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Old 12-23-03, 03:07 PM   #1
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13bT in a ......Miata!

the fine fellas at MazSport have just released a kit to drop the 13bT from the TurboII into a miata. Being the proud owner of a 96 Miata, I'm first in line to get one. Since I have to source my engine and tranny myself, I thought you guys could help me get the right motor setup. I don't know the differences between all the years of turboII's. Nor do I know what year of Turbo II to look for (if it even matters) and what parts from other RX7's are swappable as an upgrade..you get my drift. I will be looking for like 400hp at the flywheel and I dont want no stinkin turbo lag so I'll probably be looking for a bal bearing turbo. BUT, you guys are the experts so I'll just shut up and listen to your suggestions! PEACE!
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Old 12-23-03, 03:24 PM   #2
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Well all the trannies are the same so that doesn't matter. But the engines are quite a bit different.
The S4 13BT (1987-88) have slightly different porting (I think) and have heavier lower compression rotors 8.5:1.
The S5 13BT (1989-91) have lighter higher compression rotors (9.0:1), and they are half a pound lighter.
I would difinatly go with a S5, have it street ported and throw a To4B turbo on it. Your also going to want to get a different intercooler for running that much horse power.
And I know that the 13BRE from a cosmo can be swapped into a TurboII with a set of motor mounts from K2RD or fc3s.org. If its fairly easy to put one of these in your motor definatly go for it. Cuz the internals are as good as a 13BREW (3rd gen) and have the largest stock ports available.
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Old 12-23-03, 03:26 PM   #3
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Mazda did it about 4 years ago.

The president of Mazda said:"It was a handfull"
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Old 12-23-03, 03:28 PM   #4
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know where I can get a 13BRE? Does the wiring harness from the S5 TII fit the 13BRE? I will be running a standalone ECU, although I have no idea which one yet... so I don't care much for the TII or Cosmo ECU...but I don't want to end up with a motor no one uses and no one knows how to tune..so, that said, is the 13BRE a well supported motor?
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Old 12-23-03, 04:07 PM   #5
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Yeah, interanlly almost all the turbo 13B's are very similar. The 13BRE is very similar to the REW which comes in 3rd gens. The big difference in these motors vs. the second gen 13BT is the fact that they have hardend stationary gears, 3 window bearings, larger ports etc... As far as building and tuning there are almost no differences.
As for where to find one, you will need to import them from Japan, maybe Austrailia. As the newer cosmos were never imported to the US.
If you want some standalone suggestions, there is a ECU section on this site. And also make sure that there is a local tuner familiar with the EMS that you buy, that should probably be the biggest factor in your desicion.
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Old 12-23-03, 06:00 PM   #6
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Does the kit come with a pre made wireing harness?

If so you need to find out which series TII the wireing/electronics are for, because S4/S5 are not interchangeable.

Also if you are buying a kit for a 13BT into a miata, I suggest you stay with the 13BT, and don't go trying to put a 13BRE/13BREW, because the motors are not interchangable.


Also what all does the kit come with? Like motor mounts, tranny mount, wireing, .....
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Old 12-23-03, 09:22 PM   #7
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Hey cory, if he is going with a standalone EMS, the wiring isn't that big of a deal, especially since some EMS systems don't use the stock injectors or sensors.
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Old 12-24-03, 12:59 AM   #8
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I'd look for a 13BRE or if they are hard to find or expensive, then a S5 13BT engine.

It won't be that important to get a ball bearing turbo to decrease lag. If you are *only* looking for 400 flywheel hp, then as long as your turbo trims and header, and everything else is matched up well, lag will be minimal, not much more than stock.
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Old 12-24-03, 06:54 AM   #9
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Hey cory, if he is going with a standalone EMS, the wiring isn't that big of a deal, especially since some EMS systems don't use the stock injectors or sensors.


