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If you’re looking at a 2004 BMW 325i horsepower spec sheet, you’ll see a number that looks a little underwhelming by today's standards. 184. That’s it. In an era where a base-model Toyota Camry pushes north of 200 horses without breaking a sweat, 184 hp sounds like something that belongs in a museum, or maybe just the slow lane. But here’s the thing about the E46 generation: numbers are liars.
People obsess over the peak output of the M54B25 engine because that’s what shows up in the "Versus" charts. It’s a 2.5-liter inline-six that produces 184 horsepower at 6,000 RPM and 175 lb-ft of torque at 3,500 RPM. It’s smooth. Honestly, it’s arguably one of the smoothest engines BMW ever built, even if it won’t win you many drag races against a modern turbocharged crossover.
The 2004 model year was the tail end of the E46 run. By this point, BMW had basically perfected the recipe. They weren't chasing raw power; they were chasing a specific kind of balance that feels almost lost in 2026. When you put your foot down in a 325i, you aren't hit with a wall of torque from a tiny turbo. Instead, you get this linear, mechanical climb. It’s predictable. It’s soulful.
What Most People Get Wrong About 2004 BMW 325i Horsepower
One of the biggest misconceptions is that the 325i is "slow." Okay, compared to a Tesla, sure. But speed and quickness are two different vibes. The 2004 BMW 325i horsepower is delivered through a chassis that was designed to handle much more, which means you can actually use 100% of the power 100% of the time.
Most modern cars have "unused" power. You have 400 horsepower but you spend your life at 15% throttle because you’re in traffic or the speed limit is 45. In the 325i, you’re rowing through gears—hopefully with the 5-speed Getrag manual—and ringing out every last one of those 184 horses. It’s rewarding. You feel like a hero because the car isn't doing the work for you.
Another weird detail: the SULEV models. If you live in California or a state that followed their emissions rules back then, you might have the M56 engine instead of the M54. On paper, the horsepower is the same. In reality, the M56 has a sealed fuel system and a bunch of strange, expensive parts that make it a bit of a headache for DIYers. It still makes 184 hp, but it carries it differently.
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The Inline-Six Magic
The M54 engine is a masterpiece of natural aspiration. It uses a double-VANOS system. That’s BMW-speak for variable valve timing on both the intake and exhaust cams. What this does for your 2004 BMW 325i horsepower is flatten the torque curve. You don’t have to wait until the redline to feel the car move. It pulls decently from 2,000 RPM all the way up.
Is it enough for the highway? Absolutely. Merging is a breeze because the gearing is relatively short. You’ll find yourself at 3,500 RPM at 80 mph, which is right in the meat of the powerband. The sound is the real kicker, though. There’s no fake engine noise pumped through the speakers here. It’s just the mechanical whir and the metallic rasp of a German straight-six.
Real World Performance vs. The Spec Sheet
Let's talk about the 0-60 mph sprint. In 2004, the 325i did it in about 7.0 to 7.2 seconds for the manual, and closer to 8.1 seconds if you had the ZF automatic. By modern standards, that’s "economy car" territory. But the way it reaches 60 is what matters. The E46 is light. It weighs roughly 3,300 pounds.
Compare that to a modern 3-series which is basically a leather-wrapped tank. The power-to-weight ratio of the 2004 325i is actually better than it looks. It feels tossable. You flick the steering wheel—which is hydraulically assisted, by the way—and the car follows. The 2004 BMW 325i horsepower feels like "enough" because the car isn't fighting its own weight.
- Engine: 2.5L I6 (M54B25)
- HP: 184 @ 6,000 RPM
- Torque: 175 lb-ft @ 3,500 RPM
- Weight: ~3,285 lbs
- 0-60: ~7.1s (Manual)
If you’re looking at buying one today, you have to realize that 20 years of age has probably robbed a few of those horses. Vacuum leaks are the silent killer of E46 performance. If your intake boots are cracked or your DISA valve is flapping around, you aren't seeing 184 hp. You’re probably seeing 160 and a check engine light.
