rpm at set speed 450 sl

[Gurunutkins]

Hi folks
need to pick your collective brains again. I think one of my mpg problems may be related to the transmission. I have the 74 450sl, 3 speed transmission. I can feel the 3 changes but not the converter lockup. can anyone tell me the approximate revs at a set speed, say 60 mph. That way I can guage if the converter is locking up or not. Many thanks
Barri

[Bondavi]

60 mph is approximately 2900 rpm.

[page62]

Converter lockup??? Are you telling us the 450SL has a locking converter?

I could be wrong, but I seriously doubt it!

What's your mpg? You should expect to get about 15 mpg -- no more...

[Gurunutkins]

1 am getting 11 - 12 mpg highway driving, accorgding to Haynes it does have a locking converter. I am getting approx 3200 rpm at 60 - 65 mph. Plugs are clean, no soot in the system, running with good vacuum and all of the signals from the pressure sensor and temp sensors seem to be on the button according to the bosh website for the efi brain.
any thoughts appreciated
cheers
Barri

[Bondavi]

My former 450SL, a 1975 model with the D-Jetronic did lousy around the city, around 7-9 mpg, but on the highway I could get as high as 16-18 cruising at 75 mph. In '76 came the change to CIS/K-Jetronic, so not sure if that was worse off for gas mileage?

Check for a leaking cold start valve, that drains fuel. Symptoms of that would be a rough idle. Fuel pressure calibrated, and fuel distributor adjusted for lean/rich mixture?

The 500SL (107) on the other hand has gobs more power and Im still able to achieve 22mpg consistently on the highway.

[page62]

Are you looking at the Haynes 350/450SL manual? What page does it say this? I'm not refuting you at all -- I'm just curious now!

BTW: I don't notice any sort of lockup "feeling" with my '79, it feels like a garden-variety 3-speed auto. However, 3000-3200 seems on the high side at 60-65. Perhaps the earlier SL's had a higher rear end ratio...I dunno.

[Gurunutkins]

HI
guess my brain is writing checks my mouth cant cash. I cannot find the reference to it in either my haynes or Chiltons. Obviously doesnt have a lock up converter
cheers
Barri

[page62]

That's OK.

I was out on the autobahn (I-10) yesterday and checked my cruising rpm. 3200 rpm at 75 mph in my '79 450SL. And it wants to go faster. Much faster!!!

[Captain Scott]

Hi Guru,

My 74 450SL with 213K does 10-11 MPG in the city and that is about it. If I recall, the ratio in your differential has everything to do with RPM/Speed/MPG and therefor your top-end RPM/speed.

I'll check my RPMs next week, but I think I get 3000 at 70, but I am not sure of my diff ratio. She's getting new leather seat covers right now! Vacuum is solid, trigger points are new, I run 91 octane and I don't stomp on her unless I need to. Next week I am going to change from the manual breaker points in the distributor to Petronix eletronic ignition in hopes that I can clean up the occasional misses at higher RPM, show cleaner exhaust and raise my MPG.

S

Originally Posted by Gurunutkins

1 am getting 11 - 12 mpg highway driving, accorgding to Haynes it does have a locking converter. I am getting approx 3200 rpm at 60 - 65 mph. Plugs are clean, no soot in the system, running with good vacuum and all of the signals from the pressure sensor and temp sensors seem to be on the button according to the bosh website for the efi brain.
any thoughts appreciated
cheers
Barri

[Gurunutkins]

Hi Captain Scott
the new leather sounds good its on my list of to do's. Let me know how the petronix works out and if you know what number you are using for the set, I didnt know they made a set for our 450's
cheers
gurunutkins