I"m rebuilding my 13b-t from my FC TII and I was finding various people saying different things when it came to seals, tolerances, and machinework needed so I thought I'd ask some questions here.

First, I'll start with my power goal. I'm planning on running a hybrid turbo with an s5 hot side and an unknown "Garrett AiResearch T04" cold side that came with the car. (I use quotes because I am unsure of the authenticity of it, and it's lacking a nameplate so I cant search the part number.) I'm shooting for 350-450 reliable HP. As far as budget goes, I'm not looking to spend 5k on seals, but I'm willing to spend a bit more now so that I don't have to rebuild the engine again for a good while.

Now onto the seals. I've heard good things about RotaryAviation apex seals, so I was planning on going with those unless someone has a better suggestion. As far as side seals go, I haven't really heard of any aftermarket side seal brands so I'm assuming that OEM is good as long as you clearance them properly. I'm also assuming that I won't need cryo treated side seals since I'll be doing a fairly tame build. As for corner seals, I've seen solid, cryo treated solid, and OEM and I haven't seen very much about the pros and cons between the three other than solid being cheapest and cryo being most expensive. Similarly to the side seals, I've assumed I won't need cryo corner seals, but I would like to know the pros/cons of solid vs OEM. The last thing I'd like to know is whether the OEM springs are reliable long term in a modified engine or if I'll want to go with something like the pineapple racing heavy duty springs.

In regards to making sure my used parts are good, I'd like some measurements and tolerances for various things like flatness of irons and housings, runout of e-shaft, and anything else I'm forgetting. I have access to (and experience using) a surface plate and tenths indicators so I would like to check every dimension of every part to make sure it is in tolerance.

Onto clearances, I've heard that generally with seal clearances the tighter the better as far as sealing goes, but requires a longer break in. I don't mind a long break in, but I am worried about excess carbon buildup with low rpm driving since I'm running the stock ECU which I know runs rich. Other than that, if someone knows where I could find a list of all the clearances I'll need to check during the rebuild I'd appreciate it. I'm sure its on a sticky somewhere buy I haven't had any luck finding it.

Finally, we get to machining, and I'd like to know what I can to do increase reliability of the engine from a machining standpoint. I have access to a lathe and a mill, so I can do pretty much any machining work required. I know I could dowel it, but this feels like overkill since I'm only pushing for 450hp max, but if I need to do it to safely reach 450 I'm willing to, I'd just like to know if its really necessary or if just doing studs rather than the OEM bolts will be enough torsional resistance for me. I've also heard of clearancing the rotor edges by a couple thou on a lathe, would this be worthwhile? Any other machining things I can do to increase reliability I would love to hear about because increasing reliability for free is something I'm a big fan of.

Sorry for the essay, this is my first engine rebuild and I'd like to do it correctly the first time and I know the people on this forum are very knowledgeable. Thanks for the help.

 

Download factory manual for measuring wear and clearances.

For the rotary there is really no upgrade for factory seals, only downgrades sold through hype.

Regarding apex seals, my final compromise was oem 3mm apex seals after trying several "ubreakable" apex seals in 2mm and 3mm which do break and also destroy rotor housings because they are too soft on the wear surface.

With 3mm oem seals I found the apex seals are strong enough that detonation breaks the front and rear S5 housings and not the apex seals.

If you have S5/FD rotors the detonation will also dent them, but the S4 rotors I used survived everything.

I bought a brand new S5 plate which is updated to FD plate strength after a few rears and then broke a front- so...

Machining includes S4 rotors side cut for rpm and milled to 3mm slot. Tension bolts holes reamed for studs. Drilling tapping oil galleys for oil mods and e-shaft mods.

Ofc any modifications can destroy your parts if done wrong, so know your capabilities and judge mods by that.

Stock ecu and fuel system can get you to ~250rwhp, so you dont need any internal engine mods at that level. Do a stock rebuild if that is what you are going to use.

