We are happy to say we have just successfully finished and dyno tuned A 13B Bridgeported race motor running RX8 rotors, Eccentric shaft and stat gears, The motor is a rx4 style running quad throttle bodys and dry sump. The motor used to run ser 5 non turbo rotors, rx4 shaft, MFR stat gears and 3mm carbon seals all spinning in american ser5 non turbo rotor housings(they have better exhaust ports than others) and with a bit to long manifold had about 216 RWHP peak at 8500 rpm on a dyno dynamics chassis dyno.

Now with the modified rx8 rotors and crank and factory gears and not changing any configuration with the manifolds or exhaust or intake we picked up 20 RWHP peak at 8000 rpm but with a torque curve that just keeps going up until 9000 rpm when the air induction is now becoming a restriction and the hp drops about 80 hp. Its a combination of manifold length and airbox design.

We cant wait till we try this with the new air intake and ceramic seals and we have worked out how to fix the side seal clearance problem so we expect hp there. Also shortening the manifold and bringing the rev limit to 9500 will help to.

The one thing we did notice out on the track was throttle responce pick up and huge mid range torque.

We have 3 more motors to build up with different configs and theorys so we cant wait for the results.

If you want to know more just private message me and I will be happy to answer your questions.

Thanks

 

Cool...any specifics on exactly what was modified for fitment? Did you keep the blow-by ring?

 

do the stat gear just swap over? alos is the e-shaft any differnt from the rest of the 13b family? Did you deepen the apex grooves on a mill?

 

Did you leave the cut-off seals in?

 

how are the shorter seals responding to the peri-port??

 

Hi,

I will try to answer everyone questions in one reply

We dont use the blow by or cut off seals because we still use normal rotor housing which have the exhaust port, as with the renenis motor being out of the plates.

The stat gears are a straight bolt in but you need to maching a groove in the rear gear to allow for the o ring which has always been on the gear but the rx8 has it in the rear plate, so that was easy.

The shaft is like a ser6 design but has 4 holes in the rotor bearing hub, as the earlier motors have 3, I would believe its a weight thing, the front bolt on the reneisis is a 18 x 1.5 because the oil journal is bigger on the rx8 plus they have factory cross drilling on the front hub, Which i feel would be bad if you supercharged the reneisis motor as we have seen other supercharged motors with cross drilled cranks to increase oil to the crank break at the very spot,(something to keep in mind). All we did to the crank was clearance it a bit as they have good factory clearance's, we balanced it with the rotors, couterweights and flywheel . You have to run a mix of rx8 and ser6 front spacers and needle bearings and shims to get it fit but again all from mazda.

The rotors we put MFR bearings you can buy them from racing beat and we first tried to get the grooves cut down at 2mm but found that to be to hard because of the profile the groove is factory and it has a bit of a step after this, so we grooved them to 3mm to use normal style seals, we CNC electric wire cut the grooves its 100% better than milling, smoother and dead straight. we are using 3mm one piece carbon seals with twin spring on this motor, but are building another motor now with one piece 3mm ceramics twin spring, and the next with 2 piece seal ceramic, you can buy the carbons from racing beat, we do have a customer with a 13b pp running rx8 internals with rx8 apex seals and is reving the motor to 11000rpm, If you have ever driven a 13b BP race motor you will notice that there is a big power band around 8000 as if the motor got a second wind, well imagine a 13b PP race motor getting the same at higher revs about 10000 and the torque not dropping off.

We are making rx8 rotor mods to fix the huge side seal clearances now and that will go in the motor with ceramic seals, plus with the better stat gears its holds the rotors in a better postion at higher revs and not bouncing off the plates and scuffing your bearings meaning your seals have better chance of sealing.

Ive been talking to Racing beats jim tanner about our success and you should see some motors in usa like this in the future, but this year in australia we already have 3 of our customer and ourselfs racing this year with these mods

Thanks sorry about the long reply

 

Could you explain what is this side seal clearance problem you talk about?

 

Awesome info!! I love it...keep up the good work!

 

Great stuff!

Please keep us informed on how your project progresses.

By the way would it be easy to put one of these motors into an old MX-5 to use as a race car?

 

the side seal clearance is in another thread i did a while ago, someone will have to teach me how to show thread links and how to put a picture under your user name. Its basically the gap between the side seal and the corner seal we have seen up to 15 thou on some rotors, 2 to 3 thou would be ideal but we have solved this problem but dont ask as we are not telling anyone about it yet!

 

It wouldn't be hard to put one in a mx5 but who ever did the conversation would need the car to make up custom engine and gearbox mounts, I suppose you could run a ser6 gearbox as they are mounted like the mx5 boxes with a brace running to the diff.


We have done heaps of different conversations........13b turbo into ford mark 1 and 2 escorts, 12a turbos into toyota corona, Datsuns and gemini's and heaps of 20b converations but my favourite is a 13b pp race engine into a 1300 mini 2 door that was converted to rear wheel drive and every time he changed gears on the track it would wheel spin then grab traction and take off again,,,,, We nicknamed it the Rubber Band

 

wait so you have a customer running a PP motor on stock rx8 seals?

 

nope, they machined the rotors out to 3mm (1mm wider) so that they can use the old sized (the taller beam height) 2 peice seals.

 

I believe he says here that he does...

 

When posting stuff like this, there's no such thing as too long.

Hope it keeps coming!

 

Yep!

We have a customer running stock rx8 rotors with seals the 2 piece twin spring 4mm high ones on a 13B PP rx4 stle housings.

We dont have any problems running the factory seals over the PP hole and because the seals are lighter, and about as light as carbons then he has no problems reving it.

And there is an important reason why we run the old style seals in the bridge port motors mainly to do with the height of the seal, and thats because you would have to run a thicker bridge to help hold in the assitance piece of the factory seals because they are closer to the tip of the rotor, and running a thicker bridge means a small porting of the bridge especially in racing were our rules state that the bridge port cant extend past the inner water seal or as some people call it monster porting, but that doesn't make **** all HP increase and not worth the sealing requird to stop the water leaking into the motor.

 

Nice, how wide are the PP's you guys are running? 2 inch or less? There were preliminary reports here in the US about the stcok rx8 seals warping from a racing team that tried them in a streetported racing motor, there exhaust ports could have been to wide though, who knows. This is good news though, thank you very much for the information.

 

The pp are inserted into the housing and welded inside the water jacket, they are inserted from inside to out because we run a d style PP port just a bit bigger than the factory size but at around the same port timing, the port is also slightly bigger,

The rotor housing we use on the race motors are from the US from the 13B EFI motors I think they come from the GL-SLE models, they have the best exhaust ports, we bring the port timing a bit earlier and wider and then smaller as it get higher, so you get an exhaust port that comes open sooner and shut later but narrows as it does, If you can understand that.

And no a haven't heard of seals warping, I could only imagine they were running to lean a mixture and a restrictive exhaust system.