What real world difference is there between engines?

[Breaker]

Made me think the weekend. Out of the engine sizes, what real world difference is there when driving on the road?

Forget magazine articles. Forget the track. Forget "pub talk". Just driving as most owners would drive on a day to day basis.

What made me think of this was I was overtaking a couple of cars the weekend in 3rd gear. A little damp on the road in the centre. Sport button on. Accelerating from around 4,000 RPM the traction control light was flickering on and off as I went passed the cars.

Now, given the same scenario, if I was in an M version would I have got passed quicker? In a 2.5 would I have got passed slower?
With the traction control controlling things I don't think there would be anything in it! With the traction control off, the more powerful engines could have passed slower due to wheel spin! :driving:

 

[WLH]

The "M" would have the advantage of the "M" locking diff... :driving:
Which we don't have on the other models...

 

[mikedav]

Now, given the same scenario, if I was in an M version would I have got passed quicker?

Yes

Seriously though it depends on what 'real world' means. In gear 50-75MPH the 3.0 is only fractionally slower than an M, so overtaking there would be little in it. But if we are overtaking a car doing 110MPH, try the same move in a 2.5 tand an M and you will notice!

With the traction control controlling things I don't think there would be anything in it! With the traction control off, the more powerful engines could have passed slower due to wheel spin! :driving:

The TC light flickering is partly due to the wet road and IMO partly due to the car being set up pretty firmly; on A and B roads it skips over bumps, and this fools the car into thinking it's detecting slip, which is not actually a wheel spin problem. Even with DSC on a 3.0 will post a quicker 0-60 in the wet from a standing start than a 2.0, even though logic would suggest its easier to spin the tyres. So there is no way a more powerful car would be slower at overtaking speeds whatever the conditions.

 

[laser4596]

In theory, in the wet, a 2.0, 2.5 and a 3.0 with the same tyres suspension etc should overtake exactly at the same speed, assuming that both cars are capable of spinning their wheels due to lack of traction.

This is because the chassis/tyre setup will have the same grip in both cars, and both cars TC will let them operate at or close to this limit. Therefore even though one car has more power, the engines will both be operating at the same, restricted power output.

However if the the lesser cars are not facing wheel spin and TC restrictions, the more powerful car will accelerate faster because the TC will be setting a limit higher than the maximum power of the lesser engines.

 

[enfield]

I think that there may not be that much difference in rain or snow but there is one hell of a difference in the dry. My Z4M overtakes cars on 2-lane roads (country roads) like a champ. Just need a slight gap - put her in 3rd and wroom!

I have a 315 hp / 330 torque FX45 that is AWD and does a 0-60 in 6.5-6.7 seconds. Pretty quick car - but it cannot overtake in spots the Z4M can.

 

[Smokin]

I think the big thing is torque-that gives the "punch" to go. From having driven a 325Ci (nice car, but not my 2 seater, :wink: ), the 2.5 would run with the big boys once you got up to highway speed. It wasn't bad in the 0-60mph range, but it definitely took longer than with the 3.0Si in my Z coupe. In order from lowest torque to highest, 2.5l, 3.0l, M.

 

[Vroomer]

You Brits had the 2.2 for a bit, too.

 

[GP20]

In theory, in the wet, a 2.0, 2.5 and a 3.0 with the same tyres suspension etc should overtake exactly at the same speed, assuming that both cars are capable of spinning their wheels due to lack of traction.

This is because the chassis/tyre setup will have the same grip in both cars, and both cars TC will let them operate at or close to this limit. Therefore even though one car has more power, the engines will both be operating at the same, restricted power output.

However if the the lesser cars are not facing wheel spin and TC restrictions, the more powerful car will accelerate faster because the TC will be setting a limit higher than the maximum power of the lesser engines.

So basically what you're implying is - a Z4 can be as quick as an F430 and a LP640 as long as all cars are not moving.

No offense but your post just doesn't make any sense. It doesn't seem like you understand how BMW's traction control systems work.

 

[laser4596]

GP20 that is not what I am saying at all.

Via some simple physics and in particular Newton's laws, a car can only accelerate as much as the grip it has on the road surface.

As said previously, assuming the 2.0, 2.2, 2.5 and 3 have the same suspension set up and same size tyres, they will have the same amount of grip.

Now in wet conditions with limited grip it is fair to assume that all cars will be accelerating on the limit of their grip, in say 1st and 2nd gear.

Now if thrust forwards is equal and opposite to grip then it is fair to assume that on the limit of traction, all cars will accelerate at an equal rate.

