As the old saying goes, just because you can doesn’t mean you should. While putting a rotary engine into a Mazda mini truck sounds like a good idea, in practice it really isn’t and here are some reasons why.
One: Lack of torque and a peaky powerband
Rotary engines aren’t known for their abundance of torque, and a lot of the things trucks do require a good amount of torque to accomplish. Also, rotaries make most of their power high in the RPM range, trying to tow a trailer with stuff on/in it with a rotary would be a pain in the buttocks.
Two: Lack of reliability
Cue the rotary fanboys that say that rotary engines are just as reliable as piston engines, but the last time I checked, I don’t know of any rotary powered vehicles with over 100,000 miles on the original engine. Even if they CAN last as long as their piston engine counterparts, they require a lot more maintenance (and oil) to do so. Piston engines are more reliable most of the time, and reliability is one quality that makes most trucks so great.
Three: Rotary engines are gas and oil guzzlers for their engine size
Rotary engines often inject engine oil directly into the combustion chamber and that results in some of it burning up during a combustion cycle. A 2015 GLA 45 AMG which is a Mercedes crossover with a turbocharged 2 liter 4 cylinder piston engine gets 23 MPG city and 29 MPG highway, while a 2011 RX-8 with a naturally aspirated 1.3 liter 2 rotor engine gets 16 MPG city and 22 MPG highway. That, and the Mercedes is heavier than the Mazda as well, so it’s a lose-lose situation here with the Mazda.
Why am I complaining about fuel efficiency in a truck? Because the Mazda REPU is a mini truck, and those things can get great fuel economy, but they do so with a piston engine, not a rotary engine.
Four: The Mazda REPU fails at being a good truck and fails at being a good sports car
The Mazda REPU is in an awkward middle ground performance wise. It isn’t a great truck because it has a low torque, low reliability motor and it isn’t a good sports car because a truck isn’t the best vehicle for putting down great autocross times. It looks like the Mazda REPU might have spread itself too thin here.
Five: Mazda could have just made the “Mazdarati”.
This reason isn’t based of facts and statistics, it’s based on my opinion. I think the Mazdarati, a Mazda REPU truck with a 455 Oldsmobile V8 and a Toronado transaxle in the bed is amazing. It perfectly suits the style of Roadkill and with some relatively cheap mods, it can go 11.30 at 124 MPH in the quarter mile (but ended up spraying oil all over the pickup bed in the process, because Roadkill).