Without a doubt, one of the coolest small cars on the market has to be the Mini Cooper. So when we ran across Doug Bromer’s Mini Cooper engine build (dubbed “N14” in Mini parlance) for his John Cooper Works Mini (the turbocharged direct-injected 1.6L version), we were intrigued. Apparently a bad tuneup led to an overboost and lean condition, which toasted the number three piston’s ring lands. Rather than just do the bare minimum to fix the problem, Bromer decided to throw frugality to the wind, and tap Jan Brueggemann at Revolution Motor Works to build him a stout engine that will withstand more boost and spirited driving. It turns out the solution to his problem isn’t much different than what would be done to any other engine–stronger parts!
Revolution Motor Works own forged H-beam rods with ARP rod bolts, along with forged Mahle pistons were used , along with the OEM forged crankshaft
For the shortblock, Bromer reused the stock block with a 0.5mm (just a hair under .020-inch) overbore, bringing the bore to 77.5mm. The factory forged crankshaft was the only internal component retained, so with the stock 85.8mm stroke, the displacement is upped to 1.62-liters. ARP main studs were utilized to increase the strength, and custom Mahle bearings were utilized in the assembly. Revolution Motor Works forged H-beam connecting rods with ARP bolt connect the crankshaft to the custom Mahle forged pistons for a 10.5:1 static compression ratio.
The OEM combustion chambers have been cleaned up via CNC machining, and oversized Supertech valves – stainless intake and sodium-filled inconel exhaust – were utilized.
But the top end of this N14 Mini Cooper engine is where the build really shines. Brueggemann completely reworked the cylinder head; CNC porting worked wonders on the casting. Flow is increased at .500-inch lift from 143.3 cfm to 206.3 cfm for a 31-percent flow increase. On the exhaust side, flow was increased from 147.7 cfm, to 171.7 cfm for a 14-percent increase. The combustion chamber is then cleaned up on the 5-axis CNC before Supertech Manganese-Bronze valve guides are fitted. Supertech stainless intake valves, and sodium-filled Inconel exhaust valves are used. The valvetrain remains mostyl stock, with the exception of Supertech beehive valve springs and Supertech titanium retainers.
The CNC port work on the intake (left) and exhaust ports improve flow by 31 and 14 percent, respectively.
The OEM direct injection fuel system is retained, along with the VANOS variable camshaft timing system. A ported OEM intake manifold coupled with a ported OEM turbo manifold help the engine’s breating. A John Cooper Works K03 turbocharger provides the compressed atmosphere to the engine, and one-step-colder spark plugs with the stock ignition keep the fires lit.
While the stock camshafts were reused, Supertech beehive springs and titanium retainers, capable of living at up to 9,200 rpm, replaced the OEM pieces, and the VANOS variable cam timing system was retained.
“When I tore the engine down, and I saw how weak the internals looked, I realized I couldn’t put it back together with stock components,” Bromer said of his thought process for the build. However, looking back, he realizes he could have gone bigger. “Doing it over again, I would probably have gone with a stroker crank, which very well may happen down the road. I also plan to add water-methanol injection from Howerton Engineering in the near future, along with an upgraded DeatschWerks fuel pump,” Bromer related. While the dyno numbers are on hold until the Quaife limited-slip differential and new clutch are in the car, this little four-cylinder turbo engine is sure to make an impressive amount of power out of 1.62-liters.