magnumP5's RX-7 Build Thread

[magnumP5]

Im a huge FC fan, so reading this definitly beat working lol

It's good to know they're still some out there. They don't get a lot of love with the older guys/race fanatics liking the SA/FB's and everyone else drooling over the FD's. Unfortunately that usually leaves the young, cheap, broke kids who've seen Initial D too many times with the FC's. It's hard to believe now there was a Spec RX-7 class in SCCA racing and that powerhouses like Speedsource used to race FC's.

 

[magnumP5]

Got some work done over the weekend. My new hub rings came in on Friday. Despite the obnoxious color (neon teal?) they fit like a glove. This allowed me to test fit the rears with the car on the ground:

I think I'm going to try to find some plastic plugs to use as center caps to hide the hub rings/protect the axle nuts. There's a little less poke in the rear than in the front:

Granted this is with -1* of camber and I plan on increasing that to at least -1.5* but probably more like -2*. That, and a roll plus some minor pulling should give plenty of clearance.

I also finally reinstalled the steering rack. There's really not much to see other than a newer-looking steering rack in a very dirty engine bay:

My front alignment is now WAY off since I'm pretty sure I gained some steering angle by removing the piston on the rack. I "found" center on the rack by measuring the full displacement of one of the inner tie rods and splitting the difference. I then centered the steering wheel and installed the rack doing my best not to move anything.

With the steering rack reinstalled and hub rings to play with I installed the new wheels on the front hubs to check for tire-to-suspension clearance. Believe it or not but I actually gained clearance despite the setup being a theoretical 2.7 mm closer. The larger diameter wheel causes the tire ID to be greater, which is where I had problems before. With this new clearance I adjusted the camber bolts for more negative camber, leaving ~1/8" clearance with the suspension. This should allow me to easily get -3* up front with room to spare.

Now for the not so fun. I decided to mock up the front splitter. From the very beginning I knew there were going to be issues. It looks like the splitter was designed for cars with significantly wider front fenders.

Driver's side:

Passenger's side:

With some work I was able to center it the best I could:

It may fit a little better once I actually mount the front bumper cover instead of holding it one with duct tape. I also need to trim the splitter in a few locations to clear some bolts on the underside of the fender. All this is kind of pointless because I can't really do anything until the new wide fenders come in and are test fit. Even then I have a feeling installing this thing is going to be a bear. I've already started looking for some local custom body shops for assistance.

Here's a question for all you boody work experts out there. Should I try to install and align the new fenders, hood, and splitter myself and make everything work before taking them to paint or what until after paint and have a body shop do the aligning? The reason I ask is because I still need to install radiator ducting and hood pins, which are dependent on the final position of everything.

 

[bikingpro5]

body work fitting and aligning should be done before paint that way if you have to add/remove metal you are not doing it with freshly painted pieces.

 

[hat1018]

what he said

 

[magnumP5]

So what do you guys recommend for something like a hood that requires hood pins? Get everything lined up like it would be, drill/cut/installed the hood pins, and then remove? Since hood pins require pretty precise alignment is it just trial and error getting everything together after paint?

 

[Lewis7789]

I wouldn't use ugly hood pins, use the Aerocatch clips.

You can leave them on and be paint matched with your hood.

 

[bikingpro5]

I wouldn't use ugly hood pins, use the Aerocatch clips.

You can leave them on and be paint matched with your hood.

this, not only are they cleaner IMO they are a bit more secure than traditional pins I have had no issues with mine over the years. I had my first set color matched as well.

you can also leave the pin installed in the rad support when you have the panels painted. That way you know once you reinstall the hood that they will line up, to what you had pre paint.

 

[mymmeryloss]

Well i have no advice because all u other fuckers hit the nail on the head...

 

[Lewis7789]

^^^ lol! Group high five.

 

[magnumP5]

I wouldn't use ugly hood pins, use the Aerocatch clips.

You can leave them on and be paint matched with your hood.

Looked at them because everyone highly recommends them. I'm just not sure I want to spend nearly $100 on hood pins. The stock latch will still be there for the time being. The pins are just for peace-of-mind and to keep the fiberglass hood from fluttering.

this, not only are they cleaner IMO they are a bit more secure than traditional pins I have had no issues with mine over the years. I had my first set color matched as well.

you can also leave the pin installed in the rad support when you have the panels painted. That way you know once you reinstall the hood that they will line up, to what you had pre paint.

I've heard of some race teams having issues with the Aerocatch pins after minor body contact "events." Although I don't plan on having those I'd had to not be able to close the hood because I bumped something. Good point on installed the pins first though. I hadn't thought of using them as the alignment tool after everything was painted. I'm new to body work so this is going to be a learning experience, but what in this build hasn't? Now I wait...

