A160 Blue Efficiency - not that efficient!

[Apial]

Not quite true.........
While the lower rolling resistance would obviously help, the smaller diameter wheels would mean the engine would need to rev higher to maintain similar speeds.
Any advantage gained with the skinny tyres would be more than offset by the engine having to work harder.
Providing of course the gearing remained the same.

Duhhhh..... The rolling diameter of the wheels is identical. Therefore the wheel rpm and engine rpm remain the same. Wheel diameter remains the same because as the inner wheel increases in size the tyre wall reduces in height, hence radius is identical. The 17" combo actually weighs double that of the 15".


The actual grip is as a result of the coefficient of friction of rubber. The skinny tyres actually are no different than the wider tyres in that respect. What actually causes the skinnies to lose out is that they will over heat under hard cornering and this will change the coefficient of friction.

 

[MrT]

You can see my average consumption below, B150 with manual transmission. Usually get 40-41mpg on a long motorway run, or 7-10mile extra-urban commute in warm weather.

Around town, usually as low as 29-30mpg.

 

[raymont]

The actual grip is as a result of the coefficient of friction of rubber.

This is only partially true. The tread pattern interlocks with the road surface to provide grip.

 

[Sp!ke]

This is only partially true. The tread pattern interlocks with the road surface to provide grip.

I'm not sure they do or race cars wouldnt drive with slicks.

The tread blocks are for water displacement or mud.

 

[Ian Hunt]

Coming in late to this thread...
We bought a 2004 A160CDI ACS a few beeks back to replace my wifes trusty (but extremely thirsty auto 2.0 Beetle). It's done 12k (the previous owner can't have spent more than a few hours in it! Madness as it's avantgarde with leather, parktronic etc etc etc). Anyway it seems to use no diesel at all and road tax is 35 quid!
I did 480 miles in my E220CDI yesterday & even with a good 2 or 3 hours of that sat in queuing motorway tail backs (I hate the M1, the M25 and people that drive badly causing accidents & lane closures), managed nearly 44mpg. I'm impatient & don't hangabout either - the m40 & m6 toll on the way back were all a ton plus....

 

[raymont]

I'm not sure they do or race cars wouldnt drive with slicks.

The tread blocks are for water displacement or mud.

A given contact area may offer more grip if it's 'slick', ( in the dry anyway), but that doesn't mean that a tread pattern, when present, doesn't interlock with the road surface to enhance the grip offered by the friction of the road surface the rubber is in contact with. I.e. total grip is friction from the rubber in contact plus some grip from 'interlocking'.

 

[Sp!ke]

A given contact area may offer more grip if it's 'slick', ( in the dry anyway), but that doesn't mean that a tread pattern, when present, doesn't interlock with the road surface to enhance the grip offered by the friction of the road surface the rubber is in contact with. I.e. total grip is friction from the rubber in contact plus some grip from 'interlocking'.

So using your theory, a tyre with a tread pattern would have more grip even in the dry than a slick due to 'interlock'.... (bear in mind a bigger contact patch doesnt alter the coefficient of friction between the two surfaces)

Define 'interlock'?

 

[Smatt]

I think that for a smooth surface, a slick would be best, but for most roads(ie rough surfaces), a tread pattern will give better performance.
Remember, F1 tracks are very high quality, little used(compared to say a M-way) & well maintained, with no rough surface.

 

[Mactech]

I think that for a smooth surface, a slick would be best, but for most roads(ie rough surfaces), a tread pattern will give better performance.
Remember, F1 tracks are very high quality, little used(compared to say a M-way) & well maintained, with no rough surface.

Sorry but tread pattern has no value on anything other than loose or wet surfaces. Unless roads are in a very poor condition they are non movable.
Yes, there certainly is 'interlocking' between the tyre and the surface of the road but it is at a 'nano' level and most would refer to it as friction.
Given a choice all rally cars would use slicks on anything approaching a tarmac surface.

 

[Dinnie]

The Blue Efficiency models only add an extra 1 mpg or 2.
Mercedes have fitted a lighter windscreen, steel wheels and some aero tweaks incl lower front suspension (I think!)
Overall, the car is only about 15kg lighter than a standard A160 so it will hardly make any difference at all compared to BMW's efficiency dynamics whose technology really is on another planet compared to Mercedes' adjustments.

