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  #16  
Old 08-03-2014, 04:19 PM
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Quote:
Originally Posted by vtmbz View Post
That's my 8 mpg on the nose. And your experience eliminates major variables. Roof rack or rear rack?

Since I have full body pans I dont think wind resistance is much altered. But trust me-- with 76 hp at your full command, you can tell when there is one extra person in the car, let alone two!

I was treated well in Me: At one point we parked along the road to hike into the woods and when we returned there was a message on the car from someone:
"If you are broken down, call me-- I am a Benz owner too! If not, nice car!"

I called and turned him onto peachparts. He had a 59 ponton, a 300sdl, and a 240d.
Woah that's like 12 more than my 240. Must've been racing it over those hills.
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  #17  
Old 08-03-2014, 05:53 PM
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Yes, rear mounted bike racks can create huge aerodynamic drag. I keep a pair of folding bikes in the trunk of the 124 with room to spare with no fuel consumption penalty. One time I managed to fit 4 in there.

Last edited by tjts1; 08-03-2014 at 07:03 PM.
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  #18  
Old 08-03-2014, 06:02 PM
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Is your injection pump turned up?

A turned up pump might not affect mileage too much around town as excess fueling would mostly occur starting from a stop. But, when on the road you might be into the throttle pretty deep and into excess fueling constantly.
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  #19  
Old 08-03-2014, 06:19 PM
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I'm thinking it was a combination of the bike rack and the extra weight. How big were the passengers, and how heavy do they pack?
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  #20  
Old 08-04-2014, 03:50 PM
1985 190d
 
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Passengers were all under 155# and really for two women they kept it down. I kept them on their toes by saying there wouldnt be any room for anything. Actually the w201 was probably designed to get two golf bags into the trunk-- there is a lot of room back there.

I like the bike rack theory. BUT-- I was burning black smoke on hard takeoffs like when I had to get across an intersection. Is that a IP symptom? I really wonder if my VCV on the back of the IP is doing what it ought. It is extremely hard to service and so get very little attention.
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  #21  
Old 08-04-2014, 04:20 PM
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I'm wondering what vehicle we're talking about. My 84SD with a turning odometer doesn't get 30 mpg. It is more like 22. I don't know that the odometer is accurate. The valves are adjusted. I "suspect" injectors could use attention since idle is a little rough on start up.

A bike rack would have a large effect. Weight some effect but not as much as rotating mass.
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  #22  
Old 08-04-2014, 05:21 PM
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See my post # 18. Black smoke / = power , black smoke = wasted fuel.

You were probably overfueling going down the road too.
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  #23  
Old 08-04-2014, 05:33 PM
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I've used a Yakima roof rack on my 123 sedan, 124 sedan and wagon, 210 wagon, 203 wagon, and 211 wagon. A 4MPG decrease is typical with the rack in place and 2 or 3 bicycles mounted up top. I sure can't see a trunk mounted rack having as big an impact, let along 8MPG. Maybe the rack cost a bit of efficiency, but I think most of it had to be from other causes.
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  #24  
Old 08-04-2014, 06:02 PM
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Quote:
Originally Posted by jcyuhn View Post
I've used a Yakima roof rack on my 123 sedan, 124 sedan and wagon, 210 wagon, 203 wagon, and 211 wagon. A 4MPG decrease is typical with the rack in place and 2 or 3 bicycles mounted up top. I sure can't see a trunk mounted rack having as big an impact, let along 8MPG. Maybe the rack cost a bit of efficiency, but I think most of it had to be from other causes.
Take the bike you have on your roof and mount them sideways across the width of the car. The side of a bicycle is an aerodynamic trap.
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  #25  
Old 08-04-2014, 06:56 PM
1985 190d
 
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Quote:
Originally Posted by 97 SL320 View Post
See my post # 18. Black smoke / = power , black smoke = wasted fuel.

You were probably overfueling going down the road too.

My usual around home mileage without a bike rack is consistently 34mpg during the summer,tankful after tankful. So you can see that when I saw 27mpg I was pretty surprised. I had someone following me all day who said they saw black smoke from time to time, probably when I downshifted.

This current 190d has 84,000 miles and a new head gasket. It purrs really. No oil consumption this year to date. No noticeable smoking or smells when starting. Timing chain showed zero stretch when I had the head off.

But there is something amiss in the EGR electricals, and kickdown switch isnt getting any power, so I know its not 100% happy. Hopefully this winter I can dig into it. Meanwhile, no bikes without a fuel surcharge...
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  #26  
Old 08-04-2014, 07:28 PM
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Quote:
Originally Posted by tjts1 View Post
Take the bike you have on your roof and mount them sideways across the width of the car. The side of a bicycle is an aerodynamic trap.
Except that bicycles on the roof are being dragged through clear air creating maximum drag. A bicycle sitting 12 inches off the back of the trunk is in the low pressure area directly behind the car. Just doesn't feel right. Some quick googling shows typical claims of 2-3MPG impact for trunk mount racks and 5MPG for roof racks. As always, YMMV.
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  #27  
Old 08-04-2014, 09:45 PM
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Quote:
Originally Posted by vtmbz View Post
My usual around home mileage without a bike rack is consistently 34mpg during the summer,tankful after tankful. So you can see that when I saw 27mpg I was pretty surprised. I had someone following me all day who said they saw black smoke from time to time, probably when I downshifted.

Yes, there are many things that were dragging MPG down. It is somewhat difficult to see light smoke when following in daylight hours.

Some years ago I used a friends gen 1 Dodge diesel to pull a 22 ft box trailer. In daylight hours I could not see any smoke from the side exit exhaust pipe. At night when a following car's headlights provided back illumination, light smoke was visible.

Yes, the pump was turned up and the owner went to great pains to minimize daylight visible smoke as he subscribes to black smoke = wasted fuel. (A slight puff and cracking the throttle is acceptable )
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  #28  
Old 08-04-2014, 10:12 PM
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LOL 27mpg and we are complaining....the worse I got on my trip, loaded roof rack and truck was 16mpg.....I wouldn't be complaining on that figure...
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