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  #16  
Old 07-20-2006, 10:07 PM
ForcedInduction
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Here is the video. Link

The tach is jumping from a loose amp connection and the yellow light shows the water injection is active.

I had to play with the throttle a bit to keep EGT's under 1250*f.
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  #17  
Old 07-21-2006, 12:42 AM
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There is a Mercedes manual "Technical Data Passenger Cars" that has the curves for horsepower, torque, and vehicle speed for each gear. Somebody (like Leathermang) can get you the curves if he knows the year, model, engine, and rear end ratio - my book isn't new enough for a 240D. The curves are good for stock cars, of course. Once you have the curves you can then combine the torque and road speed curves into one curve and you'll see at which road speed to run a gear in. No tach needed and nothing mysterious about it. MB even puts dots on the speedometer that indicates red-line for a gear. I posted the combination curve for the 220D a few years ago.
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  #18  
Old 07-21-2006, 12:55 AM
ForcedInduction
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Quote:
Originally Posted by dabenz
MB even puts dots on the speedometer that indicates red-line for a gear.
Those are not redline. They are around 4000rpm.
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  #19  
Old 07-21-2006, 02:43 AM
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Quote:
Originally Posted by ForcedInduction
Here is the video. Link

The tach is jumping from a loose amp connection and the yellow light shows the water injection is active.

I had to play with the throttle a bit to keep EGT's under 1250*f.
I'm amazed my engines have not blown up yet. The 240D has been run with the speedometer pegged for considerably longer than you show in your video. It was run down a massive hill at full throttle, somewhere around 95 MPH (the lead car was going 100 and slowly pulling away).

It has been run up hills in Pennsylvania at 50-55 MPH for minutes at a time, then, shifted to 4th and lugged all the way down to 40 MPH, where it would downshift and climb right back to 55 MPH. No, I was NOT driving.

When the 300D Turbo was new to me, I ran it up steep hills and freeway grades at full throttle to remove crud from the engine. It worked, and the car emmited a puff of smoke on three separate occasions, which was followed by smoother running.

Mercedes must really know what they're doing.
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1981 Mercedes Benz 240D- Estimated 300,000+ mi Returned to the earth
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  #20  
Old 07-21-2006, 11:32 AM
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Can somebody do this for the 240D and 300D? It's nice when the facts speak for themselves when comparing engines. The speedo pic came from the owners manual, and I apologize for my lack of computer skills. From tables that I didn't scan, the max speeds in the gears are 33, 56, 92 and 132 km/h. Corresponds to 21, 35, 57 and 82 mph. Max hp (SAE) at 4200rpm, max torque at 2400rpm, max engine speed (redline in my opinion) at 4350rpm. Interesting point on speed plot is 4500rpm in 4th gear - why? The other gears end at max engine speed. Running at or past max hp probably isn't good for engine longetivity. The other question is whether these represent the real numbers or a "derated" set - only MB knows for sure and I'd doubt they'd tell us.
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240d rpm @60 mph-benz1.jpg   240d rpm @60 mph-benz2.jpg   240d rpm @60 mph-benz3.jpg  
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  #21  
Old 07-21-2006, 01:38 PM
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240D RPM at any speed

Hi everyone, I hope this helps!
The formula for MPH at a certain rpm is MPH = RPM x C/ T x F X 88. Or you can re arrange the formula to T x F X 88/ C = RPM. I like the second form because RPM is what we're after here!
Where: C = The driven tires circumference in feet..
T = the transmissin gear ratio ( 1 for a 4 speed tranny in 4th gear)
F = Final drive ratio ( 3.692 for a 240D, or 3.07 for a 300D)
On my 240D, driven tire circumference is 6.4167 feet (tires are 205 70 14s) This number is obtained by marking the ground and the tire ( while on the car), and rolling the car until the tire turns 10 times. Mark the ground where it matches the mark on the tire. Then measure the distance between the marks on the ground and divide this number by 10. Don't forget to convert inches to a decimal by dividing by twelve i.e 6 inches / 12 = .5 feet.
If you work this out for a 240D you will find that at 75MPH the engine is turning 3797 RPM. To me this seems like way too many revs to call it a good cruise speed. Now here's a cool little trick. Once you know the RPM at a given speed, you can create a simple conversion factor by dividing RPM by the speed. 3797 RPM / 75 MPH = 50.632 RPM per MILE per hour! Now that you have this magic number, you simply multiply the speed you want to know the RPM for by 50.632. 65 MPH ? easy! 65 X 50.632 = 3291 RPM!
Remember that each gear will have its own Magic Number.
Another thing to remember is that comparing RPM to Speed between a 300D and a 240D does not work because the cars have different gear ratios. (3.692 vs. 3.07). And yet another thing to remember is that this formula does Not take into account torque converter slip on an automatic transmission car. A car with an automatic will be turning higher RPM due to the slip of the torque converter; however, the formula will accuratly predict the driveshaft RPM.
By the By I run my turbocharged, four speed, 240D with 3.07 gears from a 300D. This gives a very relaxed 2736 RPM at 65 MPH, and 3157 RPM at 75 MPH. Magic number for this combo is 42.1026 RPM per Mile per hour.
Happy Cruisin'
Chris Rice
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  #22  
Old 07-22-2006, 12:59 AM
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Am i reading the dabenz 220D graphs correctly? It appears the car doesnt develop 50hp until 3000 rpm.
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  #23  
Old 07-22-2006, 03:55 PM
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240DieselDog, you're reading right if you want DIN horsepower.
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