German Car Zone

cawimmer430 · 05-04-2009, 11:20 AM

I am asking this question because I have seen the speedometer of my sisters 118i pegged at 235 km/h when I maxed it out on various Autobahns. Officially BMW says the 118i (143-hp) can only do 210 km/h. There's a contradiction right there.

It goes without saying that when you drive at high speeds a lot you get a feel for them. That said, I could theoretically sense that I am traveling at 200 km/h if I was in a car without a speedometer and I could definitely feel if I was traveling faster than 200-210 km/h. Given the small size of the 1-Series this might be different from what I am used to (larger cars), but at the same time the 118i is a solid little car that feels well-placed on the road at all times and especially at high speeds.

Follow the conversation between me and MX793 from Carspin below:

Link to thread: Top Ten cars I hate being stuck behind in traffic!

MX793: "Methinks your speedometer was a bit optimistic (typical for German cars)."

cawimmer430: "I have a navigation system that also displays your current speed. When I am doing 160 km/h it says I am doing 155 km/h. If I drive 200 km/h the navigation system tells me I am driving 195 km/h. If I was driving 235 km/h maybe I was actually doing 230 km/h. Either way the 118i has a high top speed."

MX793 "GPS systems aren't all that accurate either. I can tell you right now that it's not physically possible for a 118i to hit 145 mph. It doesn't have the power or the aerodynamics to pull that off. Per Wikipedia, the 127 hp versions of the 118 tap out at between 200 and 210 km/h and newer models with the 140 hp motor max out at 210 km/h even. These jive with what I would expect from a car with that body shape and power output."

cawimmer430: "We have the 143-horsepower 118i which officially does 210 km/h max. according to BMW. Why then does the tachometer show 235 km/h when I am maxing it out? huh

I'll take a look at some older issues of Auto Motor und Sport and see how fast they clocked the 118i at."

MX793 "Unless you were traveling down a hill, or had a really stiff tailwind (or some combination), a 140 hp car with hatchback aerodynamics isn't going to be able to reach those kinds of speeds. For a car with the 1er's size, weight, and aerodynamic characteristics, you'd need 142 hp just to reach 135 mph (218 km/h). But, a 142 hp car is only going to be putting maybe 120-125 hp to the ground due to drivetrain loss. With that much power available, a car like the 118 hatch is only going to be able to go about 130 mph (210 km/h), which aligns exactly with BMW's official claimed top speed."

cawimmer430: "But how come when I push it hard the tachometer needle goes to 230-235 km/h. I don't think wind has anything to do with it in this case as I have often drive "230 km/h" with the 118i.

Could it be that BMW claims 210 km/h but the car is actually faster?"

MX793 "Unless that car is making a lot more power than BMW claims, it's not physically possible. I did the math. A car with the BMW's aerodynamics will need 150 hp at the wheels (which is over 170 hp at the motor) to go 230 km/h."

cawimmer430: "Ok, but what about aerodynamic efficiency? Or maybe the 6-speed automatic has a high ratio in the last two gears that enable a high top speed?

I just can't believe the 118i is going "210 km/h" when the tachometer is showing 235 km/h. When you drive at high speeds a lot you get a feel for them. I know what 200 km/h feels like and I would certainly know what 235 km/h feels like. When I am traveling at 235 km/h it definitely feels like 230 km/h+. The size of the car has little to do with it since the 1-Series is a pretty solid vehicle."

MX793 "When I ran the numbers, I took into account the aerodynamic efficiency. A 118i has a drag coefficient of 0.29 and a frontal area of approximately 23 sq.ft. I also factored in rolling resistance (assuming that with a driver and some fuel, it weighs about 3000 lbs). It's a very simple calculation to determine how much horsepower is required to overcome wind resistance. I don't even need to consider gearing for this. Regardless of how it's geared, the fastest a 118i could ever hope to go is roughly 210 km/h. At that point, wind resistance equals the maximum amount of power the car has and it cannot go any faster. It has reached terminal velocity.

Next time you take it up that fast, have someone run a stopwatch with the mile (or km) markers on the highway and see what that tells you."

Other posts from MX793.

MX793: "Cd that I found for the 1-series hatch was 0.29 (which is surprisingly low, I would have though it'd be in the 0.32 range). I used 23 sq.ft for frontal area (width x height, I subtracted 6 inches from the height for ground clearance). Although it's a pretty minor contributor, the spreadsheet I have also factors rolling resistance, so I assumed 3000 lbs (which may actually be a little light for the automatic model with a driver and fuel).

If I'm not mistaken, 3 series convertibles were limited to 130 or 135 mph in the US. You may have been showing 145 when the limiter kicked in, but you may not have been going that fast. German speedometers are notoriously optimistic at high speeds. I've read reports of BMW M5s indicating 165 mph when their 155 mph governors kicked in (at an actual speed of 157 mph). There were some photos in I think C&D during a test on an AMG Mercedes where the speedo was showing well over 160 and the car had a 155 mph governor. Do not believe your speedometer."

SO?