Now obviously in higher gears or dry conditions or with a car capable of more grip ie ferrari or lambo it is not a fair arguement.

We were however discussing acceleration in slippery conditions.

 

[Mattt]

The 3.0 has the 6 speed box, so different ratios too.

 

[mikedav]

As said previously, assuming the 2.0, 2.2, 2.5 and 3 have the same suspension set up and same size tyres, they will have the same amount of grip.

They don't, so thats the first problem...ignoring that, different gearbox ratios, weights and overtaking in first

Now if thrust forwards is equal and opposite to grip then it is fair to assume that on the limit of traction, all cars will accelerate at an equal rate.

But in the situation described...

A faster car will accelerate harder as it begins the overtake. So when the 3.0 loses traction and the DSC cuts the power, it's moving quicker than the 2.0 is at the same point (even though both now have no power). Both cars now decelerate, then when the power kicks in again start to accelerate again. All within a fraction of a second. So when they have grip, the faster car is faster - overall its gaining on the slower car.

Surely you can only change that if one car has more grip than the other a 4WD car for example - which is why a WRX is quicker in the wet (when it has a grip advantage) and a RWD is quicker in the dry (when there is more grip available and power to weight is more important)?

 

[Herminator]

GP20 that is not what I am saying at all.

Via some simple physics and in particular Newton's laws, a car can only accelerate as much as the grip it has on the road surface.

As said previously, assuming the 2.0, 2.2, 2.5 and 3 have the same suspension set up and same size tyres, they will have the same amount of grip.

Now in wet conditions with limited grip it is fair to assume that all cars will be accelerating on the limit of their grip, in say 1st and 2nd gear.

Now if thrust forwards is equal and opposite to grip then it is fair to assume that on the limit of traction, all cars will accelerate at an equal rate.

Now obviously in higher gears or dry conditions or with a car capable of more grip ie ferrari or lambo it is not a fair arguement.

We were however discussing acceleration in slippery conditions.

But each engine will weigh a different amount, effecting each cars traction but also meaning the engines will have different amounts of mass to accelerate, so other than using a high end simulation, the only way to tell is from real world results. There are just too many variables to be able to generalise.

 

[Z4coupe]

In Real world driving there will be less of a difference than in track tested situations. A tenth in time equals out to about a car length in terms of distance. But there are so many variables. From 50-75 getting on it a split second earlier than a driver in a more powerful car can give you the illusion your car is faster. Everything equal, hp always wins. By how much is another story on the street.

 

[neilisdead]

surely it can be decided in the pub over a pack of pork scratchings... all this physics nonesense means nothing, Einstein was a fool with a cool hair do.

 

[carl]

How many miles does your car have on it? When mine was new the TCS light was on lots of the time in the wet when exiting roundabouts. But now it seems to have calmed down on that front -- I guess the tyres take a while to scrub in properly.

 

[laser4596]

A faster car will accelerate harder as it begins the overtake. So when the 3.0 loses traction and the DSC cuts the power, it's moving quicker than the 2.0 is at the same point (even though both now have no power). Both cars now decelerate, then when the power kicks in again start to accelerate again. All within a fraction of a second. So when they have grip, the faster car is faster - overall its gaining on the slower car.

But it cant start to accelerate faster if it cant get the grip to do so in the first place.........

Anyway as said by others this discussion has so many variables and dependants that it is a somewhat muddled one and thus I will bow out gracefully...... generally a z4m will be faster than a 2.0, both of which will probably be slower in the wet than say a 3.2 tt with quattro..... we could quantify situation on situation to make every arguement win.

At the end of the day its about what you like most, and what is most suited to you, not what is 1/10th of a second quicker!

 

[flyboyaj]

You guys are all super-geeks! oke:

It's all about the same given traction limitations, and the difference would not be noticable IMHO. Hell, I used to own a 2.5i and now have the 3.0si and barely notice a difference between the two on dry pavement. There is a difference, but given the fact that these cars ALL rock-the-socks-off and throw-you-back-in-the-seat it is not very noticable.

 

[epbrown]

The 3.0 has the 6 speed box, so different ratios too.

The 5 and 6 speeds have the same ratios for the first 5 gears. The 6-speed's sole advantage is more relaxed cruising.

 

[Mattt]

I assumed they would all be closer ratio'd - they seem to be in other cars I've driven with a 5/6 speed box option.

 

[AlanL]

And at the end of the day all of these engines will let you pass the slow moving bozo quickly and get back into your lane safely with a nice grin on your face. In real world driving whether one of these cars did it in 0.1 less time is pretty much like debating how many angels you can fit on the point of a pin.

Sit back and enjoy the drive......