vipernicus42

iTrader: (4)

Hey Guys,

Since I recently found out about 12a parts going NLA, I started thinking about building an N/A 13b to drop in my FB. I figured I'd come over here to ask some questions since most of the parts I'd be using for this engine would be from the 2nd Gen parts pool. In fact, it's basically going to be a second gen engine with an FB front cover and GSL-SE oil pan so that I can drop it in with the RB brace.

Anyway, I've got a few ideas, but many questions, so first I'll put forth the options I'm thinking of and see if you can help fill in the blanks.

- TII Irons (4-port)
- S5 N/A or RENESIS Rotors
- RENESIS e-shaft
- Rotor housings (does it matter which?)

I chose TII irons because I've heard that it's easier to port the 4-port irons with good results than it is with the 6-port ones. Since I'm going to be carb'd and running the existing RB "Street Port" (dual long primary) exhaust, I don't want to have to deal with 6-port actuation or anything like that.

Questions:

1. Is there a difference between S4 TII irons and S5 TII irons? What should I choose or does it matter if I'm going to port them anyway?

2. For rotors, is there any reason I can't use RENESIS rotors as long as I make sure to get all RENESIS apex seals, side seals, etc... and use a matching e-shaft, stat gears and counterweights? Someone in the first gen section said you "can't" use RENESIS rotors in an earlier motor, citing something about the apex seals. I know they're not as tall, but I don't see how that would affect things. If this is not feasible, I'll go S5 N/A rotors

3. Rotor Housings: What's the difference? Mazdatrix lists Front and Rear housings, for S4 and S5, Turbo and Non-Turbo. For some reason the S4 Turbo Rear housing is $65 cheaper than all the others. Is there any reason I can't just buy two of those, port them and call it a day?


Upgrades I had in mind:

- RB high flow oil pump
- 80PSI oil pressure regulator
- 3rd Gen corner seal springs
- Debating about solid or regular corner seals, after stuff I read over on nopistons
- Thermal Pellet replacement thing
- Race Rotor Bearings and 3-window main bearing (may not be necessary with Rx8 parts, I hear they have 3-window main bearings in the stat gears anyway)
- Lightweight steel flywheel and an RB clutch

And I will most likely get the whole rotating assembly balanced, and the rotors clearenced, just for good measure, especially if I end up using S5 rotors with an Rx8 e-shaft.

I already have a large aluminum rad and e-fan and plan on mounting an FC FMOC. The 2nd gen water pumps are already larger than the FB ones so hopefully that will all keep the temps low.

So what do you think guys? Feedback?

Jon

Frostycrowd

iTrader: (9)

I know nothing about the renisis. But s5 housing are stronger than s4's but if your going NA it won't matter because s4 housing can easily hold power unacheivalbe by a NA setup.

You also don't NEED those oil upgrades unless you plan to heavily track your car.

You have nothing to worry about with cooling. Install a FMOC and the stock radiator should be fine for your planned setup.

vipernicus42

iTrader: (4)

Thanks. I figure I'd rather go overkill on the cooling and reliability mods and "do it right the first time". You never know what the future plans for an engine are, and I figure that I'm just crazy enough that my car may go from autocross (which I do now) to track racing at some point, or I might later add some form of forced induction (I'm thinking supercharger, but anything is possible, though this would indeed be far in the future).

I don't know how attainable it is, but I think it would be cool to see close to 200 flywheel horsepower on a streetable N/A engine. I won't lose sleep if it falls short of that, but I think that would be an ideal amount of power for a little FB. I realize that going carb may make it harder to reach that kind of power, but I love the simplicity of a carb'd N/A engine and I'm willing to sacrifice a few horsepower and a bit of gas mileage for it.

For those wondering about ignition, I was thinking that I already have a CAS laying around, and a friend who's willing to sell me his Megasquirt, so I'd run the MS ignition-only with 2nd gen coils and the CAS. It wouldn't be as simple as sticking a distributor in it, but I think it would be worth the effort. Depending on how the project pans out I may start with it distributor'd and move to the MS, but ideally I'd just go with the MS right off the bat.

Jon

Aaron Cake

iTrader: (1)

Makes sense.

You're buying the Renesis eccentric because you don't have a 13B shaft spare, right? Otherwise there really isn't a reason to go with the Renesis shaft.

