magnumP5's RX-7 Build Thread

[magnumP5]

Nice man looks like its coming along good. Do you miss the p5 at all? whens the next time you are going to come down to va?

Every now and then I wish I'd have just held onto it, but as a car to "play with" the RX-7 just makes more sense. Plus, when building/tuning finally comes around I won't have to deal with the Nazi OBDII system getting in my way.

I probably won't be back in VA for a while now. I was there over the holidays for a few weeks but I got shafted on vacation this year so we have to cut back. Probably won't be back in the area until next Christmas time.

In other news I finally bought a go-fast goodie! Actually, I should probably say a "get-going faster goodies". More info on that later...

 

[2.0t03speed]

Every now and then I wish I'd have just held onto it, but as a car to "play with" the RX-7 just makes more sense. Plus, when building/tuning finally comes around I won't have to deal with the Nazi OBDII system getting in my way.

I probably won't be back in VA for a while now. I was there over the holidays for a few weeks but I got shafted on vacation this year so we have to cut back. Probably won't be back in the area until next Christmas time.



In other news I finally bought a go-fast goodie! Actually, I should probably say a "get-going faster goodies". More info on that later...

Nice we will have to get together next time you're back down here. You should check out my build thread i've gotten some more goin fast stuff since the last time you saw my car.

 

[Signal 2]

No matter how much I might like it, I refuse to be encouraging or complimentary without (pics)

 

[gprestonmoto]

That's what I initially thought but those numbers are by no means concrete. The single turbo, 13B-RE example I was using was Banzai Racing's and they put out just over 400 whp at 16 psi but I've seen numbers in the high 300's as well (386 whp comes to mind). Just like with the Proteges big time N/A builds are rare so the obtainable power is really unknown. I have read of 225+ whp on moderate N/A builds (bridgeports and modified ECU's) but nothing with bridgeport + ITB's + full standalone, etc. Either way, neither is going to be happening any time soon.

Well yeah, $3500 for the engine, but the ECU is pointless (all Cosmos were auto's). However, from what I have read, the basic cost for a 20B swap is $20k (give or take, single turbo or N/A) based on everything else that is required.

This is closer to correct. If someone can complete a 20B swap for 3500$ we'd all have one lol

 

[magnumP5]

No matter how much I might like it, I refuse to be encouraging or complimentary without (pics)

In due time Still trying to source like three other parts...

In other news...

DAMNIT, DAMNIT, DAMNIT!

I was planning on tweaking the rebound settings in the rear yesterday and when I got the speakers off I noticed the adjuster or "clicker" on the left rear had completely broken off! I'm not sure how this happened but it looks like it's fixable (replaceable, rather). I took off the right rear and the adjuster is this little assembly of parts that can be easily screwed out of the strut. Hopefuly Stance sells/replaces these, but I guess I'll find out on Monday.

After all that I went out and took out all the preload in the springs (per Stance's recommendations). Oddly enough the front ended going lower by about 1/8" so it's now basically sitting right over the tire at 24-5/8" of the ground. The rears didn't change at around 25-1/4" despite taking nearly 1/2" of preload out. I will probably bring the fronts up and the rears down a little - maybe 24-3/4" in the front and 25" in the rear?

 

[magnumP5]

Got a hold of Stance - two new adjusters on the way, yay!

Parts ordered today:
-2 new rebound adjusters for rear struts
-2 sets of helper springs for rear struts
-Differential output shaft oil seals
-Differential output shaft circlips
-Full set of Mazda Competition differential and subframe mounts
-New speedometer gear

Anyone guess what I'm working toward here???

 

[Signal 2]

Parts ordered today:
......
Differential output shaft oil seals
Differential output shaft circlips

(thumb) Should be fun. Enjoying the thread.

I think I mentioned before I'm not really familiar with the FCs, but FWIW.....
I changed a leaking differential side seal on my car a few years ago. IIRC the FSM tells you to pull the half-shaft completely to do it but I discovered that if you remove the lower mounting points you can swing the hub up as the half-shaft comes out of the differential. So completely removing it isn't necessary. On the FD this means the trailing arm, lower 'I' arm, lower shock mount bolt, ebrake cable and ABS sensor lead. But DOES NOT include the brake lines. So you don't have to wrestle with the hub bolt (which can be a royal PITA) or bleed brakes.
Also, it's been my experience that if your careful to not allow the differential to turn while the axle is out, getting it to go back in and seat is usually easier.
Figured I mention that incase you wanted to try.

 

[THE Phen]

Yep. You're raping a Miata of its rear end stuffs.

 

[magnumP5]

Let the raping begin!

Finally got everything in and started some work today.

Once again I forgot to start taking pictures until I had already started. So we start off with the differential/ring gear assembly removed from the carrier.

Next, the assembly was placed in a vice (most versatile tool in the garage) and the ring gear is removed.

Here we have the Miata T2 torsen LSD (left) compared to the GTUs viscous LSD (right)

Unfortunately that's all I was able to do today because apparently I'm out of thread locker. I'll pick up some tomorrow and the ring gear will be mated with the Miata torsen and placed back in the carrier. After that I'll need to take it to a differential shop to check/set backlash and tooth contact patch because I don't have the proper tools to do so. Once that's done I have a whole range of other goodies to go in:

First we have a full set of Mazda competition differential mounts (40% stiffer than stock). Also pictured are new circlips for the output shafts, oil seals for the carrier and the proper speedo gear for the 4:30 rear end.

