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BMW 3-Series 2005 and earlier



  • riezriez Posts: 2,361
    fjk... Is likely beyond me. Physics, chemistry, and mathematics are not my fortes. Thought we were talking about the absolute flatness of an engine's torque curve. I wasn't talking about differences in output. Differing engines have differing torque curves. BMW's 4.4L V-8 has a different torque curve than its 2.5L I-6 or its 5.0L V-12. Even within a given type of engine (e.g., the universe of all I-4s regardless of manufacturer) there are a zillion different torque curves. Some are flatter than others. Some have similar relative flatness. The differences in displacement and other factors (e.g., breathing efficiency and exhaust restrictions) lead to different outputs.

    kdshapiro... Guess I'm not a fan of mathematical models. They are nice on paper but don't always account for the real world. Real machines and people don't act like the models might indicate. Just look at the attempts to use such models to come up with acceleration figures, top speed, fuel economy? Ever notice how many people say that BMW's hp and torque units must be more powerful than their competitors because when you use a mathematical model to come up with, say, acceleration figures, the actual result in the real world doesn't accord with the model's projection (i.e., if I estimate it on paper using variables like engine output, gear ratios, weight, tires, CD, etc.). Heck, too many people seem to disagree about the value of adjusting test data for atmospheric conditions. (I prefer R&T's unadjusted numbers, which then have the caveat that numbers within a certain range are essentially statistically equivalent). As for data points, all I see are one point for torque (published peak) and one point for HP (published peak).

    So does anyone have the respective published torque curves for the 1999-2001 and 2001-2003 2.5L I-6s?
  • brave1heartbrave1heart Posts: 2,698
    Here's a dyno for the '01 325.

    ...and one for the '99 323 (not a good one, though)

    The 325's torque curve is flatter and it does not drop off fast like the 323's. Now here's the real kicker: the '95 325 has 189 hp@5900 -> 168 ft-lbs @5900 and although it is lighter by 150 lbs and it has 5 extra ponies than the E46 325, it takes 16.1 sec at the 1/4 mile while the E46 325 takes only 15.4. I think the main reason is GEARING, as well as better engine management.
  • kdshapirokdshapiro Posts: 5,751
    horsepower = torque * RPM / 5252

    Here is a link which explains it somewhat nicely:
  • locke2clocke2c Posts: 5,038
    well if we're going to be attempting to enlighten anyone, let's at least use a decent link:

    relevance to current discussions-- VANOS and other variable valve-timing technologies help an engine make torque at both high and low RPM. honestly VANOS isn't a great way to do it though, controlling only the phase on the cam(s). VVT technologies able to vary valve lift can have a larger effect on things. of course, other things can help two like tunable exhaust, variable length induction, etc.

  • kdshapirokdshapiro Posts: 5,751
    Click here for Modern Engine Design 101!. Send away for your free diploma and you can be employed by auto manufacturers as a top shelf engine designer.
  • fjk57702fjk57702 Posts: 539
    What set this off was a question about what the differences were between the 323 and 325 engines. I thought (incorrectly) that the 2001 2.5 was upgraded to double VANOS, but in fact the engine tuning was upgraded to optimize the double VANOS.

    riez: we are not talking about models here. Horsepower is NOT measured by a dynometer, only torque is measured. Horsepower is then calculated. The horsepower is a function of the engine speed and torque at that speed. So if the torque is constant (flat) then an increase of engine speed increases the horsepower - 10% faster, 10% more horsepower. This means that if the engine horsepower peaks at 5500 RPMs, then the engine must produce LESS torque at 6000 RPMs, otherwise there would be MORE horsepower at 6000 RPMs.
  • riezriez Posts: 2,361
    fjk... Yes, we were discussing the VANOS, double VANOS, and other changes, but I thought the actual underlying question concerned the output differences between the 1999-2000 and 2001-2003 2.5L I6. The former have higher peak torque but lower peak HP. The latter have lower peak torque but higher peak HP. And the peaks come at different RPMs. Is interesting that the changes didn't produce increases in peak torque and HP. Not sure if they led to any increases in fuel economy, either. Didn't that then have us discussing torque curves? Think we'd all agree that higher output (both torque and HP) is better, as is higher efficiency, and flatter torque curves that include beefy torque at lowish RPMs?

    But what happened to the 2.5L output is unlike what happened to the output figures for the change from 2.8L to 3.0L during the same time. In that case there was a huge increase in peak HP and an increase in torque. As C&D's article pointed out, only a small part of the increases were due to the 0.2L displacement increase.
  • kominskykominsky Posts: 850
    I had my car at my dealership for PA state inspection on Thursday. I mentioned that a quick stab at the brake pedal results in the steering wheel yanking to the right for a fraction of a second. The steering immediately centers itself and the car doesn't change direction. It also doesn't exhibit the light pedal pressure "thumping" of a warped rotor.

    My service manager informed me that there is a service bulletin on this and my car's going back in next week to have a "steering kit" installed. From what he was saying, it sounds like just about every bushing, bearing, and even the tie-rods will be replaced (warranty).

