BMW Has Been Hiding Horsepower in the Grenadier and a Tiny Box Just Found It
Burger Motorsports' new JB4 plug-and-play module pulls 40 wheel horses out of the BMW B58 with nothing more than software. And that's just Map 1.
One compact box for 599 dollars turns a stock INEOS Grenadier into something almost worthy of an M badge. No joke, no marketing fluff — just real dyno numbers.
America's Burger Motorsports has dropped the JB4 tuning module for the Grenadier with BMW's gasoline inline-six B58. It hooks up plug-and-play, no flashing required, and it plays nicely with locked ECUs. The maker promises gains of up to 80 horsepower and 136 N·m at the wheels.
And here's where it gets interesting. On regular 91-octane fuel, a 2026 model year Grenadier puts down 252 hp and 422 N·m at the wheels in stock form. Slap on the JB4 with Map 1 and suddenly it's 292 hp and 492 N·m. Forty horses out of thin air — no engine teardown, no flash.
Pour in 93-octane and switch to Map 2, and the numbers get downright indecent — 312 hp and 575 N·m at the wheels. For a heavy body-on-frame SUV weighing close to two and a half tons, that's a completely different machine.
But the cleverest thing about this tune isn't peak power. A heavy off-roader needs predictable low-end torque: a sudden boost spike at 2,000 rpm on loose terrain breaks traction in a heartbeat and loads the driveline hard enough to snap an axle. So JB4 lets you cap boost pressure manually in specific low-rpm zones via the smartphone app. Throttle response stays linear, behavior stays predictable — off-road that matters more than a few extra Newton-meters.
The maker is quick to add the disclaimer: the kit is intended for competition and closed-course use only. Not for sale in California, not road-legal. A formality? Maybe. But the warning sits right out front.
The conclusion writes itself. If a 599-dollar box can pull nearly fifty horses out of an engine with software alone, that means BMW left a massive reserve buried in the B58. The only real question is why INEOS isn't tapping into it itself.