One320B

I've had the original NA motor in my car, a JSPEC GTX 13BT, another S5 streetported 13BT and now I'm putting an REW shortblock in... I can tell you a lot of reasons why using the REW is a better choice over the previous, regardless of the twin turbo setup, just the block alone. If you're starting with a rolling chassis project, then I would throw the REW in..if your SWAPPING your existing NA 13BT to an REW, then maybe I'd say it'd be easier/more applicable to use a normal s4/s5 13BT. It's up to you. The answer is yes, the REW will fit and you can make it work... it will cost enough to make you cry either way you go about it, lol. It's your car, and you know your budget better than anybody... it is true that the little things will be what kill you.



BTW... no way does a 13BT from an S4 or S5 with the same port job and same turbo make the same power... it's exactly why I'm changing to the REW to begin with.. I've tested this and have dyno's on a lot of setups and the REW makes MORE power than an S5 13BT at the same boost w/ the same turbo, etc... not to mention an REW has a lot of small refinements made that allow it to make more power over the 13BT... the REW crank trigger is also easier to tune w/...

RONIN FC

Can you share this info? Cause I havnt been able to find anything radicaly different at all internally from S5 13bt and REW. Other than the factory seals and springs.



With your testing, how much of a margin did you see? Any dyno sheets?

One320B

There are two types of 13BT blocks, one from the 87-88 Turbo RX7 (FC3S GTR) and one from the 89-91 Turbo RX7 (FC3S GTX). While the older 13BT GTR block differs a lot from the 13B-REW block, the GTX block is some what a compromise in between. Most of the changes made by Mazda engineers are refinements to address the problem areas of the previous designs. For comparision purposes, the 13B-REW motor described is the one from the FD3S, not one from the Japan-only Mazda Cosmo.



One significant difference on the 13B-REW is the areas around the dowel pins on the side housings. They are reinforced and ribbed with thicker castings. This is a major problem area on high output 13BT engines, as they tend to crack at high power levels and is the main reason that the 13BT blocks are not reliable beyond 400HP. Most competent rotary rebuilders will look for this before rebuilding a 13BT motor. The 13BT GTX blocks are said to be more reinforced than the earlier motors but not as significantly as the newer 13B-REW designs. Before the introduction of the 13B-REW motors, some engine builders experimented with brazing extra metal around the dowel pins area on the side housings of the 13BT motors.



The port sizes on the 13B-REW are extremely larger than the 13BT's, especially the primary ports on the intermediate housings. This is accomplished by increasing the height of the side and intermediate housing where the ports are located and relocating some of the coolant passages inside the housings. The larger ports increase the duration and "lift" of the intake stroke, allowing more air to be ingested into the combustion chamber. While the intake ports are larger, the intake runners of these motors are still about the same size. The 13BT intake manifold has a surge tank plenum which is found to create too much pumping losses because of its large volume. The 13B-REW intake manifold is a "Dynamic Pressure Intake System" which eliminated the surge plenum tank and has opposed-facing secondary intake runners. This new design enhances intake flow by taking advantage of the strong pressure waves inherant in rotary engines. The throttle bodies on the 13BT are 3x45mm, while the 13B-REW are 1x45mm + 2x50mm.



Intake Runners: Upper, Lower

Plenum: 1, 2

Runners: 1, 2

Contrary to popular beliefs, the 13BT's and 13B-REW share many internal components. The 13B-REW rotors are interchangable with the 13BT GTX rotors, although they don't have the same part number and thus are not the same part. But they do have the same compression ratios of 9.0:1 and they weigh the same. The CR of the 13BT GTR rotors are 8.5:1. I believe the later model rotors are manufactured from a more accurate milling technique while the older ones are left partly casted. This is evident in the bathtub faces of the rotors.



Almost all the internal seals and springs are the same parts in the 13BT and 13B-REW. This includes the 3-piece cast-iron 2mm apex seals which are found on all post '86 rotary motors, both turbo and non-turbo. With the exception of the side seals and corner seal springs, all the other rotor parts of the two motors such as oil seals, rings, springs, side seal springs, and corner seals, are the same parts. The newer design corner seal springs are reccommended for use in all rotary rebuilds.



The eccentric shafts for these motor seem to all look the same, but the 13B-REW shaft has a larger oil bypass/crank pulley bolt. The newer motor surprisingly maintains the same warm-up oil-bypass pellet as the older motors. The 13B-REW motors does have larger front-end thrust bearings than the 13BT motors. These larger bearing components require the use of a different front counterweight. The larger thrust bearings allow better loading and thus a tighter torque setting of the pulley bolt. This design will reduce the chance of the eccentric shaft bending at the front section, which is sometimes a problem on high-output 13BT motors. The large thrust bearing is probably also designed for use with the pull type clutch assemblies found in the FD3S.



The front cover of the 13B-REW has one more attachment bolt which prevents the gasket from blowing out, which is a problem on the 13BT motors. These front covers are interchangable between the two motors as the bolt patterns are the same (except for the one extra bolt on the 13B-REW). The 13B-REW motors uses crank trigger sensors mounted on the crank instead of the crank angle sensor (CAS) on the 13BT. The crank trigger sensors allows a better accuracy resolution because of its wider teeth spacing. Also, torsional flex on the crank angle sensor shaft causes inaccurate readings. The two triggering systems has similarities in the numbers of triggering teeth. The 13B-REW's crank trigger has 12 syncro teeth and 1 home tooth, while the 13BT's CAS which spins at half speed, has 24 syncro teeths and 2 home teeth.



