here in Columbus and he just scrapped a fc last week. 

Does the guy in Youngstown have anything left?

In reply to EvanB :

I'll text him.  I'm supposed to contact him anyway since he seems to be interested in buying the RX-3 even after seeing the pictures.

In reply to Knurled. :

Well i have a truck and trailer if i have an excuse to go up there anyway...

EvanB said:

spacecadet said:

also, I think this is one of if not the oldest active build thread. 

I was going to gloat and say i finally beat Josh at something but then i noticed his e30 thread was started 2 months before this one.

But i did have a rallycross miata thread for this car before that until i abandoned it for this one .

Those wheels and tires got put to use fast!

In reply to eastsideTim :

Unfortunately they haven't left the driveway yet but they do look good. 

360 miles in the Volvo truck later and a rx7 diff housing is acquired. No pictures because I forgot to take one and it's dark now. 

In reply to EvanB :

So much for delivery.

In reply to Knurled. :

Yea that didn't work out as planned.

NA2 vs FC diff uterus.  Note that the FC unit is one piece, which seems to work better for the most part.

Broken thingus on the pumpkin.  Probably not important since it's squished by the super long PPF bolts, but if it wasn't important then how did it break?

Earlier this week I drove the stock rubber bushings out of the RX7 housing and installed the poly bushings. 5 minutes with the air hammer made quick work of the old bushings. 

I cleaned up the holes with a conveniently sized flap wheel I found in the back room. Then I put the housing on the diff and snugged the bolts to let the RTV cure. 

Today I got home from work and the unbroken diff spacer from Dusterbd13 was in the mail. I checked my Downstairs Diff but the spacer was already removed so I needed it after all. That meant it was time to get some stuff reassembled. 

Also installed were some KYB AGX shocks, also from Dusterbd13. I put the mazdaspeed springs on them and had to use the shock mounts that came with the KYBs since my bilstein shock mounts wouldn't fit. 

Everything is put back together. I stopped after I got all the bolts in place since it is still hot in the garage and I have all weekend to work on it. Tomorrow I will finish tightening all the bolts, fill the fluids and take it for a test drive. 

After looking at this picture I may need to reseat the passenger side axle. 

Heres to hoping i didn't sell you crap!

More worried about the agx, because i never used them. The diff thingy was mint though!

Why rx7 diff cover, and why did the stock part break? I know rallycross is a lot more brutal on parts, but im throwing a lot of torque and mechanical hatred at my diff.....

The agx are an experiment to see how much better they are than the super stiff Bilsteins. If they are blown I won't be upset but they seem fine, although I won't know for sure until I drive on them. 

The first time I broke a miata diff cover was when it was in an accident. The Miata cover has a relief on the right side as a weak point to break in an accident. I replaced it with another one and thought it was fine. I don't know why the second one broke. Maybe the diff spacer broke and cause enough movement in rallycross that it cracked the arm on the diff cover. Maybe the arm broke and the movement caused the diff spacer to break. 

The rx7 housing doesn't have the weak point machined into it and I didn't want to do this again so I figured I would just go that route this time. I don't think you would have any issues with just autocross and drag passes on the stock cover, even with more power than stock. From what I have read most failures while racing are in spec miata getting bumped by other cars. 

In reply to EvanB :

I wonder if your PPF isn't bent from the collision, too.  There's no real good way of checking that aside from putting a different one in.

On the other hand, I've been wrecking parts in the RX-7 that people have live just fine behind turbo engines making twice the torque, and even V8 swaps, so maybe rallycross is just that metal.  I mean brutal.  (No, I mean metal)

Knurled. said:

In reply to EvanB :

I wonder if your PPF isn't bent from the collision, too.  There's no real good way of checking that aside from putting a different one in.

And that is totally not going to happen (unless more E36 M3 breaks and I find myself in this place again). 

Cool. I was wondering about the diff.

And the other shocks from that lot that i tested were all good, so i feel its sage to assume these are too. Hopefully they behave like you want them to.

All finished. I've only driven it around the block so far but the rear shocks feel great. Still need to swap the fronts and deal with some oil leaks.

Dismounting the Dmacks from the Revolution wheels, I found this.

In reply to Pete. (l33t FS) :

That must have been the one that debeaded a couple times. 

In reply to EvanB :

That was on the wheel that has dirt embedded to the inside.  It smelled like your basement when I broke the bead, which I thought was funny. That basementy smell, you know?