lax-rotor

iTrader: (1)

Did a search on this and think i've found what i need to know but i'd like to just a confermation on my thought process. I am considering either running a rx8 rotors in a 13b n/a with a mild turbo installed (6 port n/a rather than the 4 port tII) running mild boost (maybe a pound or less) and either a street port or half bridge port or a 20B. I Read that i'd need to mill out the apex's of the rotors to accept either the 2mm or 3mm apex seals and get the motor rebalanced to accept the lighter rotors. is there anything else i should do/ or need to know to use those rotors? This is where i'm thinking of getting a majority of the power i want (thinking i want to make around 270-330 whp) for this car (fc-s4).

wpg_gtr

im not a rotary expert by any means. but on a conventional engine with compression like that (i think RX8 rotors are 10:1), a turbo set to 1psi will only act as a restriction on your engine getting air.

the compressor wont spin fast enough to provide even the ambient air that the engine would consume without boost. the engine will be sucking more than the turbo will be blowing.

lax-rotor

iTrader: (1)

sorry it was late last night.... ambient air pressure is 10 psi at sea level, i don't plan on running more than 16psi, until i get some one to tune it right for me. basically i don't want to blow the engine. (thanks for the look out)

SLOASFK

iTrader: (5)

16PSI is pretty high boost.

And a 20B is a completely different engine...

I understand it was late last night, but I can't understand why you listed 20B with the ports..

C. Ludwig

iTrader: (27)

Ambient pressure is 14.5psi absolute at sea level or 0psi gauge. If you plan to run 16psi gauge (ambient + 16psi positive boost pressure) on 8 rotor you have a long row to hoe. If you plan to run 16psi absolute (1.5psi gauge) wpg_gtr answered your question. It's a complete waste of time. You'll make more power with a proper NA than you would with a turbo for a cork in the exhaust stream that is only providing 1.5psi positive manifold pressure.

lax-rotor

iTrader: (1)

GAHHHHH! i feeling like a complete idiot. basically what i'm meaning to say is that i don't plan on running an extrodinary amount of boost (keeping it so it only gives me maybe 30-40hp gain). What i'm realy curious about though is if the rx8 rotors will work with just the milling or if there is anything else i would need to do to make them work.

wpg_gtr

if you really dont want to blow your engine, dont run ANY boost until you get someone to tune it for you.

blowing more air into any engine, and not accompanying it with more fuel, is the recipe for Lean conditions. lean = boom

but back to the topic of boosting the 20B. if you look at information posted by someone who works for a shop in Hawaii (FC3SPro i think) i forget the screenname of the person... he said they dyno'd a stock turbo 20B at 240whp.

he said that when they removed the turbo system, and ran it NA, it dyno'd 232whp.

i dont know if it has been discussed here, but the 20B's turbo system must be very redundant. i would say that it is supplying only a tad more air than the engine would naturally consume. (but i havent spent alot of time with 20B's so i cant say anything forsure)

if you want to make power reliably, i would say use the FC-S5 NA rotors (9.7:1 i think), and a custom induction system (maybe some aftermarket throttlebodies, and a custom airbox). also you will need the engine appropriately ported.

wpg_gtr

thats something im trying to figure out too, im curious if its possible to build an NA 20B with 10:1 compression.

if it is possible, and realistic, i might be interested in building one when im bored of my GTR.

lax-rotor

iTrader: (1)

I was weighing the possibility of using the 20B vs. the modded out 13B. If those numbers are accurate I'm thinking it's pretty close for me to make the same amount of HP while keeping weight down less than the 20B.

GtoRx7

iTrader: (5)

For the extra cost, and then cost of machining, the Rx-8 rotors are not worth it. Add to the fact almost no extra power will result, its really not worth it. Use the S5 n/a rotors and have them balanced for a all-motor 20B build, or a all-motor 13B build. Then high compression turbo is a very heated conversation, I believe in low compression turbo. Others think opposite, so do what works for you.

wpg_gtr

thats what i was starting to conclude with my research here, and elsewhere.

i think the fact that the RX8 rotors dont make much power in 13b and 20b engines, is the change in the Rotor made for the change in the exhaust ports on the RX8 (im not familiar with the change, but i understand there was one).

venturing further, is it then possible to have a Rotor custom made, to be 10:1 and intended for the 20B? or does someone already have one?

im going to scour all the rotary builders sites, and see if anyone offers something of the sort.

i would imagine the S5 rotor should suffice for the average 20B NA build, but one has to ask, how high can one go?

GtoRx7

iTrader: (5)

Nobody sells a 10:1 or higher custom rotor that I know of. However places like JHB can "build up" the material with ceramic coatings in the tub area. This can result with compression as high as 11.5:1.

lax-rotor

iTrader: (1)

what's the estimated cost for doing that and would the ceramic coatings crack/fall away during use? I imagine only a 10:1 would do for me and my purposes.

rx8 housings made a shift from the outside edge exshaust ports (as is the 13b) to the sides, like the intakes.

ericgrau

iTrader: (1)

The Renesis:

• Moved the exhaust ports to the side for better emissions. Dunno if power increased.
• Increased the compresssion ratio for more power (and 91 octane).
• Improved lubricaton, bearings and rotor balancing for a higher redline (more power).
• Uses lighter rotors and flywheel (essentially more power during acceleration).
• Uses negative split ignition timing under light cruising loads for improved fuel economy (2nd spark plug fires before 1st)
• Uses the best 64-bit ECU money can buy, for optimal engine management (power, fuel economy and/or emissions).

The 13B-REW is more heavily ported than the FC's 13B. I'll bet the Renesis is too. This improves power, worsens fuel economy and emissions. Also worsens low end power a little, but a 6 port induction system helps fight that. The RX-8 also comes with a performance exhaust & intake. You'd need to replace it with a huge, unweildly exhaust just to gain 4HP. A straight pipe with no cat or mufflers might give you 8HP.

The Renesis borrows a lot of technology from racer-modded rotaries. I'd bet a modded 13B could do anything the Renesis does, except perhaps the emissions improving side port. But I don't have experience with these things.