I honestly can't imagine that the speedometer calibration can be that far off. I can live with slight offsets such as an indicated tachometer speed of 235 km/h (but 230 km/h in real life). But when BMW says the 118i can only do 210 km/h max. and the speedometer shows 235 km/h, then something must be seriously screwed up. When I am pushing the 118i at 235 km/h it damn well feels like 235 km/h.

Tarek · 05-04-2009, 11:47 AM

Well i think it can but the thing is will u still be young when it does?

Kowalski · 05-04-2009, 12:00 PM

MB C180 K at 260 Km/h.

Tarek · 05-04-2009, 12:11 PM

^Insane,that little engine goes all the way!

Is that car stock?

ree · 05-04-2009, 12:19 PM

Probably your 118i really goes up to 230 - 235 km/h!! Maybe you just have to check it again with a GPS system - but our E 280 CDI (official Top Speed of 241 km/h) also goes up to 256 km/h on the speedo, which is about 251 on the GPS system.

Normally, every car (when it is driven in) can be a bit faster, then "official"…our old SLK 320 (245 km/h) could do more then 260 km/h…so in my opinion the speed is quite right. It's like just_me (or who was it) with the S60. Doing 240 although the offical speed says 210…

Giannis · 05-04-2009, 12:28 PM

I have also reached 240km/h with my Volvo many many times and they also claim that the car does only 210km/h...

So nothing to worry about

Quote:

Originally Posted by ree

It's like just_me (or who was it) with the S60. Doing 240 although the offical speed says 210…

BMW///MPower · 05-04-2009, 12:30 PM

I actually drove a 118i automatic today, as a replacement as my car was in for service and I must say that I was surprised by the ease this car could reach 160+ speeds (in belgium the limit is 120 so unless you have a very big wallet and some high placed friends 200+ is out of the question). I know my 318d touring (limited to 136 hp due to belgian tax system

) reaches 220 (tested in Germany) so why shouldn't a 143hp 118 reach 235 (on the speedo). My 320d with 150hp (E46) reached 235 as well, so if you deduct the 5km/h the speedo will be lying (cause it does a little) you could reach 230 IMO.
And BMW engines mostly have more power output then actually mentioned (as I have read in some car magazines so I'm not saying that cause I know for sure).
If you have a stopwatch try the test with teh stop watch, it doesn't lie.
Oh and keep on going, you might reach 240. I always love it when I drive in my old mini at 150 km/h (actual km/h, I installed a bike computer and calibrated it), cause the tacho scale only goes up to 140

, the needle then points to the km/h figure at the bottom of the scale...

ACE · 05-04-2009, 12:31 PM

On a downhill, with a tailwind... sure, no problem

.

Can a stock 118i average 235km/h (actual not indicated) for two runs in opposite directions on the same stretch of road within an hour? I doubt it.

I ran a (speedo indicated) 4.2 second 0-100km/h in my stock B8 S4 this morning. Unfortunately, I can't measure the wind speed and incline numbers, but I suspect that if I went the other way it may have been slower.

bmer · 05-04-2009, 12:51 PM

Wiki:

Quote:

Speedometers are not totally accurate, and most speedometers have tolerances of some 10% plus or minus due to wear on tires as it occurs. Additional sources of error are tire diameter variations due to temperature, pressure, vehicle load, and nominal tire size.

Modern speedometers are said to be accurate within 10% but as this is legislated accuracy, this may not be entirely correct. This can make it difficult to accurately stay on the speed limits imposed; most countries allow for this known variance when using RADAR to measure speed, although levels of some 3 km/h or 3% are also used in areas of tough enforcement. This causes many arguments due to motorists complaining that they were not doing the speed as reported. Revenue[3] is being increasingly blamed for these stricter measures. There are strict United Nations standards in place but it seems not being enforced leaving this matter in limbo for many countries. Excessive speedometer error after manufacture can come from several causes but most commonly is due to nonstandard tire diameter, in which case the

percent error = 100x("standard diameter"/"new diameter" - 1).

Nearly all tires now have their size shown as "T/A_W" on the side of the tire (See: Tire code), and the tire's

diameter in inches = TxA/1270 + W.

For example, a standard tire is "185/70R14" with diameter = 185x70/1270 + 14 = 24.20 in. Another is "195/50R15" with 195x50/1270 + 15 = 22.68 in. Replacing the first tire (and wheels) with the second (on 15" wheels), a speedometer reads 24.19/22.68 = 1.0670 times the correct speed or 6.7% too high.

How to measure the error:

Quote:

To specifically find your speedometer's error:

1) Again, find a straight section of Interstate, preferably a test section.

2) Using cruise control if you have it, or a lower gear and a very even throttle foot, concentrate on maintaining a steady indicated speed of 60 miles per hour (only do this test on a section of road where it's legal to go this fast).

3) Have your passenger start the stopwatch just as you pass the first mile marker and stop it just as you pass the second, signifying a one-mile distance.

4) Record the number of seconds elapsed. Subtract 60, and then divide that result by 60. Multiply that by 100 to find the percent error.

5) Follow the procedure at least two more times.

CarGuy · 05-04-2009, 01:31 PM

Just_Me says it can. I think he just mentioned the other day in the "What's the fastest speed you've ever traveled at" thread that he did this in this car, if I am not mistaking.

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German Car Zone

Can the BMW 118i reach 235 km/h?