2002 BMW M3: A Sticky Lock and Another Quart of Oil

My e46's door locks would do this once in awhile. Dealership claimed they couldn't find it. Shrug. Overall, not a bad thing compared to my car's engine stutter during WOT at 4k rpm.
 
I added oil to my e46 about 6 times over the course of 3 years, not including 3 oil changes. The e90 required I add oil 2 twice before its first official oil change. Is this unusual? I was shocked my mini didn't require oil anytime in the first 12 months of ownership.

Joe....that 330i ZHP sedan is calling your name. Ill make you a deal. If you buy one, Ill buy one!

P.s. I just read up a fair amount on the inherent balance and power delivery of flat fours, flat sixes, v6s, and inline sixes....seriously makes me consider never buying a 4-cylinder or v6 for the rest of my life :
 
Just curious. What makes you say this? Enlighten me.

Ed: older BMWs tend to get corrosion from moisture trapped in the door on the lock solenoid pins. If you remove the door trim and remove the solenoid you can clean the pins and see if that solves the problem. It usually does and you don't need to replace the solenoid. Worth a try!

Joe,
 
I second 730. Can you provide a link to the information you read? I'm curious as to what source you're looking at. I'd like to read up on it as well.

Hey guys,
 
Here's some reading material:
 
"Straight-6 four-stroke cycle engines are in perfect primary and secondary balance and require no balance shafts. They are in primary balance because the two ends of the engines are mirror images of each other and the cylinders move up and down in pairs, one on the compression stroke and the other on the exhaust stroke. Piston #1 balances #6, #2 balances #5, and #3 balances #4, canceling the end-to-end rocking motion that would otherwise result. (This does not apply to two-stroke cycle engines.) Secondary imbalance occurs in straight-4 engines because the two pistons on the upper 180 degrees of the crankshaft rotation move faster than the two pistons on the lower 180 degrees, creating an unequal motion. Straight-6 engines have cranks at 120 degrees to each other, so the differences in speed on different parts of the crankshaft rotation are offset by the changing number of pistons on each portion.
 
Straight-4 or V6 engines without balance shafts suffer from intrinsic secondary dynamic imbalances which can cause engine vibration and noise. As a general rule, the forces arising from any dynamic imbalance increase as the square of the engine speed - that is, if the speed doubles, the vibrations will become four times worse - and as a result, they will produce much more noise and vibration at extremely high rpm. By contrast, straight-6 engines have no primary or secondary imbalances, and with carefully designed crankshaft vibration dampers to absorb their torsional vibrations, they will seem to rev quietly and effortlessly to their rpm limits. Historically, this has made them popular in European sports-luxury cars where smooth high-speed performance combined with good fuel economy is desirable. In addition, engine imbalance forces increase as the cube of piston mass - meaning that if the size of the engine doubles, the vibrations will become eight times worse - which has made the fully balanced straight-6 a preferred configuration for large truck engines as well.[5]
 
The straight-6 is smoother than engines with a fewer number of cylinders because the power strokes of pistons partially overlap. Since each power stroke lasts 180 degrees of crankshaft rotation, while a new piston starts its power stroke every 120 degrees, there are 60 degrees of overlap on each stroke in which one piston is finishing while the next is starting. This results in a smooth delivery of power, unlike a four cylinder engine in which each piston must come to a complete stop before the next piston commences its power stroke. This makes the straight-6 engine's delivery of power much smoother than a four-cylinder engine. The fact that they are basically two straight sixes on the same crankshaft is the reason why 60°, 120°, and 180° V12 engines are considered optimal for smooth power delivery; they allow for triple overlap of the power stroke between three cylinders at all times due to the overlap from their two component straight-6 banks."
 
Source: http://en.wikipedia.org/wiki/I6
 
Some info on flat fours (which I just bought in my Subaru Legacy GT):
 
"However, the flat-4 does have a less serious secondary imbalance that causes it to rotate back and forth around a vertical axis. This is because the cylinders cannot be directly opposed, but must be offset somewhat so the piston connecting rods can be on separate crank pins, which results in the forces being slightly off-centre. It does not usually require balance shafts, but unlike flat-6 and inline-6 engines, the flat-4 is not a fully balanced configuration.
 
