MK2VR6
Posted a lot
Mk2 Golf GTi 90 Spec
Posts: 3,329
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Nov 12, 2012 17:30:44 GMT
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I was going to going to rattle off a load of schpiel about turning your engine off at the McDonald's drive thru, and ensuring you never wear undercrackers to save fuel and weight. However, it's more useful to discuss airflow under the car. My daily a4 avant is plastered with plastic underbody plates, as well as a plastic engine undertray. Friends who have lost their undertrays from running low cars have consistently cooler engine running temperatures. If a slab of plastic under the engine can make a difference to engine running temperature, I can only imagine underbody panels help airflow, and ultimately save mpgs, however minimal.
On the other hand, switching your engine off at the drive-thru and binning the y fronts surely would be worth a shot.
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Last Edit: Nov 12, 2012 17:31:55 GMT by MK2VR6
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Nov 12, 2012 19:42:53 GMT
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I suggest making it so low that you can't drive it very far, walking the rest of each journey should save a fair amount in petrol
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OUTRUN
Part of things
13...
Posts: 620
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Nov 12, 2012 21:19:09 GMT
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"2.7" ground clearance is a good minimum height to shoot for. According to Mercedes, "Lowering the ride height at speed results in a 3-percent improvement in drag."" See if Mercedes recomend lowering a car to improve aerodynamics it must be true  I have often wondered if Airmatic Mercs lower at speed to increase stability and lower drag. My dads S320 CDi can get very impressive MPG when it's 'in the zone'. An SW20 MR2 would surely be a good candidate for eco driving too (with suitable engine). That flat floor is impressive. Back to the thread... Lowered Sierra: Do this.  |
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Last Edit: Nov 12, 2012 21:20:23 GMT by OUTRUN
I need your help to get back to the year 1985.
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sowen
Club Retro Rides Member
Posts: 2,245
Club RR Member Number: 24
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Nov 12, 2012 21:21:59 GMT
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I lowered my previous mk3 Mondeo and current Rover 75 (both diesel) and found a slight improvement in mpg while doing steady motorway runs. At the time I was doing around 25-30k miles per year, and it made about 3-4mpg difference to both cars.
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Many modern cars with air suspension lower themselves at speed to reduce drag.
I know rangerovers, mercs and some Audi's do it.
But I've tried it with my old merc that's on air and not really noticed a difference. I'm guessing its prob got more to do with co2 and tax brackets and new car brochure bumf.
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Remember the days when sex was safe and motorsport was dangerous. Vintage bling always attracts pussy.  |
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v8ian
Posted a lot
Posts: 3,832
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Being an old cnut, I can remember when Sierras first came out, they got a bad reputation for falling off motorways at high speed. Ford diagnosed it as an aero problem and went into back peddle mode, eventually they came up with the solution by altering the rear door frames and fitted little hockey stick lips to the rear of the doors, I think this problem caused ford to lose a lot of sales in the first year of production, How to save fuel?  ? dump weight, fit a bigger engine, skinny tires pumped up to a ridiculous pressure, Bigger engine?? we had a 2l mk2 transit, gave around 18-20 mpg in town, we fitted a 455 olds engine and auto box, immediately returned 26 mpg, |
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Atmo V8 Power . No slicks , No gas + No bits missing . Doing it in style.
Austin A35van, very different------- but still doing it in style, going to be a funmoble
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RobinJI
Posted a lot
"Driven by the irony that only being shackled to the road could ever I be free"
Posts: 2,995
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In theory yeah it'll make a difference. As has been said it's more about reducing the air-flow under the car than reducing the frontal area. The underside of a car's a seriously messy place for air-flow, even most modern cars covered in under-trays are still going to be causing large amounts of drag from air going under the car, a quick glance at any cars underside and you can see it's a lot less flowing and smooth than the top of the car, it's clear it's going to create some drag. For the best results you'd ideally also fit a front splitter as well to move the point where the the car 'splits' through the air, making more air go over the car and less under, reducing the pressure under the car which will help reduce drag and lift.
As for comparing it to weight saving, it's true that most people will see more difference from shaving off a few kg, but it'll help at different times. The cars weight causes resistance to acceleration, but very little resistance to driving at a steady speed, especially at higher speeds. The aero does the opposite, causing resistance in relation to the cars speed, but no resistance to acceleration. Ditching the interior wont make any real difference on the motorway, and improving the aero won't really help about town, ideally you want to do both, but generally improving aero will be easier without loosing the cars practicality and comfort.
