Does anyone have experience running with/without the panels beneath their cars that would lead one to believe that it is a significant factor in drag?

I remember M-B engineers talking about the (soon to be launched) 124 diesel, having encapsulation panels beneath the engine to reduce drag, improve fuel efficiency and high-speed stability, and to maintain proper engine compartment temperature.

My 124 no longer has the rear (transmission) panel, and my 140 rear panel came loose last month, so I removed it until I source the correct bolts (thanks indie/mechanic). I really don't track fuel mileage anymore, so I don't know how much if any the rear panel contributed.

And the larger front panel? Any before/after fuel mileage data from anyone? More curious than anything.

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Gone to the dark side

- Jeff

I doubt it's significant. I have both panels for my 91 300D but have driven with them off lately (did some work, didn't get around to putting them back on). Last tank I got 29 mpg in mixed driving and using winter diesel...which is as good as I could expect with panels on. I think the best I've ever seen on the highway is in the 31-32 range.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 157k miles
06 E320 CDI "Rutherford", Black on Tan, 175k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 144k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 70k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

My E300's panels have been off for about 4 years now, but I actually have been meaning to re-install them and probably will in the next week or two now that this thread has popped up. I don't remember having any significant MPG changes, nor do I remember and operating temp changes, but I do remember the car being a hair quieter, so that alone could be a good reason to re-fit the panels.

Once I get them put back on, I will start tracking my MPG's more closely. On winter diesel and in 90% stop-and-go recently I've been averaging just under 30MPG, but both the blend, panels, and driving type are going to change soon so It'll be a bit harder for me to establish a baseline relative to my prior driving.

I can post my averages with them re-installed once I get a few tanks under my belt, although in this car that could take months given the mileage and tank size.

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1995 E300 Diesel
~300k

The '87 TD also got a 24gal tank, with my sunny-day usage it can take a lot of time and many types of driving to get through the tank, not useable data. Maybe this summer I'll take a couple of Michigan trips in her (~350miles round trip) and try to do it under similar wind/loading/speed/traffic conditions, really would take at least two-three trips with and two-three trips with panels though. I'm hoping that someone here will have tried this already, but at this point it seems like there's no data to support keeping the panels on for efficiency (other than cold-weather operation possibly).

__________________

Gone to the dark side

- Jeff

I'm sure the panels help with mileage, but the two most important reasons for having them are noise reduction and shielding from water.

Noise reduction is nice for these cars. A new hood pad and the proper panels quiets things down nicely.

The engine panel will shield the belt drive from water. The kilma relay senses belt speed and compressor clutch speed differences and cuts power to the clutch if there's a big difference. In my experience, driving through a puddle without the panels gets water on the belt drive and compressor clutch and causes it to slip when the compressor is engaged. Since the Klima rekay needs the ignition to be switched off and on to reset itself, it's a pain when it happens.

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'84 190D 2.2 5MT (Red/Palomino) Current car. Love it!
'85 190D 2.2 Auto *Cali* (Blue/Blue) *sold*
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