This is basically what I was trying to say...you reach max HP at 4K rpm. Turning the engine faster than that is counter productive as the drop in Torque more than offsets the rise in RPMs...thought my prior statement had the peak too low...I was simply trying to point out that redlining the engine will not produce maximum power.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Agreed. If the 4K figure is accurate, climbing a hill at exactly 4K would generate the maximum possible speed.

I'm somewhat skeptical of the 4K figure..........might be a bit higher.

The M/B manual states that max torque on the 617 turbo is at 2400 rpm, when we've clearly proven that it's about 2850 rpm..........so, some of the M/B figures must be viewed with the eyes of a skeptic.

I think the numbers for Tq and Hp are at the rear wheels. At the clutch it is higher. Can someone verify these numbers?

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

my 240D did just fine last summer up in the poconos

The values quoted in the German brochures for the 240D are 72 hp at the clutch with the accessories running (meaning the water pump, fan and power steering pump as a/c was not standard equipment on those cars). The US numbers may be at the wheels (a DIN vs. SAE issue?) and may include an a/c compressor hanging off the front of the engine.

The reason auto speed and hp vs. rpm come into the equation is that at 75 mph, the bulk of the steady state hp is used to punch a hole in the air for the automobile to pass through. When you begin to go up a hill, only the hp left between maximum available at that rpm and that needed to punch the hole is available to lift the mass of the vehicle up the hill at the desired rate.

Without grades posted for hills, this is a discussion of seat of the pants results. From the seat of the pants spending in excess of 350,000 miles driving a 220D and a series of 240Ds with manual transmissions there is a huge benefit to understanding how much oomph is available to lift, or on flat ground, accelerate, the car at what speed in which gear. It is one of the reasons I have forced all my kids to learn to drive on a manual transmission equipped 240D. You learn to pay attention or you get embarrassed all the time. You also learn some bad habits, like drafting. You can maintain speed a lot better close in behind another car. Try it some time. In the old days I could count on better brakes and tires but today that isn't likely to be true.

I agree that there just ain't much hp left to lift the car up a hill as you approach "terminal" velocity, which is around 82 mph, in one of these, so you slow down to go up the hill.

None of my experience included a Diesel with a tach until my W126 350SD and now my W210 E300D TurboDiesel. So, unfortunately, I am unable to point to the rpm at the terminal velocity, and without that in hand the estimates of what is available while you drive on the planet Earth, to lift the car up a hill at speed, are pretty loose. But, if you presume the top speed of 82 mph is limited by air drag (and it is, since going down hill gets a few more mph and drafting gets you quite a bit more), then if you drop speed to 70 you have reduced the hp demand to punch the hole in the air by 38%. That means you have significantly more hp available to lift the car up the hill, because hp drops linearly with engine speed assuming torque stays flat, and in this case we know torque is rising as engine speed in this rpm regime is reduced.

So, while hp is king in this exercise, it is important to know where you are on the hp vs. rpm curve, the shape of the torque vs. rpm curve and how close you are to "terminal" velocity. Also, those hours of driving make a lasting impression on you for what is really going on. That same experience tells me flooring the accelerator pedal in those situations is not the best way to eek out the last bit of performance either. If you just lead the steady state throttle position enough to get the engine to accelerate the car as you head into the hill, then squeeze a little more to maintain the speed, you get the best performance. Flooring it when the full pedal travel is being applied to the injection pump fuel metering mechanism seems to lower temps by leaving too much unburned or incompletely burned fuel in the power stroke. Turbos too. Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Brian, that would only be the case on the moon, or some other celestial body without air. If 4krpm on flat ground is at the "terminal velocity" of the 240D, you won't be able to climb anything without slowing down. The only hp available to lift the car up the hill the hp after pushing the air out of the way. Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

P/N 202 301 00 93 Here you go, I just fixed mine.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

Is that the little plastic sleeve that goes over the prongs/in the cut out? Or is that the whole joint? My dealer has had difficulty finding the part for my car. I "fixed" it with popsicle sticks, copper wire and electrical tape. Lasts about two years or so and then the vibration causes it to fall apart and I "fix" it again. Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

These are the inserts for "rectangular holes" (2) that the two prong things fit into. I have also cut wood "shims' too take up the slack if these are missing.

__________________


1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"

I did some calculations for the engine speed of a 240D with a manual transmission, 3.69 gears, and 185-70-14 tires. The results show that the engine speed at 80 mph is 4100 rpm. So, if we conclude that the Germans are accurate with a specification of 4000 rpm for maximum horsepower, you are entirely correct.

No 240D can climb any grade at 80 mph. It's physically impossible.

However, my previous statement that the best possible climb speed is obtained at exactly peak horsepower (in this case it's 4000 rpm) remains accurate. There may, or may not, be a suitable gear that will allow 4000 rpm on the specific grade encountered. However, if such a gear were available (third gear might be perfect on a 5% grade at approximately 55 mph), it would provide the best possible climb speed.

Clearly, it's not going to be fourth gear.

I just came back from a drive in the 83 240D 4 spd up the Merritt parkway in CT. Tank about 3/4 full, had a bicycle in the trunk approx 25 lbs and other stuff approx 15 lbs. I weigh about 130 lbs. Starting at exit 59 northbound (near North Haven) going uphill through the tunnel in 4th gear at 65 mph, I had no trouble maintaining 65 mph. At no point did I have to downshift or floor it. That uphill section was not that long and I thought maybe that is not the steepest grade so I kept driving northbound at 65 mph in 4th all the way to exit 67 Meriden. Between exits 60-67, I did not have any trouble maintaining 65 mph. Did not have to down shift or floor it at any of the uphills. So I turned around and as I went through the tunnel in North Haven at exit 60 going downhill, I can see this long stretch of uphill ahead of me so I got the phone out and took this video

http://s31.photobucket.com/albums/c397/funola/?action=view&current=Video_101507_006.flv

The down counter starts at 1:26 secs and there is approx 10 secs of downhill at the beginning of the video and the uphill section starts at 1:16 secs. As you can see kept the speed at 65 mph (3300 rpm). At about 3/4 of the way up the grade, the 240D started to slow down so I floored it to try to maintain 65 mph. Maybe I floored it a bit late otherwise I may have been able to maintain 65 the whole way. As you can see it slowed to approx 61 mph and actually accelerated as the grade let off a bit towards the end of the clip at counter 23 secs. I turned the camera off just at the top of the grade.

After I took the video I turned around and went north up through the tunnel and turned around at exit 61 and basically had the same results. No problems northbound and had to floor it southbound.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

That's the hill...........southbound just after the tunnel exit. Northbound is the downhill...........

So, the vehicle slowed to 61 mph by the time it reached the point where slope started to decrease. You might have held 65 mph on that grade.........but, I sincerely doubt it. If the grade was longer, the 61 mph might have decreased as well.

A conclusion can only be firmly drawn when the vehicle is at steady state on the grade. If it's losing energy at any point, the available horsepower is insufficient to maintain the speed and the grade.

If it could hold 61 mph........steady state..........on that hill, it would be quite an achievement.

I agree with your assesment Brian. Are you going to try to find out what the grade of that section of the Merritt is? What's your guess?

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I do want to find out the grade on that section. My guess is that it's 4.5%. It could be as high as 5%.

Going west out of Denver on I-70 there are a number of 6-7% grades. I've only climbed those grades with the 617na with at least 3 passengers. But there is no way in the world the car will hold 55mph on those grades. Someone just drove a newly purchased 240d on that route eastbound and had to downshift to 1st gear at the Eisenhower tunnel.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13