I"m doing my first rebuild of a JDM S5 13B. I've got the engine apart and am deciding what to do about some of the parts. The front and rear gear bearings are shot. Is it better to have new bearings pressed in or replace them with good used parts? I ask because I remember reading that some builders don't like replacing the rotor bearings because they will not hold as long as the oem pressed bearings. Is the same true of gear bearings?



Front gear

http://sphotos.ak.fbcdn.net/hphotos-..._7803560_n.jpg



Rear gear

http://sphotos.ak.fbcdn.net/hphotos-...1_333458_n.jpg

i personaly wouls replace the front and rear gears with rx8 gears, there hardend and race clearanced from the factory with multi window bearings. and there half the cost of aftermakarket gears or even thirdgen gears. plus there set screwed into place wich is nice. another little trick that i have been doing latly is to dry ice the bearings and heat the gears and rotors to 300deg f. and coating the outside of the bearings with green locktite. use a heat gun , not an open flame though. since i started using this process i have had zero bearing failure.

Won't I need an RX8 E-shaft? Do you have any links where I can read more about swapping gears?



Also I noticed near mirror image wear pattern on my stationary gears. The front wear including all discoloration not just copper showing ranges between 10 and 3 oclock position. While the rear wear is between 6 and 10 oclock. Could this be from overtightening belts? or simply normal wear patterns?

i have run both the REW and the 13b and 13bt eshafts with the 13bMSP gears. have not had an issue. the only thing you need to watch for is the rear gear and some of the front gears from the MSP because the oil holes do not line up. easy fix is to elongate the gear hole so the oil passage lines up. easly can be done with a dremmal or a die grinder and a carbide 1/8" bur tool. also the rear gear of the MSP does not allow for and O ring seal so a small amount of grey sealent is needed.



as far as the ware pattern of the bearings, that seems pretty common, yes it could be because of belt tention but its also caused by deflection from the rpm and combustion.

I had a very reputable engine builder advise against using the RX8 gears. I'm told the FD were/are the best to use.

lets see here , one 13bre with an rx8 e shaft and gears making 500 plus hp no issues what so ever with bearing ware or any other issues, 4 E Production 6 port road race 13bs all running near 10000 rpm with rx8 gears one with an rx8 shaft with no problems. 2 fds running the rx8 gears again with no problems.



i think ill stick with what i said and use the rx8 gears

I'll read up on FD gears, but in an effort to reduce any chance of user errors I'm wanting to keep my first rebuild as OEM as possible. If I'm sure reliability comes first I'll consider some modifications but my goal isn't to create a frankenwankel. That being said, I do appreciate the feedback and advice and I'll research and consider all advice tossed my way.

fd gears and rx8 gears are both hardend , both have multi window bearings with set screws, the rx8 gears are clearanced for race aplications also from the factory. yes you need to mod the rear gear oil passage wich anyone can do in 5 minutes.



i choose to use the rx8 gears because of avalibuilty and cost. the fd gears where on back order for a long time and cost almost 3 times what the rx8 gears do at my dealer price. i stick to my guns and use all rx8 internals minus the rotors as the weight is less on the e shaft and the gears are clearanced better and they are more readly avalible at a less cost then the fd stuff.

I believe I have read that the Renesis has more clearance than older engines, and that either the crank or bearing has even more clearance on the rear half of the bearing then the front half. All good stuff. The crank tends to flex into an "S" shape at high revs and this produces extra wear on the outer ends of front and rear bearings. Engines run at high boost then produce wear that bends the crank away from the spark plug side of the engine. Not unusual and reduced in the Renesis bearings. Higher oil pressure and windowed bearing shells help as well.



I think the Renesis rear bearing comes in 4 sizes, and the biggest would be used in hard street use or racing.



Very few of the holes that connect the stationary gear oil hole and the one foot long drilled hole in the rear iron will line up perfectly. Use a small ball stone to enlarge the stationary gear hole to the extent that none of its edges appear in the line with the hole in the iron. The hole in the gear is plenty big enough at 100+ PSI oil pressure. The gear is hard all over and drilling it is nearly impossible. The alignment tab is still there so the reason for the set screw through the bearing has escaped me. If you loose oil pressure and weld the bearing to the crank, that set screw will be in the pan with a bunch of other swarf.



