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Bumping your car's horsepower can get expensive quickly, especially if the car's European and modern. And when the engine is naturally aspired, the payoff of modding can be underwhelming. But sometimes a little research, a trip to the junkyard, and some willingness to turn a wrench can make some noticeable gains for not a whole lot of money. That was the goal of this BMW project.
The last time I reported on upgrading my beloved E82 BMW 128i, I discussed installing a three-stage intake manifold followed by properly flashing a European, OEM E87 130i engine tune—otherwise known as the 1 Series that we truly should've gotten here.
Legend has it, this mod can add a hearty 30-whole-horsepower to the 1er's 3.0-liter N52 inline-six, at the crank. I was in for less than $300 for the manifold, new seals, DISA valves to properly direct air around inside, and a free tune from BimmerLabs.com.
And finally, I found out what kind of numbers my little Bimmer is truly making. Sadly, I didn't quite achieve the power I was hoping for. But there were still some solid benefits to scientifically behold.
The Dyno Doesn't Lie
When I say scientifically, I mean measuring the BMW's horsepower output to the rear wheels with a dynamometer. Just in case anyone's still not following: It's like a giant treadmill for a car. I paid a visit to the good folks at Advanced Engine Dynamix in Corona, California, who are incredibly friendly and just as stoked about doing pulls in my heavy little Bimmer as they are in heavily tuned hardware that they normally have the pleasure of working with.
After installing the manifold and following all the steps on BimmerLabs to properly flash the ECU (to let it know how to operate and take advantage of this new-to-me form of induction), the car felt substantially peppier. Now, I wanted to know exactly what my car was putting down post-manifold and tune. Before the change, AED measured 202 horsepower and 181 lb-ft at the rear wheels, which anyone would call healthy, especially looking at the smooth curves written into its results sheet.
In preparation, I changed out the coil packs and spark plugs to ensure the Bimmer was getting as good of a spark as possible, as well as cleaned its air filter and made sure it had the freshest 91-octane gasoline in its tank.
Following a widely accepted drivetrain loss formula of 15 percent (meaning, about 15 percent power generally doesn't make it from the engine to the road), I math'd that my 128i was making 232 horsepower and 208 lb-ft of torque at the crank with Turner Motorsport intake and Magnaflow catback exhaust, but before my new/used manifold and engine tune. So, slightly more than it was rated stock.
Moment of Truth
After ratcheting the 1er down and doing three pulls, the best it put down was 208 horsepower and 199 lb-ft of torque (not on the same pull)—not quite as much as I was hoping for. After all, the E87 130i was rated at 260 horsepower at the crank, and my car's bigger brother the U.S.-spec E9X 330i claimed 255 horsepower when new. Taking the lower of the two into consideration, I was hoping my car would put down at least 214 to the tire.
I wasn't bummed, though. In fact, there was plenty to celebrate.
Firstly, six horses isn't a huge deficit. Secondly, the N52 revved up quite healthily. At no point was Toby, owner of AED, concerned with how it felt, or how its power curves looked on the graph. Not bad for 95,000 miles and plenty of track miles.
Next: Low-end torque was laid on thick. The torque curve looked great before, but it looks even better now. It makes so much power down low, which would explain why the thing makes sixth-gear passes on the highway a non-issue.
Finally, Toby pointed out that the engine wanted to keep on going when it hit redline. Where the car used to trail off with the stock tune, it now wants to keep building power, possibly for another 1,000 RPM or so. I'll have to do my research, but it's safe to say that a tune that'd raise the redline a tad would not only be perfectly acceptable reliability-wise but also potentially make a few more ponies.
The Next Steps
I've got a few theories as to why my car isn't making 255-260 horsepower at the crank. The Euro 130i tune could indeed be quite European in that it's tuned for the continent's higher RON fuel—their octane ratings are far better than ours, especially California's sadly low 91.
Toby also mentioned that heak soak was very much a thing in this situation. My Turner intake is designed to keep the heat out pretty well due to being closed off from the rest of the bay with the hood closed, but the car's intake and cooling system don't work quite the same way strapped to a dyno as they do on the road. Perhaps I could figure out a way to duct more air off the front end towards it.
Finally, I might look into an aftermarket tune that takes all the positive aspects of the three-stage intake manifold and improves upon them. Some folks report significant gains by just going with this method, though it may not be square with my local emissions restrictions. Further exhaust work could be in the cards as well. Stay tuned, my friends!