240sd?

[Panzermann]

So, I've been thinking about mental experiments and came up with an idea that I've been throwing around.

Everyone wants to put a more powerful engine to go faster, but suppose one goes to the other extreme and accepts poorer performance for possible improved mpg?

So how 'bout putting a 240 (616) engine into say a 1983 126 300SD chassis, making a 240SD, of sorts.

As close as I can figure it, the weight of the 617.95 turbocharged 5-cylinder engine adds about 308# to the weight of a 123 chassis over the non-turbo 4 cylinder 616.

Translating that to a 126.120 1983 300SD chassis, with a curb weight of 3773#, placement of a 616 motor into the chassis would reduce curb weight to about 3465#, still about 250# more than a 1983 240D. The "240SD" would benefit from the 126 chassis' greater aeordynamic efficiency.

My guess is that the performance of the car would be about equivalent at low-speed (city) driving to the 240D, which is, sluggish. But could this yield improved fuel efficiency at higher speed, long distance cruising (60-80 mph), where acceleration is not really the issue, but speed maintenance is? Perhaps the efficiency could be improved by changing the 126 to manual transmission as well?

Ok to say I'm Just an idea I've been toying with for the last week that I wanted to share.

[Skippy]

I don't think it would help the mpg. I say this because I looked up the EPA fuel economy numbers for my car (turbo 5-cylinder 123) and the equivalent 240D, and mine was actually rated about 1 mpg higher in city and highway. The turbo motors apparently have enough of an efficiency gain that you can have the fifth cylinder without a fuel economy loss.

[JimmyL]

It's after midnight and you are obviously suffering from a lack of sleep. Maybe rest will jolt you back to reality....

[tram]

A smaller engine has to work harder to propel a heavy car. On the old 108/ 109 chassis gas cars, having a 6 cyl. over a V8 was hardly worth it, for example. You saved a couple MPG with a 6, but not enough to make it worthwhile missing out on all the fun of a V8. Not worthwhile at all.

From everything I've seen ,the 300D and 240D get almost exactly the same MPG. In the 22-30mpg range. I've seen some 240D's that can squeeze into the 32mpg area but with the extra bulk of a W126, you would more likely get less MPG than a stock 300SD.

I can see only one way of getting significantly better MPG than a 300SD. Installing a turbocharged OM601 (Never built, it would have to be made) or a Turbo OM602. A turbo OM616 is possible, but would still have to work hard to best the OM617's numbers.

[t walgamuth]

saying the fuel economy wont improve. it would for sure, especially if you keep the very high rear end ratio. and you probably could convert it to stick as well. if converted to a stick you would need to change the rear ratio to the 369 of the 240. your estimate of the weight difference for the motors is i think way off. i bet the 240 only weighs about 125# less. but if you converted to stick it would save another 40 or 50.

the performance would be very poor, worse than a 240, though not as much worse as you might imagine. if you put in a 240 rear end in, in the end you will find that the sd body wouldnt be all that much heavier than a 240 and it is slicker and i think not any bigger in frontal area. it might beat a 240 in highway fuel mileage. the extra weight will always affect the acceleration. but a 240sd would be about the same weight as a 240 with one large passanger, i bet.

still, i wouldnt do it myself and wouldnt recommend it. i would just get a nice 240 and enjoy the simplicity of its less elaborate design. and a good 240 retains its value excellently. a 240sd would be difficult to sell, i think.

tom w

How slow can a 240 go?

W126 body
Automatic
2.47 LSD diff
A/C
1 "large" passenger

Would it move?

[t walgamuth]

when i was in morrocco in 1973 they had as taxis 55 chryslers (how do you say large?) that were running small four cylinder diesel engines. for best results you would have to change the diff. but it would drive with the 247, i think. you might have to get up to 75 before letting it shift into fourth and the takeoff would be very liesurely but as i said, the sd isnt that much heavier than the 240 and a lot of it is in the engine and tranny.

my 74 240 weighed almost as much as an s class and it took off in second unless floored. to be sure it was painfully slow but then again, i didnt recommend doing it i just said you could.

tom w

[Hatterasguy]

And that little engine would have to be run to the stops to move the thing. A 500SE would probably get better mileage.

