a bit confused on the tachometer readings

[zixtus]

We have a 6.9 [1]that hovers around a 1000 revs @ 110k...and we just bought another older one [2] that revs at nearly twice that tach reading for the same speed...[his and hers]
1 is a really nice well kept machine and uses very little fuel for such an engine size..and still roars like a lion...the other ..2..even on gas uses a lot...

Is there some kind of automatic overdrive in some gearboxes??..optional rear end ratios etc..
Z..

 

[John S]

A W116 6.9 is geared to roughly 38.5 k's / 1000 revs, so 110 should be about 2800 revs. Mercedes of the earlier years were under-geared to give then great acceleration at around the 100 mph /160 K’s mark, so what year are your models? Your diff should be stamped 2.65:1.

Even the late model Holden’s with the 6 litre V8 engines, which are very high geared for economy, need about 1600 revs at 110 K’s, so I tend to think your rev counters may be inaccurate.

 

[Styria]

Hi Zixtus, as JohnS has stated, 6.9s run a 2.65 to 1 ratio differential which translates to roughly about 38-39 km/hour - I can look it up for you if so needed.

Okay, you say that No. 1 'roars like a lion'. By that, do you mean that it is a 'sharp tool' acceleration wise (as you have previously stated) or does it just have intake roar ? Australian Market models can be quite 'roarty' under the bonnet when you put your foot down. To me it sounds as though the No. 2 car runs the more accurate tachometer. Regards Styria

 

[zixtus]

Thanks for the info guys...I hooked up a second tacho to no1..same results...is there some sort of optional overdrive that could have been an "add on"..it does drop right down to around 1000rpm at just over 100k..great for milage costs and...
..it roars literally...noise wise and simply jumps like a startled cat when "pressed"....Love them both but surprisingly how different they are...I appreciate the info and will keep digging away..
Z

 

[Styria]

Thanks for the info guys...I hooked up a second tacho to no1..same results...is there some sort of optional overdrive that could have been an "add on"..it does drop right down to around 1000rpm at just over 100k..great for milage costs and...
..it roars literally...noise wise and simply jumps like a startled cat when "pressed"....Love them both but surprisingly how different they are...I appreciate the info and will keep digging away..
Z

Well Zixtus, I am probably still none the wiser. To the best of my knowledge, it is quite unlikely that any particular rev reduction item or component has been fitted to your No. 1 car. I know that there is a company in the States that's been mentioned as being able to fit some sort of overdrive, but I believe the cost is somewhere in the region of about three and a half grand.

You know, Zixtus, you tell us that there are two totally different cars that you have on your hand - right ? Well, don't you think we ought to be afforded the opportunity now to test and evaluate your findings ? There is no need to be shy or coy, and WE ARE terribly nice people, full of diplomacy and praise of appreciation of our fellow members' prides of joy. (.......NSW Concours on soon......!) Regards Styria

 

[Michel]

I concur with the Godfather....

You need to bring them to the next get together and afford us the ability to visualise them and if need be test them for you...

 

[zixtus]

you were right on the money...a quick check by an expert.....and the tach in no1..was out and is now a non goer at all..I guess the difference in performance is just 1 is well maintained and tuned and on petrol.....and 2 is on gas..lags a bit on acceleration and is much less well maintained....I'll take some piccies side by side today and post them...and yes it would be nice to meet up with you all..
Z

 

[zixtus]

heres some piccies of the two deviates..."2' is the car just auctioned on ebay..needs about a week of body work and rust removal...and then a complete respray...should be ready in about 90 days at my speed..but it drives very nicely and is mechanically sound..the car on the left is "1' and is a beautiful car from Queensland..almost consourse but not quite...that spent nearly 20 years locked up in a garage after its owner died..we live on a farm..so mud is a constant unfortunately
Z

 

[zixtus]

and I'm still learning about piccy attachments

 

[Styria]

Well, you know Zixtus, you have already been accepted as a most valuable member of the topklasse fraternity - not one, but two red cars, constitute a passport to star status on the site - just ask Michel, and he will confirm it.

Rust Repairs, repaint - are you going to do it yourself ? There are a couple of bods on the site that would steer you in the right direction. I guess it is a little unfortunate that you don't live in a dust free enviroment as it does take extra time to keep cars in pristine condition.

With the upholstery - do you have leather, or velour and is the normally accepted beige/cream/parchment ? Anyway I guess, we shall see you sometime in the future. Regards Styria

 

[zixtus]

thanks for the comments..on a day when little is going right I certainly appreciated that....and yes I will do the body and paint.... not quickly but in 90 days or so it will have no rust and new paint..and no bingles [ nsf mudguard and nsr door]..my brother and I owned a smash repair shop for a long time....it was some time ago now tho and
1..has cream velour interior in as new condition and 2 has leather also cream..not quite so well loved...but still ok..

 

[motec 6.9]

Hi Zixtus good to see the red6.9 sc 609 went to some one who may be able to save her if you look on the last page of the www.m-100.cc registry on 6.9 there is a photo off what she once looked like in the 90's it belonged to my next door neighbours brother inlaw and i have photos from wheels in Canberra in 98 off that car when it was a concourse winning car when i saw it on ebay i was saddened to see what only 12 years ago had been an outstanding car become what it has become today all i can say is best off luck

 

[zixtus]

thanks for the info...the picture surely does look nice...the car will never be a concourse winner again because it will be a daily drive...to keep 1 in almost concourse condition but it will be a nice serviceable machine and nice to see on the street. The paint at the moment makes it look far worse than it is and the mastic and gunk used around the front and rear windows to attempt a seal make it look doubly atrocious
the pictures on ebay made it look heaps worse than it is. The suspension works fine and it drives, steers and stops as it should and the body damage is not that severe...a nsr door nsf guard and the front bar... we already have the parts so its just a matter of time
the rust is a straight forward thing..cut the rust and bondo out and just make new sections...it does take time especially when I cant get to it full time...but its very driveable and as we speak the blond has driven to Gloster which is a a 6 hour trip from here and it performed well..wish me luck on the project
Z