Author Topic: M110 989 compression ratio  (Read 279 times)

Big Tiny

  • Enthusiast
  • *
  • Posts: 32
M110 989 compression ratio
« on: 12 July 2020, 04:50 AM »
Hello people,

Not often I’m here, but after picking up a w126 to add to the 116 I thought I would ask if anyone knows about the m110 989 engine.
From all accounts it is 185 hp engine, 9:1 compression.

Was there a reduction in compression on Aus delivered cars or just added pollution gear and reduced timing ?

Mike

Big Tiny

  • Enthusiast
  • *
  • Posts: 32
Re: M110 989 compression ratio
« Reply #1 on: 25 July 2020, 03:58 PM »
Ok,

Looks like from all accounts the M110 989 came in two configurations.
9:1 and 8:1
The Australian delivered cars according to the 'updated' section in the owners manual says it is a 8:1 compression engine with 125kw.
Including all the Air pump/ EGR system and reduced ignition advance of the Euro cars.

I

BCDC

  • Enthusiast
  • *
  • Posts: 48
  • W116 Enthusiast
  • Location: Tasmania
Re: M110 989 compression ratio
« Reply #2 on: 25 July 2020, 07:02 PM »
Hi there, According to the factory specs the compression ratio does not change with any of the M110 engines which makes sense, only the pollution/emission gear and any hydraulic suspension pumps added "should" lower power output. That's my take anyway. All the Australian derived cars were "Euro spec" as far as I can tell. These cars fitted with the excellent straight six are a wonder to behold on the road given the engineering heritage with this type of engine configuration. Enjoy.   
1978 280SE Cream with blue interior. With SLS

Big Tiny

  • Enthusiast
  • *
  • Posts: 32
Re: M110 989 compression ratio
« Reply #3 on: 25 July 2020, 10:48 PM »
Hey,

Thanks for your reply.
From what I could tell the engine was indeed a 9:1 compression and if it had lower compression wouldn't actually be a M110 989 but something other number. The engine number on my car is a M110 989 and numbers match the VIN from factory. So I hope it does have the higher compression because that means it will have a few more herbs.

Currently overhauling the entire car, largely servicing, cleaning, replacing as needed. The EGR system made a good ol mess of the intake track so that is being cleaned as we speak. Can't wait to get her on the road.

« Last Edit: 26 July 2020, 04:56 AM by Big Tiny »

Big Tiny

  • Enthusiast
  • *
  • Posts: 32
Re: M110 989 compression ratio
« Reply #4 on: 26 July 2020, 02:58 AM »
I see you have a 280se also  :)

Any idea what this pipe circled in Red is ?

Big Tiny

  • Enthusiast
  • *
  • Posts: 32
Re: M110 989 compression ratio
« Reply #5 on: 26 July 2020, 04:52 AM »
Just for reference and some further digging.

This is from Mercedes engine manual.

M110 989 not mentioned in this manual, but from other sources it is indeed a 9:1 and should be around 10-12 Bar compression.


Big Tiny

  • Enthusiast
  • *
  • Posts: 32
Re: M110 989 compression ratio
« Reply #6 on: 26 July 2020, 04:54 AM »
Compression ratio

BCDC

  • Enthusiast
  • *
  • Posts: 48
  • W116 Enthusiast
  • Location: Tasmania
Re: M110 989 compression ratio
« Reply #7 on: 26 July 2020, 11:04 PM »
The pipe circled is a vent valve pipe. I found this diagram in the engine manual. Looks like a good job you are doing, makes me want to clean my engine!
1978 280SE Cream with blue interior. With SLS

Big Tiny

  • Enthusiast
  • *
  • Posts: 32
Re: M110 989 compression ratio
« Reply #8 on: 27 July 2020, 03:57 AM »
Thanks for the diagram.

It actually clears it up for me. One pipe vents to the airbox which is only under light vacuum especially when throttle plate closed 'idle'.
Vent valve is under vacuum at all times, increasing with load, AKA PCV valve. So this is pretty critical to the system and will need removing and cleaning as necessary.

Above pic isn't my engine, but mine is getting there and will be super clean when done. Just waiting on a few small parts to complete it. For note my intake was filthy, throttle plate and intake runners were very sooty and 'carboned' up. I highly suspect the EGR system to be responsible for this. Simply getting everything clean will help the performance noticeably I'm anticipating. Vacuum lines to throttle body were all intact however the ports inside the throttle body were completely blocked. So there would't have been any ignition advance to the Dizzy. No way of knowing this will simple vacuum line checks.


Big Tiny

  • Enthusiast
  • *
  • Posts: 32
Re: M110 989 compression ratio
« Reply #9 on: 27 July 2020, 03:59 AM »
Throttle body before

Big Tiny

  • Enthusiast
  • *
  • Posts: 32
Re: M110 989 compression ratio
« Reply #10 on: 27 July 2020, 04:00 AM »
after

Big Tiny

  • Enthusiast
  • *
  • Posts: 32
Re: M110 989 compression ratio
« Reply #11 on: 27 July 2020, 04:03 AM »
The intake manifold was even worse. Heaps of degreaser and a gernie have got it clean. Just going to clean ports up a tad more.

Big Tiny

  • Enthusiast
  • *
  • Posts: 32
Re: M110 989 compression ratio
« Reply #12 on: 27 July 2020, 04:07 AM »
Air metering plate

Big Tiny

  • Enthusiast
  • *
  • Posts: 32
Re: M110 989 compression ratio
« Reply #13 on: 27 July 2020, 04:08 AM »
after

revilla

  • Classic
  • **
  • Posts: 318
  • W116 Enthusiast
  • Location: Aix-en-Provence, France
Re: M110 989 compression ratio
« Reply #14 on: 27 July 2020, 05:48 AM »
Nicely done!
It wouldn’t hurt to disassemble the air metering body to remove all the gum. That includes the arm, the metering plate, the weight, the electrical copper contact  and the main piston, but without disassembling the diaphragm assembly, just removing the piston from underneath.  This is hyper delicate as the piston has a very tight tolerance fit to the cylinder. Make sure it’s not dropped. The arm axe, balls and springs can be cleaned and lubricated too. Easy job and sure it’ll have a positive impact on perfo, idle and acceleration. Make sure the plate ends up perfectly aligned to the neck. Without any interference, free to move. I had this issue in the past (hesitation under starting and acceleration) but once cleaned and balanced things got a lot better. If the plate isn’t perfectly centered and/or the piston is sticky, the pump will run before actually passing the igt key to start position. That’s a sign.

Good job!
Robert
Robert
W116 1977 280SEL & 1979 280SE