MPG vs Speed - Page 10 - PeachParts Mercedes-Benz Forum

BobK · #**136** 04-16-2013, 03:06 PM

Well, I finally brought in my MB data book. Looking at the numbers for a non-cat engine: 90kph=25.85 mpg, 120kph=20.66mpg. With a cat, the numbers were a bit worse. So it looks like your 70mph numbers were reasonable. Your 55mph numbers say" you screwed up the motor!". Something is just wrong with the way it runs at low speed, that's all. If you are only going to drive it at 70, maybe leave it alone. If you want/need to do 55 with better economy, get busy and find the problem. BTW, the book specs a 117.965KE engine at 245hp @ 4750rpm and 297 lbs @ 3750rpm. This is for a non-cat motor. Cat motor comes in with a torque peak at 2500rpm and maybe 30 less lbs.
All this is interesting to me as I have an '88 560SEL 9second one I've had) and I would love to get better mpg out of the beast.
Now my '84 190D I just putter along in the right land doing 65 and most leave me alone.

The Clk Man · #**137** 04-16-2013, 04:44 PM

My V8 Mountaineer gets 35 mpg when it's rolling down a hill in neutral.

JamesDean · #**138** 04-16-2013, 05:43 PM

Quote:

Originally Posted by The Clk Man

My V8 Mountaineer gets 35 mpg when it's rolling down a hill in neutral.

and thats with the engine off!

Man...you should have got a mac!

The Clk Man · #**139** 04-16-2013, 07:02 PM

Quote:

Originally Posted by JamesDean

and thats with the engine off!

Man...you should have got a mac!

If Macintosh made a car, I would have one.

pmckechnie · #**140** 04-16-2013, 08:28 PM

Quote:

Originally Posted by BobK

BTW, the book specs a 117.965KE engine at 245hp @ 4750rpm and 297 lbs @ 3750rpm. This is for a non-cat motor. Cat motor comes in with a torque peak at 2500rpm and maybe 30 less lbs.

Bob,
Great information and I thank you. I have a question about the above segment. It says the non-cat has a peak torque at 3750 rpm and that feels right. Then it says the Cat motor comes in with a torque peak at 2500 rpm. Did you mean 3500 rpm? I do know this was a non Cat motor with duel exhaust and it now has an original single exhaust. The left exhaust manifold was missing but the right one was still on the engine and it did not have provisions for the cross over pipe, That is why I had to go back to the US exhaust. The exhaust could have a bearing on my problem.

Thanks again,

Paul

t walgamuth · #**141** 04-16-2013, 10:15 PM

Yeah, I bet its the muffler bearing.

BobK · #**142** 04-17-2013, 08:10 AM

I am curious about that torque spec too. My 560 is spec'd at 3500 for the torque. Suspect a misprint. True dual exhaust motors with their different cams and what-not gives like 300HP with no cat. You would probably have a hard time recreating the original dual exhaust with the tri-y pipes and all. Do you have an O2 sensor? Hooked up? Wonder what it is reading across the rpm range on the road. Just so you know, the EPA specs for my 560SEL are 13 and 16 and that's pretty accurate. Lotsa fun torque, but you are gonna pay for it. 117 is still one heck of a motor.

pmckechnie · #**143** 04-17-2013, 12:40 PM

Yes Bob, It does have an O2 sensor, and yes it is hooked up, but has no control over the engine. I use it to adjust and monitor mixture. I haven't checked it very closely at lower speeds, but I will. At around 2500 rpm (75 mph) is goes full lean (.2V) at high vacuum (down hills), shows rich (.6 to .7V) under load (up hill) and is around .5V in between. This is after 20 miles or so and the engine is thoroughly wormed up and stabilized. Before that it is a little rich at around .6 to .8 when not coasting or pulling. These fuel systems just amaze me. I've seen many computer controlled engines that can't do that good.

For any one else reading this, the above data is flawed. It should not be used for any decision making. It can not be documented or proved. Use at your own discretion.

Tom, the muffler bearing problem can be solved easily. I will just remove the mufflers. Problem solved.

Paul

JamesDean · #**144** 04-17-2013, 12:47 PM

Doesn't the CIS system need the oxygen sensor to control the system? Im not that familiar with first gen gas cars

pmckechnie · #**145** 04-17-2013, 01:06 PM

Yes, US spec cars use the O2 sensor to control mixture. This engine however is not a US spec engine and does not use the O2 sensor. The fuel distributors are different on the non US engines and the control's can't easily be installed. I have been giving that a lot of thought but haven't found a simple way to add fuel control to these engines. I have tried using a JY fuel distributors but haven't found one yet that works better than what I have now.

This is just trivia. I have seen quite a few gray market cars that had been 'Converted'. They all had O2 sensors but I have never seen one that actually worked. When NC had emissions test, my 500 never failed the test.

Paul

t walgamuth · #**146** 04-17-2013, 01:55 PM

Quote:

Originally Posted by pmckechnie

Yes Bob, It does have an O2 sensor, and yes it is hooked up, but has no control over the engine. I use it to adjust and monitor mixture. I haven't checked it very closely at lower speeds, but I will. At around 2500 rpm (75 mph) is goes full lean (.2V) at high vacuum (down hills), shows rich (.6 to .7V) under load (up hill) and is around .5V in between. This is after 20 miles or so and the engine is thoroughly wormed up and stabilized. Before that it is a little rich at around .6 to .8 when not coasting or pulling. These fuel systems just amaze me. I've seen many computer controlled engines that can't do that good.

For any one else reading this, the above data is flawed. It should not be used for any decision making. It can not be documented or proved. Use at your own discretion.

Tom, the muffler bearing problem can be solved easily. I will just remove the mufflers. Problem solved.

Paul

Whew! That's a relief!

neanderthal · #**147** 04-17-2013, 06:10 PM

To be fair, the guy who stated that his Porsche 911Turbo got better fuel economy at 110, didn't state the units.

110kmh. yes.
110mph. NO!

The Clk Man · #**148** 04-17-2013, 06:46 PM

Quote:

Originally Posted by JamesDean

and thats with the engine off!

Man...you should have got a mac!

To be totally honest, I had eaten a bunch of broccoli, cabbage and beans the night before and I was strapped to the back of the car. Talk about natural gas.....

MS Fowler · #**149** 04-17-2013, 10:26 PM

Here is a little reading on measurement, and the uncertainty of it--not so say errors.

http://www.ncids.com/forensic/metrology/Introduction_to_Uncertainty.pdf

And its just an intro to the subject of measurement.

After reading this I bet you don't have any idea what your mpg at any speed is.

Brian Carlton · #**150** 04-17-2013, 10:29 PM

Quote:

Originally Posted by MS Fowler

After reading this I bet you don't have any idea what your mpg at any speed is.

I do.