The rotor housings on the 13B-REW motors are refined for reliability. Since the motor is designed for higher standard output, the wear surface on these housings has a carbon-graphite coating which is said to exhibit 32% less friction than the 13BT motor's fluorocarbon resin coating. The new coating actually allows less oil to be injected into the combustion chambers, thus the 13B-REW requires only two oil injectors instead of four. In addition to this coating, these rotor housings has the water passage machined around the spark plug areas to increase cooling at the spark plug tips. This modification is similar to the ones done on race motors.



The stationary gears on the 13B-REW are factory hardened. They are interchangable with the 13BT's, provided that the 13B-REW's thrust bearings and front counter weight be used. Inside the stationary gears, the standard main bearings on the 13B-REW motors are the multi-holes type and are locked into place by an anti-rotation set screw. This design, similar to the "3 window-type" bearing is pioneered in the earlier LeMans and IMSA motors. The holes allow extra oil to flow around the oil groove thus providing a thicker oil film for the eccentric shaft to ride on. The 13BT has standard bearings with no oil holes. Oil pump capacity and pressure are also increased in the 13B-REW motors. The oil pumps are not interchangable. The 13B-REW oil pressure regulator is interchangable with the 13BT motors and is a reccommended upgrade when power output is increased. Also, a new oil pan design on the 13B-REW motors helps to minimize air induction into the oil strainger. A thinner pan with a inner bulge maintains oil level to keep the oil strainer submerged in oil. The 13BT GTR blocks use mechanical oil metering pumps, while the 13BT GTX and 13B-REW blocks use electronic oil metering pumps.



The water pump of the 13B-REW is probably the only reverse rotation water pump assembly found on any Mazda rotary engine. It is driven by the back of the serpentine belt. The water pump housing assembly on all the rotary engines are interchangable, but the appropriate front cover/pulleys/etc... must be used.



Fuel injectors used in the 13BT motors are 4 standard Nippondenso top feed rail injectors rated at 550cc. Depending on production dates, the 13BT motors had both low and high impendance ratings. The 13B-REW motors has 2x550cc injectors for primary and 2x850cc injectors for secondaries. This higher fuel capacity is for higher power levels. These injectors are side-feed rail types with high impedance so it can operate cooler. They are not interchangable with the 13BT injectors.



The engine mounts locations of the 13B-REW are under the rear side housing, while the mounts on the 13BT are located on the intermediate housing. Because of this, interchanging the motors between the FC3S and FD3S chassis is a very involved project.



The tranny bellhousing bolt patterns are the same on the 13B-REW and 13BT motors, thus the trannies are interchangable with the appropriate clutch/flywheel assemblies.



In summary, because of these and many other refinements, the 13B-REW is a much more potent powerplant which can easily handle high HP output beyond for which it is originally designed for. Many of these refinements are shared in the designs of the 20B-REW and 13B-REW of the Mazda Cosmo.

One320B

All this being said, the REW is actually a much better motor... a lot of things can be upgraded on the 13BT motor to compensate for the differences, however... typical 350-450hp 13BT(GTX or GTR) blocks cap out and start having severe issues above that 450 mark... 450 is a lot for an FC, and most would be happy with that... my current goal is now set at 525whp, and the use of the refined REW parts makes me feel a little safer and secure in the engine build.



Is it worth it to do the swap if you have a T2, not really... get your 350-450hp out of it and have fun... i'm not in the business of being ordinary though...



I can only provide dyno sheets of a mildly streetported T2 (GTX) vs a mildly streetported FD with the same turbo, the FD made 47 more whp at 1psi LESS boost.



When i complete the new motor and get it in the car along with a **** ton of new stuff i'll have an REW dyno for you...

RONIN FC

So, the intake manifold and port runners gave 47 HP?



Somethings drastically different in those 2 cars...

iceblue

S5 vs S6 housings is only the casting along the spark plug hole. The rear iron dowl section known to fail on S4 S5 and S6 and RE can be the same. Some S5 irons in no order from mazda had the hardened rear and some also had the hardened rear with triangular reinforcement. So this is not a correct comparison. Really the only difference was a little bit different intake plenum changing the DEI to match with the port timing changes. Not that big of a deal. There is a 10deg earlier opening from S5 to S4 also.

There is really nothing worth while to warrant this engine.

mazdaspeed7

All S5's had hardened stat gears, as well as all S6's. S4's were not hardened though. S5 irons are reinforced more in the upper dowel area, but not as much as S6. The S6 irons are nearly twice as thick in that area.



The stock ports on the S6 are bigger than S5, so a mild port on a S6 is more of a port than a mild port on a S5.



But youre still trying to tell me that despite being a strong block, which can support more hp more reliably, having a more accurate ignition triggering system, etc., that theres really nothing better about this engine?

iceblue

Not so! Like I said some received the hardening and some also received the hardening with the triangle reinforcement making it the same thing as FD.



Hardly worth the effort or cost.

tandolla

personally if i was expecting to drop that much money into a swap. i would do the 20b swap..

j9fd3s

somewhere ive got a 12psi 139rwhp dyno of a 20b....