Injected Diesel 56cc 2 Stroke, Will it ever work?"

Home Model Engine Machinist Forum

Help Support Home Model Engine Machinist Forum:

Lloyd-ss

Well-Known Member
HMEM Supporting Member
Joined
Mar 8, 2019
Messages
284
Reaction score
158
Location
Charlottesville, VA
Learning Process on Diesel Injectors..... Slow

It has been almost 6 months since my last post on this project, but I have been working on-and-off on a diesel injector. After numerous attempts and failures I have accepted the fact that I will not be able to make 100% of the injector myself. Some of the componenets are beyond the capability of my equipment, but mainly, me. I have been spending some time on one of the antique diesel engine forums to learn about injectors. The Pump-Line-Nozzle system, like Find Hansen makes (my hat is off to that gentleman.... more like I am in awe) for his diesels is popular. But the thought is that the 2 stroke diesel really "needs" a unit injector, which is where the pump and nozzle are consolidated into a single piece. The Detroit Diesel (GM) 2-strokes all had unit injectors.

I attempted to use the Yanmar injector nozzle, and injector pump, to make a single piece unit injector. It almost worked and would occasionally throw out a beautiful mist, but it leaked too much and basically didn't work. If it had been built perfectly/accurately, it should have worked. But it was a learning process.

Here are pictures of the original Yanmar parts, the unit injector parts, the assembled unit injector, and a drawing of it. There are some differences between the injector and my drawing. The ijector is MUCH smaller than the original parts, but still maybe too big. The only parts that I used from the Yanmar (in this version) were the nozzle and needle. It was a fail, but wow, did I learn a lot.

I am now working with a Detroit Diesel Unit Injector (type HV6) to see what makes them tick. And I have a good diesel engine mentor in Australia who has a lot of experience and patience.
Lloyd

OEM Yanmar diesel injector and pump
Inject-and-pump-purch-sm.jpg


The unit injector that I came up with. The Yanmar needle and tip are the only parts I didn't make.
UnitInjectorAttempt.jpg


The finished unit injector. Too bad it didn't work.
YanmarUnitInjectorSm.jpg



YanmarUnitInj-A.JPG
 
Last edited:

weir-smith

Bruce W-S
Project of the Month Winner
Joined
Jan 30, 2015
Messages
79
Reaction score
67
Location
Perth Western Australia
Lloyd

It is interesting to hear about your journey in respect to building a true diesel using diesel as a fuel. I noted your comments regarding others who have built small diesels however, I think you will find that they are not using diesel as such but a mixture of either and light kero. Using this type of fuel requires much less compression and far less fuel pump pressure. I have made these comments previously on these pages as I have been down this journey myself.
I am not going to go into any great detail however, I am happy to help with any question you may have.

There are some important things you have to remember. You can scale the engine but you can't scale the physics. That is, if the full size engine requires 500 psi to compression ignite the fuel, you also need to have 500 psi. I ended up using six rings to achieve this. I tried many forms of self designed pumps but the best failed at 1200 psi eg not good enough. Ended up using the same pump as you have with some modification to suit my model. My thoughts were if it worked, then I would machine it down to better suit the engine. On the bench it would achieve 3000 psi without trouble. In respect to injectors, I tried many designs and found they all leaked one way or another. Dripping injectors don't work that well. I ended up purchasing the smallest Kubota pintal injector replacement nozzle which was about 0.5 inch dia and made a housing for it. A bit fiddly but after several attempts the result worked well. I set the pressure at about 2000 psi which gave a good atomised spray which was so fine, it was difficult to see - more like a fine mist.

Bruce W-S
 

Attachments

  • Screen Shot 2022-08-31 at 2.42.14 PM.png
    Screen Shot 2022-08-31 at 2.42.14 PM.png
    665.4 KB · Views: 0
  • Screen Shot 2022-08-31 at 2.42.48 PM.png
    Screen Shot 2022-08-31 at 2.42.48 PM.png
    456.7 KB · Views: 0

ajoeiam

Well-Known Member
Joined
Aug 14, 2020
Messages
597
Reaction score
174
Location
blank (like some others I've noticed)
Lloyd

It is interesting to hear about your journey in respect to building a true diesel using diesel as a fuel. I noted your comments regarding others who have built small diesels however, I think you will find that they are not using diesel as such but a mixture of either and light kero. Using this type of fuel requires much less compression and far less fuel pump pressure. I have made these comments previously on these pages as I have been down this journey myself.
I am not going to go into any great detail however, I am happy to help with any question you may have.

There are some important things you have to remember. You can scale the engine but you can't scale the physics. That is, if the full size engine requires 500 psi to compression ignite the fuel, you also need to have 500 psi. I ended up using six rings to achieve this. I tried many forms of self designed pumps but the best failed at 1200 psi eg not good enough. Ended up using the same pump as you have with some modification to suit my model. My thoughts were if it worked, then I would machine it down to better suit the engine. On the bench it would achieve 3000 psi without trouble. In respect to injectors, I tried many designs and found they all leaked one way or another. Dripping injectors don't work that well. I ended up purchasing the smallest Kubota pintal injector replacement nozzle which was about 0.5 inch dia and made a housing for it. A bit fiddly but after several attempts the result worked well. I set the pressure at about 2000 psi which gave a good atomised spray which was so fine, it was difficult to see - more like a fine mist.

