bedrock83

I went to rotary performance in california, and the gentleman there said that I could change the rotor housings, apex seals, and rotors, do a port and polish, and then if I decided to turbo it, I would be able to push more boost due to the lower compression. I was wondering if anyone can tell me would it be bad to use the 2nd gen rx7 rotors because of the lower compression? The guy at rotary performance says he's seen people do it with no problems on a FD but not on an 8.

HEVNSNT

Not so sure about the rotor housings cause previous 13B's had their coolant oring grooves on the side housings. The renesis has them on the rotor housings.

The extra weight of previous 13B rotors might reduce the rev limit and the stationary gears may not be able to handle the extra weight.

wakeech

yeah, i dont' know why he wants you to change the housings.

as for the rotors, well, you COULD just grind down the stock 10:1 rotors (would be tricky, and probably cheaper to get the old 9:1's) which would keep the rotors super light.

people are bitching about the new seals (shorter beam hieght), but they're made of a better composite material than the old Mazda seals (which a lot of sub 9.0s racers say are better than any other seal made), are of the good ol' 2 peice design, and super light (for better sealing). they're still 2mm thick, but again, stronger than the old Mazda seals.

as for turbo'ing the 6 port, i still think it's a stupid idea. if you change any of the housings, make it the side housings (to the auto stock parts) with a good porting, and slap a turbo on that 4 port mother.

bedrock83

I was afraid that by grinding down the renesis rotors they would FAIL under pressure. (like boost!) That's why I was considering changing the rotors altogether.

rotarygod

The new 4 port engines are nowhere near similar to what the old 4 ports were. The old 4 port engines had nice large outer ports that flowed wonderful amounts of air. They also had some nice sized intake runners. The new Renesis 4 port is absolutely nothing like this anymore. The outer ports are essentially the 2 lower outer ports on the 6 port housings but enlarged by only a few degrees. Almost not worth the effort. The runners are also only a little over an inch in diameter. These new 4 port engines can't flow air worth a crap compared to the old 4 port engines and they don't have anywhere near the port timing of the old 4 port engines. For all intents and purposes think of the 4 port Renesis as a 6 port Renesis that has the auxillary ports disabled. That's an awful lot less potential. With less air flowing through the engine it will take longer to spool up a turbo. Also with less intake runner area, there is far less potential to blow more air into the engine.

The 4 port engine would be a good candidate for a positive displacement supercharger. This would help build boost for daily driven vehicles without the worry of the longer lag time that the small port area would give. A turbo should spool much faster on the 6 port engine. The supercharger could be made to give a broad increase in power and not have the need for a higher redline. This engine could also accept more boost due to smaller ports. Sounds weird but the 6 port engine has more time to push more air into the engine since it has far more port and runner area. While the actual compression ratio stays the same, the amount of boost and the time there is to get it in the engine affects the effective compression ratio (not the same). More boost with a shorter port timing can be the same as less boost at a longer port timing. The total amount of air entering the engine in cfm and not the pressure it is at to do so is what counts. I would personally consider a supercharger over a turbo for the 4 port engine. However I would rather use the 6 port engine as a first choice for forced induction in general.

GTRay

It looks to me like there won't be too many problems in swapping rotating assemblies to make a motor more boost friendly. I haven't seen any oil system flow charts so i don't know if the oil passages in the eshafts are compatable - i'm assuming they will be. It looks to me as though REW rotating assemblies would work nicely in the Renesis block. the extra side seal is just there to prevent blow-by into the crank case.

someone will have to correct me here if i'm wrong but it was my understanding that mazda was using strengthened stationary gears in all of their new motors wince they developed the REW - which means they should still be able to handle moderate boost and high rpms.

picking the right size turbo for this is going to be the real kickker, and then activating the AUX ports will be another fun chore!

Ray

rotarygod

All of the stationary gears since the introduction of the 3rd gen have had harder stationary gears. This was also the time when the bearing size changed slightly as well. You will also need to proper front and rear counterweights as well.

Opening the aux ports will be simple. You can do this with the entire system if you wish. Unlike what some have said, the actuators on the Renesis are vacuum actuated. I know that there is a wiring schematic that shows power going to them but this is almost correct. There are vacuum actuators that open electrically to allow air to reach the vacuum solenoids but they are not servo controlled. Since they run off of pressure you can actually set everything to open off of boost if you wish. Since you most likely won't be at very high rpms without boost, you will probably never have the aux ports open except when under boost. You have 2 options: Open them when boost becomes positive. Even if they opened eraly it isn't a bad thing since boost will keep packing more air into the chamber regardless of rpm. The larger port timing isn't needed at low rpms without boost but under boost as long as there is positive pressure it is a good thing and beneficial. The other option is to use the factory solenoid but instead supply it's air from the turbo boost rather than an air pump. Either way will work fine.