Project FD RX-7 Restomod: Part 1 – Introduction

The 3rd generation (FD) Mazda RX-7 is one of the best driver’s cars to ever come out of Japan.  Unfortunately, its turbocharged rotary engine has a bad reputation for being unreliable, and it’s pretty common to see them swapped out for V8s.  The rotary is just too awesome to give up on, and it’s not difficult to make a lot of power out of them.  However, most modified RX-7s do not have the fundamentals in place to keep them cool and prevent them from blowing up.  This project will show you how to make a rotary reliable and highly capable with the right approach, proper engineering, and modern technology.

MotoIQ Project Restomod FD RX7

There’s something quite special about the “FD3S” RX-7.  Its lightweight engine and chassis give it a 50/50 weight distribution, it has a double-wishbone suspension front and rear, and its driving dynamics could be considered a benchmark for any sports car of any generation.  The “FD” is a true “driver’s car” in every sense.  Think of it as a 7% larger Miata that’s stiffer (being a coupe) and has over twice the power and torque.

Billy Johnson Tod Kaneko Datsun 510 13B Turbo RotaryI’ve always been a fan of rotaries and thought the FD RX-7 is one of the best looking JDM cars from the 90’s.  When I was approached with the opportunity to consult on the build of a FD RX-7 to a modernized OEM+ level, I was excited to be part of it since I actually got my start racing cars in time attack competitions driving a 1972 Datsun 510 powered by a turbocharged 13B rotary engine.

Billy Johnson Racing Driver Development DriverMy background racing cars professionally and as a development driver for programs such as the LeMans-winning Ford GT race car, the Ford GT road car, Shelby GT350 and GT500 Mustangs, among many others; I have a lot of OEM and motorsports contacts and suppliers that can help solve the inherent issues of the rotary engine, and to advance the RX-7 platform.  Since I grew up around people who built and raced rotary engines for decades, I have a lot of expertise to lean on.

We will dive into the details in future articles, but the biggest challenge of the rotary engine is keeping it cool, which has been poorly addressed by most products on the market.  We will show how to properly cool these engines and develop some products along the way.

Mazda RX7 FD 13B DrivetrainThe RX-7 uses one of the most unique internal combustion engines ever used in a car, the 1.3L turbocharged “13B-REW” rotary engine, designed by German Felix Wankel in 1929.  This engine delivers insanely smooth thrust in a very power-dense package.  This engine works essentially like a 2-stroke and has very few moving parts; with no pistons, connecting rods, valves, valve springs, or camshafts.  The main rotating components are the rotor and the eccentric shaft (crank shaft).

13B Rotary Engine WankelIn fact, the rotors themselves spin at 1/3 the speed of the eccentric shaft.  So, when the rotary is spinning to its 8,000rpm redline; the rotors are actually only spinning at 2,667rpm.  In other words, for the rotor to make a complete revolution, the crank makes 3 full revolutions (or 1080*).  Each rotor has a displacement of 650cc’s, so the two rotors together total 1,300cc or 1.3L.

A normal 4-stroke internal combustion engine has a power stroke every 720* of crankshaft rotation (2 full turns) per piston, while a 2-stroke has a power stroke every 360*.  The rotary is considered a 2-stroke because it has a power stroke every full revolution of the crankshaft (per rotor face), and since it does not have valves or camshafts with the intake and exhaust port shape determining the engine’s timing.  This makes its 1.3L of displacement more comparable to a 2.6L four-cylinder engine.

23 comments

  1. As a fellow rotor head and FD owner, i am very excited for this build. I am currently working on improving my car so that it can better perform at the track and give that OEM + feeling while driving it on the street.

    i also work at Ford and had the pleasure of working on both the Voodoo and GT500 engines. I’m excited to see what this FD can do with Billy behind the wheel.

    1. Way cool! We sort have somewhat worked together on those awesome products! Stay tuned to see the path I am choosing to make this car more reliable faster, and more refined!

    1. Great to hear! Yes, and we will cover all of the things that happened to the car before that video was shot 🙂

  2. Be interested to see your take on things; the car looks like a decent starting point and there’s a lot of really interesting options for drivable, reliable power on these cars nowadays. Not that I’m a Mazda fanboy or anything (OK, I am) but it’s really nice to see an OEM do stuff where so many of the fundamentals are basically right.

    1. It really is a great starting point. Miatas are such good sports cars and the RX-7 takes that to another level in terms of chassis stiffness, power, and torque. Mazda has always been sports-car and driver-focused and the FD RX-7 IMO is one of the best cars they ever made. This is going to be a lot of fun working with this car.

  3. “Series 8 (produced from 1998 to 2002) was the final series, and was only available in the Japanese market. More efficient turbochargers were available on certain models, while improved intercooling and radiator cooling was made possible by a redesigned front fascia with larger openings.”

    Is it possible to get parts from these last models? Seeing how this is a ‘restomod.’

  4. I had and FD for a little over 5 years and the last couple years of ownership I tracked it almost once a month. I loved that car, it was reliable, made decent power and handled really well. I’m actually more paranoid about my current stock engine S2000 blowing than I was about my FD lol. If I had the money, space (and wife’s approval) for a dedicated track car it would 100% be an FD.

    1. Those are both great cars. I’m actually going to do a track comparison of the S2K vs the FD. Stick around!

  5. Love the way you lay things out in your write ups. Very analytical without being too wordy.
    We’ve had a few theories on heat management as well as practical results on these motors after applying both Deep Cryo and WPC to race rotaries . We believe that thermal dispersants and thermal barriers should be tested and applied on internal components in key locations. Of course along with DCT and WPC as major contributors to longevity and performance gains. 😇

    1. Thank you, that’s what I strive for in my articles. What components have you had success with cryo, WPC treating, and coating?

      1. All internals really for the WPC and Cryogenics. The rotors and select areas in the motor for the coatings. We can discuss in person if you like…. Hit up Martin to Mike for our contact info.

  6. Love the FD….. I ended up with Project S2000 because I needed a reliable daily driver. You’ll have to drive it after it’s boosted. I FINALLY have a timeline for dropping it off to get the fab work done. I was talking with my coworker Billy J today and it sounds like he’s got his S2k lined up for the track comparison with you. Gonna be fun to watch!

  7. That radio was pretty decent back in the day. Time alignment, 3-way crossover and the ability to control multiple (!) disc changers. Ok, so maybe the last feature isn’t that great. But it will probably bring a couple hundred bucks on eBay or DIYMobileAudio

    1. Thanks! I’ll look into that when the head unit is replaced. The far bigger issue is what was done to the speakers.

  8. I loved my 93, and I’m anxious to follow your build, as I did with Dave Coleman’s articles in “Sport Compact Car” to guide me through my mods. As you mentioned, I took care of overheating at the track with all front “mouth” air being fully ducted to the upgraded intercooler, and the intake air taken in from a separate side opening. I do feel it’s confusing to liken this engine to a 2 stroke, given the fact that it is a 4 stroke engine that lacks the 2-stroke porting that interrupts the cycles near BDC.

Leave a Reply

Your email address will not be published. Required fields are marked *

*
*