In addition, four-stroke cycle flat-4s have a problem common to all four-cylinder engines: the power strokes do not overlap. With a piston starting its power strokes every 180 degrees of crankshaft rotation, and the crank throws 180 degrees apart, all the pistons must come to complete stop and reverse before the next one can start its power stroke. This results in a gap between power strokes and a pulsating delivery of power to the flywheel. By contrast, in engines with more cylinders the power strokes overlap, the next piston starts its power stroke before the previous one has finished, and the deliver of power is much smoother. As a result of the relatively high manufacturing costs and lack of smoothness of the flat-4, most manufacturers now choose the straight-4 engine for economy models and have moved to straight-5 or V6 engines for ones requiring more power. "
 
Source: http://en.wikipedia.org/wiki/Flat_four
 
The boxer 4 is amazingly balanced at speed, but the pulsating power delivery and rocking on the vertical axis is definitely noticeable at a variety of times.
 
Anyway, I found it enjoyable reading and hope you do too!
 
Joe

I've got a question for the Edmunds LT Drivers - have you played with the SPORT button at all and does anyone actually keep it on when they are driving the M3?
 
The SPORT does not give any extra HP like in the latest M5. All it does is increase throttle response so full throttle is attained when the pedeal is only 50% pressed down. It makes the car more responsive at the expense of fine-adjustments in throttle position. I've used it occasionally but I feel it is more gimmicky than useful. If I want WOT, I'll stomp on the gas.

Joe-
 
60 degree V6s suffer no primary imbalance so a balance shaft is not needed.

Hey chavis,
 
This is what I found on 60 degree v6:
 
"The most efficient cylinder bank angle for a V6 is 60 degrees, which design is very compact and tends to minimize vibrations. While they are not as well balanced as inline-6 and flat-6 engines, modern techniques for designing and mounting engines have largely disguised their vibrations. Unlike most other angles, 60 degree V6 engines can be made acceptably smooth without the need for balance shafts. When Lancia pioneered the 60° V6 in 1950, they used a 6-throw crankshaft to give equal firing intervals of 120°. However, more modern designs often use a 3-throw crankshaft with what are termed flying arms between the crankpins, which not only give the required 120° separation but also can be used for balancing purposes. Combined with a pair of heavy counterweights on the crankshaft ends, these can eliminate all but a modest secondary imbalance which can easily be damped out by the engine mounts.[1]"

Joe,
 
Thanks for posting all of that information man. Good stuff. It makes me wonder why we don't see more manufacturers using a straight six configuration.
 
Are there any inherent problems with a straight six that anyone knows of? Are they more costly to produce, or do they just take up more space, are they less efficient or what? Anyone know of any downsides?

They use up a ton of space....it's a very long design (think about it, it's about twice as long as a V6, which splits the two banks in half).
 
So packaging is tough. Less likely to be used in a FWD application (though
 
Glad you enjoyed the info. I certainly did.

crowb: inline 6 are inherently superior as noted and not more expensive to manufacture. I suspect the V6 is simply easier to use in different applications because it is a more "square" engine. The straight 6 in my 1965 Austin Healey 3000 was very smooth running even though it was essentially a glorified tractor engine. Another example is the old 225 c.i. slant six Mopar engine that was virtually indestructible.

I have an inline 6 in both my cars - Jeep Wrangler and BMW. The Wrangler is not remotely smooth compared to the BMW!
The basics are there, but I have a feeling that the pistons etc are nowhere near as closely matched in the Jeep, leading to increased vibes.
Still love it!

Yeah, when I owned my '97 Wrangler Sahara 4.0 5-speed (I miss that vehicle...) it never hit me that this was the vaunted "inline six" because that engine was not exactly the smoothest thing on planet earth. Obviously, it can be made not to love to rev. :)
 
That being said, I remember reading articles about early BMW's that would just sing at 6500-7000 rpms all day long....a big advantage over the competition who didn't break 5000-5500 at the time and therefore couldn't produce as much horsepower for equal displacement.
 
Joe

There are a lot of factors in smoothness other then engine configuration.
 
Over the years we've had a straight 6 in my folks 1980 225 cid Chrysler, my sisters 1977 Ford 200 cid and my 1995 Jeep Grand Cherokee 4.0.
 
None were what I would call a smooth engine.
 
The 1.4 inline 4 in my Colt was very smooth though.

firstwagon: My Colt too! I was amazed it was so smooth for a 4 banger and it revved very freely. The Ford 200 cid was a great engine with 7 main bearings and hydraulic lifters so you could hop it up significantly. The main issue with that engine was the crummy intake manifold. I remember the dragsters in the 60s would put an Offy intake manifold on it with three single barrel rochester carbs.

My 2.0 liter Honda K20z3 is amazingly smooth (and would be even smoother with a traditional throttle body instead of drive-by-wire)...but it does use dual balance shafts.
 
But I can still tell a difference between it and driving one of BMW's 3.0 liter inline six engines. Don't know what BMW does to them, but man those things can just sit at high rpms all day long and if you didn't look at the tach or your gas mileage, you'd never be able to tell.
 
Joe