Could the big hole in the bonnet cause poor mpg?

[squeaky2]

Was having a think about this and looked at a few e70's at BMW this morning as i was picking up what should have been a gold plated mirror glass (for the price)
There were a few LCI x5's there and the difference would be the flaps in the grille.


Against what i have


Would not having the flaps both add to the drag coefficient of the car and also increase the cooling of the engine so that more fuel is used.

Any thoughts?

[X5Sport]

Dunno, but the E53 had them too. Some only close when the car is stationary so as soon as you're moving they open up. Others are power operated. These things are appearing on other cars too, Ford advertise them on one of their new models so they must work. Doing what I don't know - other than temp control/maintenance.

I suspect whatever drag increase there may be is being overcome somehow. Like under the car. Most of the underneath of my X6 is covered in flat covers and shields to allow air to flow underneath unimpeded. Add the improvements in engine management and tuning and it probably balances out.

There are no flaps on the current X6, so maybe they'll appear on the LCI due in a few months time.

[pvr]

At least when I wash the car, I am not spraying all over the engine as I have nicely closed flaps when the car is stationary

[storminmike]

[quote=""X5Sport""]Dunno, but the E53 had them too. Some only close when the car is stationary so as soon as you're moving they open up. Others are power operated. These things are appearing on other cars too, Ford advertise them on one of their new models so they must work. Doing what I don't know - other than temp control/maintenance.

I suspect whatever drag increase there may be is being overcome somehow. Like under the car. Most of the underneath of my X6 is covered in flat covers and shields to allow air to flow underneath unimpeded. Add the improvements in engine management and tuning and it probably balances out.

There are no flaps on the current X6, so maybe they'll appear on the LCI due in a few months time.[/quote]


apart from styling the idea of blocking off the engine/rad withe vents is half baked. Perhaps they aid overcooling of the water from cold or on a cold day but from an aerodynamic point of view I'd say fail.

Unless you're Adrian Newey and the air ingested in the front not being used to cool water is being directed to a blown diffuser or out the tailgate spoiler the wouldn't the front gills be the ones better to close off pushing the air around the car instead of inflating/pressurising the engine bay?

[Chompers]

These flaps are part of the ED upgrades that BMW put on LCi cars. The OH's 1st has them 08/57 plate. They are supposed to aid engine warm up from cold and thus improve fuel economy.

[squeaky2]

I think im going to have to try and access the hidden menus as im interested to know the engine temp when driving along........considering the way a lot of the engine bay is sealed i do wonder whether it actually adds to the drag.

More akin to driving a 7.5tonne truck with a flat front. If we actually had a temperature gauge i would be tempted to block up the grille and see what kind of difference it actually makes to the economy.