Since I'm waiting for parts I've started looking into a well-known brake upgrade for RX-7's. Some of you may recall the 929 master cylinder upgrade for the Protege; apparently it's also an upgrade for the RX-7. The easiest install is to swap over the MC and brake boost from a '92-'95 929 with ABS. I don't recall the specifics but I'd be going from a smaller, single-diaphragm booster and 15/16" MC to a larger, dual-diaphragm booster and 1" MC. This supposedly results in more braking power and decreased brake pedal range while maintaining a "stock-like" pedal firmness. The only trick is the 929 MC has two ports whereas my stock MC has three so I'll need to tee the front brakes to one port.

I never originally intended to do this upgrade, but the same can be said about a lot of things. What got me thinking was in order to match the accelerator pedal range to the new TB actuation range I had to raise the pedal a decent amount. This increased the mismatch between the accelerator and brake pedals and I fear this will make heel-toe'ing more difficult. I've already found a MC and booster from a '94 929 w/ ABS with 161k for cheap locally so if everything checks out, why not?

 

[Lewis7789]

Ya know what I love about this thread, Jon? You do everything first and I just follow along with your build and pics. You da man!

 

[magnumP5]

Ya know what I love about this thread, Jon? You do everything first and I just follow along with your build and pics. You da man!

At this point it'll be a miracle if this car ever starts. One of these days I need to start drafting up a "To-do" list of things that need to be done prior to first startup. You know, stuff like fill oil, bleed brakes, etc.

On a superficial note I got Tirerack to send me 8 new "ENKEI" and infinity decals for my wheels since they were somehow lost in the original transaction.

 

[THE Phen]

Jon, I find it funny that you bring up the 929 MC swap. No one does that any more on the Proteges... they just buy bigger brake setups.

 

[magnumP5]

Jon, I find it funny that you bring up the 929 MC swap. No one does that any more on the Proteges... they just buy bigger brake setups.

They must enjoy having to push the pedal to the floor the lock the brakes I wonder how that works out with the ABS system...

I don't see myself upgrading to larger brakes anytime soon. Vented discs front and rear, 4-piston calipers up front and 2-piston calipers in rear should be enough to stop me even with the higher speeds I'll be able to hit. The only thing I see myself ever doing is upgrading to a 2-piece hat/rotor setup.

 

[magnumP5]

I have a problem...

No, I really do, but more on that in a second.

I went to a salvage yard this weekend to look at another 929 brake booster/MC combo. They're in great shape and the price was right but the car is buried under a "stack" of three other cars. The yard is going to uncover the car and pull the parts for me this week so I can pick them up next Saturday.

Here's where I have a problem. While waiting for the paperwork to go through on a whim I asked, "Do you guys have any Miata transmissions?" To keep a long story short I ended up coming home with this:

It's a 5-speed transmission out of a '96 Miata with 6x,xxx miles. The input/output shafts turn freely and smoothly in all gears, the price was right, and I was able to take it home the same day so I snagged it.

Up until the early 2000's Mazda only had two types of RWD manual transmissions: types "M" and "R". There have been several revisions and upgrades to each but they've remained essentially the same. The "M" transmissions were found on lower-powered, N/A cars: old RWD 626's, N/A RX-7's, older B-series pickups, and Miatas. The "R" transmissions were beefier and were found on the RX-3's and RX-4's, turbo RX-7's, and newer B-series pickups. Basically, whatever transmission you have you can swap it for another of the same type with a little work. In my case the gear set from a Miata can be swapped into my transmission by swapping the bell and tail housings and doing some slight machining to the input shaft. Aside from the old RWD 626 gear set, which is outdated and weaker, the Miata gear set has the closest ratios. In the end I'll end up with and updated gear set with slightly taller 1st, 2nd, and 3rd gears and a much shorter 5th gear. With this setup I should only have to shift into 4th on the front straight at Mid-Ohio.

So onto some work. Those more familiar with my "build" should remember a picture similar to this when I smashed the speedometer drive gear in my first transmission.

In similar fashion the bell housing is removed exposing the input shaft and bearings as well as the 1-4 gear sets:

I then proceeded to break down my spare RX-7 transmission to the same level. The RX-7 transmission is the one with the big harmonic balancer on the output shaft:

I decided to call it quits at this point. I'm a little stuck because I don't know if I have to swap the output shafts to keep the harmonic balancer, if I need to swap the 5th/reverse housings, and if there's an easier way to remove the input shaft than described by the FSM, which is basically taking the whole things part. When I get all that figured out I plan on fully cleaning up and painting all the housings and replacing all the necessary seals.

