Why do I want to put a rotary in my NA Miata?

This was the case before our kits came on the market. And yeah, if there was money to be made there would be a rotary kit as well.

Dave Estey speaks trOOf. You better beat it like it owes you money.

I went through some recent soul searching, thinking I might swap my 13B out for a SHO V6 or a Lexus V8, and I kept coming back to the original reasons I went doritos in the first place, to wit: a rotary is NOT the same experience as a V8. It reminds me of the old days of piston port 125 two strokes; you gotta be on your toes all the time. Some like it, some don't. I like them because they rev so fast and in a light car are downright frightening compared to the same thing powered by a heavy V8.

I also like being the outlier, the 1%, whatever you want to call it. V8 Miatas are common, relatively speaking.

I'd also go a different way if the same question was posed concerning a 2nd gen RX7. That's a larger heavier car, too heavy for a rotary in my humble opinion, and gains much from a V8 swap.

z31maniac wrote: So why do I want to do this?

Why do I want a K24 /K20 hybrid in a Miata? Or F22C1?

Rotary + Miata sounds like fun.

Curmudgeon wrote: I'd also go a different way if the same question was posed concerning a 2nd gen RX7. That's a larger heavier car, too heavy for a rotary in my humble opinion, and gains much from a V8 swap.

This is why I'm pulling 400+ pounds out of my 2nd gen.

Keith Tanner wrote: It's telling that there are a number of people who are serial V8 converters, but nobody ever seems to do a second rotary.

Very true.

I'm also not at the level that I can justify $15k or so to put a V8 in a Miata that is 95% a track car.

Ironically, the Targa Miata was a turbo Miata originally taken off the road to have a rotary installed. The car got stripped down and I think there was some welding done to the front subframe, but the conversion never happened. I put it back together as a high compression naturally aspirated four-cylinder, and now it's got a V8. So someone's tried just about everything on that poor chassis.

Do you remember why you initially decided against it?

If I had fab skills like yours, I'd put any damn motor in there I want. But since I'm a remove/install kind of guy, I have to go with what's simple. (Plus I don't like to spend that much time tinkering).

So I'll likely still go the route of high-comp, +2mm BP4W with big cams, standalone and headwork. That level of power with some more spring rate would easily get the car to time I want to be at my local track.

But this crazy idea stuff is fun!

I wasn't planning on the rotary, that was the previous owner. I took over the car after the rotary conversion failed to happen and he was ready to take his 200,000 mile shell to the metal recyclers. I think he'd lost access to the garage he was using.

z31maniac wrote: Do you remember why you initially decided against it? If I had fab skills like yours, I'd put any damn motor in there I want. But since I'm a remove/install kind of guy, I have to go with what's simple. (Plus I don't like to spend that much time tinkering). So I'll likely still go the route of high-comp, +2mm BP4W with big cams, standalone and headwork. That level of power with some more spring rate would easily get the car to time I want to be at my local track. But this crazy idea stuff is fun!

The BP-Z3 (I think that's the designation, the 01+ motor with VVT) is the current favorite for the NA track-rat segment. Modern aftermarket ECUs are able to control the VVT without issue and it really does make a big difference. OTS aftermarket cams for this motor are out there, but perhaps not as common as the non-VVT motors.

949 Racing's Crusher is one of these, and Keith has crew-chief'd that happy car.

EDIT: also, the lore I always heard was that the location of the eccentric shaft was the major headache for the rotary swap - something about the fact that the "crank" is in the center of a rotary motor as opposed to the bottom of a piston one, and things simply not lining up. But what do I know, I went with a BP engine for my swap :)

Kenny_McCormic wrote: In reply to crankwalk: Pics? I have a strange attraction to bastardized 911s.

Garrett Syclone liquid to air IC did great in hot weather. It would have ficked major @ss in a Miata

Don't let anyone tell you that Crusher's engine is "just a few off-the-shelf parts". That car was built with a pretty high attention to detail.

I spoke to a number of rotary Miata owners when writing the latest book. They noted their biggest challenges as being cooling and noise control - even the naturally aspirated ones were hard to keep cool. And the only one that gave me weights acknowledged that his turbo rotary Miata weighed about the same as a V8. Although it's a lot harder to find a V8 with a 9000 rpm redline. And yes, the lower engine position does cause some headaches.

peter wrote:

z31maniac wrote: Do you remember why you initially decided against it? If I had fab skills like yours, I'd put any damn motor in there I want. But since I'm a remove/install kind of guy, I have to go with what's simple. (Plus I don't like to spend that much time tinkering). So I'll likely still go the route of high-comp, +2mm BP4W with big cams, standalone and headwork. That level of power with some more spring rate would easily get the car to time I want to be at my local track. But this crazy idea stuff is fun!

