BEST OF 2019: The Amazing 10,000 RPM Turbo 3-Rotor 20B Mazda MX-5! Kyle Mohan’s American Ethanol/Mazdatrix Formula Drift Monster

The engines 37 psi of boost is provided by a Precision Turbo Gen 2 PT7275 turbo.  The turbo features a 72mm, 2618 forged billet compressor wheel, CNC machined to final shape.  The forged billet wheel is stronger which enables the use of thinner blades and a slimmer hub profile for better aero and flow.  The compressor wheel features an extended tip inducer which makes for faster spool from lower shaft speeds. The wheels aero is CFD optimized for good efficiency.  The wheel sits in a 4″ inlet 3″ outlet ported housing which reduces surge sensitivity.

The 75mm turbine sits in a free-flowing .96 A/R turbine housing and the whole thing spins on low friction for fast spool dual ceramic ball bearings, center section.  Unlike some turbos, the PT7275 has an air-cooled center section so you do not need to run water to it.  This is great for a competition car where you are always trying to simplify things in the engine compartment. The turbo’s maximum power rating is 1015 hp and it is designed to be exceptionally fast spooling with good transient response for its power rating.

The Precision Turbo sits on a Nameless Performance fabricated manifold which is set up for anti-lag. A custom KMR 4″ stainless exhaust pipe gets rid of the exhaust exiting the turbine. Anti-lag is critical in keeping the tiny 2-liter rotary with the big turbo on the boil at all times to give the kind of response needed for drifting a big sticky tired pro car sideways with good control.

Primary boost control is handled by the two smaller Precision PW46mm wastegates.  As a very interesting feature, a huge Precision PW66 wastegate activated by the ECU is used to help control exhaust backpressure.   Having anti-lag with a big turbo means that under certain modes of operation, you need a lot of wastegate valve and exhaust area with a rotary to control boost and backpressure.  Having the back pressure relief valve also means that you don’t need to try to fit a huge exhaust in the cramped underbody of the car.

Kyle’s engine is known to blow huge flames out of the wastegate discharge pipes which the fans love.

Kyle is using Precision Wastegate as part of the anti-lag system.  It takes pressurized air from a charge pipe and feeds it to the exhaust pre-turbine.  The ECU can add fuel while retarding spark while the throttle is closed allowing the fuel to burn in the exhaust manifold making heat to keep the turbo spinning while the throttle is closed.

A big Turbonetics Godzilla blow-off valve is also used to control surge when the throttle is closed.  The delicate balance of wastegates and blow off valves are all ECU controlled to help keep the turbo on the boil so the small but powerful engine can stay on boost.

15 comments

  1. This car really needs a Power Distribution Module (Motec, Ecumaster, Racepak).
    That organized mess of relays and fuses looks like a pain in the butt to troubleshoot

  2. Going to dig into this more later, but any issues with premix on rotor housing lubrication with ethanol? I’ve seen some anecdotal evidence from people who had housing damage on E85 that worries me.

    1. I am pretty sure that Kyle uses an alcohol specific premix oil, I think its made by redline. I had that discussion with him a couple of years ago and kinda forget the specific oil now.

  3. What kind of benefits are seen from the Wisefab kit, is it worth it for a weekend track car if the funds are there?

    1. You can lower the car a lot without messing up the geometry although its not exactly a bolt in, you need to swap to a BMW steering rack and modify the cross member for it. It is also more for drifting with a lot of steering angle.

  4. I do like the everything and the kitchen sink approach. Lag? Use anti-lag and NOS. Knock? Use ethanol and water injection.

  5. If the throttle is closed, is there any chance of the intake air being blown into the exhaust flowing back upstream into the engine?

  6. Intense build. Looking at the amount of modification,definitely wow factor and dedicated workmanship,That’s a fully fabricated racecar with high levels of craftmanship, im from New Zealand,I follow mad mike with his quad rota mx5 chassis, so all credit to those driver’s that can put high amounts of Rotary horsepower down through a short chassis. Nothing short of insane,

  7. OK, digging into this a bit more, finally.

    I don’t expect confirmation but looking at the power per boost I suspect street ported of some description, which wouldn’t be totally surprising in a “keeping all the gasses moving in the right direction” sort of way. I find it interesting that the old Mazda dry sump cover is up to the task for a 20B, though I suppose there is a version with bigger gears for more flow. When NGK surface discharge plugs get brought up, are they the standard Mazda race plugs or something different? I tried chasing that once with Champion surface gap plugs and never got anywhere useful.

    Looking at the turbo setup, the backpressure reducing wastegate is funny – does FD have noise restrictions? It just seems a weird way of dealing with that. I also wonder if a lot of the hardline going to turbo components is going to eventually have fatigue issues, as it looks like it’s connecting between the chassis and engine. It seems like there’s various capped off bungs and stuff… between that and the variety of stuff going on (antilag, nitrous, water injection) it seems like there’s some extent of trying to have multiple options going on to home in on what’s “best” perhaps; will be interesting to see if the RX-8 retains all of them.

    This sounds kinda weird but I feel like the rest is kind of “cut and dried”, though I do wonder how much Megan Racing is in those custom valved Megan Racing shocks if you get my drift. I also kind of feel like someone should do a decent LSD for the Winters QC, though I suspect that everyone’s engineers have gotten used to setting up around the spools.

    1. There are a few different LSDs. I use an Indy Competition Products plated unit and I think both ATS and OS Giken made some.

  8. Pretty awesome car. Definitely cool to see engines other than LS and 2J. Its also really nice to see people finally using fresh air in something other than rally and (more recently) circuit racing.

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