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Are REW's only the right answer for high HP builds?
Hey all,
I am doing tons of research to swap a 13B into my NA miata for mostly AutoX. I would maybe like to turbo eventually but probably not anytime soon since I am a menace with tuning my own turbos reliably.
Engine doesn't need to be comfortable on the street so much as it can perform on the track. I am interested in the idea of PP for non turbo power and the sounds
Other than my relentless content consumption of Dahm, I know very little about rotaries otherwise.
I think the Mazda Factory Race P-port rotor housings are only available with the coolant o-rings in the rotor housing, so you want the old 13B side housings .
4 port and nitrided
If you are having P-port rotor housings made (a little less power because exhaust sleeve area is too big/wrong shape) then 13B-REW is the best base (biggest thrust bearing, best oil pump, hardened gears, more pins in rotors).
Interesting, long term the non REW housing are good enough for sold boost as well or are these completely different build paths? Like prepping a Piston engine for ITBs all to turbo it later anyway.
For auto-x you absolutely do not want a peripheral port intake turbo.
Peripheral port (intake always open to intake and/or exhaust strokes) turbo has huge driveability issues. Torque is dependent on turbo rpm and turbo rpm doesnt relate directly to throttle position.
This is true on all port types, but exacerbated with the peripheral intake.
P-p turbo will "get on pipe" at almost any throttle input- just be delayed a bot longer at the lower throttle inputs/lower rpm while "clearing throat". Coming off throttle the power will feel "latched in" - basically full torque till the BOV vents or the throttle plates are all the way shut- not a progressive decrease.
You can do bridge port for ~250rwhp NA and turbo on top of that (better driveability when turbo as rotor sides close intake at some point).
You can do semi p-port (small axilliary p-port) which drives and makes power like bridgeport (rotor face blocks small p-port flow sometimes).
Still, turbo bridgeport or semi p-port is going to work with too big a turbo for auto-x. They just get exhaust choked with sub 500rwhp capable turbos.
Streetport turbo is what you want for a little turbo (400rwhp) and auto-x, but streetport 13B-REW will only make ~200-230rwhp when its Naturally Aspirated.
So I'll keep asking so long as you have answer but I like the idea of a steetport rew with a turbo but I am also curious about high RPM builds. are they feasable? Do you autoX? What is an ideal build for an AutoX purpose built 13b?
Yeah, I auto-xed my turbo FC RX-7 2004-2012, my FD RX-7 2008-2020, my RX-8 2014-2017.
I dont know what you consider high RPM build, but I have the revlimit on my FD 13B-REW at 9,000rpm without issue. Power drops on the sequential twins after 7,000rpm, but its nice for when you would waste time shifting.
I did an EFR 7670 on my FC for the 2014 season and loved the response/torque. Having torque drop hard at 5,000rpm actually makes it easier to hook back into traction with throttle modulation when you get wheel spin.
Im piecing together another EFR set-up now for my FD even though the turbos have doubled in price.
What I ended up building/liking for auto-x was not what I started out with. It was a journey.
I found for my turbo builds I liked small early opening, but barely later closing than stock street ports intake ports or stock porting. Paired with stock exhaust ports.
This gave me more low/midrange power and predictable torque input w/ throttle.
I also found I liked to clean-up the port runners in the housings and intake manifolds, but not port them larger volume. This gave best off load throttle response.
I think 350rwhp/rwtq will be good for 295/30-15s on your miata. No need to shoot for the moon. Focus on driveability.
9K is high to me considering a high rpm Miata BP build is lucky to make 8. lol The goal would be to stay in first or 2nd always. I did this last weekend in a 2023 Hyundai Elantra N and the course that was setup allowed me to not leave 1st. it was nice. This is all great info and something for me to ponder on. I'm wondering if starting off with an older engine no turbo to get used to the tuning and gimmicks of it all before I spend big bucks on an REW. It also looks like it hooks right into my power train with no issues. The wiring will be annoying but completely doable and the Megasquirt will have to go for something better suited for Rotary.
I do have a dual ball bearing knock off Garrett 2860R from Pulsar and it spools real nice. Not sure if I keep it or not but this is all really good info.
That video is sick. I have been wanting a rotary swap since before my last swap so I think it's time. I bought the car for an LS swap but man, too much torque in a Miata is reckless fun but you're not getting anywhere quick with it.
When talking swaps there's a bit more to it in my opinion. Do you want center mounted motor mounts, rear, or a front cover bar? Do you need space for any sort of steering linkage or subframe?
I'd be more concerned with those things in a chassis such as a Miata before I'd particularly worry about the power goals in a future iteration as essentially any rotary config can withstand more than enough chamber pressure/will have enough torsional rigidity to make a Miata very fast and the oiling mods that have been done on an REW can be relatively easily adapted to any iron.
04-03-23, 03:58 PM
Are REW's only the right answer for high HP builds?