 

+1, also use the FD manual, its a lot more detailed as far as specs go. or look at the Japanese FC manual, its even more detailed, although you need the US one for the words

you turbo could/should make the car a lot of fun, but its realistically 280-300hp, around 15psi. there are a bunch of good threads on hybrid turbos,
best place to start is to measure the wheels and see what you have. the stock hotside limits power no matter what.
the wheel (hot and cold) choice are kind of a balancing act, if the compressor is too small (like stock) you get boost spikes and then it falls off, if the compressor is too big, its really laggy
so hopefully they went with an upgraded turbine wheel (a stage 2 T3 wheel drops in), and something reasonable on the compressor side (V trim, U trim).

for the engine, at these power levels it should just be build carefully. think blueprinting it. you do want the FD oil pressure regulator (N3A1-14-230), it bumps the oil pressure to FD spec.
use the 89+ tension bolts, if its not already. the FD bearings are an upgrade too. i personally like the stock apex seals, they work. also the stock side seals.
i've been using 0.0025" clearance lately, i think i can get it more consistent. (also check the clearance of the side seal vs the groove in the rotor)

for corner seals the stock ones seal better, and are a little more flexible which seems to just work better. the solid ones might be stronger, but also might just break because they are more brittle

for 280-300hp the 9.0 rotors are fine, if you're planning on stepping up the power later over about 450hp its worth thinking about the 8.5's.
over like 550hp the JDM tuners machine the 8.5 rotors to 8.3.
you can machine the rotor tips for a little side clearance, but if you're spinning it that hard (over 9k) you'd need a bigger turbo.

you will want to run colder spark plugs, and make sure the wires are routed so you can't get any "spark leakage" or "inductive cross fire"
car needs new fuel filters. you need to verify the voltage at the pump. it would be nice to actually run a volume and pressure test on the pump too, but its big and messy.
basically the more stuff you test and verify as good before you bolt it to the car the better.

 

Ive heard about running colder spark plugs, someone told me to run all leading or all trailing plugs, but I cant remember which. Do you recommend stock plugs or swap out for different ones that are even colder?

 

Trailing= Top plugs
Leading= Lower plugs

Spark Plugs really depend on how hard you are pushing your set-up.

The downside to colder plugs is they foul more easily which for an OE means more emissions/damage to catylitic life (which they must warranty for 10 years unlimited miles).

Therefor OEM plugs are going to err on the hotter side.

Stock NGK is 7 Leading and 9 Trailing.

If the Trailing plug fouls the Leading will still have ignited the mix- it just wont be as complete a burn.

If the Trailing plug however acts like a glowplug from too much retained heat it ignites air/fuel mixture during the compression stroke- pre-ignition. Very hard on the engine.

Changing to all colder 9s does not mitigate pre-ignition (as Trailing plug has not changed) , it does reduce how thermally deformed the rotor housing becomes around the Leading spark plug though- so, less wear on the trailing side of the apex seal.

On my stock engine stock turbos FD I run the NGK 16601-11 11 heat range plugs recommended by Mazda Motorsports because it is primarily a race car.

Sometimes the plugs foul out a bit driving around town and I have to boost it to get them to come back in. It also has a wandering idle if sitting for a while as plugs foul/defoul.

You wont hurt your engine using a colder plug. You could melt your catylitic down (which in turn could hurt your engine).

Recap-
I have been using NGK 6601-11 without issue.

Mazda Motorsports entry

part# 0000-10-R601-11 @ NGK SPARK PLUG/11.0

Notes: R6601-11 S&P PORT

RX-7
RX-7 TT

 

Platinum R6725 in heat ranges 9-10-10.5-11-11.5
Iridium R7420 in heat ranges 9-10-10.5-11
have long been recommended for high power applications as well, most recently recommended for the leading position due to the ground strap possibility of becoming a hot spot on the trailing.
So 6601-10 or -11 suits the trailing position better as recommended above.

Depending on power levels and use you can go stock 7-9 all the way to 11.5-11.5.
I've ran all 10's on twins at 17psi as a daily with an upgraded ignition with no fouling, all 11's fouled as a daily.

