WHY are air intakes down there?? Aprilia!
vbr md
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Down there the air is cooler and therefore denser, so you get more oxygen (and hence combustion) per unit volume. Less performance-oriented vehicles - expedition-spec Land Rovers, for example - have enormous snorkel intakes.
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Down there the air is cooler and therefore denser so you get more oxygen (and hence combustion) per unit volume. Less performance-oriented vehicles - expedition-spec Land Rovers for example - have enormous snorkel intakes.
So Mr. WDB. Are you suggesting that my Renault Master van, GT + GLF and stuff is NOT performance orientated cos its intake ain't "down there."?? I'll 'ave you know........................
vbr.............MD
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I thought temperature was cooler the higher the altitude:) Albeit slightly less dense. Air close to tarmac must be warmer than that taken in at say 1.5m. so the snorkle could give a boost to power as well as avoiding nasty H2O ingress.....
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Some of the cars mentioned above, have headlamp level intakes, which is about as high as you can get without a chimney.
So, maybe the water becomes a bow wave, or get's swept up by other cars.
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"Down there the air is cooler"
I'm not sure that 2 feet makes a significant difference to the density, even if all roads were at sea level! You could argue the reverse for temperature, as the air near the road is likely to be hotter on anything like a warm day...
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Snap!
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Any balloonists here? Yes, tarmac on a hot day gets hot, which must also affect the air close to it. But that air then becomes less dense than the cooler air above it, which sinks and pushes the warmer air upwards. Simple convection - if you want cool air, look low down. It's why your radiators (or convectors, to be more accurate) are mounted at the bottom of the wall, not the top.
This may not be the only reason - there could also be considerations of turbulence, which I expect will be less in air close to the the ground. Possibly aesthetics too.
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So really we are no nearer knowing why diesel cars have low intakes and get "hydraulicked" and petrol cars don't and don't! As someone with some knowledge of weather and structure of the atmosphere I can safely say that a 2 foot height difference isn't going to do anything and people who have said the air near the road will be hot are correct, on a hot day and on tarmac obviously!
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I don't think it has anything to do with diesel or petrol, AS. Both need oxygen for combustion, so both would prefer denser air. My drowned Saab had a petrol engine, for what that's worth. I confess I didn't know where its intake was but since I was in three-inch deep water that suddenly started coming through the doors, I doubt it would have helped me much if I had.
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WDB - I had just been left wwith the impression, apparently held by others, that overall diesel cars have low intakes and petrol cars don't, although your petrol SAAB proves the exception. With cars having turbos and intercoolers and lots of very high temps I can't think there would be any disadvantage, temperature wise, in taking air in thru a duct at the front of the car, to the side of radiator to get fresh cool air straight from the atmosphere and not via the radiator matrix. The density of the intake air isn't going to measurably affected by two intake locations, one under the car and the other at the front.
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Some years back, whilst driving in particularly foul weather in South Devon, whilst driving up a main A road, I came across an AA van blocking the road (Ermington towards Ugborough). As there was no obvious reason for it, I got out to query what was what. He advised that there was an RAC van at the other end of a 5 mile stretch and that between them they'd decided to close the road, to prevent them having to continuously attend their members who would try to drive through the major flood in the middle...and get stuck.
Good bit of initiative, but what a stinging indictment of the lack of sense of some drivers. They come across a flood, no thought on 'how deep' and then plough on through regardless.
I'd want to know how deep it is first, even if it meant parking up and walking it.
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Good reason to keep the Defender and forget the Roomster idea then. Even a bog standard Landie has reasonable wading capability.
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When we experienced heavy rain in the past I took my Saab in for a service and they had 3 cars just recovered to them with the same problem.
Are saabs particularly prone to this ?
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>>Are saabs particularly prone to this
Any car going too fast through deep water fast could suffer,and often do..
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My colleagues Mondeo TDCi 130 suffered this fate some months back - went through no more than a few inches (say 3) following another car, but there was enough splash for it to go straight up the intake and into the engine.
A local garage managed to dry/restart it, but the turbo failed soon after - fortunately said owner didn't mention about the water and a new turbo fitted under warranty.