At this point I think I've officially messed with every inch of this car.

 

[Installshield 2]

I'm not positive on harmonic's with rotary engines, but i bet its a good idea to keep that. Does the Rotary have an engine mounted balancer, too? More like a piston/crank engine?

For a 'normal' engine, the gear box and clutch itself is actually a damper for the crank...it'll absorb harmonic oscillation when driven in gear, where a crank mounted balancer does most of its 'job' in neutral or when rev matching...

rotaries don't make resonance the same way, as there aren't parts starting and stopping hundreds of times a second...A rotary engine fundamentally has perfect primary and secondary balance...where a piston engine usually has primary balance, but secondary will be all over the place depending on firing order...the rotary will put very different types of stress on a driven gear box (i'm not saying more stress, just at a different frequency)...or, at the very least, the gear boxes balancer may be simply to be used with a higher revving engine...

in either case...I don't think its something to just skip, but i'm not positive...

 

[magnumP5]

I'm not positive on harmonic's with rotary engines, but i bet its a good idea to keep that. Does the Rotary have an engine mounted balancer, too? More like a piston/crank engine?

For a 'normal' engine, the gear box and clutch itself is actually a damper for the crank...it'll absorb harmonic oscillation when driven in gear, where a crank mounted balancer does most of its 'job' in neutral or when rev matching...

rotaries don't make resonance the same way, as there aren't parts starting and stopping hundreds of times a second...A rotary engine fundamentally has perfect primary and secondary balance...where a piston engine usually has primary balance, but secondary will be all over the place depending on firing order...the rotary will put very different types of stress on a driven gear box (i'm not saying more stress, just at a different frequency)...or, at the very least, the gear boxes balancer may be simply to be used with a higher revving engine...

in either case...I don't think its something to just skip, but i'm not positive...

Wankels don't have harmonic balancers as far as I know. At least Mazda's variants don't. They do have "counterweights" on the front and rear of the engine that are very important to engine balance but they aren't damping vibrations. I almost wonder if the balancer on the transmission output shaft has something to do with the higher engine speeds the Wankel is capable of. Stock Miatas go up to what, 7000 RPM, whereas my year RX-7 was 9000 RPM. Perhaps there are some higher frequency responses in the transmission that need to be damped. I'm not aware of anyone swapping the output shafts when doing this swap but it would be required if the balancer is necessary as the Miata output shaft doesn't have provisions for it.

 

[Sport23]

929 Brake cylinder

When I put 06 MS6 brakes on my MSP I skipped the 929 master cylinder because the bore on the MSP (626 V6) brakes are the same as the bore on the assessor's 06+ MS6 brakes and I liked the stock pedal feel and travel.
I you are increasing the bore size on your calipers the 929 master cylinder is a great upgrade. If you want less pedal travel it is also good, otherwise skip it.

 

[Installshield 2]

^^yeah man, thats kind of what i was thinking too...if its not vibration, its probably something to do with higher rev capabilities...

I'm not one that has been tearing down many different gear boxes...but it could be a combination of both things (harmonics AND high revs)...because a lot of high revving piston engines do not have a gear box balancer of any kind, at least form what i've seen around various forums...as in i've seen some S2000 boxes apart, and there isn't a balancer similar to what yours has...and that is also a 9,000 rpm transmission...when i say i didn't see a balancer, i mean i saw a bunch of pictures of complex metal parts coated in oil...none of which had a blatant circle around something being labeled as a balancer haha...so, again, maybe it did have one, and i just didn't know what i was looking at.

but its probably just another mystery thing Mazda did without really telling anyone...and it also could simply be a revised addition to that series of gear box...meaning, it may not be a critical 'rx-7' thing; but more something added at some point in a refresh of that box...which gear box is newer, production wise?...If that line of boxes is anything like the G-series in proteges...it seemed like every year something was changed, and no one spent the time to detail what the changes were...or how important they were...

my best guess is that either way its not a immediate problem...that balancer may aid in the life of the box attached to an RX-7...skip it, and it may wear out a little faster...but still last 100k or something...harmonic balancers are important, but their purpose is often misunderstood...its not like a 'take it off and s*** will break right away' type of thing...and i don't know your power goals (which will increase all harmonics within the drivetrain)...keeping relatively mild output, i doubt you'd ever have a problem skipping the balancer swap...a crazy ass increase in output...might have a grenade, but even then...probably not until after a good bit of thrashing...

 

[mymmeryloss]

Yes you have to swap the output shaft.