The Renesis rotors are a better design but there really has not been a proven power gain using them. Also they need to be machined for the deeper apex seal when used with peripheral exhaust ports. It's a lot of trouble for little gain.

Well....They all bolt together but S4 and S5 have the spark plugs in slightly different places. You need to use two housings of the same series. The turbo housings don't have the exhaust diffusers but do have a coolant passage for the turbo water feed that must be plugged. And you can always swap exhaust sleeves or grind the diffusers out of the NA housings.

I think in you case, going 4 port might be easiest. Then you need to find a 4 port 13B manifold.

S5 are stronger around the dowels. In an NA application this isn't very important unless you are revving high.

Why? Use a TII oil pump.

Shim your existing regulator.

OK. This is pretty standard.

Mazda has stuck with two piece corner seals for a long time. There must be a reason.

If you go with the RX-8 stationary, they are already hardened and have multi window bearings.

vipernicus42

iTrader: (4)

Yes I don't have any parts to start with so I'm going to be collecting all of them and building the engine from scratch. That's why I figure I can hand-pick everything. The Renesis shaft is (amazingly) cheaper than the other 13b shafts new anyway, going for about $200 vs the $400 the others cost. Of course I'm sure I can get a used S4 or S5 shaft in good shape for less than that, but why not spend the little extra?

So the Renesis' half-depth apex seals are really an issue with the old peripheral exhaust ports eh? I suppose I can see how that makes sense. I do know of a place that can machine them for deeper seals, but you're right it probably wouldn't be worth the trouble. It would be quite cool to do though, I'll have to check the price of the machining and make my decision based on that. The "wtf, awesome" factor of having Renesis rotors in a franken-13b in my FB just might be worth it, even if it doesn't result in much power gain.


I'll keep that in mind. What's the difference between "Front" and "Rear" though? I get the feeling it's probably something that doesn't matter unless you're building a stock motor, like an egr passage or something.


Yeah, I was thinking about that... I'd be interested to know if a mid-70s 4-port 13b carb manifold can be made to work with my Sterling and this frankenmotor... If not then this may be the trickiest part... I'm pretty sure there are Holley manifolds for the FC 4-port 13b, so I might have to buy one of those and make an adapter plate for my Sterling...


Good to know. I guess I'll keep my eyes open for S5 ones, but not lose any sleep over it if I find a cheap set of S4 ones.

A friend of mine actually suggested using an FD oil pump. Has anybody done this?


Hmm.... this is one of those things that I've always been wary about, like the people who "tap" the end of it with a hammer. As far as I'm concerned the RB one isn't expensive enough to warrant doing it "cheap" instead of "right" for the same result. I only want to have to build this engine once.


Yeah, I know people even use them in 12a builds now. It's just a much better design.


That's what I was thinking. It would have been easier and cheaper for Mazda to just use solid corner seals, so there must be a reason they favor the 2-piece design with rubber insert for so many years and even use them in their high output turbo engines. Some of the choices Mazda makes can be chalked up to "it was cheaper" or "it helped emissions", but if it doesn't fall into those two categories then there must be a much better reason for it!


Yes, which is nice. They have different clearance than the other ones though, so I would match the stat gears/bearings with the shaft. This works great since I was planning to use the rx8 e-shaft anyway.



But if I use a Renesis e-shaft with S5 rotors, I'm going to need to have the rotating assembly re-balanced. Any suggestions on a good shop to do that?


Jon

Nismo Convert86

iTrader: (7)

Keep in mind when using the rear RX8 stat gears you have to massage the oil passage in the flange so it matches up with the TII iron, and they don't use the "o" ring like the earlier engines so RTV is used to seal them.

Jon I also have a set of S5 TII irons kicking around the house I can get some pics for you if you like.

Nismo Convert86

iTrader: (7)

The FD regulator is 35 bucks from Mazda I went that route because like you how much is too much or not enough? And you don't have to shim the front regulator, it has the same passing pressure as the FD, at 156psi.

glenrx7

iTrader: (1)

Do not use the 8shaft if you are looking for any real power numbers. I have had an engine destroy it self on the dyno, the reason is the 8 shaft bent at around 370ftlb of torque. You can ask Jrat, and many others I have a bit of experience and I would stay clear of this shaft.

vipernicus42

iTrader: (4)

I have heard that from at least one other person but since I'm aiming for less hp than the rx8 has stock I don't think I'll be running into any issues. A 200hp N/A shouldn't have an issue running an 8's e-shaft. 370ft/lbs is probably almost double what I'll be putting down.