The gray stuff on the bearing is only about .0005" thick and in the old days we just scraped off the rear half of the bearing with a knife blade. Some builders press in a new rotor bearing and bore out the gray stuff a bit of the copper to get extra bearing clearance. The copper is a fine bearing material. So, when you wear through the gray stuff it looks real bad, but is of little matter performance wise.



I would use the Renesis gears, just from the cost stand-point. All of the gears have been hardened for years so not a factor.



Lynn E. Hanover

thank you lynn. this is what i was trying to say but i can never relay my point across as well as yourself.

Well how nice of you to say..........



I should have added that real racing bearings used to be made of a seamless steel tube. No longer the case. The bearing is just a strip of sheet stock rolled into a tube with a puzzel lock feature crimped together. The area of the puzzel lock is not allways smooth, so they grind down the ID in this area a bit, so it does not touch the crank. As you would imagine, this forms a bit of a path for high pressure oil to escape in both directions, reducing oil pressure and adding to the already excess oil foaming problem.



The tube may not be round while in the box. It becomes truly round only when pressed into the bore of the gear. So it is important that the pressing operation go along perfectly. In my case I chamfer the start edge of the bore just slightly to be sure no material will be scraped off the OD of the bearing and end up trapped between the bearing and the bore wall.



I was making grooved gears and windowed bearings before Mazda. Probably most builders were as well. A builder (whos name escapes me) was loosing front rotor bearings. So he rigged up a rotating seal to fit over the crank nose. Drilled through the seal plug and the bolt to get an oil pressure reading at the crank shaft center. OOPS. 13 PSI, at full blast on the dyno. Now at the time most folks were running an extra oil line to the front stationary gear, and jacking up the oil pressure to 85 or 90 PSI. And that seemed to work out. But this guy knew why the failures were happening. Trying to force oil into the end of a fast moving tube against the centrifugal load was just not as easy as it should have been. That and the oil squirting holes for rotor cooling make this a difficult problem. There is no resistance at all to oil flowing out of the squirter holes, but considerable resistance to flow to the front rotor bearing. Once the oil column length to the rotor bearing exceeds the length of the column going into the crank, you start to gain a bit of pressure, but it isn't much. So we put scoops in the crank leading to the oil gallery in. And wiping trays out of the gallerys leaving the crank. VW is a big believer in this, so I do it as well.



I also use a 180 Weber main jet in the squirter hole bottoms, and 100 PSI oil pressure. I do not know if Mazda reduced the squirter hole diameter when they went to 110 PSI or not. But that put more oil through the front rotor bearing, and the waste oil from the bearing cools the rotor as well as oil that is just squirted in and does nothing for the bearing. Remember cooler oil means lower charge temperature and that means more charge entering the chamber on each cycle and that means more power, and less chance of detonation.



Lynn E. Hanover



The taller idiot is me.

the oil jets in the rx8 e shaft have been changed , same oiling set up on 2 motors, REW oil presure regulators rx8 gears both 6 port E Production engines both have the crank plug in the front of the motor. one engine uses the RX8 MSP e-shaft the other an s5 eshaft. the s5 motor with 20w50 oil cold presure is 120 hot 100psi the rx8 eshaft motor same oil cold is 125 and hot 115 psi.



now granted there could be a diferance in the gauges but that is a large number on almost identical engines with differnt eshafts.



anyways Lynn I always like the way you word things so people can understand. great to have a fella like yourself in the rota comunity.



randy

the FD and RX8 high power (and cosmo) all use the same bearing. the low power rx8 uses the 74-91 parts...

I appreciate all the useful info

this is an incorrect statement. the last 3 13bRE cosmos i tore down and they are the only 3 i have build all used a single hole none set screw bearing. and the RX8MSP bearings are not the same as the 13bREW rear gear. the sizes are differnt between the REW and MSP as far as clearance goes and part numbers.