I believe the problem is the lack of a suitable definition for the grade. Some statements imply that the 240 can climb a grade at 80mph. Since this is very close to maximum horsepower on level ground, it's clearly impossible.

Others maintain that they can hold 70 mph on a grade. If the grade is 1%, this might be realistic.

However, I'm quite certain, and both you and Steve have confirmed, that the 240D cannot climb a 4.5-5% grade at 65 mph. It's a physical impossibility.

First, cool green seats! Awesome!
Second, and more important, I would like to know the story behind the tachometer in your 240D. Nice! Hopefully there is a thread I must have missed on that???

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

I would also agree with that, I don't know if everyone understands how steep a grade 4-5% is. A 617 turbo (with twice the power) is working pretty hard to maintain 75 on those hills, the 616 does not have a chance.

My auto 240D will creep up to 80 on level ground, but that's about all. It will go up and down most "normal" highway hills (probably only 2-3%) at 65 without a problem, but I'm not sure it could hold 65 indefinitely (in most places the hill aren't that long).

As I mentioned, the SD with the 2.88 gears cannot maintain 70 mph on those hills.

In fact, I'd venture to say that the SDL with 150 hp can barely maintain 75 mph on those hills. I had the SDL on a very long 6% grade and it held 68 mph without using maximum available power (but way into the pedal)..........so, I make the assumption that it could hold 75 mph........but, even that is not assured.

Green seat hehehe Lousy phone cam and bad lighting = green seats! They're actually more beige in color.

See this thread about the tach I installed in my 240D

DIY tach for 240D w EGR- easy!

__________________
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 sounds right, with 2.88, you are probably around 3000 rpm at 70 mph, so you are not really at peak power/torque. That's the main reason I'm a little reluctant to go to 2.88 gears, the 3.07 gears do get you a couple 100 rpm closer to peak power.

Both the 2.88 and 3.07 are a compromise for flat roads. With the hp peak at 4400 rpm, neither ratio is ideally suited for maximum horsepower. Additionally, neither ratio allows the use of 3rd gear to assist the situation.

The 2.47, however, would allow the vehicle to easily maintain speed on level ground in 4th gear and would be ideal for climbing grades in 3rd gear (rpm of about 3650 rpm at 70 mph).

The only downside is the 4-3 and 3-4 shift requirements...........fairly often if you frequently climb hills.

I wouldn't want to go that far, I like to be able to cruise at 75-80 without any shifts. With 3.07, I can do that everyplace except the real mountains, it just gets a little buzzy at 3500 rpm.

If I drove 80 mph on a routine basis, I'd use the 2.47. The engine is dead quiet at 2900 rpm. That's the current engine speed with the 2.88 driving 68 mph. It's perfect at that speed.

If I had to downshift for upgrades..........so be it.

Actually, if you assume 1 hp = 550 ft-lbs/sec (http://en.wikipedia.org/wiki/Horsepower#Mechanical_horsepower), and the car weighs 3100 lbs, then we need 5.64 hp to lift a 240D 1 foot per second. A 5% grade at 65 mph is 4.76 ft of lifting per second [(5280)(65)/3600][0.05], which means you need about 26.9 hp [5.64 sec-hp/ ft][4.76 ft/sec]. If the top speed of the car is 83 mph, then the hp needed to get the machine to overcome air resistance at 65 is: 65/83 raised to the third power times the rated hp of 62 which equals 29.8 hp. If I add 29.8 to 26.9 I get 56.7 hp as the needed minimum. Now, with an rpm to auto speed conversion and a horsepower vs. rpm curve, we can tell if we get there or not. My bet is we do, as the torque curve is rising as the rpm is dropping in this rpm range, so the hp won't drop linearly with rpm until we get to the point where the torque curve is flat. Which means all we have to have is a slope that is about half that of the region where the torque is flat. That likely doesn't happen until you get near or below 3,000 rpm.

The poor bastards driving up over 70 from Denver going West will be dead meat in a normally aspirated car. They will be gasping for air in Denver, while the turbos should be relatively unaffected. This climb starts at a mile elevation, and then climbing to over 2 miles elevation to pass through the Eisenhower Tunnel. Not a really fair comparison for a 240D as half the available air pressure at sea level is missing, and that can't be made up with manipulating the fuel mixture.

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)

I'll have to decide what I want to do someday, I'm probably not going to change anything until it's time to do my engine. I might do something with the gears at the same time, haven't decided. Hopefully, I have a little while to think about it.

One problem with the analysis:

1) The requirement for 26.9 hp to climb the grade is correct. This horsepower must be at the rear wheels. With a typical drivetrain loss of 25%, the required power from the engine is 35.78 hp.

2) The requirement of 29.8 hp to overcome air resistance is based on the engine rated power of 62 hp.

So, in reality, we need 65.6 hp, engine rated power, to climb that 5% grade at 65 mph.

This is not happening.

Brian, we went through a bit of the engine rating question earlier in this thread, or so I thought. My German brochures for the car say it makes 72 PS (Pferdestaerke, or HP) at the clutch with the power steering, water pump and alternator pulleys/belts. The US rating is 62 hp. I was under the impression the US rating was at the wheels. That may not be the case, but the fact remains, the car is running on margins at this point - whether or not you can pull this off will depend quite a bit on the condition of the car. Dragging brakes, wider tires, underinflated tires, windows open, and so on will be noticeable since you have no margin left. I will also reiterate the point I made earlier, drafting with one of these cars in this kind of situation makes a big difference, as will driving in the middle of a pack cars and trucks.

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)

All the powering comes from the rear wheels, including the power that does the lifting. So we should just discount the 62 hp by your drivetrain efficiency loss value of 25% if that is what it is, to 46.5 hp. The hp needed then is 22.3 for air resistance (the value is calculated using the cubic speed vs. hp relationship and uses the maximum hp available at the wheels) and the same 26.9 hp to lift the vehicle at 65 mph going up a 5% grade. This still exceeds the engine rating at the wheels, by .6 hp, without allowing for any hp droop from peak to the value at whatever rpm we have at 65 mph. So, we are truly working in the margins here, and I would not conclude quite as readily as you that this is not happening. 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)

thanks,
I looked about everywhere for them. I thought it was available as a complete assemby.
Tom