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Old 04-27-2021, 06:24 AM   #21 (permalink)
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Originally Posted by Vekke View Post
Few more pictures of the car found. The air suspension makes it difficult to estimate things, but we know the wheelbase of the car which is 3210mm.

With that data you can calculate that the wheel diameter is around 760mm that could then be 255/55R19-->763mm.

After this you can measure ground clearance under the car to be around 140mm at least in the picture I looked.

You can also measure the heigths of the tire flaps. In front they are around 45mm height and lowest point is at 100mm. Accuracy of measurement is +-5mm

at rear the flaps are little smaller. Heigth of the flap is 25mm. Accuracy of those measurements I would say is +-7mm more towards the plus side as there is no clear pictures of the flaps alone with wheel specially from rear.

Now remember the car has air suspension and lowers itself at higher speeds so flaps will come even closer to ground.
Yes, having adjustable air suspension is a very good thing. Lower it whenever you wish, or alternatively, have it lower automatically with speed. I am often a bit puzzled why more Ecomodders don't do it.

I've seldom regretted designing, building and installing my own system (although having said that, it was even more complex, and more work, than turbo'ing my car).

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Old 05-26-2021, 03:49 AM   #22 (permalink)
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Got answer from Mercedes on how much it lowers itself:
--------
The EQS reaches the cd value of 0.20 in the driving mode SPORT, Vesa. The EQS is lowered in this mode by 20 mm.
The level control is part of AIRMATIC. It keeps the ground clearance constant irrespective of the vehicle load, but also makes changes. By way of example, in COMFORT mode the vehicle body is lowered by 10 mm at high speeds above 120 km/h, and another 10 mm at over 160 km/h to reduce aerodynamic drag and increase handling stability. If the vehicle drops below 80 km/h, the body level returns to the initial position. Up to 40 km/h the body can be raised by 25 mm at the touch of a button, above 50 km/h it is automatically lowered back to normal level.
-----------
That is not very big drop in heigth and that means about 0,005 drop in drag coefficient as 40mm drop is about 0,01. Just enough to make it 0,20 in advertising.

Main reason why most people don`t install air suspension is the cost. Ready set price tag is 3000-5000 euro range on aftermarket units. So paypack time is long. If you build it yourself it has no TUV approval and is illegal. We had self made air suspension system in our CityCab project car and it did not work very reliably. Ofcourse if you are able to write the control code yourself it would have been propably ok solution.

Lowering car with steel spring set will get you the efficiency gains cheaper and payback time is reasonable. Ofcourse if its new car cost is not so big thing if you plan to keep it long, but most ecomodders drive older cars here as they are more efficient and cheaper to run.
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Old 05-26-2021, 04:09 AM   #23 (permalink)
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Quote:
Originally Posted by Vekke View Post

Main reason why most people don`t install air suspension is the cost. Ready set price tag is 3000-5000 euro range on aftermarket units. So paypack time is long. If you build it yourself it has no TUV approval and is illegal. We had self made air suspension system in our CityCab project car and it did not work very reliably. Ofcourse if you are able to write the control code yourself it would have been propably ok solution.

Lowering car with steel spring set will get you the efficiency gains cheaper and payback time is reasonable. Ofcourse if its new car cost is not so big thing if you plan to keep it long, but most ecomodders drive older cars here as they are more efficient and cheaper to run.
Sure, air suspension is not cheap - but it's very unlikely to be 3000-5000 euro in most parts of the world and on most cars.

In my book on custom air suspension (one, incidentally, that almost no one has bought), I use a second-hand compressor from a BMW, air tank from a Porsche Cayenne, off the shelf Firestone rear springs (all really cheap), custom front struts (not cheap and not easy), programmable PIC modules (cheap and easy, but not as good as the programmable ECU I then went to), Range Rover height sensors (cheap and easy) - and so on.

Unless you are considering the aerodynamic advantages alone, I don't really think you can compare air suspension to lowered steel springs. In terms of ride, handling and versatility, air springs are in another world compared with lowered steel springs.
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Old 05-26-2021, 04:38 AM   #24 (permalink)
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Mainly aerodynamics and the cost, but if you build your own system challenges/problems comes also from damper settings meaning to get it working well you need to change damping characteristics of the dampers also. Adjustable dampers are also expensive. So if you just put many thousand euros to your suspension it should also perform better than the steel spring ones does. Ride quality is usually always better but handling takes time and effort also in the tuning like any setup. The parts if you buy them seconhand etc arent that expensive, even I have most parts needed in shelf from some scrapped cars.

But this topic is about the EQS aerodynamics. I am still trying to find underside picture of that car to see the underside and tire front flap design better. Weird that they don`t have any show models of the car even in big city showrooms like Dusseldorf :/
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Old 05-26-2021, 05:51 AM   #25 (permalink)
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Quote:
Originally Posted by Vekke View Post
Mainly aerodynamics and the cost, but if you build your own system challenges/problems comes also from damper settings meaning to get it working well you need to change damping characteristics of the dampers also. Adjustable dampers are also expensive. So if you just put many thousand euros to your suspension it should also perform better than the steel spring ones does. Ride quality is usually always better but handling takes time and effort also in the tuning like any setup. The parts if you buy them seconhand etc arent that expensive, even I have most parts needed in shelf from some scrapped cars.
Most air suspension kits run adjustable dampers. I have adjustable dampers front and back on my Insight's air suspension.

Obviously handling (and ride, too) requires tuning and set-up. Just as with steel springs.

Basically, air suspension craps on steel springs for ride, handling and aerodynamics from a great height.

But yeah, you need to spend money and effort. A bit like any decent car modifications, in fact.
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Old 07-18-2021, 09:32 PM   #26 (permalink)
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This car has a .20 cD.
So the Mercedes matches it ( not counting the frontal area of course ! )


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Old 07-18-2021, 10:27 PM   #27 (permalink)
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Add sufficient frontal area to accommodate four passengers and you have the Volkhart-Sagitta V2 with the same Cd. Add more and you get the Mercedes.
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Old 07-21-2021, 11:17 AM   #28 (permalink)
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clamshell

Finally had a moment to go back and look.
In 1978, Giugiaro did the Isuzu Piazza, which auto journalists claimed at the time, to be the first production car to have the 'clamshell' hood. It's elegant, using an existing visual cut line on the nose to serve as a real body cut. leaving the uncluttered upper surface.
https://gunpowderblue.com/isuzu-piazza/
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Old 07-21-2021, 11:36 AM   #29 (permalink)
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another Cd 0.20 Mercedes-Benz

With a set of 'Tesla-esque' side mirrors, the Kamm-form, Mercedes-Benz Bionic Boxfish ought to come in at around Cd 0.20 as well.
As a daily-driver, and millimeter for millimeter, the Boxfish appears to be the more efficient envelope, requiring 'less car' to generate the same Cd.
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Old 07-21-2021, 01:18 PM   #30 (permalink)
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Quote:
In 1978, Giugiaro did the Isuzu Piazza...
Badged in the USofA as the Isuzu Impulse. A guy I worked with at La Cie had one.

He offered the design to VW for the Sirocco (IIRC) but they passed on it.

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