 

[hawk20]

The Blue Efficiency models only add an extra 1 mpg or 2.
Mercedes have fitted a lighter windscreen, steel wheels and some aero tweaks incl lower front suspension (I think!)
Overall, the car is only about 15kg lighter than a standard A160 so it will hardly make any difference at all compared to BMW's efficiency dynamics whose technology really is on another planet compared to Mercedes' adjustments.

Just not true. Go and compare the mpg figures before and after Blue Efficiency and the difference is very significant.

 

[J400uk]

Just not true. Go and compare the mpg figures before and after Blue Efficiency and the difference is very significant.

He is correct, original a150 was listed as 45mpg combined, latest a160 blue efficency is listed as 47mpg combined.

 

[hawk20]

He is correct, original a150 was listed as 45mpg combined, latest a160 blue efficency is listed as 47mpg combined.

I wonder how much has been taken by the change to EU5 (current engine) compared with EU4 (the pre Blue Efficiency version). The diesel gains much more- up from 57.6 to an amazing 64.2 mpg.


My brother has averaged over 60 mpg over 40,000 miles in his 2005 A160cdi and will soon be swapping for the new one. It will be interesting to see what the real world gains are.

 

[Robbo]

The Blue Efficiency models only add an extra 1 mpg or 2.
Mercedes have fitted a lighter windscreen, steel wheels and some aero tweaks incl lower front suspension (I think!)
Overall, the car is only about 15kg lighter than a standard A160 so it will hardly make any difference at all compared to BMW's efficiency dynamics whose technology really is on another planet compared to Mercedes' adjustments.

I think that the problem with the A class is that the engines are quite old designs so they are scratching around for improvements. When the new model is launched, I fully expect to see variants of engines based around the new C220Cdi engine and C180 blue efficiency petrol engine to be used which will make a big difference to the performance/economy of the new model.

 

[timskemp]

I imagined this was due to larger wheels also typically being wider too and it was the width that increased the rolling resistance.

The way I see it, the width affects fuel consumption by its increased width increasing aerodynamic drag not due to rolling resistance. For the same tyre pressure the contact area will be about the same, maybe slightly less due to the stiffer sidewall, and the sidewall deflection will be smaller. As heat generated (energy turned to heat) is lower with lower deflection the lower profile tyre will have lower rolling resistance and lower mechanical drag.

So going from 225/55/16 to 265/35/18 increases the width of the tyre by 40mm each side, therefore increasing the frontal area of the car by an amount (80mm x ride height, say 150mm, so additional 0.012 sq m), and increasing aero drag. Rolling resistance is decreased. Depending on the wheel/tyre combination weight may be increased too.

 

[Mactech]

The way I see it, the width affects fuel consumption.

So going from 225/55/16 to 265/35/18 increases the width of the tyre by 40mm each side, therefore increasing the frontal area of the car by an amount (80mm x ride height, say 150mm, so additional 0.012 sq m), and increasing aero drag. Rolling resistance is decreased. Depending on the wheel/tyre combination weight may be increased too.

All very true! But in practice the construction of the tyre makes a big difference from one manufactuer to another. The material and direction of the plys will optimise the tyre for certain charatoristics That's before we start on tyre pressures and geometry....
So the rolling resistance can often be increased along with aero drag.

 

[J400uk]

I wonder how much has been taken by the change to EU5 (current engine) compared with EU4 (the pre Blue Efficiency version).

I am 99% sure its the same 1.5 95hp engine just with a few little tweaks to squeeze out the extra mpg and bring the co2 down.

I think that the problem with the A class is that the engines are quite old designs so they are scratching around for improvements.

IIRC they were all new and developed exclusively for the A and B back in 2004 (or was it 2005) when they came out. Again comparing to the 1.6 in the Golf/ A3, the Merc unit is newer.

Mercedes use these engines as they need to be specific size and design to fit in the engine bay, they wouldnt be able to fit in the 1.6 from the CLC and C-Class.

 

[Robbo]

The A Class petrol engines date back from the W168 so they are well over 12 years old in design. They made minor improvements when the W169 was introduced, but the basic engine design remains the same. The W169 diesels, I'm not so sure, but I bet are essentially very similar to W168 diesels but with later generation CDI technology.

Yes, other engines in the MB line up don't fit in the A Class. I was referring to the A class replacement, which I bet that is able to take a wider range of engines. I suspect the current W169 A class is stuck with the engines it currently has.

Although having said that, there is that B class F Cell which might fit in a W169, so who knows.