• BMW N20 turbo four-cylinder versus N55 turbo six-cylinder - Testing the 2013 X3 xDrive28i and X3 xDrive35i

                    
      		   
      Published on 11-17-2012 01:15 AM
      1 Comment Comments
      Always fun to see these comparisons especially with how much stronger 28i models have gotten now thanks to the new N20 turbocharged 2.0 liter four-cylinder. Insideline decided to see just how big the difference between the N20 xDrive28i and the N55 xDrive35i are. The result is that even though the new N20 four cylinder is a considerable improvement over the N52 naturally aspirated 3.0 liter inline-6 but the N55 is still a much stronger motor.


      How much stronger? Well almost 7 miler per hour of trap speed and almost a full second in the 1/4 mile. Definitely a considerable difference. Is that worth a difference in base price of $3305? Certainly seems to be on paper. Full comparison numbers below.

      2012 BMW X3 xDrive 35i 2013 BMW X3 xDrive 28i
      0-30 (sec.): 2.1 2.4
      0-45 (sec.): 3.7 4.2
      0-60 (sec.): 5.8 6.8
      0-60 with 1-ft Rollout (sec.): 5.5 6.5
      0-75 (sec.): 8.3 10.1
      1/4-mile (sec @ mph): 14.1 @ 97.0 15.0 @ 90.8
      30-0 (ft): 31 33
      60-0 (ft): 123 127
      Skid Pad Lateral Accel (g): 0.80 0.83
      Slalom: 64.4 63.3

      Vehicle: 2013 BMW X3 xDrive28i
      Odometer: 1,671
      Date: 10/23/2012
      Driver: Chris Walton
      Base Price: $39,395
      Price as Tested: $52,095

      Specifications
      Drive Type: Front-engine, all-wheel drive
      Transmission Type: Eight-speed automatic
      Engine Type: Turbocharged, direct-injection inline-4
      Displacement (cc/cu-in): 1,997/122
      Redline (rpm): 7,000
      Horsepower (hp @ rpm): 240 @ 5,000
      Torque (lb-ft @ rpm): 260 @ 1,250
      Brake Type (front): 12.9-inch ventilated disc with single-piston sliding caliper
      Brake Type (rear): 13-inch ventilated disc with single-piston sliding caliper
      Suspension Type (front): Independent MacPherson struts, coil springs, stabilizer bar
      Suspension Type (rear): Independent MacPherson struts, coil springs, stabilizer bar
      Tire Size (front): 245/45R19 (102V) M+S
      Tire Size (rear): 245/45R19 (102V) M+S
      Tire Brand: Goodyear
      Tire Model: Eagle LS2
      Tire Type: All-season, run-flat
      As Tested Curb Weight (lb): 4,179

      Test Results

      Acceleration
      0-30 (sec): 2.4 (3.0 w/ TC on)
      0-45 (sec): 4.2 (4.9 w/ TC on)
      0-60 (sec): 6.8 (7.4 w/ TC on)
      0-60 with 1-ft Rollout (sec): 6.5 (7.0 w/ TC on)
      0-75 (sec): 10.1 (10.8 w/ TC on)
      1/4-Mile (sec @ mph): 15.0 @ 90.8 (15.4 @ 90.9 w/ TC on)

      Braking
      30-0 (ft): 33
      60-0 (ft): 127

      Handling
      Slalom (mph): 0.83 (0.79 w/TC on)
      Skid Pad Lateral Acceleration (g): 63.3 (63.0 w/ TC on)
      Db @ Idle: 42.2
      Db @ Full Throttle: 66.3
      Db @ 70-mph Cruise: 60.7
      RPM @ 70: 1,900

      Comments

      Acceleration:       Plenty of torque down low, but a fairly lazy launch nonetheless. Plenty of gears to keep engine on the boil and smooth/rapid upshifts. Same results from Sport and manual-shift mode, as it auto-upshifts regardless.

      Braking:       First stop was the shortest, and the remainder were tightly grouped and slightly longer. Firm pedal and it remained so throughout.