Ooopps, I don't know why I forgot about that. I guess I'm always thinking everyone else is on a budget to
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Old 12-24-03, 01:02 PM   #10
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j200pruf: Thanks a lot for the info about the 13BRE. I still havent decided what I'm doing yet...I orig. wanted to do the 20B but $20k is out of reach for me. (not to mention stupid since I can get a damn nice FD for $20k)

Cory Simpson: the kit consists of a redesigned front K member, redesigned oil pan, Transmission mount, modified rear axle shafts, and something for the rear carrier to fit the TII diff properly. NO wiring, Mazsport recommends standalone ECU, but will help with questions and such if you wish to use stock ECU. I will definitely be using standalone (always wanted to do this) I'm even redesigning my dash to permanently mount a laptop. I may be completely re doing the rearend using Martin's V8 kit stuff (Ford 8.8 IRS) Depends on budget restraints. I am for sure having hubs made to convert to 5x114.3.


Question: The guys at racing beat tell me to get the S4 TII engine because the rotors are lower compression so I can boost higher. Any thoughts? OR, are rotors interchangeable? I will be most likely rebuilding the engine and doing a full porting job...maybe I can pick and choose which rotors to use??
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Old 12-24-03, 03:34 PM   #11
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The S5 engine, underwent quit a bit of redesign from the factory, and it put out about 40 more HP than the S4, if it is in your budget (probably not that much more), I wold suggest that you just buy an S5 TII J-spec motor, and then have it rebuilt. The compression rations are different by like .4-.5 to 1 if I remember right, because the S4 TII is something like 8.7 to1, and the S5 TII is like 9.1 to 1. Someone correct me if I'm wrong.
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Old 12-25-03, 08:06 AM   #12
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The S4 is 8.5:1 and the s5 is 9.0:1 according to Racing Beat. After exhaustive research, the S5 motor does seem to be the better motor. Better port design/flow/etc. Someone suggested using the S6 intake manifold on a fully ported S5 motor. Do you guys agree?

When do you need 3mm apex seals over the 2mm ones?

For those of you who wish to see the topic about this kit on Miataforum.com http://forum.miata.net/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=34;t=001457

I have directed all the interested people from the Miataforum to this site for info about rotaries...please be patient if they ask the same questions over and over!
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Old 12-25-03, 08:23 PM   #13
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Quote:
Originally posted by Slipstream
The S4 is 8.5:1 and the s5 is 9.0:1 according to Racing Beat. After exhaustive research, the S5 motor does seem to be the better motor. Better port design/flow/etc. Someone suggested using the S6 intake manifold on a fully ported S5 motor. Do you guys agree?
Yes, that is a good idea, although not completely necessary. Really depends on how much power you want and if you really need that extra flow or not.

Quote:

When do you need 3mm apex seals over the 2mm ones?
As far as 99% of rotary engine builds are concerned... never. The factory 2mm seals are excellent quality and will work great. The 3mm will give you that little extra margin of error incase your tuning isn't perfect, but you need to pay to have your rotors machined to accept them, as well as you won't make as much power compared to 2mm. There is a big thread about this in the Rotary Performance forum if you do a search and are patient enough to read through it all.
Stick with the stock 2mm seals unless you plan on running high boost (say over 25psi)

Last edited by Sponge Bob Square Pants; 12-25-03 at 08:29 PM.
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Old 12-25-03, 08:28 PM   #14
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Oh and all rotors from 2nd and 3rd gen engines are interchangealbe (1986+ 13B engines).

As you already know the S5 is a far superior platform to start with, and the price difference is usually only slightly more than an S4 engine.
The slightly higher compression ratio should not be a problem unless you plan to run very high levels.
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Old 01-05-04, 02:39 PM   #15
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So, not including the purchase price of the core motor-assuming it runs, How much cheese am I going to spend on a S5 TII motor, S6 intake, turbo, etc to achieve my 400hp goals??? Keep in mind that becuase of the application, I will not be trying for 500hp later...I'll save that for my FD project. So I won't need to "overbuild" the motor in anticipation of future upgrades.

Mazdatrix doesn't "dowel" thier housings...do I need to do this?