Jon

vipernicus42

iTrader: (4)

I'll keep the oil passage thing in mind for sure. Feel free to send those pics over to my email which is very original: vipernicus42 (at) hotmail (dot) com (don't want spam harvesters picking it up based on the @ sign)

Good tip on the FD regulator. That's cheaper than the RB one and will serve the same purpose without the need to use a hammer!

Jon

Sideways7

iTrader: (7)

I have noticed the same thing. My NA motor had 2 rear Turbo housings with the coolant passages plugged and it worked great. Just be aware that there really is a noticeable increase in volume when running TII housings due to the lack of exhaust diffusers, if that matters to you.

As for e-shafts, if you are on a budget (which it doesn't sound like you are) you can find used e-shafts in excellent condition for cheap on the forums.

arghx

iTrader: (3)

I recently upgraded from s4 to s5 irons for my turbo engine. I will say that the s5 T2 irons do have larger ports in the sense that the runner section of the secondary ports are physically bigger. The s4 LIM gasket is too small to work with a set of s5 T2 irons. That's why I am getting an s5 LIM now. J-rat runs s5 irons with s5 manifolds as well. Also, the port timing is slightly different between s4 and s5 T2 irons but you are porting them out anyway.

The s5 and s6 (FD) rotor housings had a coating on them to reduce wear, and the FD housings also have some slight improvement in the coolant passages. If you can afford it, go with new s6 rotor housings or really low mileage used JDM ones.

I would stay away from the Rx-8 E-shaft and rotors. There are no proven gains from them. Just go with used s5 n/a parts there and put the money you saved towards new rotor housings. You could go with the Rx-8 stationary gears though.

And don't sweat the cooling system at all if you never plan to go with forced induction. I made 172rwhp all motor on all s4 parts and never had cooling problems turning 6000 rpm for 20 or 30 minutes at a time. With the original almost 20 year old radiator it would only get up to 210F (and not one degree higher) which is fine for the track. Can you fit an FC oil cooler in there?

Black91n/a

You'll probably be better off to just buy a used, complete TII engine to save yourself from having to buy all the little things that can add up very quickly. You can get JDM engines for about $1000, then just rebuild it with the only big changes being street port and S5 NA rotors and you should be good for street use.

misterstyx69

iTrader: (142)

I honestly don't think that Vipernicus wants to go TII.I am getting the Impression that he Wants New Parts under the hood and not some "Jap Crap" that was run it's last Mile before being put out to pasture.The TII engine though would give him a good starting point though,If he was to go with Used.Anyways JON,I'm at a new place now,so I'll you'll have to travel 5 more miles to get a Engine hoist!

Black91n/a

My point was more that with all the parts that he'd be buying to piece one together, that he might as well buy a whole engine, then even if he gets rid of half the parts, he'll still be further ahead. Even if it's just manifolds, wiring harness, e-shaft, stat gears, oil pump, injectors, fuel rails, etc, that'll add up to over $1000 really quickly, so might as well buy it all conveniantly pre-packaged.

4 port 13B = TII engine.

Aaron Cake

iTrader: (1)

Keep in mind that the machining could get a bit tricky. Mazda has a fairly complicated method of machining the grooves in the rotors. They take three points of the face of the rotors themselves to assure the grooves are in the correct place (remember the rotors are cast and the non-machined faces prior to S5 can be a bit rough). Most machine shops will just follow the original groove so unless their mill is in perfect shape, you can get some wobble.

You're correct. It doesn't matter if you don't need to pass emissions. I think the only difference is in fact the EGR ports.

My guess is that the older 13B four port manifolds would fit fine. The only possible area of concern is the EGR port on the center iron and the bolt holes. If I had the manifold off of my Cosmo I would check for you, but I don't. Going with the Holley style manifold might be the easiest. A carb spacer is pretty easy to make out of resin.

I'm pretty sure the drive gear is different as the FD uses a different front stack. No CAS gear on the FD...

http://www.aaroncake.net/rx-7/shimoil.htm

I believe the two piece design with the rubber plug was built to reduce chatter.

Yep. It's easier then machining the existing gears for multi window bearings.

I think you'd just need to use the appropriate counterweight. Mazdatrix may have this info on their site.

Yep. This is a very good idea.