If you want a high mpg car look elsewhere old MB's are not the best choice. Think VW TDI.

[barry123400]

Gotta go take my meds after reading this thread. I have been trying to grasp the concept of this but it will not jell. I really tried. :Will try again. Remove a turbo five cylinder motor from a pretty large car and replace it with an anemic four cylinder producing about 1/2 the horsepower and less fuel milage. Still will not jell and I like 240ds. Would not exactly blow the doors off but on second thought if you removed all the doors it just might help acceleration. Actually really like to read whatever is posted as there are some good inherent ideals that pop up from time to time. Some occasionally miss the mark but they are usually mine.

[t walgamuth]

if you applied a 240 engine with the correct rear end ratio, 369 you would get as good or better mileage on the highway with it in an s body. as i said, the s class is not that much heavier (126) has the same frontal area and is more aerodynamic.

now to get significantly better than a 240 is not likely.

but a good 240 will do 30 on the highway at maybe 65 or even 70 and one in and s will do the same, i think, with a stick. maybe a half mpg better.

tom w

[barry123400]

One can never totally discount an ideal. For example when diesel hits 150.00 per gallon that 1/2 mile per gallon or so would be critical. The other aspect is it might allow me to quote that I can travel faster than a 126 diesel with my 240ds. Just will not specify which particular 126 in my conversations. Go for it.

[Panzermann]

Originally Posted by Hatterasguy

And that little engine would have to be run to the stops to move the thing. A 500SE would probably get better mileage.

If you want a high mpg car look elsewhere old MB's are not the best choice. Think VW TDI.

thanks for the valuable input. I will not at this point start looking for a 300SD and 240 to cannibalize to make into "The Car That Never Existed" (Though I do like the cachet of having a completely unique Mercedes; in my Walter Mitty world, I had even figured out how I was going to change the rear insignia to read "240SD" and "Diesel." Only the "In crowd" (like anyone reading this) would understand. I could then describe it as a rare "Euro" model. But I digress....). I do however reserve the right to make this car. You can't stop me.

Logic here for me was (a) the 126 chassis is more comfortable to "be" in. It was the flagship model at the time. though I have a couple of 123's, their comfort does not match that of a well maintained 126. Sorry. (b) I drive long distances sometimes and would be willing to trade acceleration for mpg. That is what I thought the trade-off was. So how then would I extract as much high-speed mileage out of a 300sd 126, with the caveat that I am willing to trade away acceleration down to the level of a 240d? What partly gave me this idea was the newer gas engines which are able to drop a cylinder to save fuel. This is just a way of permanently dropping a cylinder, and a bit of weight to boot.

And as regards diesel at $150 per gallon, soybean oil at Costco (I don't mean WVO. I mean unused virgin VO) is $2.59 a gallon and diesel#2 here in Tucson is $2.73-2.79. While there is seasonal fluctuation, as regards price, did one ever think that virgin VO would be cheaper than regular diesel"? No filtering. So I wouldn't count that $150 per gallon out of the realm of possibility....

given that most threads seem to be focused on extracting as much acceleration out of these cars as possible (i.e. turbocharging a 240D), I think my thread is a little different. Everyone knows we're not gonna be drag racing in these things, so let's look at other measures of performance. I know that DaimlerChrysler is, with the claim of 800 mile range on one tank of fuel the new S-class with a newer diesel engine. And if I wanted to drive in a VW diesel, I would be on the VW Diesel forum, not the Mercedes Diesel forum.

[Hatterasguy]

Well the simple solution would to just swap a 560 diff into it. Higher rear gears = lower highway rpms. If you live in the flatlands this is a good option. Up here in hilly New England, well down shifting to 3rd all the time would get old.

[Panzermann]

Originally Posted by Hatterasguy

Well the simple solution would to just swap a 560 diff into it. Higher rear gears = lower highway rpms. If you live in the flatlands this is a good option. Up here in hilly New England, well down shifting to 3rd all the time would get old.

So would I be able to drop the 560 sel (?) diff and axles directly in to the 300sd?