Stupid Aircon question

[scanner]

Unless every single factor on both runs were exactly identical there is no way of telling if the 5% reduction was due to using aircon or not.

It can indicate a likelihood that it has an effect but not exactly how much.

Perhaps the superior torque of diesels means they are less affected.

As I say, when I was driving without an aircon belt last year I noticed no appreciable difference. The Bongo didn't perform 5% better or get 5% more MPG.

I can however see that using aircon might have more impact on a petrol, especially a 2 litre.

[Simon Jones]

As the AC compressor has a clutch which allows the pulley to freewheel when it's not switched on, taking the belt off will not reduce the load on the engine any more than leaving it switched off.

Every vehicle I can recall driving (either petrol or diesel) of any engine size or power has had a small but detectable drop in power when the AC is on. Many years ago, when I had use of a Peugoet 405 diesel as a pool car, my colleagues refered the AC button as the 'turbo boost' button: you turn it off and the car goes a lot faster .

Plenty of modern cars will disengage the AC when you floor them so as to maximise the power available at the wheels.

[mikeonb4c]

I agree with all scanners points. You never get nothing for nothing but the % hit on a diesel Bongo is about as low as it gets short of driving a truck. And hey, what did you buy your Bongo for?!?

[scanner]

taking the belt off will not reduce the load on the engine any more than leaving it switched off.

I didn't remove the belt - it "removed" itself.

Whilst "removed" (which I hadn't realised) I noticed absolutely no other effect other than wondering why I felt hotter than usual.

[Simon Jones]

Auto Express test shows an average 8% reduction fuel economy with AC on. During city driving test, it dropped from 25 to 20 mpg which is a 20% change. The least difference was at motorway speeds: http://www.autoexpress.co.uk/car-news/3 ... ythbusters

[mikeonb4c]

Auto Express test shows an average 8% reduction fuel economy with AC on. During city driving test, it dropped from 25 to 20 mpg which is a 20% change. The least difference was at motorway speeds: http://www.autoexpress.co.uk/car-news/3 ... ythbusters

I'll be controversial and suggest a diesel Bongo might notice it's smallest difference around town. It simply wastes that torque revving up and down until the autobox engages lockup in top gear. Similarly, knocking a few mph off you motorway cruising speed will probably offset aircon penalty. Averages mean diddly squat with an un-average car like a Bongo

[scanner]

- Air-conditioning makes a big difference when driving at low speeds, but has very little impact on the motorway.

That test was done on an Astra where (IMHO) the extra "drag" of the aircon is more significant than on a Bongo. It is also more significant still around town because the engine is performing at a tiny fraction of it's potential and so the fixed amount of power (around 2 or 3 BHP so I've read) sapped by the aircon is a huge proportion of the power actually being produced. At normal cruising speed it is far less significant.

[helen&tony]

Hi
It depends on speeds, really....You can't drive without the aircon in the summer here, and I have absolutely no complaints...around 30 MPG with speeds of 50-60 MPH....In fact, I think the Bongo's damned economical for what it is....PLUS what it does.....I can't speak for other folk who have owned their chariot for a long time, but there sure ain't a queue selling them on the grounds of fuel consumption....and the way I see it, is that if it seems a bit too thirsty, there's always plenty of other van-type things that use less juice....but they aren't going to step up to the functionality of Bongos
Cheers
Helen

[Simon Jones]

- Air-conditioning makes a big difference when driving at low speeds, but has very little impact on the motorway.

That test was done on an Astra where (IMHO) the extra "drag" of the aircon is more significant than on a Bongo. It is also more significant still around town because the engine is performing at a tiny fraction of it's potential and so the fixed amount of power (around 2 or 3 BHP so I've read) sapped by the aircon is a huge proportion of the power actually being produced. At normal cruising speed it is far less significant.

Depending on the exact engine they had in the test vehicle, Astra 1.9 CDTI SRi will be either 118 or 147 BHP, the first is pretty close to the Bongo and the second is a fair bit more powerful. Even the 118 BHP engined vehicle is likely to out perform a Bongo because it will have a more efficient common rail injection engine and the whole lot will be considerably lighter. With that in mind, and the fact that Bongo has an aircon system twice the size of the Astra, why would the Astra show a more significant reduction in fuel consumption?

[scanner]

- Air-conditioning makes a big difference when driving at low speeds, but has very little impact on the motorway.

That test was done on an Astra where (IMHO) the extra "drag" of the aircon is more significant than on a Bongo. It is also more significant still around town because the engine is performing at a tiny fraction of it's potential and so the fixed amount of power (around 2 or 3 BHP so I've read) sapped by the aircon is a huge proportion of the power actually being produced. At normal cruising speed it is far less significant.

Depending on the exact engine they had in the test vehicle, Astra 1.9 CDTI SRi will be either 118 or 147 BHP, the first is pretty close to the Bongo and the second is a fair bit more powerful. Even the 118 BHP engined vehicle is likely to out perform a Bongo because it will have a more efficient common rail injection engine and the whole lot will be considerably lighter. With that in mind, and the fact that Bongo has an aircon system twice the size of the Astra, why would the Astra show a more significant reduction in fuel consumption?

Much more modern engine all that "efficiency" comes at the cost of being much more sensitive to the slightest drain of power .

Put simply you notice it far more as at city speed the Astra engine is hardly working and the loss of even 2 or 3 bhp is a massive loss. At those speeds the Astra may only be producing 20 or 30 bhp and 2 or 3 is a 10% loss.

I doubt if the hit on a Bongo is anywhere near 10% at any speed.

However - It might be if Bongos did 40-50mpg around town.