Too many variables to make a calculation. Tire size, axle ratio, clutch slippage, etc.

Maximum rated RPM's are 5200.

 

Well, let's say with everything stock. Stock tires, stock axle ratio…
There must be some kind of info, like 135 km/h @ x rpm.

I'm asking because I'm wondering if I'll be at 5000 rpms when driving around 130 kmh, or if I'll be able to drive more relaxed at 2500 rpms.

Actually, what I'd need to know, is the speed of the car in 4th gear at around 2500 rpms.

 

It all depends on your tires/rear end ratio, but I'll make some assumptions for you.

Assume you had original bias ply 14" tires with an 82 aspect ratio, the tire would have an OD of 25.3" so a rolling distance of 79.5"/revolution or 6.62'/revolution.

Your quoted top speed is 83.89mph which is 7382 ft/min.

traveling 7382 feet in a minute with a rolling diameter of 6.62' gives you a rear wheel speed of 1114.5 rev/min.

The stated final drive ratio on the internet for your car is 3.92:1 which means the engine is turning 4369 rev/min (which is coincidentally close to max torque for your engine).

Now, what size tires do you actually have?

 

Stock tires*…*apparently 175 SR 14. When the engine is running 4369 rev/min, is that at 135 km/h / 83.89 mp/h in fourth gear then? It would make sense at least. So I won't be able to drive at that speed without ruining the engine. Some cars can drive at their top speed all while being at a reasonable 2500 rev/min, so I was wondering if it's the same on the 220D. I'm wondering why they put this as the top speed of the car, anyone driving at that speed with the engine revving so high would probably ruin it. Then again, my grandmother said she always drove the Mercedes full speed at 140 km/h (probably 135 but it says 140 on the speedometer).

What would happen if I mounted bigger wheels, like the 15" wheels that you find on the W115 ambulance and wagons for example? The rolling distance would be bigger and the car would be slightly faster, no?

BTW, at 2500 rpm, using the data above, you are traveling 48mph

In 4th gear you mean?

 

BTW, at 2500 rpm, using the data above, you are traveling 48mph

 

As Fonzi said, changing your tire size isn't going to make a huge difference. For example, if you went with a 15" wheel and ran 205/70/15 radials, you only increase tire diameter by 4% so now at the stated top speed, you are turning 4203 RPM. Yes, this all assumes 4th gear, a 3.92 rear end, no slippage in clutch etc....

What you do gain is more tire on the road. going to a 205 width from the stock bias (which I think were 175) you gain 17% more road contact area. I happen to like more tire on the road. I run 205/75/14 on my W108 chassis. That is about 3% larger diameter than your stock tire.

Anything you do to reduce engine speed is going to drop the rpm below the 4200RPM (max torque) which may actually reduce your top speed as that little engine will run out of power.

 

Thanks for explaining guys! I will most likely leave the car in stock condition. I will be driving mainly in the city with it, so I won't reach high speeds anyway and acceleration is more crucial even if it's just a minimal difference on this slow car

Larger tires would mean I'd have to get larger wheels, and in that case I would want to get Mercedes wheels from that time. I really like them. I would most likely have to get them from the W108 or another chassis that had larger tires. I know that you don't see the look of the wheel when the hubcap is on, and that I could get just any wheels, but I still want Merc wheels

At some point I was thinking of getting the 15" wheels for the W115 because they look more proportional with the rest of the car. If the car will be slower at accelerating I won't do it (even if it's just minimal). And in combination with the white-wall-tires, the car looks more proportional anyway, even with 14s:

So yeah, most likely leaving everything stock.

 

Thanks for explaining guys! I will most likely leave the car in stock condition. I will be driving mainly in the city with it, so I won't reach high speeds anyway and acceleration is more crucial even if it's just a minimal difference on this slow car

You could put on aluminum wheels 5 1/2 x 14 from a 1981 240D. That would change your wheel weight from 23 pounds to 11 pounds. Reduce weight in other ways. Take that York compressor that is under the hood and throw it in the trash - you'll never use it, I promise. Short of a much-needed engine swap, I don't think you are going to be able to do much to improve the performance of a 220D.

 

Don't know what images don't work, and no edit button (??).

 

You could drive less than 130 km/h.... Just an idea...

 

Yeah, that's what I'll be doing if I don't want to ruin the car. That's why I said it will take me more than a few hours to get there.

I have to see if my TomTom can be set so that the maximum speed I'll ever drive is lower than 130 km/h, otherwise I will always get wrong information about when I'll arrive at which place!

 

Putting to much diameter with larger tires can and will cause vibration issues


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Mercedes engines were designed to run at high rpm's all day long.

Driving a few km/hr slower will only add 10-15 minutes to your travel time.

 

Yes, I heard that old MB diesels should be pushed. But does that also count if I drive for hours? Do you think it could damage the vehicle?

As for the time, it does make a big difference. If I was driving 135 km/h non-stop for 507 kilometres (the distance to our vacation home), it would take 3,7 hours to get there. If I drove only 100 km/h (and at that point the engine is also revving pretty high), it would take me 5,07 hours.

 

Do not drive the car at top speed WOT for more than a few minutes! I owned one and when I first got it, the poor car could not get out of its own smoke cloud. By the time I had changed all fluids and filters, taken care of the deferred maintenance, and put a few thousand highway miles, she was able to hit top speed. She was much happier at 120 kph, but did travel fine at 140 for a kilometer or two.

You do want to drive it like you stole it. Italian Tune ups are needed, and puttering around town should be limited. My car was a stick shift, with no AC, no Power anything. Manual locks and windows, no sunroof. BASIC car, as light as the factory could make it. At 135 kph, the car SCREAMS and will demand you slow down a bit. Drive for four hours and a bit at under 130 kph