hi, can anybody with a tachometer in their 240d , give me an accurate rpm reading for 4th gear at 60 mph. mine seems like it revs about 3500 but I'm only guessing (no tach ) thanks mark

I do about 2950rpm.

3000rpm is 63mph.

Not much of a freeway rider

Better to keep it under 50.

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1978 300D - Somewhere around 188k miles, no reverse, no a/c, no instrument lights, sunroof only works when it's really hot outside, trying it make it more road worthy....
1999 328iS - My Baby

what about 70 MPH and 85 MPH, whats the tach read on that? how do u get a tach on ur 240D ?

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Hmm yeah, i been wondering about this myself...... And if 3mph difference from 60 to 63mph in 4th = 50 rpm then 84 mph compared with 63 must equal 3350rpm (given 63mph = 3000 rpm). Is this correct?

And given whats being said here, I'm thinking the optimal 240D power band runs from 2900 - 3400rpm but will comfortably race even higher up to 3600rpm at lower speed mph's where less torque gets eaten up with wind resistance, etc.

And what the hell's the official redline rpm for the 240D? Thats another thing I'd like to know. And if you, ForcedInduction with your tachometer, will please provide actual redline speeds in mph at all 4 gears then I'd be immensely grateful to learn that too.

Great thread here that can finally resolve the mysterious 4-spd 240D power band.

Matt, jc whitney in Chicago has tachs that run off the alternator. Haint heard of anybody settin up the MB clock/tach combo into the 240D from an automatic 300D - but that sure is something we'd all like to see.

Well, I don't have the 240 engine installed. I've basicly converted it into a manual 300D.
It no-load redlines about ~5300rpm. Under load, it tops out at about 4800rpm. Well past the 85mph speedo peg.

This is a no-load revv from my old 300TD (The engine that's in my 240D right now). I didn't just floor it, I kinda pumped it.
Link

EDIT: Also, the dots on the speedo are NOT redline.

Thanks, but got to believe the 240D calls for a much lower redline then what the turbo 5cyl offers. Wholeheartedly agree with you on speedo shift points not being redlines, I treat em like minimum power band points for the next higher gear - kinda like reverse redlines that caution against bottoming out the gears and lugging the engine. For example, 4th gear on my 240D rarely sees anything south of about 57mph.

I am probably wrong but think there is a mark on the speedometer at about 90 mph on standard transmission 240ds. My understanding was over this you are overspeeding the injection pump. Because of this I usually try to stay under 90 mph as well. Although it's a struggle. Mercedes engines usually do not mind a little higher revs than some engines although the speedo mark may be for the engine itself. I am not sure.

I have already done the math on this several times - calculating the gear ratios, axle ratios and tire diameters.

The engine RPM in the 240D, (in 4th gear), is always the speedometer speed divided by 2 multiplied by 100. So at 60 MPH, RPM is 3,000. At 70 it is 3,500, at 80 it is 4,000.

My 240D is a 4spd manual, but I believe the 4 speed auto has the same gear ratios.

does anybody have a tach in a 240d , that could just give me the reading right from the tach. this is my first diesel car and I don't want to damage the motor by going at 75 to 80 for extended periods of time. thanks

I don't think any 240s have tachs. You should be fine at 75-80 MPH

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I just found a small tach that can be added to any diesel motor . the transducer is clamped around an injection line and the pulse is read by the tach. It has an 8 ft. cord and could be mounted someplace in the car. Its really a neat setup. check it out at www.manddsmallengine.com/tinytach/diesel.html:)

I don't have a tach in my 240D, but if I ratio the tach readings from my 300D by the gear ratios, I get similar answers. Personally, I'm not comfortable running a 240D at 75-80 for very long. But, it seems pretty happy at 70 for hours on end.

I'll see about making a video of 4th gear tomorrow. I have an 85mph speedo so I don't know what the exact top MPH is. Should be up around 8pm.

I have ran my 240D 4spd at 86.8 or 140 km, she can cruise at 135 Km well too.

That tiny tach sounds very reas priced. Had anybody tried her yet?

I guess got to clamp the transducer closed to the injector. I have touched the injector that it vibrates/pulse on every firing.

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