Well, i figured i'd start a project thread. I picked up a 87 N/A FC last spring for a trifling $300. Its a South Carolina car and is virtually rust free. Aside from some major and minor issues, the car seems to be in OK shape. I have the typical leaking sunroof along with a semi-dead motor. This is also my first rotary car/rebuild

The motor will start right up and run, but its eating oil and coolant like a kid eating PEZ. 1/2 a quart of oil in 30 minutes and its a mosquito fogger with the coolant its burning. the idle also is off - it rev's and dies down, rev's and dies... Is this TPS related?

Interior is a little rough, cracked vents, a little dirty and the shifter boots need replaced as they are missing. It also has a dent/scrape on the quarter panel/door but that is minor.

The plan at the moment is to secure a used S5 N/A motor and do a hybrid build consisting of:
S5 N/A rotors/c-weights
S5 N/A Intake
S4 N/A front cover (to retain mechanical MOP)
Ported 6-port irons w/ pineapple 5th/6th port inserts
S5 N/A trans
EGR Blockoff

Not sure on the rebuild kit yet, possibly going to go atkins with cryo treated apex, solid corner and side seals.

Second phase after getting the rebuild running and broken in on stock S4 electronics will most likely be a Megasquirt ECU. Not sure if this is going to be the PnP MS (based on the MS-II Extra Microsquirt) or the MS-III (if its out of beta by the time im done)

I have some questions regarding ideas i have for the build.
1) is bridgeporting the 5th/6th ports worth the time?
2) What RPM should i limit the motor to after the porting and rotor swap? (IIRC 8K is the S4 redline and the S5 redlines at 9K)
3) Is there anything else that can be done to the motor that would be beneficial in a pre-mild turbo build? (retaining S5 rotors on said turbo build)
4) with a header and cat-back exhaust, is there enough pressure to actuate the 5th and 6th ports or do i have to run an electrical or air pump based alternate method?
5) Is there an LSD that fits the N/A rear end? or is the LSD limited to the T-II?? (i've heard GXL and miata, but which Miata gen?)
6) Is a radiator replacement and an oil cooler a good idea on this type of build

In addition, there are some parts that i will be in the market for used or new (will update as needed )
1) pineapple 6-port porting template
2) header and cat-back exhaust for an N/A 6-port motor
3) Flywheel stop


Advice, input and suggestions welcome and encouraged

 

good job bro. make sure you change the wheel bearings as they might be poop. change all the lines you can, and replace all teh fluids you can .

 

1. Say NO to aux port bridging.
2. S4 = 7k, S5 = 8k. With S5 rotors, front counterweight, rear flywheel you should be good to 8k.
3. S5 rotors are 9.7:1, if you are a good tuner you can do this. If not you may want to back off to S4 rotors, 9.4:1, or throw in a set of S5 turbo rotors at 9:1.
4. They will open, but they may open really late depending on the exhaust. Racing Beat has a header with the split tube for the exhaust sleeves and that should work just fine.
5. N/A models have LSDs, look for S4 GXLs, 88' GTU, or GTUs. Or rebuild yours with a new LSD from mazdatrix.
6. Radiator replacement is always a good idea, the oil cooler is plenty big enough.

 

1. no
2. stock s4 ecu stops around 7800. once you get the ecu sorted, 8500 is a good place to stop revving
3. use the t2 oil pump, and FD oil pressure regulator

5 any 84-85 rx7, 86-88 gxl, or 94-05 miata diff will work
6. you probably will want a radiator, but you probably don't need one right away. stock oil cooler is fine, if anything it needs more airflow.

 

Ok, as for aux bridgeporting it seems the general consensus is not to

It seems like the streetport is the best route to go ATM

What is the difference between the N/A and T-II oil pump? I read about the FD regulator (runs 100+PSI IIRC)

BTW, does the N/A even come with an oil cooler stock?

Also ,for the aux ports, when i go with a better exhaust, i should be running Megasquirt by then and im thinking about having a solenoid switch the aux ports open and closed based on RPM.

 

TII oil pump pumps more oil then the N/A.

Oil cooler comes on all FC's.

Good idea for the aux ports, that way there will be no doubt that they are opening and closing.

 

The car doesn't look that bad. I would say good score. You can run a bridgport with a stock S4 ecu, but I wouldn't recommend it. Definately rebuild time. Don't get too upset if you tear the engine down and find the front iron has a rusted out spot at the bottom of the coolant ports.

 

I'm suprised no one caught this. If you're using the S5 intake with it's VDI system, the aux ports will be opened by the air pump and not exhaust back pressure as the S4 models. If you're not using the S5 VDI then disreguard this.

 

the turbo ii oil pump pumps i think around twice as much oil as a NA oil pump. i could be wrong on the twice as much part but i know that the tii oil pump DOES pump more then the NA

 

Well, got to spend 3 days with the 7 this weekend. Got the motor pulled and almost ready to tear apart. Had to "persuade" the crank bolt to loosen up (3' breaker bar and a jammed flywheel works ) and the flywheel nut needed a 5'-6' pope on a breaker bar + gravity to finally pop it loose.

