E300TD RPM's at 60 mph

[graysilm]

I was wondering what the tach should be reading at 60mph on my 99 E300TD. Mine is reading about 2200 rpms. Does this sound about right?

[TMAllison]

Don't drive 60, but 80mph is 2950rpm for me.

[chazola]

My '94 E300D with a 4-speed auto box is doing 2500 @55mph, so yours with the the 5-speed auto (I presume) sounds about right to me...

[nhdoc]

Originally Posted by TMAllison

Don't drive 60, but 80mph is 2950rpm for me.

2950RPM÷80MPH=36.87 RPM/MPH
36.87RPM/MPH*60MPH =2215 RPM So your 2200 at 60 is about right.

I don't drive 60 either...75 for me is about 2750 RPM which is also about 36.67 RPM/MPH or 2200 RPM at 60.

Since we have lockup TCs the curve should be more or less linear and these calculations therefore should predict what our cars would show at 60 MPH.

[JimmyL]

E300TD? Wow, this is certainly new ground for me.....

[TMAllison]

Originally Posted by JimmyL

E300TD? Wow, this is certainly new ground for me.....

The trunk badge (like the W123 turbos) says TurboDiesel. Pretty common useage on the furom across numerous models.

Marty - Doesn't our TC actually "lock up" only above 3K rpm? Pretty certain that below that RPM it slips.

[KarTek]

Originally Posted by TMAllison

Marty - Doesn't our TC actually "lock up" only above 3K rpm? Pretty certain that below that RPM it slips.

If this were the case, it would explain why the link between the engine and the tires seems to be "sloppy". I've never tried it above 3k RPM.

It would also seem counterproductive for the best highway mileage...

[nhdoc]

Originally Posted by TMAllison

The trunk badge (like the W123 turbos) says TurboDiesel. Pretty common useage on the furom across numerous models.

Marty - Doesn't our TC actually "lock up" only above 3K rpm? Pretty certain that below that RPM it slips.

Normally the auto designers will make TCs lock at any steady speed above 45-50 MPH but I can tell you that if ours does that it is a very smooth lock since I have never felt it. While I do not know this as fact, I suspect on the 722.6 the transmission sends a lock signal anytime the car shifts into 5th gear. That's considered "overdrive" to our cars for highway cruising. So I think the combination of 5th and lockup takes place simultaneously and you can't be in 5th without the TC being locked. That's why these cars will downshift out of 5th pretty easily - I have even noticed it on steeper hills with the CC set that it will downshift.

[graysilm]

Originally Posted by TMAllison

Don't drive 60, but 80mph is 2950rpm for me.

What kind of mpg's do you average at that speed?

[TMAllison]

30-31mpg pretty consistiently. (no D1 here in winter).

110 miles a day
80% @ 65-80mph
20% @ 5-20mph