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Seth
South East
MorrisOxford TriumphMirald HillmanMinx BorgwardIsabellaCombi
Posts: 15,542
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"2.7" ground clearance is a good minimum height to shoot for. According to Mercedes, "Lowering the ride height at speed results in a 3-percent improvement in drag."" Why stop at 2.7"? ;D |
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Follow your dreams or you might as well be a vegetable. |
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AB car pix
Posted a lot
Car mag' snapper
Posts: 1,337
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Any tenuous reason to lower your car is good...... so yes, it will help. Get it done. ;D
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1979 Chrysler Horizon 1.3 GL 1980 Ford Granada 2.8 Ghia 1985 Ford Sierra 3dr 1985 Ford Escort Mk3 1988 Ford Sierra Sapphire Cosworth 1989 Ford Escort 1.3 Popular 1995 Volvo 960 1996 BMW 525i 1998 BMW 323i 1999 BMW 530d 2003 BMW 530i . www.facebook.com/ABCARPIX |
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Nov 13, 2012 10:30:39 GMT
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In theory a lower car will do more mpg, however lowering a Sierra screws up the rear wheel alignment. If you don't reset it properly you'll increase rolling resistance as well as wear out the tyres.
If you're that bothered that you need to get a few more MPG then maybe you should be looking at getting something more modern and efficient or buy a push bike.
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Volvo back as my main squeeze, more boost and some interior goodies on the way.
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Nov 13, 2012 12:20:55 GMT
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When I first got my Sierra, I did a lot of reading up on history and sensible subtle improvements...when the mk1 series first came out there were indeed a good few rear end lifting on a motorway issues and that resulted in ford adding the hockey sticks on the back edge of the rear 3/4 windows, never the less the Sierra still had a .34 drag coefficient (big technical term) the same as an f40 hence the early names they got of "salemans spaceship" and "jellymold" so improving aerodynamics would prove a challenge. Long story short lowering it anyway it has to be done think about the consequences later |
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mt2man
Posted a lot
Posts: 1,366
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Nov 13, 2012 14:48:24 GMT
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I shall be getting the angle grinder out at the weekend and cut the coils anyway have a splitter in the garage somewhere too! I do cycle to work and the car rarely gets used, to be honest this topic was abit of a curse word take but some thought went into it haha Need to think of a way of explaining why I am lowering another of my cars! The girlfriend often moans at the ride comfort of my cars haha |
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mym
Part of things
Posts: 443
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Nov 13, 2012 16:31:26 GMT
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lowering reduces the frontal area, so less drag.
personally, i'd give the car a good going over so :-
fresh engine and gearbox oil (reduce internal friction)
check tyres (check pressure, replace for decent eco tyres if need replacing to reduce rotational friction)
check tracking (reduce wear & friction)
clean car (internal and external, weight = fuel) plus a clean cars nicer!
might also be worth checking that the carb is setup correctly and not overfueling
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Last Edit: Nov 13, 2012 16:35:29 GMT by mym
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ToolsnTrack
Posted a lot
Homebrew Raconteur
Posts: 4,128
Club RR Member Number: 134
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Nov 13, 2012 19:59:18 GMT
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Never run with more than half a tank of fuel. Your carrying excess weight, just stop and fuel up more often.
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Nov 13, 2012 21:15:52 GMT
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Covering the top 1/4 of the wheel (partially boxing it in) gives almost identical results to fully covering the wheelarch in terms of reducing Cd Sideskirts that extend below the level of the sills help airdams at the front, with splitter-style-extensions help smooth the airflow under the car do NOT think about trimming the rear bumper upwards - it will actually cause a buttload of turbulence behind you Certain spoilers can help reduce drag (depending on the body style) As they create a small "ball" of turbulence between the roofline and the spoiler, giving the overall effect of the air coming away from the bodywork much smoother. Note: the whale-tail is NOT one of these  Any pics of the front of yours? |
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Last Edit: Nov 13, 2012 21:27:01 GMT by chairchild
You're like a crazy backyard genius! |
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Nov 13, 2012 21:17:33 GMT
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"2.7" ground clearance is a good minimum height to shoot for. According to Mercedes, "Lowering the ride height at speed results in a 3-percent improvement in drag."" Why stop at 2.7"? ;D  That's probably too far; creating extra friction will increase your fuel consumption. |
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1989 Peugeot 205. You know, the one that was parked in a ditch on the campsite at RRG'17... the glass is always full. but the ratio of air to water may vary. |
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? dump weight, fit a bigger engine, skinny tires pumped up to a ridiculous pressure, 
