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  #1  
Old 05-19-2002, 01:49 AM
Benz240D
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Post 240D Top Speed ?

I have often wondered if my 78 240D is one of the few or normal to run up to 94 mph.
What I use, strictly Amoco Premium, Diesel Kleen by Power Service and Mobil Delvac 1300 moto oil, a can of STP for extra lubricity. It has 240k miles on it, doesn't smoke or leak any fluids.
Uses about one quart of oil per 1600-1850 miles, which I assume this is normal.
As to Amoco Premium diesel fuel, I called Amoco, the fuel has a minimum Cetane rating of 50.
I mix the Diesel Kleen to gain the 6+ points thereby running about 56 - 57 cetane.
The car will easily do 80-85 with 3 adults in the car. Is this normal? Or do I just have a strong running euro-gray-market car?
I have noted that after running wide open for 3-5 miles at 90+ and back off the throttle, a large puff of black smoke appears behind - I was told big trucks may do this too.
This is the car my wife hated, now likes driving it as much as I do. She has even made mention she'd like to get another Benz -

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  #2  
Old 05-19-2002, 04:43 AM
XN6guy
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That is unusual for a 240D, but I can believe it. There are simply some cars out there which perform better than average... a lot of it depends on tuning--careful valve adjustment, proper injection timing, balanced injection pump and injectors, etc. General mechanical health plays a big role too. Even seemingly little things like throttle adjustment are important--otherwise you may not be actually "flooring it".

-Joe
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  #3  
Old 05-19-2002, 02:04 PM
Benz240D
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I had a slight problem - stuck wide open on a 35mph post limit street, had to keep shifting to keep motor from over revving. I figured out the problem and vowed that wouldn't happen again! Very scary! So where that small tube is (spring inside) above the starter and in front of the firewall - I drilled it and put a roll pin in there, I get positive solid throttle control - it opens to the screw bolt on the pump. I've not ever messed with the bolt, so far as I know it is factory setting. That Diesel Kleen I swear added 5-10 hp's!
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  #4  
Old 05-19-2002, 08:50 PM
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MB records the 4 spd manual cars of this era to top out at 138 km/h, about 83 MPH. The 4 spd automatic was 133 km/h, about 80 MPH. Different size tires or speedometer error could explain some of the difference, if not all of it. No difference was noted between Euro or US cars, which my info source is very good at stating.
Gilly
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  #5  
Old 05-19-2002, 09:45 PM
turbodiesel
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These old 123 speedos are not very accurate. You were probably doing 85-88 at best.
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  #6  
Old 05-19-2002, 10:02 PM
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I don't know how accurate it was but I have seen 90 mph on the 240D I gave to my neice for the summer. I backed out of it because I really didn't care for the noise.
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  #7  
Old 05-19-2002, 11:30 PM
Benz240D
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The tires are exactly the size called for in the MB manual. I know the speedometer is correct, I've seen the Digital speedometers beside me and they register within a mph or two of just what I am running. Plus have had a fiend of mine follow me in his '98 Chevy Astro-Van. No the speed is correct. I was already warned by a county sheriff - I used the excuse tires were off size (liar), no it is correct speed registering. I have already done the 60mph test for 5 miles straight, it is right on the money.
When I got the car, I was lucky to get 82mph, but after running 70 to wide open most of the time, it has gradually gotten to where it will run up to 90 with ease. Just got back from eating, ran 80-90+ most of the 18 miles back on the freeway. I can throw out of gear at 60 and coast a bit over one mile. (flat asphalt road)
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  #8  
Old 05-19-2002, 11:41 PM
Benz240D
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Remember, I am running a solid link to the pump - No Spring - I drilled through that part and pushed a roll-pin through. I have no pedal, just a rod. That pedal is part of what stuck the throttle wide open! I threw it in the trash!
I know what the MB tech stuff says about 82mph, but I garantee I am running up to 94, I can get about 96 down an incline, but doesn't seem to want to go beyond that 95mph mark.

This why I asked the Question in the first place, wondering if other 240D's were running this fast too.

But then again, maybe most MB owners don't take their MB out everyday to see how fast it'll go or just drive their's wide open much of the time. I would Love to know what the Torque is on this engine. It has to be pretty high! Take off in first, wind out and speed shift into second gear, watch the front rise drastically, it is quite impressive!
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  #9  
Old 05-20-2002, 12:10 AM
XN6guy
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Actually, the peak torque figure is pretty low for a 2.4 liter engine... however the torque curve is reasonably flat--that is what's important.

Most of the time (but not all the time) a manufacturer's specs tend to be a little conservative... representing an average set of numbers that *most* people would attain. Some of us can squeeze more from the same car--by shifting faster, by spending a great deal of time tuning the engine, etc.

The data in an automotive magazine is similar--the final numbers are usually an average from several runs.

It is obvious that you have one of maybe just a few 240Ds that will attain such a seemingly high speed. Keep her tuned up good!