 

I'll definitely be doing a standalone and fuel system with this rebuild (I never really trusted the stock 80s EFI and I have a hook up for fuel systems), and I don't mind lower power than I was expecting, It'll be a daily/autox car anyway so I value suspension over power. As for oil/e-shaft mods if you had any threads I could look at for different modifications and their reasoning I'd appreciate it, and if not I'll spend some more time with the search bar, I'll figure it out eventually.

As for the 3mm apex seals, where can I find OEM 3mm seals? Do I use ones from a 12a? I didn't find any on Atkins and mazdatrix that said they were for a 13b.

I appreciate the advice on the FD oil pressure regulator, I'll be using that. As for compressor wheels I measured and it was 70mm, and I was planning on using the hot side from the stock s5 turbo. As for the V trim or the U trim, what is that? I can't find anything online other than a DSM forum talking about it.

So as far as seals go I'll be going with OEM everything and 3mm apex seals. I've heard FD corner seals and springs are better, so I think I'll go with those. I appreciate the recommendation. My goal with this eventually is to make it a fairly high rpm and low boost engine so I suppose I'll need a turbo upgrade in the future.

That spark plug information is very useful, thank you. Melting cats isn't an issue for me because I don't have one (thanks Oklahoma). I'll probably go with 10s all around to split the difference between the OEM trailing and your 11s that foul with daily driving. Would it be a good idea to run a hotter plug like a 9 for daily driving to reduce fouling and then switch to 11s for track days?

 

The 1974-1985 13B engines used the 3mm steel apex seal parr # n304-11-300a.

I order Mazda parts through Mazda Motorsports. This is through Mazda and is how they provide racers with a great discount on parts.
You can get membership with race results (autox) in a Mazda or Mazda powered car. They say you can get membership with info on your project race . I found its easier to race your friends miata.

 

Turbonetics was a big seller of turbo stuff in the 2000's and we still kind of use their terminology, even though they don't exist anymore.
the V trim compressor was 55/70mm aka Turbonetics 20325 or Garrett 409179-0025. you can either put it in a T04B housing, Garrett 408173-0025, or bore out the stock FC housing. the Garret housing is a 0.6 a/r, and it will flow a bit better
the U trim is 54 and 70mm, so slightly smaller. same deal, you can either use it in the stock housing or a T04B housing. this one is easier to find, nowadays its also called the T04B25
H was the other option, its 58.4/70, its too big for the stock compressor housing, so you need the Garrett one. its also going to be pretty laggy

https://www.rx7club.com/2nd-generati...-parts-921510/
https://www.rx7club.com/2nd-generati...stion-1072833/

 

this is all IMO... the factory ran the 7/9's up to 280hp, so provided you keep mixtures around what they did (11:1), you're fine too. over that power, or leaner mixtures, you want something colder.
and then the other variable is how you drive it. when they raced at Daytona, they ran 13's, but its basically full throttle for a day. on the street you aren't able to do anywhere near that.

i'd think 10's would be fine, 11's if you're making big power and or live somewhere where you can hit the gas for more than 10 seconds

 

So the SCR Power Seals stuff are worse than OEM then?

 

at the risk of speaking out of turn, i think the point Blue TII was trying to make is that there are no (or virtually no) aftermarket apex seals that can do what the OEM seals do all around. you can get seals that are more resistant to detonation than OEM, but they will usually wear the housings faster over time and if (or when) you find the point where they break, they will do the same, or worse, damage OEMs do when they let go.

 

Exactly.
As it relates to apex seals-

Do you want OEM apex seals that can break and ruin your motor if it detonates but work perfectly in normal use...
or aftermarket apex seals that ruin your motor in normal use and have a slightly higher chance of surviving detonation while they are doing it.

In drag racing the answer is obvious since a season of 1/4mile passes adds up to a couple miles on the engine.

 

sure wish you had tried the 1-pc 3mm Iannetti ceramic seals …

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