      Handling:

      Skid pad      : Very slight advantage in dynamic (Sport +) mode here, but still very little interference from ESC either way. Steering is precise but vague-feeling. Effort and build-up feel manufactured. Doesn't self-center the way it ought to.

      Slalom      : Nondefeat ESC on a BMW?! Non-linear steering response, combined with firm chassis provides a threshold that's hard to predict. Best way through was slow-in/fast-out to maintain progressive throttle — seems to keep ESC at bay. Dreadful steering that doesn't provide intuitive response given the input.


      Vehicle: 2012 BMW X3 xDrive35i
      Odometer: 3,694
      Date: 03/06/2012
      Driver: Chris Walton
      Base price: $42,700
      Price as tested: $53,845

      Specifications
      Drive Type: Front-engine, all-wheel drive
      Transmission Type: Eight-speed automatic
      Engine Type: Longitudinal, turbocharged, direct-injected inline-6
      Displacement (cc/cu-in): 2,979/182
      Redline (rpm): 7,000
      Horsepower (hp @ rpm): 300 @ 5,800
      Torque (lb-ft @ rpm): 300 @ 1,300
      Brake Type (front): 12.9-inch ventilated discs with single-piston sliding calipers
      Brake Type (rear): 13-inch ventilated discs with single-piston sliding calipers
      Suspension Type (front): Independent MacPherson struts, coil springs, stabilizer bar
      Suspension Type (rear): Independent MacPherson struts, coil springs, stabilizer bar
      Tire Size (front): 245/45R19 (102V) M+S
      Tire Size (rear): 245/45R19 (102V) M+S
      Tire Brand: Goodyear
      Tire Model: Eagle LS2
      Tire Type: All-season, run-flat
      As Tested Curb Weight (lb): 4,225

      Test Results:

      Acceleration
      0-30 (sec): 2.1 (2.5 w/ TC on)
      0-45 (sec): 3.7 (4.1 w/ TC on)
      0-60 (sec): 5.8 (6.3 w/ TC on)
      0-60 with 1-ft Rollout (sec): 5.5 (5.8 w/TC on)
      0-75 (sec): 8.3 (8.9 w/ TC on)
      1/4-Mile (sec @ mph): 14.1 @ 97.0 (14.4 @ 96.9 w/ TC on)

      Braking
      30-0 (ft): 31
      60-0 (ft): 123

      Handling
      Slalom (mph): 64.4 dynamic mode (63.0 w/ TC on)
      Skid Pad Lateral Acceleration (g): 0.80 dynamic ( 0.78 w/ TC on)
      Db @ Idle: 41.6
      Db @ Full Throttle: 73.7
      Db @ 70 mph Cruise: 64.7
      RPM @ 70 mph: 1,900

      Comments:

      Acceleration:       Holy guacamole! This was an utter surprise to me because I hadn't looked at the ungainly badge on the side of the X3 (xDrive35i). Strong AWD launch, but then at 4,000 rpm the afterburners light and the X3 really comes alive. Default/first run in Drive + Normal mode; subsequent in Sport Drive + Sport Plus. The close-ratio gearset keeps the engine in the sweet spot after each velvety upshift (with spark retard or some such) exactly at (or slightly over) redline. Holds a gear past redline (to 7,300 rpm) and also performs matched-rev downshifts.

      Braking:       Medium-travel medium-firm pedal never wavered. Moderate-to-light dive, straight and steady, with slight increase in distance in middle runs that disappeared by the last.

      Handling:

      Skid pad      : Dynamic-mode (nondefeat) ESC was virtually nonexistent on the skid pad, allowing the X3 to pile on gentle-yet-terminal understeer at the limit. Good balance and tractability but no chance of rotation. Steering goes light as understeer builds (as it should). Slight difference with ESC on, where it imperceptibly bled throttle.