-Joe
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  #10  
Old 05-20-2002, 12:53 AM
Benz240D
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The fellow I bough the car from was raised by a father that had his own machine shop, and he now lives here in the US and is a Machinist too. His priorities on his cars are the mechanics of them, how well they run and perform, he cared little for the body and it shows it. All of his cars, 2 other MB's and a Ford AeroStar all ran like a swiss watch. He said he was very particular to how his cars ran. The suspensions had to be like that of a race car. He Raced a few years professionally in S. Argentina. So, maybe part of his knowledge went into this car. To date, it has no leaks! You can run it wide open for 3 hours and park it on clean cment and not one drop on the cement!
I don't know how many readers remember in the 50's and 60's when Ford, GM and Chrysler (all of them did it), they'd take out several cars, the highest speed a car got or the highest horsepower found, all cars then had it. Th spec sheets reflected this. Then in 1976 everything changed to a net horsepower a rated averaged out hp.
My dad had a rare Ford Torino, one of only 500 made and his was by far the fastest, just an oddball car. Of course Ford wanted to by it back.
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  #11  
Old 05-20-2002, 12:31 PM
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240D top speed

The torque of the 240D is about 103 lb.ft at 2400 rpm.

With my 84 240D 72hp 5speed, I can maintain quit easily (when the road is flat of course) 90/92 mph on the clock and when the road go down, it's possible to reach 100mph and more.
According my MB owner's book, the theoric top speed is 87mph in 5th (and 89mph in 4th !).
Probably the speedometer is a little bit optimist !

The picture attached show a 240D 4speed at about 170 kmh (106mph).
Attached Thumbnails
240D Top Speed ?-vitesse.jpg  
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in France : 240D 1981 380 000 km
240D 1984 252 000 km
300D 1978 325 000 km
in the US : Ford Tempo 1993 70K
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  #12  
Old 05-20-2002, 02:02 PM
Eberhard Weilke's Avatar
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Two reasons....

...why old Benz tend to outrace their catalog data easily:

a.) The speedometer usually is a little optimistic. They are usually set 7% plus.

b.) Mercedes tends to post rather conservative figures. Mercedes owners used to be pretty conservative, a lot of the drivers were elderly people who did drive rather slow. But even these slow engines should be able to reach top speed on the dial, so that the customers didn't worry.

Fast running diesels might also have a problem with compression. Diesels are different from gasoline engine in that respect. Less compression means they can rev higher. Better top-speed, less torque.

Kind regards
Eberhard
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  #13  
Old 05-25-2002, 12:00 AM
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I agree with Eberhard in regards to speedo accuracy, regardless of what has been observed by the owner at 60 mph, etc.
This we can compare with a torque wrench:
If you want a torque wrench to be completely accurate, the best route is to get a torque wrench that was designed for only one particular torque, ie non-adjustable. The disadvantage is that we all need torque wrenches to work at a variety of torque settings. Good quality variable torque wrenches will never be as accurate as a purpose-built non-adjustable torque wrenches.
With speedometers, you can get the most accurate reading if the speedometer was calibrated at one speed. But that would be almost as useful as a non-adjustable torque wrench (although non-adjustable torque wrenches are used on assembly lines).
The speedometer will have variations in it because it is meant to be somewhat accurate at all speeds, but usually is dead-on accurate in one or two speeds. Typically the speedo will be the most inaccurate at the highest speeds. It doesn't surprise me that the speedo would be accurate in the measured-mile test.
You could maybe calculate what the measured mile time would be for the higher speeds and do a test run at that speed to test your speedo.
Gilly
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  #14  
Old 05-25-2002, 04:00 AM
turbodiesel
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Eberhard,

Your compression statement kind of makes sense, but dosen't fully click in my brain.

Yes, if the compression is high, there is more 'drag' on the motor. BUT, if the compression is indeed high, you have a healthy engine producing more horsepower and torque to reach the high speeds.
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  #15  
Old 05-25-2002, 05:14 AM
Eberhard Weilke's Avatar
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More Power with a Diesel...

....a few years ago some guys here in Germany prepared a 240 D 3.0 (should be you W 115 300 D) for the 24 hours Cup at the Nürburgring for historic touring cars (you usually meet Alfas, Ford Cortinas, old BMW and alike)

They got about 125 hp out of the old fivecylinder. Off course the polished the head, increased fuel flow at the pump and alike.

The mayor increase in hp came by lowering the compression ratio so that the engine didn't need so much power for compression.

That this engine would start after a cold winter night is the other story ;-)

Regarding the speedometer:

Here in Germany you find the kilometer-markers at the Autobahn.

I did set the cruise control on 100 km/h straight and count the time for 10 km: 6 minutes, 22 seconds.

After some rough calculation I set the cruise on 107 km/h for the next 10 km: 5 minutes, 59 seconds.

Viola, thats how I know that my speedo ads 7 %

On a dark night with no traffic I will try the same with 100 mph ;-)

Kind regards
Eberhard
(having the 3.07 rear axle instead the 3.58 in his W 123 230 E)

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