Diesel Engine Operating TRPMs

[JohnH]

I own an R-27 with the 4BY2-180 engine, but I think my question applies generally to all BY series engines. On my boat, wide open throttle is 4050-4100 RPM. I believe that the engine's continuous operating RPM is stated as about 3600 RPM. Recommended break-in is stated as about 85% load, which works out to about 3400-3500 RPM. Continuous operation even after break-in is also recommended to be at relatively high load, which I assume means ~3400-3500 RPM.

I believe that the BY series engines are BMW engines designed for automobile use and adapted by Yanmar for marine operation. In automobile use, it is very unlikely that the driver could keep his license and operate for sustained periods of time at high load. So -- my question is: If it is OK to operate the engine at light loads for automobile applications, why is it not OK to do so for boat applications?

Obviously, I'd like to be able to run my boat at 6-7 knots without feeling guilty or having to to run at high load for 5-10 minutes out of every hour.

-- John H

 

[baz]

I believe the general recommendation is to occasionally run the engine up to around 3800 rpm for a few minutes every now and then when cruising along at low rpms. One should not run the engine at the 3800+ rpms for more than 30 mins.

I take the "occasionally" to mean once every few hours after running at low speeds.

I always run the engine at 3800 rpm just before I reach my destination if I can, time allowing.

I'm also told that diesel engines like to 'work hard'... but don't really know what this means in terms of RPMs or continuous running at certain RPMs.

 

[Shared Dream II]

It is essentially the same engine with a different brain, ECU, and a different turbocharger. The engines are designed to run continuously at 3600 RPM. If you choose to operate the engine at lower RPM's, which you most certainly can do, you must cycle the engine to higher RPM's periodically. If you don't, you will run the risk of carbon buildup in the cylinders and injector tips as well as premature turbocharger wear. This will result in lower performance and additional maintenance expense.
It is great that the engine allows for continuous optimum performance or a more fuel conservative (enjoy the journey) approach to cruising. You get to choose, but you have to take everything that comes with the choice.

 

[baz]

You can also run the engine RPMs up with boat at standstill by depressing and holding in the large button at base of throttle lever. In this manner the engine can be run at fairly high RPMs briefly to clear out carbon and clean injectors.

 

[Todd]

Running the RPM up when not in gear is not the same as running the engine under load. Diesel engines have no throttle plate so will fill the cylinders with air with each intake stroke. All this air with little fuel such as in a no load condition will not build the heat and pressure that will occur under load.

Better to put it under moderate load for a few minutes once in a while. My normal cruse is 5 - 6 kts at 1400 RPM 1.0 GPM. Do that all day long. When I get an opportunity I will run 3500 RPM for 10 minutes and try to do this once every day or two.

 

[bbrh842]

My philosophy is same as Todd. I run 1600 to 2000 rpm most of the time. On the way back to the marina I will run 2600 rpm for 5 minutes. Once every tank of gas I run wide open for ten minutes. Now I don't know if all this is right or wrong. I can only say, it has been working for me for 5 years and 850 hours.

 

[rt11002003]

Interesting discussion. I seem to recall the Yanmar instructions for their 30hp engine used in the R21EC. They suggested several short bursts at max rpm proir to shutdown. Note, max rpm, not max rated rpm. That means running with the transmission disengaged since that's the only way to attain max rpm (normally). A prop that is not pitched correctly can also attain max rpm (another discussion topic).

That small Yanmar is not a turbo charged engine, perhaps that makes a difference. However, it's a good idea to follow Yanmar's instruction. They are the warranty providers.

gene

 

[knotflying]

Another coincidence! I just came back from a 4BY2 class at Mack Boring and we discussed RPM. Per the instructor the engine in netral at WOT should hit about 4,500 RPM. Under load it should be 4,000 RPM. Run the engine at any RPM you desire. If you are going slow for a while at idle get your RPM's up for about 10 to 15 minutes to bring the engine temperature up and this will reduce carbon build up and remove moisture from your oil. Never run the engine at WOT for more than 1 hour total time in a 10 hour period. He also recommended using a lazar Tach to calculate the RPM and compare it to the RPM on the Yanmar display and if they are different the engine computer should be adjusted to the appropriate reading by a technician.

 

[baz]

The following is what I learned from my Yanmar engine technician -- and I posted this a year or two back...

Explanation for the "4BY2-150" engine designation
4 = number of engine cylinders
B = BMW (Yes, the auto maker. Yanmar took the BMW engine and marinized (sp?) it) Y = Yanmar
2 = Engine revision level
150 = HP rating

1. Whenever possible run the 4BY2-150 engine at a minimum of 2600 RPM. This allows for proper level of turbo boost to keep the turbo seals seated in properly. Running with less than 2600 RPM for any extended time is AOK so long as the engine's RPMs are raised up to around 3600 for maybe 15 to 20 mins every 4 hrs.

2. The 4BY2-150 engine can be run all day at 3600 RPMs without issues.

3. If the 4BY2-150 engine is run at WOT with it being around 4000 RPM it should not be run at this RPM level for more than 30 mins.

4. Before shutting the 4BY2-150 engine down after a cruise place the throttle lever in neutral position, press the release button in the base of the throttle lever to disengage the gear box and move the throttle lever into reverse all the way (WOT) while holding the button in. Run the engine in this WOT 'throttle only' mode for some 15 to 30 seconds. Note that once the throttle lever has been moved into the reverse position you can let go of the button. This will ensure all the crud etc in the engine exhaust gets blown out and will avoid 'exhaust smoking' next time the engine is started.

5. When changing the gear box oil it's important to realize that the exit and return tubing that carries the gear box oil to the oil cooler need to be primed with the gear box oil. Thus, fill empty gear box with proper oil (it's almost invisible to see oil on the did stick) and when checking the level be sure to screw the dip stick in all the way (about 7 full turns) and fill until level is no higher than the top line marker on the dip stick. Now replace dip stick and screw in and perform the following to prime the two oil cooling tube/pipes with gear box oil.

Start engine and do following 4 times -- Move throttle lever from neutral to just when forward engages and then immediately return lever to neutral and then continue moving lever to just engage reverse momentarily, and then back to neutral.

The above will prime the two input/output gear box oil cooling tubes.

Now remove the gear box dip stick and check oil level and top up as needed -- but be sure not to overfill beyond the top line.
As the oil is almost invisible to see on the shinny dip stick the best method for determining the oil level is to place the dip stick on a cloth after being removed from the gear box and then rotate the dip stick on the cloth to see where the oil residue resides with respect to the dip stick's top line.

I hope all this is useful to others...