Author Topic: Sharing some of my diesel discoveries .  (Read 218 times)

Offline Minh Thanh

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Sharing some of my diesel discoveries .
« on: May 14, 2022, 06:10:35 AM »
Hi All !

Sharing some of my diesel discoveries:
1/ Injection time: More precisely the time the lobe begins to contact the pump piston: 22 to 45 degrees before TDC
2/ Engine runaway : Should be worried?
If your design calculates lobe timing, intake and exhaust ports....exactly like a full size diesel engine then you should worry. But with a small engine you can easily stop the engine.
With many tests, my engine can not runaway
3/ Injection : Fuel vaporization-Atomized fuel . How to inject fuel
3A/ Fuel vaporization-Atomized fuel : It is necessary but not all.
Fuel vaporization-Atomized fuel will give you an objective view of the efficiency of the pump and injectors: the pressure generated by the pump, the tightness of the injectors....and when the engine is running it will have very little smoke.
" Not all " because when i make some test with my engine the injectors just "inject " fuel - as in the picture (Some cases are even worse)- -and the engine is still run 

 This leads to 2 cases: a/ the engine runs but a lot of smoke and some unburnt fuel (it looks like mud) comes out the exhaust pipe and b/ the engine a lot of smoke . Solve this problem: simply increase the compression force of the needle spring
3B/ How to inject fuel :
fuel injection : radiates from the center - good
Fuel injection is left or right: it doesn't matter
With a full size diesel engine, the fuel vaporization-Atomized fuel, the fuel injection, ... needs to be really good because it concerns the performance ... of the engine, and that's what is really needed.
But with a homemade diesel engine, you can stick to that rule if you want, and that's how I do it with my engine.
If you only need one engine running then it shouldn't be too important. And the engine has running, you can easily adjust the make the engine run better
   One important thing is : the injector must be completely sealed .
If the injector is not completely sealed it will affect the pressure in the cylinder and the oil pressure in the oil pipe
Hope this gives those who are or intend to build diesel a little more confident

Offline Roger B

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Re: Sharing some of my diesel discoveries .
« Reply #1 on: May 14, 2022, 03:18:01 PM »
Thank you Thanh  :)

The working small true diesels I know of (Don Comstock, Find Hansen, Erich Beyer) all use a sealed mushroom/poppet type injector.
The Dux appears to use a fine scratch as the injector nozzle but I have not studied it. The Lister 6-1 runs with a diesel/ether mix. Hobbynut was building one on here but hasn't posted for some time.
Best regards


Offline Admiral_dk

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Re: Sharing some of my diesel discoveries .
« Reply #2 on: May 14, 2022, 09:16:03 PM »
Yes - it would be fair to state that the two off you are part of a very select and small amount of people that ever got a miniature diesel engine to run as a diesel  :praise2:   :praise2:  I know that there is historical documentation for two more that Roger mentions, back in the 1930's ....


Offline Minh Thanh

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Re: Sharing some of my diesel discoveries .
« Reply #3 on: May 15, 2022, 03:46:12 AM »
Hi Rogers !
Just a little info as I do some testing with my engine. It gives a different perspective on the possibility of making the engine run
    And if someone is designing and building a diesel engine will be more confident and not have to worry too much about that problem.
  Of course , doing the best possible is the best approach ( that's how I do it ) , but maybe someone just needs an engine running .
  Hi Per !
What I can say "I can and you can too"
  It's not too difficult for a lot of people on this forum or elsewhere, the point is: " You are patient and meticulous enough "

Offline cnr6400

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Re: Sharing some of my diesel discoveries .
« Reply #4 on: May 15, 2022, 06:15:56 PM »
Great tips on injectors and diesel builds in general Thanh!  Thanks! :cheers: