The oil pump was super tight. 




DATE                    June 9, 2020

ROTOR HOUSINGS      FRONT                          REAR

A WIDTH                    3.14908                         3.14958


B WIDTH                   3.15008                          3.14988  


C WIDTH                   3.14978                         3.14985                                           


D WIDTH             3.14975                          3.14985


                                     .001                                .0003                                     

MAZDA MAX  WIDTH VARIANCE .0024                                                                                                                               


STANDARD  0-1/32 inch                      





             FRONT                                             REAR

            3.14465                                          3.14448                                                      

           3.14425                                           3.14422           

           3.14445                                           3.14405         

SIDE HOUSING TO ROTOR  CLEARANCE                              

          .00443                                                .0051    

WEIGHT GRAMS           4479                     4480                                        


SIDE  IRON HOUSINGS    NEW MAZDA              FRONT             MID                 REAR

WARPAGE LIMIT .0016                        .   

SIDE SEAL WEAR LIMIT .0039           

SIDE SEAL OVERLAPPING OIL                            

SEAL WEAR .0004                                


SEAL WEAR  .0039                               

OIL SEAL WEAR  .0008                        



BRAND     ROTARY SPECIALTIES (REC) RACE COATED                                                  

SIZE                                  2 MM        

                      FRONT                                REAR

 APEX 1      ALL SEALS .0025 TO GROOVE                           

APEX 2                                                                                                     

APEX 3                                                       

SEAL TO GROOVE (.0015-.004 LIMIT .006)                                        


APEX  1                                                    

APEX 2                                                

APEX 3                                                   


STD .130  LIMIT .067
                                                FRONT               REAR

APEX 1                                                                                                                    

APEX 2                                      

APEX 3                                      

FREE HEIGHT LONG             

STD .246 LIMIT .181                           


THICKNESS .026-.027                            

CLEARANCE TO CORNER SEAL                           

(.002-.006 LIMIT .016)

CPR TARGET .002          ALL 12 SEALS AT TIGHT .002                              


(.001-.003 LIMIT .004)                             

 MINIMUM PROTRUSION .020                                                        


OUTER DIAMETER (.4327-.4336)

HEIGHT (.268-.276)
MINIMUM PROTRUSION (.020)                                                       



OIL SEAL O RING        NEW MAZDA                              

WIDTH OIL SEAL LIP (.020)    .01                                                    



STATIONARY GEAR BOLTS     10.9 RATED ZINC COATED TORQUED 25 FT POUNDS                                                    

MAIN BEARINGS        NEW MAZDA                         



1.69368  1.69382   1.69405  1.69392


 1.69035   1.69145  1.69135 1.69037 

MAIN CLEARANCE                                        

 .00333  .00237  .0027  .00355     

(OUTER .0032-.0043 MAX .0051)

(INNER   .0024-.0031 MAX .0043) 



                    FRONT                        REAR

 SHELL DIAMETER                                     

                 2.91452                      2.91450

JOURNAL DIAMETER                                         
                2.91212                       2.91168   

                 .0024                            .00282 

(.0024-.0031 .0039 MAX)                         


RUNOUT (MAXIMUM .0047)              .000                         

ENDPLAY (STANDARD .0016-.0028 LIMIT .0035)                     



WIDTH   .00314

LOBE TO ROTOR                       .005


PUMP BODY                             .006

(.0079-.0098 MAX .0118)                   


SPRING FREE HEIGHT (2.87 INCHES)                                      


 Engine Coolant System Integrity Test   PASSED 30 PSI




FRONT   141  138  138

REAR      135  135  135









Most of the time we are buzzing around on the primary ports. Perhaps Mazda was thinking better low end response by keeping the velocity up using small primaries. I have found that making them as large and non-restrictive as possible i have excellent response. At highway speeds, say 75, on a level road cruise on just the primaries yields 21 mpg at 13.9 AFR. 

The other reason for enlarging the primaries is to add balance to a situation where most of the air is coming from only one side of the rotor. Enlarging the primary moves toward flow balance. A larger primary also matches up better with larger primary injectors. I have found that many incoming motors that have been ported are only ported on the secondary. 

The secondary ports have a better shape and are fairly large as are the runners. While i do quite a bit of shaping to encourage flow the big change in the secondary ports is the timing. Earlier open and later close.

Their are a lot of subtleties to good ports. For instance the inboard area that supports the oil rings. Mazda cast a shelf and that supportive shelf acts as a flow barrier. Many people just make it disappear. I retain it as it provides importan support for the oil ring. I do shape the 90 degree step into a 45 degree slope.

Another very key area is the runner profile as it approaches the opening of the port. It should thin and have a contour similar to the trailing edge of an airplane wing.

The exhaust port offers significant opportunity as well as potential problems. Think of it as a rectangle. The bottom is the open and the top is the close. There are both important timing issues as well as mechanical issues that can be effected.

I open the exhaust early so as to drive the turbo harder.

The exhaust port may be the most important key to the motor's extraordinary power capabiity. It is huge, it is PERIPHERAL and it is open a long time. Having a rotary peripheral exhaust port is similar to being able to lift the head of a piston engine to vent the exhaust. It is amazing. 

Unlike the primary intake ports, the exhaust does not need to be bigger.

The width must not be enlarged as the apex seal needs all the support it can get from the shoulders around the port. It does not need to be enlarged at the top as this is the close. If you port upwards you are increasing the overlap which adds exhaust into the intake stroke. Exhaust is hot and has no oxygen so it encourages detonation. 

i spend around 4 days on the 6 ports. My objective is to create a low flow restriction motor that has a broad power curve. Most dyno posts focus on top tick power. From my 22 seasons of serious racing for a National Championship i know that it is horsepower under the curve that wins races. If you have a ton of power at 8500 and you shift you are looking at under 6000. You need power around 5500 to get back to 8500. As much attention should be focused at 5500 as 8500.

While i check the power box in mid range my ports do not lie down at top end.

Here's a log from some prep work for the Texas Mile where i (still) hope to break 200. This is a dyno run to 8604 RPM but not in fourth gear, it is FIFTH GEAR to 205 mph...

Eighteen seconds at 100% Throttle  in 5th around 575 rwhp.


                         REAR ROTOR

It was so impressive to see that everything attached to the primary castings had a confirmative paint dab on it. Everything? Yes, everything. How about this paint dab next to the bearing pin screw.

I was somewhat concerned to see these results. Generally the motors i build do about 125-130 on the compression table if they have honed used rotor housings. The motors I build with new rotor housings are in the 135- 140 area. i also was concerned about the one rotor face at 105.

                                                                                                                         Stay tuned 

O K, time to reduce this beautiful new motor to pieces and find out just what a just-built 13 BREW looks like behind the curtain.

First up, the oilpan. i was a bit surprised how easy it separated from the block. I believe Mazdabond is a sealer made by Threebond. Threebond makes pretty much all the silicone sealers not made by Permatex and is a global company in Ohio. The sealer looked a bit like Hondabond but did not stick as well. When i remove a pan i sealed with Hondabond the last 25% of the rail remains a major struggle. Not so here. My primary takeaway was that the "stick" is nowhere near Hondabond.. 

After installing the flywheel stopper the front crank, er E shaft, bolt was loosened and attention turned to the flywheel.

Off with the flywheel. The nut was properly torqued (like Everything on the engine) around 400 ft pounds. I did find something interesting. Looking for thread locker on the flywheel nut threads i found silicone! Give that Mazda knows what they are doing i will use silicone going forward. 

          FRONT ROTOR

Well, Hello and welcome to CPR


Back into it's box, off to my customer and ready to rock and roll. I will provide a timing map that matches the ports and we will do some AFR tuning. For those interested in the details my Spec Sheet follows.

Straight from Japan, via Ray Crowe, just built by Mazda and totally unmolested. My curiosity meter is pegged. How about you?  Given the aging of our motors along with the increase in their value it is becoming a more attractive option to trade off the aged motor down the food chain for a couple of thou and spend the $4000 or thereabouts for a brand new motor. Let's put the new motor under the CPR microscope and then turn it into something special

Before we turn it into a pile of parts, let's check three items.

First up coolant system integrity. We pressure the system to 30 PSI and check for leaks... as expected a rock solid needle. Next crankshaft endplay. Very nice at .002

Next up the main event... COMPRESSION.

onto the compression table:

If you have read my Tension Bolt Tech Section (strongly recommended) you might be surprised to see the motor is retaining the stock tension bolts. Given the motor will not see over 425 and often much less AND the fact that the tension bolts are NEW i am comfortable, and recommend, their retention. My view is that if you are going to see 500 rwhp stock tension bolts should be replaced with either the Turblown or Chips stud offering. Be very careful as to looking at other 16 stud kits as some offer approximately half strength of OE! 

I have two reasons for using the stock bolts... one power output and the other, the fact that the bolts on the new motor are.... wait for it... NEW. That means that no previous builder has had the chance to overtorque them. The factory spec is 28 and that needs to be observed. As the motor warms it expands and stretches the high quality bolts Overtorque them and they get stretched to the point of Yield where they lose elasticity.

No risk here as these bolts were only torqued by Mazda. And me... to 28. 

Another added hardware item is an oilpan brace. While it may be a stretch to believe it strengthens the block, it certainly helps reduce oilpan leakage. The oil level in the pan at rest is ABOVE the oilpan/block mating area which creates a significant challenge. Unless you are adding a new oilpan i can promise you that it was bent upon removal. Obviously you straighten it but it will remain, shall i say, somewhat different than new. The brace provides a huge help in further straightening the pan and reducing leakage risk. David Garfinkle designed the ultimate brace as he recognized the brace had to lie flat on the pan rail yet the rail has raised stiffeners so he machined out clearance. I use both Chips and IRP braces. IRP further simplified the brace by just opening the brace around the flutes. I like simple.

Not only do the primary ports, uh, suck but the primary runners require significant enlargement which can be seen in the following picture. Note i am half way into the process of opening them.

The final hardware addition to the motor is a 7/16 X 1/2 Allen plug into the rear iron to replace the throttle body coolant return tube. Who would want hot coolant anywhere near the charge air? 