It looks like the rear seal was leaking and i found a piece of metal embedded in the flywheel side of the clutch. Also looks like the PP/FW have some discoloration to them. Can the stock flywheel be resurfaced? I'm thinking about seeing how much a rebuild kit for the trans will cost or whether to look into the miata gear set swap. Hoping to find out soon what the motor is hiding inside. (good compression but coolant/oil consumption) Any input or observations welcome

On the lookout for S5 N/A rotors/counterweights and VDI intake as the S5 motor i had lined up fell through

 

 

Got the ports back from hot tanking and made some interesting discoveries: the motor has been rebuilt before. The crank pulley bolt was lathered in blue loctite and the center iron is DEFINITELY newer than the front and rear irons. I measured the wear on the irons and the center and rear irons only came up with .002-.003 step wear max. the front iron came up with .004 step wear Is this beyond the limitations of lapping? How much can you take off the irons with lapping and still be OK? If they aren't able to be lapped due to wear, i am working on a deal for an S5 long block to use so hopefully i can use those parts...

the rotors also seem to have a lip of sorts on the back part of the apex seal groove. Is this normal wear? the apex clearances were in spec before the rotors were totally pulled apart.

Also, can you lap the housings to eliminate pitting around the water seals? (if you look at the pics, i doubt my housings are useable anyways...)


Rear Iron (notice how rusted the hose nipples are)




Center Iron (notice how new and fresh the nipples are and the general condition of the iron)


Center vs rear


Front Iron (worst step wear of .004)



Front vs center

 

Rotors (lip edge and weights)

Lip i mentioned before

Rear rotor

Front rotor


Rear housing (im gonna guess bad wear but some input on the wear and wear patterns would be appreciated)

 

Front Housing (again, bad wear and im guessing an unusable housing )

 

I think you might be able to get away with using those housings, but personally I wouldn't if I didn't have to. The corner seal wear is kinda bad, but upon assembly I'm pretty sure you can put the apex seals in the opposite way so the new corner rides on the smooth side (if you do this you simply won't be able to generate quite as good of compression compared to using housings with no appreciable corner seal wear, all other things being equal of course). When I was gathering parts for my motor I bought a core motor and one or two other pairs of housings and picked the BEST ones to use and sold off the rest. You have a bit of chatter wear, too, but it's hard to tell how much by just looking and photos can deceive. If you can feel the chatter marks distinctly with your fingers it's bad news.

 

from what i could feel' the housings were smooth except for the edge wear. I see what you mean about flipping the apex seals (as this motor was running 3-piece seals anyways) but I wanted some input. The edge flaking had me a bit concerned as did the wear patterns on the main chrome even though there wasn't really a discernible grove on the larger wear patterns.

Im working on getting a spare S5 N/A to work with and we'll see from there.

Also, The other big question is how much can the irons be lapped without adversely affecting the engine build? i've heard anything from .002 to .006 is acceptable lapping depths...

 

I'm not sure on lapping them, I didn't have that done on mine. From what I understand though you can't go very deep because of the nitride coating they have, too deep and you'll go through that hard coating leaving a softer surface exposed. Maybe try to contact a good builder like Kevin Landers or Mazdatrix and ask.

 

Both Mazdatrix and Pineapple say lapping is a good idea. It has also been debated (here and elsewhere) that the nitriding wears off relatively quickly (sub 80K miles).

The main question i have is how far can you lap before you have messed up the coolant seal grooves or the overall length of the motor and whatnot. If i can only take off .002 before the housings will not seal or work right, then my front housing with .004 step wear is essentially dead. Hence why i would like some input

 

What about getting those rotor housings Cermet coated at JHB Performance?

 

That would be nice, but i don't think i can afford another $1000 on this rebuild (350 per housing + SH&H) Hopefully the S5 i have lined up will be in better shape...

 

Ok, whats the deal, i moved my pictures around on photobucket but i can't edit my own posts to fix the links???

 

I think you only get so much time after making a post to edit it.

 

I don't think this is possible, unless you build the engine back to front? When assembling the engine you insert the springs under the apex seals after the rotors are inside the rotor housings on the stationary gear at a 6 or 12 o'clock position then the little corner peice, then the iron. Rotor housings only go one way, I don't belive you can build a engine back to front, because you'd have to insert the tension bolts up??

I wouldn't reuse those. $800 for new housings(used to be) and the motor will fire right up if everything is done correctly. If you reuse those, expect lots of hard starting/flooding and probably take some time getting it to start for the first time.

Good luck though, nice progress!

 

good point. Attempting to think while tired at work doesn't always work lol

Yeah, im not planning on re-using the housings. They are a bit tore up for what I'd like to do.

i wish a pair of new housings was $800, but from what i've seen, its near $800 EACH

 

I can't find the receipt but I'm pretty sure I paid around 400 each back in ~2002?... Mazdatrix now has them at $570 & $530 for 86-88 turbo... yea like 1100 before shipping, ouch. $525 at Atkins...

Good luck!