      Slalom      : Again, dynamic-mode ESC is rather lenient unless yaw and steering are crossed for too long. If this happens, the run is scrapped anyway, so it's really an "Oh sh*t" safety net. Good front-end bite and quick to react in transitions. Very trustworthy, so I was able to coax some lift-throttle rotation to snub understeer when approaching the limit. With ESC on, it used the brakes sparingly to maintain smooth arcs between cones but wouldn't allow lift-stab-lift-stab. Remarkable speed and agility for something this size.
      This article was originally published in forum thread: BMW N20 turbo four-cylinder versus N55 turbo six-cylinder - Testing the 2013 X3 xDrive28i and X3 xDrive35i started by Sticky View original post
      Comments 14 Comments
      1. spool twice's Avatar
        spool twice - 11-17-2012, 08:16 AM
        I don't understand why BMW sets the shift points above optimal levels? Both engines are screaming for an up-shift by 6,200rpm
      1. Sticky's Avatar
        Sticky - 11-17-2012, 08:42 AM
        Click here to enlarge Originally Posted by spool twice Click here to enlarge
        I don't understand why BMW sets the shift points above optimal levels? Both engines are screaming for an up-shift by 6,200rpm
        I'd shift at redline...

        Click here to enlarge
      1. StinkyM's Avatar
        StinkyM - 11-17-2012, 10:32 AM
        I wonder why the brake test was so much different. Exact same brake setup, exact same tires, and the 28i weighs less. Probably just more wear on the 28i.
      1. Sorena's Avatar
        Sorena - 11-17-2012, 11:10 AM
        Click here to enlarge Originally Posted by StinkyM Click here to enlarge
        I wonder why the brake test was so much differen
        So as the slalom and skid pad G. The 28i should have performed better than the 35i.
      1. inlineS54B32's Avatar
        inlineS54B32 - 11-17-2012, 12:42 PM
        Click here to enlarge Originally Posted by spool twice Click here to enlarge
        I don't understand why BMW sets the shift points above optimal levels? Both engines are screaming for an up-shift by 6,200rpm
        What do you mean by this? The engine is still making power all the way to redline. Torque is falling off quickly, but that's normal for these engines. If you shifted at 6,200 (i.e. before peak power is made) - you are losing time - wasting the last 1000 RPM of power, and falling back farther in the power curve for the next shift. A lot of guys dispute the shift point on the 335i - saying you should shift early because of the torque dip. That makes little sense, HP = (RPM x TQ) / 5252 - even though torque is dropping, it isn't dropping faster than the RPMs are climbing.

        Looking at the dyno graph that Sticky just posted, it looks like there is a small power drop near the end. But again, look where you will be in the curve if you shift at redline @ the next gear - you will be in the power peak. If you shift at 6200 - you will be much lower than this - and you will have never reached peak power (right above 6200) to begin with.

        I am curious what you mean by this though - is this style not for optimum acceleration or something?
      1. Sticky's Avatar
        Sticky - 11-18-2012, 02:04 AM
        Click here to enlarge Originally Posted by inlineS54B32 Click here to enlarge
        What do you mean by this? The engine is still making power all the way to redline. Torque is falling off quickly, but that's normal for these engines. If you shifted at 6,200 (i.e. before peak power is made) - you are losing time - wasting the last 1000 RPM of power, and falling back farther in the power curve for the next shift. A lot of guys dispute the shift point on the 335i - saying you should shift early because of the torque dip. That makes little sense, HP = (RPM x TQ) / 5252 - even though torque is dropping, it isn't dropping faster than the RPMs are climbing.

        Looking at the dyno graph that Sticky just posted, it looks like there is a small power drop near the end. But again, look where you will be in the curve if you shift at redline @ the next gear - you will be in the power peak. If you shift at 6200 - you will be much lower than this - and you will have never reached peak power (right above 6200) to begin with.

