Sprocket's Competition

[j2k4]

I heard that.

[Detale]

What do you drive bud?

[clocker]

You've asked that before.

[clocker]

Because of the upcoming Mother's Day weekend, Sigfrid opted to take Friday off to work on the car.
A lot fewer interruptions with no family units around.

We had two major projects lined up and got them both done in good time.

The new (junkyard) harmonic balancer was installed and really helped (in fact, probably eliminated altogether) the engine vibration over 4k RPM.
Excellent.

Sigfrid has not been happy with the brake pedal feel and I agreed that it could be better.
I had recently procured the booster/MC from a Subaru and it was prepped for install into the Beast.
Here it is, cleaned, painted and configured for his brake lines...




And installed...




Brakes are now absolutely superb...best setup I've found to date, I'm off to the junkyard today in search of a similar set for my car.
I love it when a plan works out.

We also addressed a few smaller issues, the car now runs better than ever.

Assuming she survives another week of commuting- and I have every expectation she will- we will probably start on the interior next weekend.

Now that the mechanical platform is nearly complete, the diff has been exposed as the final big weakness.
It just ain't right and is the last remaining part of the original drivetrain, which automatically makes it suspect in my book.
It doesn't lock up consistently and makes weird, vaguely scary noises.
We may also have to upgrade our axles but won't know till we pull them.

So, the search has begun for a new differential, preferably one from an automatic with 3.90 gearing.
Our current 4.10 diff renders 1st gear all but useless, the 3.90 should not only help there but highway mileage should improve as well.

Replacing the diff while maintaining our alignment will require dropping the entire rear subframe as a unit...a fairly big job.
We decided to do this because it will also expose the fuel tank, which has a pretty complex system of vents/check valves/separators that we need to freshen up. All of this nonsense is situated on top of the tank is is not accessible till the tank is off the car.
It's a crappy job but needs doing.

Soon as we locate a diff, this will get slotted into the schedule.

[j2k4]

What sort of bore size has that MC got, and I'm gonna recommend a 3.73 rear ratio; should be easy to find.

You've got the 5-speed, after all, and 1st is pretty low; you've got low weight and lots of power.

If he doesn't like the way the mill pulls that gear, then build in more power.

How many overdrive gears has that box got, anyway?

[clocker]

MC bore size is 1 1/16".

3.73 would be nice but Mazda only offered 4.10 and 3.90 stock, so that's what we have to choose from.

We actually have the six-speed and I believe 4th gear is 1:1, so both 5th and 6th are overdrive.

[j2k4]

Oooh.

Brain fart.

Are those standard ratios for the RX7, or are there some automatic ratios you could swipe from another Mazda diff?

[clocker]

I don't know about interchangability between different models.
The ideal solution would be to get the Cobra diff mount kit and have access to all the gearsets we could desire.
"Ideal solution"= $3k, so it might be a while.

[j2k4]

That car's starting to run into some real money.

[clocker]

Yes, it is.

Saturday she comes for another extended stay in my garage.
We're going to pull the dash and repair the (inevitable) damage we find behind it- primarily wiring and the heater core.
Since we won't know how extensively it's screwed up till we get it apart, there's no real timeline on this job but since I'll have full-time access, we should be able to button it back up by the following weekend.

With the dash reinstalled, cosmetic improvements can proceed on the exterior dash plastic- going to cover it all in black Alcantara (looks like suede)- and a permanent gauge panel. I have a Miata gauge cluster that looks like a suitable candidate but it's hard to tell if it will work until I try.

Meanwhile, as usual, I have a few pet peeves with the car that I plan on addressing while I have it.
#1 on the list is fixing the gas fill door release, which is broken on our car.

Every Mazda in the junkyard uses the exact same setup to operate this door...and of course, the RX7 is completely different and unique.
And stupid/poorly engineered.

It's the perfect example of the lengths Mazda went to to decrease weight in the 3rd gens...instead of using two cables and levers to open the hatch and the gas door, they use one cable to perform both functions, saving maybe an ounce of weight.
The mechanisms attached to the cable are absurdly Rube Goldbergesque and brutally expensive to replace.
I'm going to attempt a replacement using the parts from a 626 (already pulled at the yard, total cost for everything, $5).

Yeah, it's a small thing but it drives me crazy.

No luck yet sourcing a diff, the search continues.

The car is running well on Sigfrid's daily commute, our idle issues seem to have been solved and vibration has been virtually eliminated.
He complains about lack of top end- I have no idea where he's getting the car up to that kind of speed driving to work- but we can address that after the rest of the project has caught up.
He absolutely loves the new brake setup, says it's the best he's ever felt.

Things are looking pretty good overall.