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Why the 325i is Actually Better Than the 330i for Some
Wait, what? The 330i has 225 hp. Why would anyone want the 325i?
Well, it’s about the revs. The 2.5-liter engine is slightly more "over-square" in feel, even if it isn't technically. It feels a bit more eager to spin. The 330i is torquier and objectively faster, but the 325i has this sweet, rev-happy nature that makes it a blast on backroads. Plus, you can usually find 325i models that haven't been beaten to death by wannabe drifters as much as the 330i or M3.
Maintenance That Saves Your Horsepower
If you want your 2004 BMW 325i horsepower to stay at factory levels, you have to be proactive. These cars don't handle neglect well. They aren't Hondas. You can't just change the oil every 15,000 miles and hope for the best.
- The Cooling System: This is non-negotiable. If it overheats once, your head gasket is toast, and your horsepower becomes zero. Replace the water pump, expansion tank, and thermostat every 75k miles.
- VANOS Seals: The rubber seals in the VANOS unit harden over time. When they leak internally, you lose low-end torque. Replacing these with Teflon seals from a company like Beisan Systems can actually make the car feel like it gained 20 hp.
- Spark Plugs and Coils: Standard stuff, but the M54 is sensitive to ignition quality. Use NGK BKR6EQUP plugs. Don't cheap out.
- The DISA Valve: This little flap inside the intake manifold changes the intake runner length. If it breaks, it can be sucked into the engine. Not good. A rebuild kit with a metal flapper is a smart move.
Modifications: Can You Get More?
People ask if they can tune a 2004 BMW 325i horsepower up to 250. Short answer: No. Not without a turbo or a supercharger.
Naturally aspirated BMW engines are tuned pretty tightly from the factory. You can add a cold air intake, but you’re mostly just getting more noise. A cat-back exhaust might net you 3-5 hp, but it’s mostly for the soundtrack. An ECU tune can sharpen the throttle response and move the rev limit, but don’t expect a massive jump.
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The best "mod" for a 325i isn't power—it's gearing. If you swap in a differential from an automatic 325i (which has a 3.46 ratio) into a manual car (which has a 3.15), the car will feel significantly faster. You aren't adding horsepower, but you’re multiplying the torque that reaches the wheels. It’s a night-and-day difference.
The Verdict on 184 Horsepower in 2026
Is a 2004 BMW 325i horsepower rating of 184 enough for today? If you’re a driving enthusiast, yes. It’s plenty. It’s a car that teaches you how to maintain momentum. It’s a car that rewards good shifting and proper line selection.
We live in a world where cars are becoming isolated bubbles of technology. The E46 is the bridge between the old-school mechanical world and the digital era. You get ABS and traction control, but you still get a cable-driven feel (even though it's technically drive-by-wire, it’s one of the best executions of it).
If you find a clean, one-owner 2004 325i with a stack of service records, buy it. Don't worry about the fact that a minivan might beat you to the next stoplight. You’ll be having more fun, hearing a better engine note, and driving one of the most iconic shapes in automotive history.
Actionable Next Steps for Owners
If you just bought one or are looking at a listing, do these three things immediately to ensure you're actually getting all 184 horses:
- Check the Intake Boots: Look for cracks in the rubber bellows between the airbox and the throttle body. Unmetered air causes a lean condition and saps power.
- Scan for "Shadow" Codes: Even if the Check Engine light isn't on, the BMW-specific computer might show codes for Camshaft Position Sensors. These sensors failing will retard the timing and kill your acceleration.
- Clean the ICV: The Idle Control Valve gets gummed up with carbon. A quick spray with carb cleaner can restore a smooth idle and better throttle transitions.
Maintaining a 20-year-old German sport sedan is a labor of love. But when you hit that perfect downshift and the inline-six sings at 5,000 RPM, those 184 horses feel exactly right. Forget the spec sheet. Just drive the car.