        I am curious what you mean by this though - is this style not for optimum acceleration or something?
        I think you're correct and you would want to go to redline especially considering the RPM drop down on the shift.
      1. BlackJetE90OC's Avatar
        BlackJetE90OC - 11-18-2012, 11:22 PM
        The msrp difference on bmwusa is $5,100.
      1. Sticky's Avatar
        Sticky - 11-19-2012, 07:21 AM
        Click here to enlarge Originally Posted by BlackJetE90OC Click here to enlarge
        The msrp difference on bmwusa is $5,100.
        Seems Insideline made a mistake then.
      1. spool twice's Avatar
        spool twice - 11-20-2012, 06:37 AM
        Oh i see, i forgot that the N20 powerband stays relatively level after peaking. I always that the N54/N55 powerband should upshift at 6,000-6,300rpm? Or is that just for 6MT?
      1. fast4door's Avatar
        fast4door - 11-20-2012, 09:18 AM
        Ive been driving an X3 28i loaner for a few weeks now, and these little engines definetly have a some get up..
      1. ajm8127's Avatar
        ajm8127 - 11-20-2012, 10:28 AM
        Gas mileage?

        Aside from the initial price difference, this will account for a difference in the cost to drive the vehicle over the long run. I suspect this is equally as big of a deal as the initial price difference when people are making a decision about which car to buy.

        Isn't the entire reason we are putting turbos on small displacement engines so that they can maintain their small displacement MPG figures, while delivering large displacement torque (assuming the large displacement engine is sans turbocharger)?

        http://www.thecarconnection.com/spec...i_fuel-economy

        http://www.thecarconnection.com/spec...i_fuel-economy

        Assuming 15,000 miles per year and 4 dollars per gallon, this is a difference of 356 dollars per year (coincidentally, one dollar per day - except leap year) using the combined mileage figures from the above links. So you would have to keep the vehicle for 14 years to see equal savings from increased mileage and decreased sticker price, assuming a $5100 difference, again from the above links.

        So while the increased fuel efficiency will turn into more money in your pocket, the difference in sticker price is more significant, because I doubt most people will keep their X3 14 years. However, there is still a difference, and when you consider the difference in sticker price and the difference in MPG, a lot of decisions will be made based on this information.
      1. Sticky's Avatar
        Sticky - 11-20-2012, 10:49 AM
        Click here to enlarge Originally Posted by fast4door Click here to enlarge
        Ive been driving an X3 28i loaner for a few weeks now, and these little engines definetly have a some get up..
        How you liking the X3?
      1. fast4door's Avatar
        fast4door - 11-21-2012, 10:27 AM
        its ok, surprised by the little four banger engine..that little thing moves for what it is...still missing my M5 though, but I should be getting it back to day with a brand new transmission Click here to enlarge
      1. inlineS54B32's Avatar
        inlineS54B32 - 11-21-2012, 03:23 PM
        Click here to enlarge Originally Posted by spool twice Click here to enlarge
        Oh i see, i forgot that the N20 powerband stays relatively level after peaking. I always that the N54/N55 powerband should upshift at 6,000-6,300rpm? Or is that just for 6MT?
        Yeah, that's sorta what I meant by the 335i comment. I have read a lot of posts where people tell other people to shift their 335i before peak RPM due to the pretty drastic torque drop-off at the end of the curve. If you think about it, the case where you are making less power in a higher RPM than a lower RPM is almost never true. Just because the torque is falling fast does not mean that you are not still putting more power and more power to the ground... Without taking gearing into consideration to simplify, since HP = (Torque x RPM) / 5252 - unless the torque is dropping faster than 1 lbft for every single RPM that is increasing, you are better off holding the gear since power will still increase... In other words, one foot-pound of torque lost is made up by increasing the RPM by one (assuming a 1:1 ratio - again, no gears). The horsepower will remain the same; you have almost 1000 RPM left to play with on the N54/55 if you are shifting at 6,300 - that would require a huge dip in torque to make up for.

        I found a decent article - he explains this exact scenario in detail in the last couple paragraphs: http://www.rubydist.com/Family/Power.html

        Looking at a chart your car's torque at the wheels at X RPM for each gear - you can determine this for yourself. I found a chart for you online - here are the recommended shift points (for maximum power to the ground) that came out of it:

        1 to 2 = Redline
        2 to 3 = Redline
        3 to 4 = Around 6725
        4 to 5 = Around 6350 (6700 for auto)

        Hope that helps.