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Manufactured By: Rogue Engineering
Website: www.rogueengineering.com
Application: E46 M3

Free horsepower? Maybe not quite free but pulleys are an interesting mod in that they do not actually let the engine produce more horsepower but rather let it put more horsepower to the wheels. Confusing? Well, not really. Think of it this way - when engine power is measured at the crank it in modern terms includes the parasitic effect of having to drive all the accessories attached to the motor. Just like it takes power to turn the wheels and move the car it takes power to turn the water pump, power steering, AC, alternator, etc. All of these accessories actually add up to a significant drain on the motor meaning that a good chunk of the horsepower the motor is making is being spent turning things other than the wheels.

So what do Under Drive Pulleys do? Pretty simple actually - under drive pulleys are LARGER and if well made lighter than OE pulleys. This means that they spin the accessories on the motor more slowly than the smaller OE pieces. Because turning something slower requires less power more power is sent to the wheels than before. In this sense under drive pulleys do not make power, rather they free it up.

Is there a fine line? Yes, there most certainly is. OE pulleys are designed on the conservative side of the equation. OE engineers have to build cars for the worst possible scenarios and then some. Thus pulleys are designed in a sense with some fudge factor from the start. After market pulleys such as the exquisite set manufactured by Ben at Rogue Engineering get rid of some of the over build factor in the OE design. The goal for a manufacturer is to design a pulley that slows down the accessory enough to make a difference in rear wheel power but not enough to encroach on the safety envelope required for reliable operation of the vehicle.

Typical under drive pulley sets come in either 2 or 3 piece configuration. 2 piece sets typically include a water pump and a power steering pump pulley. 3 piece sets typically add an alternator pulley. Some manufacturers of the 3 piece sets like EvoSport (and Turner who sells EvoSport pulleys under their own name) offer 2 alternator pulley options - 1 being a larger pulley and the other in OE size but lightened (which they recommend for people with additional electrical draw like stereo equipment, etc). I chose to stay with a 2 piece set because every BMW I've ever owned has had electrical issues and I did not want to under drive the alternator. The "lightened" OE sized alternator pulley seems like a rather bogus concept since the OE pulley is tiny to start with (around 2" in diameter). If I were building an all out race car I'm sure I would opt to under drive the alternator as well but since I need the thing to start every morning, no thanks… People have also manufactured crank pulleys in the past though I've yet to see one for an E46 M3 - this is a VERY bad idea as harmonic issues are likely and that is a very bad situation.

Anyway on to my thoughts on the Rogue under drive pulleys: As always with Ben's products everything was top notch, including the service and shipping. The kit includes: Water pump and power steering pulleys, new belt (since it now has to be longer), a set of plastic pins in case you break the pins holding in the radiator shroud and fairly basic directions (this is where I come in :-).

The install was pretty uneventful with the exception of a misprinted torque value for the water pump pulley which seemed odd enough that I looked it up in TIS (thankfully). The pulleys are obviously larger than OE and significantly lighter. Machining and finish are both impeccable.

Butt dyno's are not accurate and I did not do a pre and post install dyno run. Others have shown gains in the 8 to 11 rear wheel horse power range from this mod. Honestly I really believe the claims - the car definitely spins up faster and feels like it pulls a bit harder - this is not a slap in your face difference but certainly noticeable. This is seriously the cheapest horse power by far for these cars. I have not noticed much difference in engine temps - the water temp may run a hair higher but hardly noticeable on the gauge. Oil temps seem to be pretty consistent - as I write this review I have only run autoX with these without any heating issues - I have been stuck in traffic for some time without anything that would even raise an eyebrow since the install. There might be tad more weight to the steering (which is a good thing in the over boosted M3) but it may well be in my head as well. I have not had any noise or other issues in about 2K miles since the install.

My only real complaint is that Rogue should have made these things black like OE's so they would be even less noticeable in the engine bay (not that I don't want to dress the engine bay up, well maybe I don't, but I don't want the SA noticing them either).

All in all the Rogue under drive pulleys are a hell of a great way to get some noticeable extra horses to the back wheels and while they will not transform the car into a 996TT killer they won't put a huge hole in your bank account and give you real results.

Hope this has been at least somewhat helpful…

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