Finally we have (clockwise from top-left): aluminum spherical bearings for rear control arms, delrin DTSS (rear steer) eliminators, delrin subframe mounts, adjustable vertical link and helper springs for the rear coilovers.

Also, I've started a Picasa account to store all my pictures. Full album can be seen here: https://picasaweb.google.com/107026160716137803287/RX7Work?feat=directlink. Most pictures are already in the thread somewhere but there are a few (redundant) ones I've never posted. I'll be posting all my "RX-7 Work" pictures in that album.

Hopefully more tomorrow night!

 

[THE Phen]

very cool man. Looking forward to seeing more progress.

 

[PrinceValorum]

For some reason I had in mind that you were going with something more 'aggressive' than a 4.3 rear end. Did plans change or is my memory failing me?

 

[magnumP5]

Long post...

For some reason I had in mind that you were going with something more 'aggressive' than a 4.3 rear end. Did plans change or is my memory failing me?

The goal was 4.30:1 all along. It's only like a 200 RPM increase over what's in there right now but it's the easiest/least expensive/most readily available swap. I think Mazdatrix actually has 4.875:1 and 5.12:1 ratios available but they're ~$1000 and require you to send in you current ring and pinion. I paid $350 for an extra carrier, viscous LSD and 4.30:1 ring and pinion.

I'm basically working my way forward. After an aluminum driveshaft my next project is to swap in the gears from a '94-97 1.8L Miata as the ratios are closer than the RX-7's. Along with a new clutch and aluminum flywheel I should have a pretty good setup for road courses without having touched the engine.

So I made a little more progress today. Picked up some red lock-tite and with the aid of a vice and some clever tightening of the ring gear bolts I was able to mate the ring gear to the Miata LSD.

And after fighting with the carrier for about 15 minutes (the whole assembly weights about 65 lbs) the new differential is in.

All the white marks you see are paint marks so I could keep everything in the same location so hopefully the backlash isn't out by too much. The bolts on the bearing caps are only hand-tight as they must be torqued such that the distance between two reference points meets Mazda's specifications. Along with setting the final backlash, this is something a shop will have to help with as I don't have a set of dial calipers large enough.

In other news I was finally able to sell my Sparco Torino II's. However, putting the stock seat back in ending up being a job requiring retapping the mounting holes. Now that all that is done I'm left to decide what seats to replace the Torino's.
I'm looking for something with a fixed-back, fiberglass shell, FIA-approved, 5/6-point harness ready and as small and lightweight as possible. The options I'm currently considering:

Sparco Evo (most common)
Sparco Rev Plus (smallest)
Sparco Corsa (recommended by a friend, cheapest)
RaceTech RT1000 (lightest, also recommended)
Cobra Suzuka Pro (really neat looking design)

May go with a roll bar first as I will need that and a harness before installing any new seat.

 

[THE Phen]

Is there much of a difference between the bellhousing itself for the FC transmission and the NA transmission? I wasn't aware of gear swaps being possible... this is all new to me. Probably easier to talk about this over a beer next time I see you... LOL.

 

[magnumP5]

Is there much of a difference between the bellhousing itself for the FC transmission and the NA transmission? I wasn't aware of gear swaps being possible... this is all new to me. Probably easier to talk about this over a beer next time I see you... LOL.

It's not that the transmissions themselves are swappable, rather the actual gearset can be swapped between them with a little modification to the Miata input shaft (needs to be shortened). In the end it's still the RX-7 bellhousing and transmission (the N/A versions aren't separable) but with different internals. Basically, the Miata's 1st through 3rd are a little taller, 4th is the same (1:1) and 5th is a little shorter so in the end it's a much closer-ratio'd gearbox, which I think would be pretty good for HPDE and beyond.

 

[THE Phen]

Got it. I didn't think that the transmissions themselves were swappable. Good stuff to know.

 

[PrinceValorum]

Are you swapping the internals yourself? I almost shudder to think about cracking one open and having to put it back together in working order.

 

[magnumP5]

Are you swapping the internals yourself? I almost shudder to think about cracking one open and having to put it back together in working order.

I plan on doing the actual dismantling and reassembly, yes, but a shop will be doing the input shaft modification. It'll be complex but it shouldn't be too hard with the aid of a FSM. I haven't really looked into it too much yet, but my biggest concern is the requirement of specialized tools (Mazda's "SST's"). With things like this I rely on marking parts before removing them and taking lots of pictures.

Today, I dropped off the differential at a local transmission/drivetrain shop. They sounded a little confused over the phone but when I showed up they knew exactly what I wanted and it shouldn't be a problem. Hopefully I'll have it back tomorrow.

 

[Signal 2]

I'm with the Prince. I have just a little experience with transmission internals and never messed inside a differential. Those scare me for some reason.

Keep it coming.

 

[Lewis7789]

Your motivation now is to have it ready for the BBQ, sucka. Get crackin.

 

[magnumP5]

Ugh, sorry for the delays. I have everything I need to start the swap, but I haven't been able to find the time. Between classes ending for the quarter and renovating the house there hasn't been any timefor the RX-7. Hopefully I'll get started on Thursday.