Does "S" have to have worse fuel economy? Electronic disable?

[rsplodge]

Brand new here. Getting a 2008 Mini Cooper Clubman S, this coming Friday.

I did bit of searching on this but didn't find much. If this has already been discussed, I'd be happy to be sent the links to the threads.

Basically, I'm wondering why the turbo S, has to get worse fuel economy, even if driven conservatively, with rpms kept low, and no quick acceleration? Along similar lines, does no one make turbos, (de-!)tuning kits, or whatever that allow you to kill the turbo (or reduce boost) if you actually wanted the best economy as opposed to best acceleration and speed? I did a Google search and I did come up with one blog by some guy suggesting that technically you could provide an electronic disable of the turbo in order to do exactly this, but I'm presuming this doesn't exist in the market.

I guess the marketeers figure someone buys an "S" for performance and if they wanted economy they would buy a non-S, but why couldn't it be selectable?

Are the worse published fuel economies related to the manner in which the testing is done, or is there some fundamental technical reason (extra weight or turbo load, or whatever) that the turbo has to get worse mileage?

Thanks, ..Roger

[James]

You could get technically get a remap to have better fuel consumption and less power i guess, I know someone who bought their son a cooper and had it detuned and limited so he couldn't drive too fast.

[rsplodge]

Ouch that's sinful!

Quote: Originally Posted by James (original)

You could get technically get a remap to have better fuel consumption and less power i guess, I know someone who bought their son a cooper and had it detuned and limited so he couldn't drive too fast.

[Angib]

I don't think 'turning off' a turbo would help. To some extent the engine of a turbo has already been detuned so that when the turbo is working at full chat, it doesn't blow up the engine. So when the turbo is not working much - which is a lot of the time when not accelerating or running at high speed - the engine's efficiency is lower, so fuel economy is worse.

Checking the usual compression ratio changes, I'm impressed - in the second generation cars the ratio only drops from 11:1 in the Cooper to 10.5:1 in the Cooper S, so there's not that much efficiency lost there.

A turbo can be disabled - for example by holding the waste gate open - but that just reduces the efficiency further. It would be fine as a way of preventing full power being produced but not as a way of increasing efficiency.

[alexcannas]

From my theoretical understanding, a turbo engine should actually be more efficient than a non-turbo one.

In the past certain manufacturers would put more fuel than necessarry in the mixture to allow for a certain lubrication of the parts from the fuel. I am not sure if this practise is still used and to what extend.

[Angib]

Quote: Originally Posted by alexcannas (original)

From my theoretical understanding, a turbo engine should actually be more efficient than a non-turbo one.

It certainly can be - but the turbo must be working effectively at normal operating speeds.

That's why the new Fiat TwinAir engine is only a 875cc twin cylinder with a turbo (virtually half a Cooper S motor) - the turbo will be working hard much of the time and working hard means good efficiency.

Of course what Roger really needs is a diesel, which have good part-load fuel efficiency whereas petrol engines tend to only have good full-load efficiency. That's why small petrol engines are more economical (because they're working hard more of the time) whereas you can run a big diesel engine gently and it will still be nearly as economical as a small diesel.

[Kev50027]

From what i've seen, it's only about a 1 or 2 mpg difference between the Cooper and the S. For all that extra power the S produces, that means it's a lot more efficient than the Cooper.

Like you said yourself, if you got an S, why do you want better gas mileage? Enjoy your car, don't cripple it!