Afterword: Single Turbo Conversion

With the single turbo conversion complete, I figured it’d be good to shed my insights and add closure. This was easily the most rigorous and difficult project that I have personally pursued. I know you can cut corners and convert a car to single turbo fast and cheap (~sub-$6k), but this is not acceptable to me. It became extremely time-consuming and involving to wade through a job of such magnitude and scope. There were literally hundreds of different items that required individualized attention.

It was an absolute frenzy making countless trips to Vic Hubbard‘s, Dale’s Hardware, and various other stores to seek out specific parts and fasteners. In the end, I’d estimate that the cumulative total time I’ve invested in achieving the single turbo conversion equates to around 700 hours. This includes all the researching, shopping, parts-getting, and labor. Albeit I was busy accumulating the necessary inventory of parts many months in advance, I did not start the physical disassembly of the stock setup until mid-December. I finished the conversion mid-March.

Depending on your perspective, my timeframe is either slow or relatively fast. During the past 3 months, the majority of my days were very long. I had to maintain a constant rhythm of work in order to complete the project in the time that I did.

As you can imagine, I am very relieved that I can finally take a breather. The deed is done. This project has provided serious relativity to me. “Normal” life now seems oddly slow-paced and easy-going. I can also appreciate anyone who has undertaken a similar task, because this wasn’t a small feat. I had to thoroughly learn the process from scratch by pouring over diagrams, seeking assistance from others, and conducting a bountiful amount of searching. You need to have steadfast perseverance and concentrated diligence. Simply said, an unmotivated or inept individual is not the right candidate.

Now, let’s summarize the objective-oriented achievements that underpin the effort exerted. It wasn’t a small decision to tear down a 25,000 miles stock engine and convert it to single turbo. But after careful consideration and deliberation, I knew it was a necessity.

As nice as the idea of sequential turbos may be, its benefits are heavily outweighed by its complexities. The sheer number of vacuum lines and solenoids required to make the system function is insane. Debugging an issue here would have been a nightmare.

My fundamental goal with this car is to simplify and modernize. Allow me to outline the factual points that substantiate the superiority of a single turbo setup:

• Immensely reduced complexity and fail points.
  • There are now only 6-7 vacuum lines, which are ALL easily visible and accessible.
  • The multitude of solenoids has been reduced to just one.
  • Mechanical simplicity: Boost is controlled off of the wastegates’ springs, which is about as robust and reliable as you can get.
• It’s important to remember that the 3rd Generation RX-7 is now 20+ years old. This was an opportunity to bring core components out of antiquity.
  • The turbocharger is now cutting-edge technology and features all of the latest features (double ball bearing, built-in heat sink so it’s only oil cooled, aerodynamic CEA, etc.)
  • The fuel system is also modernized with high-grade Injector Dynamics injectors. Additionally, the Fuel Pulsation Dampener feature is now integrated into the Weldon Fuel Pressure Regulator. Before, the stock FPD was a major culprit of dangerously leaking fuel when old.
• The new turbo system is overbuilt and worked far below capacity.
  • 12 psi is very minimal for the turbo. It is realistically efficient up to 30 psi. For reference, the stock turbos are only suitable to about 14 psi before they turn into nuclear hair dryers.
  • The max injector duty I’ve seen so far has been around 67-69%.
• Overall increased accessibility. Everything is now so much more reachable and open. This greatly helps with maintenance, because you no longer have to tear down a million things that are in the way. I can put a wrench on every clamp on every radiator hose and intercooler coupler. Removing the UIM now takes under 10-minutes, whereas it took over 30 minutes before. The entire turbo system is now sitting in plain view – and not hidden under a layer of various intake and intercooler piping.
• Better flow, better cooling.
  • The stock system was subject to finicky boost creep. With just the addition of a midpipe, you can experience overboost issues. Now, with the dual 44mm wastegates, boost creep is a thing of the past (I’m actually experiencing the opposite of creep).
    • Greater flow and less restriction in the exhaust also aids in reducing under-hood heat.
  • A V-Mount is a superior design and package. Although the weather is still cool and I have only done preliminary testing, water temperatures average around 85*. IAT’s are usually below 40*. This is a phenomenal leap in performance over stock.
• Lighter weight. A single turbo setup is significantly reduced in weight and offers the best power to weight potential in a rotary application. I’d estimate about 40 lbs was saved from the conversion. A single turbo 13B is about the same weight as a N/A 20B.
• More power! And a far higher ceiling for power (if ever desired).

And there you have it! A stock sequential setup is great on paper, but does not translate as well in reality. Proponents of leaving a car like the RX-7 99-100% stock are living in the past, they are advocating an untapped platform. I like to approach the matter in a more pragmatic fashion.