Time To Learn About ‘The Other K-Series’ Engine: Mazda’s Mean Little 1.8-Liter V6
Many cylinders with minimal displacement makes for some interesting engineering.
Mazda’s K8 1.8-liter V6 was something special. It was the smallest of Mazda’s K-Series engines in the early to late ’90s, with an original intention of providing as much power as possible in Japan’s sub-2000cc tax bracket. Despite the potential threat of being dubbed Car Bibles’ Official Fozda Historian, it’s my duty to introduce you to this angry little engine.
Mazda’s K filled this purpose pretty well. But we all know the real reason why the creation of this engine was so intriguing: cramming as many cylinders in as small of a displacement as possible makes for fascinating engineering, plus the coolest induction and exhaust sounds.
Arriving on North American shores under the hood of the MX-3 in 1991, the K8 was Mazda’s answer to competitors’ high-revving, decent-horsepower-per-liter engines, such as those from Honda, and even GM. It produced a perky 130 horsepower and 115 pound-feet of torque, which wasn’t bad for the tiny MX-3 coupe and its 2,580-pound curb weight. This got it to 60 MPH in 8.2 seconds — not terrible. Motorweek had some really nice things to say about it back in 1992.
The K8 sort of made the MX-3, at least in my mind. It was the only car to receive this fun little engine in North America, and it was as pleasantly bizarre back then as it is now. Really? A tiny V6 in a tiny coupe? Besides this aspect, the actual engineering to make it viable for the mass market was equally as fascinating.
Good Ol’ Fashioned Forum Bench Racing
My deeper research into this little lump took me down many rabbit holes. How come it had such a short life? Why aren’t people swapping them into everything they’ll fit in? Why aren’t people putting independent throttle bodies on them as much as the bigger, 2.5-liter KL-ZE?
The numbers certainly make sense. Some genius went hard in the paint when it came to figuring out all of its details, which added up to it indeed being a decent candidate for tuning. Another enthusiast even made the swap into a Miata a reality.
According to naprotejay on forum.miata.net, the K actually has the upper-hand over Mazda’s beloved BP inline-four:
“– the cylinder head’s stock Round ports are the same size as the KL’s (so either the KL ports are small….. or the K8’s are big for its displacement….) … The K8 is 75mm bore x 69.6mm stroke with a rod length of 140mm. Rod ratio is a super high 2.01. Honda F20C by comparison is 1.82, Honda B16 is 1.74, BP is 1.56, etc
The forged crank’s main journals are 61mm, rod journals are 48mm – both larger than the BP.“
OK, that’s a lot of engineering speak, and a little confusing. But what he’s basically saying, and the Grassroots Motorsports forum helps clarify, is the K8 has a pretty ideal rod ratio, with the potential to make decent torque, and be responsive to mods.
A Tiny V6 Equates To Awesome Noises
Short of going HAM with precision aftermarket ECU tuning, changing valves, porting and polishing, and all that jazz, modest intake and exhaust mods really up the K8’s theatrics. This video on YouTube is some of the best recorded V6 symphonies ever:
It’s just glorious and would be even more glorious if paired with standalone engine management, independent throttle bodies, an upped compression ratio, etc. I’m thinking it could sound like a freaking F1 engine under the hood; imagine a flame-spitting variant beneath the hood of a little NA Miata track beast?
Alas: Oiling Issues, and No Replacement For Displacement
Unfortunately, according to other folks on the Grassroots Motorsports forum, and elsewhere, these engines just don’t stand up to abuse. They apparently spin rods pretty easily when put under pressure due to oiling issues. One company sells an upgraded oil pump that apparently remedies this, though from my research I haven’t found anybody with an angry, F1-sounding K8 with this modification done.
Also: there’s no replacement for displacement.
The bigger, 2.5-liter KL-DE came in the Ford Probe and Mazda MX-6 and made around 170 horsepower, stock. The easily-swappable JDM cousin, the KL-ZE, made 200. Both of these easily swap into an MX-3, or Miata with a bit of work. This engine has far more aftermarket development thrown at it as well, with YouTube being a fine example. Since more MX-6s and Probes were sold here, the 2.5 is just far more common. It seems as though these were less prone to issues. Or, maybe people weren’t as keen on tuning the hell out of them, since their power was already pretty excellent from the factory.
It definitely has a heartier tone, too. Again, let YouTube do the explaining:
When most people hear “K-Series,” they think of Honda’s venerable four-cylinder. But now that you’ve read this blog, you’ll be able to chime in and show off your true nerdiness by introducing people to this odd and tiny low-displacement V6… a.k.a. “the other K-Series.”