The BP-Z3 (I think that's the designation, the 01+ motor with VVT) is the current favorite for the NA track-rat segment. Modern aftermarket ECUs are able to control the VVT without issue and it really does make a big difference. OTS aftermarket cams for this motor are out there, but perhaps not as common as the non-VVT motors. 949 Racing's Crusher is one of these, and Keith has crew-chief'd that happy car. EDIT: also, the lore I always heard was that the location of the eccentric shaft was the major headache for the rotary swap - something about the fact that the "crank" is in the center of a rotary motor as opposed to the bottom of a piston one, and things simply not lining up. But what do I know, I went with a BP engine for my swap :)

VVT engine is the favorite for midrange grunt from advancing the cam, BUT apparently there is nasty harmonic around 7400rpm and there is a very poor cam selection.

The 99-00 head with springs/solid lifters is good to 8500. I'd like to have a safe shift point around 7500-7600 with plenty of over-rev protection if you miss a gear, or get caught between gears on track.

Keith Tanner wrote: Don't let anyone tell you that Crusher's engine is "just a few off-the-shelf parts". That car was built with a pretty high attention to detail.

I keep confusing the two 949 orange cars with the VVT swaps: Crusher is the NB, and ??? is the 95? Engine bays look confusingly similar. My mistake. The 95 with "just a few off-the-shelf parts" puts down some nice numbers.

The '95 also has a JDM VVT engine, so .5 more compression and a squaretop intake manifold.

Before I swap I plan to exocet. Or so is my thought process currently. Although I believe my friend went from 1.6 to 1.8 NB1 motor pretty budget price wise

If I were going to build a Sevenesque car, a 1.8 Miata motor would be way up there on the powerplant short list along with a NA 13B.

And, Keith: tell the guys who are having trouble keeping rotaries quiet and cool that it ain't that hard. Mazda was able to do it with the rotaries, maybe copy them a bit? It's a wise man who lets others do the hard engineering work for them.

Just checked with my buddy his 146whp NB1 swap cost him 1500 bucks

Curmudgeon wrote: And, Keith: tell the guys who are having trouble keeping rotaries quiet and cool that it ain't that hard. Mazda was able to do it with the rotaries, maybe copy them a bit? It's a wise man who lets others do the hard engineering work for them.

Hey, I'm just reporting what actual guys who have done it (as opposed to internet imaginers) said when I asked "what was the hardest part?". It wasn't an answer I expected.

If you want someone else to do the hard engineering work for you, then I can ship you ever single nut, bolt and ziptie you need to do an LS3 conversion

In reply to crankwalk:

I own that car now, it is in Wi.

Keith Tanner wrote:

Curmudgeon wrote: And, Keith: tell the guys who are having trouble keeping rotaries quiet and cool that it ain't that hard. Mazda was able to do it with the rotaries, maybe copy them a bit? It's a wise man who lets others do the hard engineering work for them.

Hey, I'm just reporting what actual guys who have done it (as opposed to internet imaginers) said when I asked "what was the hardest part?". It wasn't an answer I expected. If you want someone else to do the hard engineering work for you, then I can ship you ever single nut, bolt and ziptie you need to do an LS3 conversion

I'm not a religious man, but having driven the Flyin' Miata V8 NC, Atomic Betty, I must admit that car is heavenly. Any other engine swap is duuuuumb.

Except maybe a flathead Ford. Or an MGB engine. Or Iron Duke. Or any '80s diesel engine. Because LeMons C Class.

viking wrote: In reply to crankwalk: I own that car now, it is in Wi.

Excellent! It was a fun car in the time I owned it.

In reply to crankwalk: It still is, it is my favorite ride. Would like to find another built TII motor for it for backup.

Jaynen wrote: Just checked with my buddy his 146whp NB1 swap cost him 1500 bucks

Good for him, that's a typically unrealistic price. Any of the reputable salvage yards want nearly that much JUST for the motor.

Add in an RB header/test pipe (already have the midpipe and muffler), a standalone ECU (the stock 1.6 ECU is not going to come close to that level of power on a swap engine), aftermarket intake and some tuning time............and you have blown well past that number.

I hate when people pick an extreme outlier and the act as though it's typical.

I'm a huge Mazda rotary fan and I'd consider dropping a rotary in most any small, light car. But I have no interest in NA. Turbocharging turns the purring kitten into a snarling beast.