RotaryEvolution

iTrader: (30)

perhaps he put them in but i would be surprised if the engine lasted more than a few months. the renesis side seals are already the weak point in the engine and nearly twice as thick as the FC/FD generation side seals, an exception could probably be made with the earlier REPU/cosmo/RX4 13B rotors with the thicker side seals, but those aren't RX7 rotors.

fidelity101

iTrader: (11)

So let me get this straight...

you need to mill the rx8 rotors to to FC/FD apex seals to run in an FC engine, why?
Since the renesis is a non peripheral exhaust like the rx7? or is it because of intake port timing? Would this still be necessary to perform to the rotors if it was a full peripheral engine?

I understand that that the apex seals are shallower and that there is an extra oil control ring and that the side seals are moved more towards the outer edge of the rotor face so this whole modify the rotors doesn't make much sense to me. I understand not being able to run FC/FD rotors in an rx8 engine because of the port shape/timing.

Also I don't see why the front cover wouldn't swap over to a renesis. you can use renesis front cover gasket on FC engine (also covers the water pump housing) and the oil pan bolts are in the same location and size where the front cover would bolt to the pan and front iron.

Now in regards to a direct swap using a complete renesis powerplant in an FC would be tricky since it is CANBUS even just swapping over the complete harness/ECU etc and giving it power/ground may be iffy. Then you still have custom engine and trans mounts or utilize a FC trans just worry about engine mounts.

also front pulley and hardware has not changed since the 70s.

Monkman33

iTrader: (28)

Perhaps the rx8 apex seals are too shallow to safely bridge a large peripheral exhaust or intake port.

j9fd3s

iTrader: (3)

the Rx8 uses shorter apex seals than the previous engines. if you buy a new apex seal for an FC, its something like 11mm tall (2mm wide and 80mm long). the Rx8 seal is like 7mm tall (2mm wide, and 80mm long). basically they did this because iron seals are heavy, so this is a quick way to make it lighter, and since it doesn't need to go over a port opening, there is no issue.

however if you use an Rx8 seal in a peripheral exhaust engine, it can sag in to the port.

so the shorter apex seal is one change, they also moved the side seal out closer to the edge, which allows a larger port.

the 3rd modification is the cutoff seal, they found that with a side intake and side exhaust there is a space where exhaust can flow from the exhaust port to the intake port in the space between the side seal and the rotor oil seal. so they add a cutoff seal, as it just cuts off this passage.

this is all covered in the Rx8 SAE papers

the bolt pattern is the same, and all the important stuff works, at least FC engine to S1 Rx8, the only problem MIGHT be that the Rx8 irons are thicker, so the front cover is slightly shallower. the S2 Rx8 has a completely redesigned oiling system, and nothing swaps over

the canbus is there, but it isn't some omnipotent thing, so it might not be that big of a deal.

RotaryEvolution

iTrader: (30)

i think the RX8 seal discussion is being a little over thought through, an RX8 apex seal should work fine on a peripheral exhaust port engine.

why? because the OEM 3 piece seals did it. but i wouldn't trust them on a turbo engine, nut not so much due to the shallow seal but for the compression is simply too high to make any real power with.

it was adopted that it would NOT work because one shop mentioned build specs which included milling the rotors, but i don't see why they wouldn't work if you dropped a complete stock RX8 rotor and all hardware into an early engine. the real question is why do people think it is superior? more power? likely not, but that is for someone to prove right or wrong.

j9fd3s

iTrader: (3)

i know the JDM shops run GSL-SE rotor housings on renesis engines, with no mention of milling anything, or using different apex seals, so possibly you are correct.

i think its been proven the Rx8 rotor makes less power than the 9.7s? it certainly doesn't make more power. it may be a case where the chamber shape is more important than higher compression ratio.

fidelity101

iTrader: (11)

I finally stumbled upon some renesis SAE papers and gave them a read.

Personally I don't think that the rx8 apex seal would work fine on a peripheral exhaust port engine because they shortened the seal due not needing to go over a peripheral port based on the new side port design. Sure it WOULD work but for how long is the question, since the apex seals were engineered to be utilized differently.

running rx8 rotors would be superior because of a few things:
.25lbs lighter each
10:1 compression
side seals moved to the outside edge allows for greater port opening with a streetport/side ported engine.

I wouldn't say just dropping the rotating assembly would make vast improvement over s5 NA rotating assembly (power wise I think it would be tiny if any) but with the right streetport you can open that sucker up a lot more due to the seal tracking in the rx8 compared to the rx7 rotor setup.

I haven't really looked up much on the S2 stuff and its hard to get your hands on any of that but 04-08 renesis stuff keeps popping up! lol.

Also regarding canbus, it looks racing racingbeat will flash your PCM for 300 dollars so you can use it in a custom environment such as an FC or sand rail and etc. So its not a big deal, now I just need to find a wrecked rx8 or buy an rx8 and give it some coilovers that give it suspension travel.