Hi Ole,
in my 43 years at the Dealer this is the only reference I have ever seen stating approximate comp test figures.
Although they are for earlier engines it shows a wide variation over the then model range. Bear in mind these engines have comp ratios in the 14:1 to maybe 16:1 range.
As for the differences of increase of comp values measuered over a period of time could be attributed to the things already mentioned above, also other conditions that would effect the data recorded are:- hot or cold test, different gauge, different coupling method from gauge to engine, IE, long pliable hose verses steel tube, the length of running time (hours) to bed or run in engine, this veries according to loads on the engine in service.
The main criteria in my opinion is the relative evenness of the readings, level of crankcase blowby (this was the main engine test we were using when I retired), changes in oil/fuel consumption, ease of starting, level of diesel knock when cold compared to hot. Can you do a bollard pull test which we used to do at commisioning time of the engine installation to get propper repeatable test results for future reference, and thereby compare the results.
I have come accross lots of owner quoted anomalies when testing marine installations for lack of performance, like:- extra long range tanks fitted, gin cupboards added, navigation gear, propeller changed or dinged and restraightened with a pitch change thrown in, hull soaked up a ton of water and fouled, the list goes on.
It seems like your engine is in good condition as you have only found the variation at yearly check times, and maybe have not seen a change in performance.
Hope this helps,
Cheers,
Eddie B.

Hi edb,
That's the most information I've ever seen on compression pressures:D
By any chance do you have any info. on combustion pressure. What little I have indicates somewhere around 800 -900 psi but not very specific.

Based on your post it would seem the 550-580psi would be right where you want to be for a turbo engine.

Hi OM & Team,
I trust you all had a wonderful Xmas.

I do not recall ever seeing data on combustion pressures in Cat Engines.
I have compression ratio figures for D397-8-9 at 15.5:1, and D326-337 at 17.5:1.
Maybe with some deft figuring some one can get close with the formula for BMEP(Brake Mean Effective Pressure). I found when dyno testing my D337 that if I used this formula for the different RPM and BHP loads that with a change in Rack Settings, from the Rack Setting Book, the BMEP remained the same value.
I have scaned the only BMEP figure I have published in a 1937 brochure on Cat Diesel Engines, form No 4253. It covers D17000, D13000,D11000, D8800, D7700, D6600,and D4400. I will post the D4400 as being the closest to a D333!!!. I have no CR data for these engines.
I believe the maximum BMEP line covers when the engine is lugging on the Torque Spring in the Governor--I do stand to be corrected on this.
Later in the week I will try and search other literature for data.
Hope this helps,
Cheers,
Eddie B.

Hi edb,
For some reason.....don't know if it's at my end or not....but that graph would only part load. How does it look at your end? Anybody else see just a partial version?

Yep, looks like the top half only here also.

Just back from christmas visits and I find this lot of replies. Great!

* The ship is NOBILE, image attached. During the winter she is based in Hamburg.

* To get it chronologically right:
- Approx. 1965 the steam engine has been replaced by a D333 marine engine.
- Approx. 1993 the engine pushed a con rod through the crankcase. A remanufactured engine from a 977 traxcavator was found and installed in the ship, taking some parts (exhaust manifold etc) from the broken engine. We don't know which parts have been taken from which engine.
- Approx 1998 a compression test has been made and showed values from 22-24 bar (320-350psi). About this time the first of us, who are still with here, started spending their spare time with the vessel...
- 1999 the exhaust manifold was rusted through and had to be replaced. During the repair work the cylinder head has been removed.
- Also 1999 another compression test has been done, it showed slightly worse values from 19 to 24 bar (275-350psi). Unfortunately it is not clear whether this was before or after the repair work.
- No compression test is remembered until Dec. 2007, with the known values of 38-40 bar (550-580psi).

* It looks as if no significant change has been done to the engine between the compression test aside from maybe a change of the head gasket. And acc. to my calculations the gasket should be about 2 mm too thin to explain this increase of pressure. I tend to drop this explanation.

* The measurements have been done with different instruments. As far as I know all done by turning the engine with the starter. But we will try to find out whether it was necessary to remove the precombustion chamber for the older tests. This could explain the increase.

* And I learn from your posts that we should not be too concerned about the absolute values, Cat does not care for compression values. Acc. to the attachement of EDB's post the high figures should be OK.

* @Old Magnet: My English fails at one point: What do mean with "spinning rod and main bearings"?

Many thanks for your thoughts and opinions! If we find something I'll post here.

Ole

Hi Ole,
Nice old sailing vessel:)

Spun bearings, a slang term, for referring to the rotation of the bearing inserts within their journals. Usually due to a combination of bearing clearances, distortion of the journals and excessive loading, probably poor oiling as well.

Was/is common to the early D330 and D333 engines which evolved through a. b, & c versions finally ending up as the 3000 series of engines which are much more durable than the "D" series throughout the early 1960's

Seems unusual to me to do a compression test with pre-com chambers removed.

The 977H, 53A would be a turbocharged engine. Are you running the turbo?
Earlier versions of the D333 were not turbo.

Hi Team,
did only post the area of the graph covering the above data as the BB wouldn't allow full graph at the DPI I normally like to use for clarity.
Here is a scan at lower DPI.
Cheers,
Eddie B.

Hello Everyone ! Ole, judging from my experience and research your Cat motor was probably in tip-top shape ! I could not find specs for Cats but Detoit Diesel lists 475 psi for their turboed 2-Strokes and up to 565 psi for supercharged 2-Stroke engines (averaged new).Mack specs range (4-Stroke) from 460 psi to 635 psi depending on engine model ! Mack also gives Compression values according to altitude,which reminded me that your results would be at their maximum !Both Detroit Diesel and Mack specify doing the compression test with the engine running @ operating temperature !Glen