Most everything else in the motor was beautiful. The rotors were ONE GRAM apart! Wow!. 4479/4480. 

                                                                     WHAT'S IN THE BOX?

The last entry on the right shows 330.1 KPH which is 205.1 mph. This was using my high flow CPR turbo manifold which plumbs the wastegate back into the 3 inch downpipe. Street friendly yet deadly.

Moving on from the ports, sideseals are next up. Patience is the key. While the difference between .002 and .005 might seem minimal the reward is significant. I was able to do all 12 sideseals at a .002 gap to the cornerseal. A .003 feeler gauge won't go.



Things will now get interesting as the rear iron is removed and feeler gauges become the tool of choice. My suspicions re the compression numbers were confirmed. The important sideseal to corner seal clearance was... sloppy. My guess is that this is almost the only procedure that can't be automated... it must be left to humans. While i don't know this, it certainly appears so as i found the following gaps:

Front Rotor .007, .007, .01 & .008, .006, .009

Rear Rotor  .007, .007, .003 & ..003, .002, .007

Sideseal gap is similar to the top ring gap on a piston motor. Piston technology has found a way to have a "gapless" top ring. We can't quite do that but .002, which i use, pretty much gets it done as will be seen in the later part of this Section.

The .01 gap and the .009 gap were on the same rotor tip and that accounts for the 105 reading. 


Besides just curiosity and confirmation, the primary reason to tear into a brand new Mazda build was to ready it for higher power output. Mazda did a wonderful job engineering the motor for 217 rear wheel horsepower. This particular motor will be tasked to doing between 400 and 450. While some might yawn at the number, as everyone on the internet is making 600, 425 is 96% more than the output for which it was designed.

While that really is a monster increase in output, it is surprising how few things do need to be swapped out. Doubling the output of a piston engine would fill a whole trash barrel with the discards.

Our swap in list is really short... 

Apex Seals need to be traded in. Combustion chamber pressure and heat relate directly to output level. Mazda properly engineered the apex seals for the stock output level and they are inappropriate for a modded 13BREW. Too brittle. The newer apex seals are more malleable and resistant to breakage. Big time. Apex seal failures have significantly dropped with the newer seals. I will be using Rotary Specialties coated seals in this motor but i also like I Seals, E & J, RX Parts and Goopy.

Just like you would be changing the rod bolts on a piston engine (think ARP) so as to cope with the heavier loads i change out the 12 bolts holding the stationary gears to the side irons. OE is Grade 5 which of course is fine for stock output but... the stationary gears really hold the entire rotating assembly together! The smallish (1.69 diameter) bearings locate the crank, the teeth index the rotors and the bolts limit crank endplay. Buh By Grade 5, hello Grade 8 torqued to 25 foot pounds.


The crank was straight to the ten thousandth and had jewel like journals. i wanted to put it under my pillow.


As you would expect all the bearing clearances were on the money and of course i checked them all. Specifics follow at the end of this section.

That's about it as to adding hard parts. i do not re-use the compression and coolant seals even though the motor hasn't been run so technically the new seals are an add.

Let's now discuss removing things from the motor... that would be cast iron, chrome and aluminum... 

The rotary is a 2 cycle motor that goes round and round. It is a 2 cycle because every time the combustion chamber (within the rotor face) says hello to the spark plug power is generated.  Another characteristic of a 2 cycle motor is that there are no valves to decrease flow. 

Importantly, the port location determines intake and exhaust timing, amount of overlap and duration. Port and runner shaping determine flow. During the 17 seasons I raced a piston engine (SCCA Nationals B-Sedan) I worked with Competition Cams and we, together, designed my billet camshafts. I am no stranger to valve timing.

Turbocharged piston engines require a significantly different camshaft than NA engines and this carries over directly to the rotary. I designed my 13 BREW ports with a degree wheel.  

Mazda uprated the ports on the 13BREW and they work well for the 217 rwhp. Of course you can add a larger turbo, crank up the boost and easily double the power without touching the ports. Unfortunately you would be pounding a square peg into a round hole. The turbo would have to work harder against the restrictive ports and therefore output much hotter charge air. 

So what you say.

The "boost" measurement is really a measurement of restriction. Boost and FLOW do not necessarily travel in a linear relationship.  As boost rises out of the compressor so does TEMPERATURE.

A Borg Warner S300 SX-E 62 at 17 psi at the compressor outputs air at 360 F. Up the boost to 25 and the number is 460 F! Less restrictive ports allow the turbo to work less at a given manifold pressure and thus decrease intake air temperature. 

Cold charge air is more dense, has more oxygen. You know your turbo'd car is much faster in October than August assuming you are in the Northern Hemisphere.

Proper ports encourage low restriction flow so the turbo doesn't work as hard and the motor gets more oxygen. 

This important dynamic is at work delivering benefits all the time, not just when your right foot is on the floor.

Lets optimise the ports.

First up are the primary ports. They are tiny, miniscule, microscopic, nanoscopic, dwarf sized and small. i could go on. They are also very poorly shaped... it is almost like Mazda wanted to choke the wonderful motor they had designed.