We did a test drive, first real try on plane, no success.
Oil pressure problem is still there but not as bad as earlier when diesel leak in oil. My friend is chief engineer on big cruiser ship and have some knowledge at big diesels and monograde oils, he was onboard and asked why oil temp is that high, I thought it was low. I didn't know that big engines have usually very low oil temps, like 40C, Volvo D13 oil thermostat start open at 70C. Monograde oil viscosity change a lot when temp changes. Cold engine had pretty good oil pressure but it still drop when oil temp go up.
Here is few tests, oil pressure drop rapidly when rpm go up so I pull throttle back. I think oil cooler wasn't full and oil level drop after thermostat force oil there and dry sump tank had too low oil level and pump suck air. Pressure come back when rpm get down, need fill just more oil.


First engine make very thick oil smoke because last drive oil get thin and go through turbos, too small breather caused turbo housings over float. Transmash have under 100C EGT at idle so no oil will burn but when loaded it start smoke. Brather was too small because I delete vacuum pump and forgot to modify breather work better without vacuum.


Next try it doesn't smoke gray or blue smoke anymore. Boost get to 0.7bar at second gear, boat try to get up but too low prop shaft speed, have to try at third gear but oil pressure get too low so we idled back home.


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Little boat builder likes new boat.


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Solution to get oil pressure up to 12bars is reduce oil temp from 70 to 30-40C so I modify thermostat valve to be in hot position all the time. Because this must not be too easy, surprise oil pressure drop more even at cold!!
I start to think that Volvo D13 filter housing have some choke for oil flow and problem get worse when oil thermostat close the oil cooler passing port. Oil cooler itself are from big truck allison automatic transmission, it will flow enough, hoses too. Next thing to solve this endless nightmare is measure oil pressure from pump, if it is significantly more than oil pressure to main galley then I have serious problem inside filter housing.

I need to buy straight sae50 oil too, these huge ancient engine just need stiff oil. Another wierd thing is prelube pump, I tried prelube when oil was hot, that tiny 1.4cc pump can make 0.5bar oil pressure! If engine have too much internal leak, prelube won't make any pressure so this is second reason to doubt filter housing problem.

Few weeks ago when we did tests driveshafts or props had pretty bad vibrations. I lift front side of engine 50mm up to get better angle for driveshafts when drives are fully down, it helped an pretty much all vibration is gone.

Flow restrictors will also generate heat in the fluid.

175psi is some serious oil pressure.

Low oil temps and marine generally not so good from condensation issues.

Very complex system, sounds like you could use many oil pressure sensors with a digital readout.

Glad to hear the driveshaft vibes got reduced.

Isn’t the point that you want 12bars when the oil is at working temperature, to make sure it gets to where it needs to get, not when the oil is cold?

Or is oil pressure in a diesel engine measuring something else?

Or is the Transmash supposed to operate with luke-warm oil?

IMO 12 bar oil pressure is to high for any kind of motor, I would want something half of that

Hyvin se mene
 

Endless nightmare you may call it. Unbelievably interesting nightmare to us readers.

I've been following this build for quite a while, ever since I saw OP in facebook seeking for a suitable material for power transmission shaft and I though what would be the application where you need so much power to transmit through such a thin shaft. It has become one of my daily update checks during the past year. To me this whole project with the constant progress being made is something exceptional and I'm glad to see it happens in my home country. I'm sure you'll get this sorted in no time.

Also to me this oil pressure of 12bars sounds a lot. That size of an engine will have quite a bit of oil flow in operating temperature and viscosity considering the amount of components being lubricated. Would be kind of understandable if the volvo housing for a lot smaller engine with half the moving parts wouldn't flow enough. The sudden drop while increasing the rpm is not really explained solely by that. Are you sure the flow through the drysump tank is not too fast to let the oil settle/release the airbubbles. Wouldn't be the first drysump application suffering of oil foaming. Especially if the tank volume is not too large. As you thought yourself you may have gotten air in the pump after filling the cooler.

