Why do cars still have bonnets?
Discussion
Seriously... big opening panel with hinges and catches and cables, that has to be hand-aligned at the factory and does less than nothing for structural rigidity. Why bother? It wouldn't be hard to make all the routine service stuff accessible from underneath, little flip-up panel at the base of the windscreen for access to fluids, and then the 'bonnet' could be a bolt-on structural panel which adds rigidity and better crash protection. Manufacturers can also do away with all those big plastic engine covers (that crack around the fixings the first time anyone tries to remove them). Doesn't matter how ugly the engine looks, if no-one can see it...
And taking it a step further, once you have done away with the need for a big lightweight hinged panel up front you can start completely rethinking the way the front end of a car is designed.
On the downside, any major mechanical repairs would involve dropping the engine and transmission out from underneath, but a lot of modern designs are heading that way already. Is it just that customers want to know they can open the bonnet, stare at the engine and wiggle some connectors when it breaks down, before calling the AA, or is there something I am missing?
And taking it a step further, once you have done away with the need for a big lightweight hinged panel up front you can start completely rethinking the way the front end of a car is designed.
On the downside, any major mechanical repairs would involve dropping the engine and transmission out from underneath, but a lot of modern designs are heading that way already. Is it just that customers want to know they can open the bonnet, stare at the engine and wiggle some connectors when it breaks down, before calling the AA, or is there something I am missing?
You've not looked closely at some modern French designs, then? 
207, Modus, Kangoo, etc. All tiny bonnets that really only give access to the dipstick and washer fluid. You would have to take half the car apart to remove the rocker cover, as the engine is tucked in under the wiper linkages and scuttle panel.
207, Modus, Kangoo, etc. All tiny bonnets that really only give access to the dipstick and washer fluid. You would have to take half the car apart to remove the rocker cover, as the engine is tucked in under the wiper linkages and scuttle panel.
devnull said:
You just answered your own question. Because it would be pretty stupid to drop an engine for routine service work?
Audi did something for the essentials though, the service hatch:
It's pretty stupid to have to lift the body off the chassis on a 4x4 to change the clutch, but that didn't stop Land Rover. Depends what you define as 'routine'... most US manufacturers now specify 100,000 mile intervals for plugs and timing belts, by which time most cars are on their third or fourth owner, and the manufacturers have washed their hands of them.Audi did something for the essentials though, the service hatch:
Audi managed to retain all the disadvantages of an opening bonnet without any of the advantages. I have absolutely no idea why they made a bonnet that still had hinges and catches but needed a special tool to open it.
911p said:
New Porsche 991 doesn't have a bonnet as such, a little different from the front engines cars you're talking about though.
It does have a massive bonnet at the front, giving access to the brake fluid and all the luggage.There's a huge bonnet on the front of my Elise, most of which is a grill letting air out from the radiator. Which is why the S2 just got a couple of tiny access panels - it makes much more sense.
kambites said:
So how on earth do you, for example, change the spark plugs on that 911?
Since those plugs are sticking out the sides of a DOHC boxer head on either side of the engine, even access to the top of the engine wouldnt do much good. For boxer maintenance (especially DOHC ones) you need decent space around the sides of the engine, which the 911 wouldnt provide anywayMister3man said:
Seriously?
OP I get the impression you've never done any major work on cars...
I've run a marque specialist repair/restoration business for the last eight years. Right now I'm posting rubbish on the Internet to delay having to start a monumental chassis welding job that I really don't feel like tackling today. Apart from that...OP I get the impression you've never done any major work on cars...
Vitorio said:
kambites said:
So how on earth do you, for example, change the spark plugs on that 911?
Since those plugs are sticking out the sides of a DOHC boxer head on either side of the engine, even access to the top of the engine wouldnt do much good. For boxer maintenance (especially DOHC ones) you need decent space around the sides of the engine, which the 911 wouldnt provide anywaykambites said:
Do the plugs really stick straight out of the ends of the banks? I'd assumed they came out of the side (as in the top, the way the engine is aligned) of the heads?
I'm no porsche specialist, but i've lookd into some DOHC boxer engines, and the plugs sit between the camshafts, like they would in a normal cilinderhead, in other worse, directly in the length-direction of the cilinder/piston, so in order to change the plugs on a DOHC boxer you end up having to take them out of the heads with only the space between the head and the enginebay sidewall to work with, which in some cases might be easier from below rather then the top, bonnet or no bonnet.Gassing Station | General Gassing | Top of Page | What's New | My Stuff