Mainly what I'm getting at, is can I build a 400hp S5 13bT for $4000 including the ECU?
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Old 01-05-04, 05:25 PM   #16
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new miata with a turbo 2 rotor..
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Old 01-07-04, 09:10 AM   #17
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Well, Razorback...unfortunatley it's a M1 miata (1996). Although I am ditching the pop-up headlights in favor of the Re Amemyia style lights and dropping on a phat wide-body kit. When I'm done, it'll look like a miniature FD!
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Old 01-08-04, 07:00 AM   #18
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Quote:
Originally posted by Slipstream
Mainly what I'm getting at, is can I build a 400hp S5 13bT for $4000 including the ECU?
Not even close. Want a break-down?
Let's say you start with a JSpec used engine at $800.
Rebuild and porting will be pretty important for 400 hp, so there's $2000.
Now you need an EMS. $1000, if you tune it yourself, more with a professional tuner.
Now you need a new turbocharger... $3000 for your premade kits.
Now you need fuel to support it... say, 2 720CC, 2 1200cc injectors and a fuel pump... $500.
Now you need to intercool it... for something decent... $600-$700.
Exhaust from the turbo... $200 custom jobby.
Then you'll need a rad to support that power... $300
Clutch to support the 350+ ft-lbs of torque.. $300
This is just a start, doing the installs yourself, and costs listed are a MINIMUM.

Dowelling won't be necessary until around 550 hp at the flywheel.

Lower compression rotors are not a neccessity for higher boost if your tuner knows what he is doing. (Higher compression gives better power at the same boost levels, gives better off boost response, and spools slightly faster).

The rotors are NOT interchangable between series... the S4's and S5's are different weights and compression ratios, and use a different counterweight balance.
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Old 01-08-04, 07:02 AM   #19
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Someone suggested using the S6 intake manifold on a fully ported S5 motor. Do you guys agree?
Not for 400 hp.

When do you need 3mm apex seals over the 2mm ones?
When your tuner sucks.
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Old 01-08-04, 07:09 AM   #20
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Quote:
Originally posted by Cory Simpson
The S5 engine, underwent quit a bit of redesign from the factory, and it put out about 40 more HP than the S4, if it is in your budget (probably not that much more), I wold suggest that you just buy an S5 TII J-spec motor, and then have it rebuilt. The compression rations are different by like .4-.5 to 1 if I remember right, because the S4 TII is something like 8.7 to1, and the S5 TII is like 9.1 to 1. Someone correct me if I'm wrong.
Wrong. The S4 13BT was rated at 182bhp, and the s5 200BHP, a difference of 18 hp. The 40 hp difference was between the S5 Naturally aspirated and the S5 turbo engines.

Compression rations were as follows:
S4 NA: 9.4:1
S4 Turbo: 8.5:1
S5 NA: 9.7:1
S5 turbo: 9.0:1
S6 TT: 9.0:1

Use the highest compression rotors your tuner is capabale of.

S5 J-spec is typically only $100 more than an S4. It featured (relative to this swap) a much better stock turbocharger, stronger rear iron (more meat around the dowelling), lighter, higher compression rotors, more boost (5.5psi on the S4 vs 7.5psi on the S5; the main reason for the power increase), slightly better intake manifolds, 10 degrees more intake timing on the ports, and a better-placed knock sensor.


If you would like to talk more in depth about this, I am sure I can answer any question you might have. PM me, add me to AIM, MSN, etc. Not a whole slew of real rotary guys check in here that often as this subforum is mostly concerned with piston swaps.

Last edited by scathcart; 01-08-04 at 07:11 AM.
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Old 01-13-04, 11:31 PM   #21
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Originally posted by SureShot
Mazda did it about 4 years ago.

The president of Mazda said:"It was a handfull"
got a link to an article or something, im interested... me and my brother kicked this idea around for a while, never did anything with it mainly because the miata engine still worked
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Old 01-13-04, 11:31 PM
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