The lad is a sensible driver, and the water was no more than a puddle. He did get told that it was a known 'issue' with the Mondeo, and recommended he remove the lower part of the intake !
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is it possible to fit something to your low down intake.....something akin to a hoover/ tumble drier hose and re -route it higher into the engine bay......maybe even have it facing backwards, so that a quick surge of water wouldn't do this?... even if it had a mild negative performance issue
you'll probably realise i'm not technically minded in the slightest, but good at ill conceived theory!
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The Mondeo air intake tube starts at headlamp level then drops down low and back up again. I suspect that if the lower section is under water then any leaks in the tubing, which is not sealed, just push-fit together plastic pipe, will suck water in in considerable amounts and hence the damage.
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hmm.......so if that set-up were to be properly water proofed, for the cost of a few quid....then it would negate several thousand pounds on an engine re-build
seeing double there with a repeated post - rubbed it out ! - PU
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BFFS..........Big fat finger syndrome
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This does seem to be a recent thing though - for 20 years I drove company cars through places where I'd certainly think several times about taking my own car. My tactic was to approach and drive through as fast as I though I could possibly get away with - thinking if the car did conk out then the momentum would have a chance of carrying me through.
I never had a moments trouble.
I did have a Capri that would break down due to soem random electrical problem as soon as there was water on the road, but leave it for a few minutes and it would be OK again.
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I think Diesels are much more prone to this because the compression ratios are a lot higher than in a petrol engine (typically around 20:1, as opposed to 9:1 on the petrol).
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The reasons for the air intakes being low down are, I beleive:
1/ Hot air rises, the lower the cooler, the cooler the denser, the denser the more oxygen, the more oxygen the greater the efficiency. thus not negating the great job done by the intercooler.
2/ Low down though above the spliter is an area of high pressure, much preferable to an area of higher pressure which would negate to a degree the great job done by the turbocharger.
The Mondeo intake is 9" or so off the ground so unless the car is driven slowly through 10" deep water or fast enough to create a bow wave in shallower water it should not be a problem.
However it would be a good idea to have some kind of buoyant flap that redirects the intake upwards as the water level rises.
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I pumped 150 mm depth of water out of my inspection pit last Friday and another 150 mm yesterday. Not expensive, but definitely tedious.
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L\'escargot.
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The higher compression ratio in diesels means that a much smaller volume of water is required to cause the problem.
The problem has obviously been solved in jet-skis and other marine applications.
I've not seen this problem on motorcycles either.
Am I right in thinking that some air filters are much better in protecting the engine than others ?
I thought that K&Ns, for example, would starve the engine of air rather than let water through.
Modern induction design obviously puts water intake problems at a low priority.
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It's amazing how many cars are damaged by driving thro' "1/2 inch of water at 5mph".Incidentally I see racing at the Southwell all-weather track has been cancelled due to "bad weather".
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The Mondeo intake is 9" or so off the ground so unless the car is driven slowly through 10" deep water or fast enough to create a bow wave in shallower water it should not be a problem.
Heavy spray can be a problem. Lots of spray gets sucked in and accumulates in the intake trunking. It takes very little water to cause major damage. Take a 2.0 Diesel engine. Each cylinder is 500cc. At 20:1 compression that means 25cc compressed volume - or about 5 teaspoonsfull. A couple of teaspoons of water in there could spell engine damage.
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All the 'on the spot' news reports throughout last week showed most cars in the background travelling at ridiculous speed through deep puddles, hardly surprising that we're now hearing about problems.
Do people have no sense at all?
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Sorry that should be:
2/ Low down though above the spliter is an area of high pressure, much preferable to an area of LOWER pressure which would negate to a degree the great job done by the turbocharger.
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WHY are air intakes down there?? Aprilia!
I dont know about other makes, but on my 2.0 TDI Audi the air intake is just below the bonnet shut line, so not too bad.
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In reply to Kevin - Mon 18 Jun 07 20:38
I could hardly type I was laughing so much. They've even got a helicopter view of it.
They were asking "where are the emergency services". Here's a thought, get out and get your feet wet you dimwitted airhead!
Reminds me when we had a similar situation around here. Guy drives his Mercedes into the water, breaks down and then expected me to wade in and carry him out. He was given 'suitable words of advice
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