    I'm wondering if anyone else has had this done or if anyone else's car exhibits this behavior. Under normal driving conditions, I've never noticed it. It only rears it's ugly head during those cool 70-0 MPH panic stops on a congested highway and on occasion when I need to scrub off speed in a hurry when that upcoming corner is looking tighter than I had initially thought and I must slow down NOW!.

    FWIW, my car is an '01 330Ci w/retro steering installed.
  • fjk57702fjk57702 Posts: 539
    The change in size from 2.8 to 3.0 makes it difficult to judge. Torque is a function of engine size to some extent. The increase in size would suggest that the 3 liter engine might have produced about 220 ft-lbs with the same tuning. So perhaps the 3 liter engine has less torque too, but more horsepower.
  • Instead of peak torque and HP I think it would be more useful to know the area under the torque and HP curves from 1000rpm to the redline. This would be more useful.

    It is interesteing that the M3 makes 333HP and only has 261 lbft of torque.

    I think the new 350z makes 280HP and 270lbft of torque at the peak -- correct me if I am wrong. How is it slower 0-60 than the M3? I think it weighs less too.

    FWIW: 4 month birthday of my M3 is in 2 days and I have over 8000 miles. I live 1.8 miles from work, but I find myself taking the long way everywhere.

    FWIW: $1.85 for 93 octane in Houston (Chevron)

    FWIW: Have hit 155mph in the M3 twice and it is solid as a rock and still stops great from that speed -- no fade (Total time spent cruising at 155mph: 12 seconds).
  • skobolaskobola Posts: 207
    As much as I have followed E46's engines' specs, there was no change in displacement: both 323 and 325 had 2.5-liter displacement. However, 325 was re-tuned to increase horse power, because this was what people were looking at. You probably already know that the smaller 3-series was named 323 only to make it more distinguished from the 328, as BMW believed that less people would opt for 2.8 for quite the money difference if the car was "only" 0.3 liters beefier.
  • riezriez Posts: 2,361
    skobola... My wife has a '00 323ia. I know it has 2.5L. There wasn't any change in displacement for this smaller I6. But the 2.8L I6 did grow by 0.2L, from 2.8L to 3.0L. The above cited C&D article discusses what caused the changes in reported output for these motors from MY 2000 to MY 2001.
  • nyccarguynyccarguy Stamford, CTPosts: 7,093
    So you did finally get your M3. Congratulations (I know it is a little late). Awesome car. WHat color combo did you end up getting?

    2001 Honda Prelude Type SH/ 2011 BMW 328xi / 2011 Honda Pilot EX-L w/ Navigation

  • BMW, I think, leaves us with one true dilemma.

    How many of you were one the fence about the coupe vs sedan decision? What did you decide to go with and what was your rationale?
  • kominskykominsky Posts: 850
    Coupe - Quite simply, my decision was based on styling. I have two children who are large enough to crawl into the back seat by themselves and small enough to not mind doing it. If I had car-seats to deal with or carted adults around regularly, I may have chosen the sedan. Either way, I don't think you can go wrong.
  • fedlawmanfedlawman Posts: 3,118
    How does the convertible factor in?

    I have been leaning towards the coupe for the same reason that Komisky articulated above. However, I'm now considering just going whole hog and getting the 330Ci Convertible (I've always wanted one).

    Does anyone have personal experience regarding how much performance I will lose by going topless? By performance, I'm referring to body tightness, acceleration, etc. In other words, all of the things that make the 330i so much will they be muted by losing the top?

    To be honest, I'm having a difficult time deciding which 3 series to get. I was impressed with the 325i sedan, but each step up from there delivers more and more satisfaction. The only one I would never consider is the M3 Convertible because it's just too much money. Where to draw the line (and the cheque) is the tough part!
  • denkdenk Posts: 75
    I can't comment on how performance might be affected by a convertible design, but I have owned two convertibles(not BMW)in my younger days and can point out some of the things you should consider:
    -The seats get dirty very quickly and the sticky sap from the trees must be continually wiped off.
    -Convertibles are very hot in the summer so get used to sweating a lot.
    -The top will rattle after a few months.
    -Both of my convertibles developed leaks where the top meets the windows.
    -There will be a lot of wind noise.
    -Don't remember if there was a higher insurance premium.

    On the other hand, if you don't mind a little dirt in your eyes, a convertible can be very enjoyable on summer nights after the sun has set.
  • fedlawmanfedlawman Posts: 3,118
    I can well relate to your experiences. I had a '79 Alfa Romeo Spider when I was in college and the top rarely went up (I lived in So. Cal.). When it was up, the top leaked noise and water like you wouldn't believe, and the tan vinyl seats were filthy.

    More recently however, I owned a '94 Mazda Miata and never experienced any of the issues that the Alfa was plagued with. It was tight, quiet (relatively), and rarely rattled or leaked.

    Funny, although the Miata was superior to the Alfa in every way, if I could choose one again today, I'd take the Alfa in a heartbeat.
  • seivwrigseivwrig Posts: 388
    For any Houston BMW CCA members, the local chapter will be offering a Car Control Clinic. See link below for details.
  • dave330idave330i Posts: 893
    I got a sedan because I only had to wait a month for it (the one I wanted was on its way to the dealer). Coupe would have taken 3 months.
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