I agree with the other guy mentioning that maybe making the oil thicker by grade or temperature is not a good way to increase pressure. It may be that some smaller oil channel does not have enough flow then.

I also work on ships with big engines. Generally these sub 50degC are seen on large two stroke diesels. But fourstrokes are usually operated in the range of 70-80degC. Comparing to ship engines this is quite a different use case in terms of power output/displacement. I would aim for 70-80 degC oil temp to make sure the oil with its additives is operating as intended and to minimize any moisture sticking in the oil.

Tsemppiä loppukiriin!

I know this engine has been completely modified, but it might still be interesting to hear the opinion of the mechanics who used to service the T-55 in your army. After all, it hasn’t been that long since the last ones were retired, and there must still be some seasoned veterans who know this engine like the back of their hand.

Original soviet handbook for T-55 tank told pressure hould be 10-12 bars at high rpm. I think very high oil pressure is needed because all oil to bearings come from front end of cranksaft that is machined hollow to lubricate all bearings. There is rotating fitting that feed oil in crank, main bearing, thrust bearing and rod bearings are feeded from crankshaft. There are no oil galley or channels in cylinder block. Centrifugal force may affect pressure somehow or high pressure is needed to keep good oil pressure in last bearing too. I don't know better answer but all tractor pulling Transmash engines and original battle tanks have over ten bar oil pressure, I really don't want to test if less is good.....

I'm not afraid of cold oil and water contamination, oil will get hot enough under pistons and other places to boil water off and oil change interval is so short that it should work. It will be better if oil temp is over 70c, that's true but engine have to keep enough oil pressure, it's more important.

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Back on engineering table. I try find any restrictions, there are few 90 degree elbows and maybe too little filtration surface. Solution is modify filter housing, I take by-pass filter off and modified housing to have three main flow filters instead of two.

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By-pass were feed from already filtered oil from main filters. I have to machine and sleeve old feed and make some new feed from dirty oil side.

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One hole had to plug, another get pipe inside for external oil feed tube.


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Voith automatic transmission banjo oiltube get new life in Transmash. Some heat and different angles

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Filter thread was different too.

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Now filter housing have over 200% more flow. One more filter and I figured out that long life filters are better flowing, filters I used before was 21 microns and long lifes are 38 microns. I put three longlifes first and if problems go away then change tighter filters back one by one.

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Oil cooler may have too low flow too, one bar shortcut valve past cooler if pressure differense are bigger than 1 bar, now this thing can't be restrictor anymore.
I take oil thermostat out from filter housing and simplify circulation as much I can. All oil go now from pump to cooler, then to filter housing, excess oil go to piston coolers, main flow in engine. Turbos and injection pump is reduset to 4 bars. Should work.

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I remove pump too. Idle quality was so poor that I decided to change pump "controller" from RQV to RSV. RSV have better adjustment and control for idle and will not control fuel above idle by rpm, it's just like throttle blade in gasoline engine.

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Finland best injection pump shop Akaan Diesel will change controller and adjust pump in this week.
Maybe next week we could see will these modifications work. Stay tuned!

Sorry for butting in.
I noticed somewhere that you’ve kept the gearbox and can shift gears. If I’m right, then I’d suggest putting it in a lower gear for the first tests. That way you’ll reduce the load on the engine, which is probably a good idea for initial testing, and you’ll also increase the torque on the propeller shaft. Once everything is working properly, you can try accelerating at full throttle with the safety margin provided by the gearbox to test whether the transmission can handle the torque.

Viscosity, temperature and pressure go hand in hand.

You cannot consider oil pressure on a stand-alone basis.

First gear is for slow no wake zone driving, we tried to get plane in second gear but not enough prop shaft speed, it was close to get up. Next test run I will put 3. gear in to get plane but we need enough oil pressure before that.