Bruce W-S
Very interesting
I am learning to travel using the experience of my fellow travelers - - - I am finding there just isn't enough life to make all the trials myself.

AIUI that atomized mist is exactly what will give the best combustion on a compression ignition engine (or diesel if you wish).

It is reassuring to know that this can be made to work.
 

Lloyd-ss

Well-Known Member
HMEM Supporting Member
Joined
Mar 8, 2019
Messages
284
Reaction score
158
Location
Charlottesville, VA
Lloyd

It is interesting to hear about your journey in respect to building a true diesel using diesel as a fuel. ...............

Bruce W-S

Bruce, (and I see that Joe just posted about this, too),
When you call it a journey, I know that you understand. It is as much about the process as the end result. The challenge of it. I always enjoy your candor and insightful comments regarding the difficulties faced along the way. I like the expression, "It is easy to make one that works. It is difficult to make one that works well." However, the meaning of "easy" must be adjusted for each project, LOL.
Your comments about the laws of physics are well taken and understood. I faced that with much of my airgun work. Try as I might, conventional methods yield conventional results.
And I love your project photos.

Let me ask you about bore and stroke for a model diesel. The combustion process of a diesel is limited in its flame-front speed. But Yanmar has little 3600RPM single cylinder engines with 55mm stroke 68mm bore. I think that might be pushing the limit of flame front speed and combustion duration, and therefore piston speed.

I am thinking in the neighborhood of a 50mm stroke, but slow speed, maybe 1200 or 1500rpm max. Anything faster would have increasingly foul exhaust from poorly combusted fuel. The governor would be the ultimate RPM limiter, but the physical restraints applied by the engine construction would also make slow speed the prudent choice. And the bore would be smaller than the stroke; but with the full length skirt required of a 2-stroke piston, either a very long connecting rod or a cross head are required.

Right now, getting past the most difficult components: the blower and the injector, are the first priority. I think the engine will end up being designed around the final injector configuration, LOL.

One final thought on the diesel fuel. Have you ever tried a cetane booster to help with ignition? I can possibly see that as "acceptable" for a true diesel. What do you think?

Lloyd
 

minh-thanh

Well-Known Member
Joined
Dec 29, 2016
Messages
1,218
Reaction score
747
Location
Viet Nam
Hi !
With a lot of testing, with some injectors on my engine
My conclusion is - fuel atomization : Good but not so important - if you just need the engine running
The most important thing is : The injector must be completely sealed. + The oil pump must create enough pressure to inject into the cylinder - The injection time depends on the pressure created by the pump, can inject from 45 to 22 degrees before TDC
 

weir-smith

Bruce W-S
Project of the Month Winner
Joined
Jan 30, 2015
Messages
79
Reaction score
67
Location
Perth Western Australia
Lloyd

To answer your question, the bore of my engine was 40mm with a 80mm stroke. The piston was 80mm long to accomodate the rings and lubrication was via drip feed. The combustion cycle was four stroke and the target RPM was 300 however, could not achieve it and it ran better at 500 to 700 RPM.
I was told by a diesel mechanic that slow revving in a model of this size is difficult as the cylinder head etc tends to cool down (not enough mass) between strokes and makes smooth running almost impossible therefore the need to up the rpm. For me, I don't know but upping the rpm certainly made it run more consistently. I also needed to increase the flywheel in size and weight to about 5kg and use valve lifters to be able to start it. I did have to resort to using a product available here in Aust. called "Start you Bastard" as used by farmers to start engines etc, to get the engine to initially to fire.

I have moved on from this engine and have now completed a model of the Fairbanks Morse three cylinder igniter engine (1910). Also, I have all but completed an Otto Langen engine. In progress is a model of a single cylinder air blast diesel. Now there is a challenge for you. I have only come across one model that almost made it but the builder had to resort to solid injection. The big problem is keeping the compressor cool enough with inter coolers etc so it doesn't start to motor on its own. I only have access to machines one day a week these days having down sized to an apartment and having to sell my workshop equipment. I guess that is life when you are in your mid seventies.

Bruce W-S
Western Australia
 

Attachments

  • Screen Shot 2021-06-28 at 5.09.47 PM.png
    Screen Shot 2021-06-28 at 5.09.47 PM.png
    399.4 KB · Views: 0
  • Screen Shot 2022-03-01 at 12.21.16 PM.png
    Screen Shot 2022-03-01 at 12.21.16 PM.png
    718 KB · Views: 0

Lloyd-ss

Well-Known Member
HMEM Supporting Member
Joined
Mar 8, 2019
Messages
284
Reaction score
158
Location
Charlottesville, VA
Bruce,
You are a busy guy! Beautiful work! I am impressed.

40mmB x 80mmS for the diesel. Wow, that's 100cc, which hardly falls into the "model" classification, LOL ;) .
I guess you had to use a cross head in the design?
 

Lloyd-ss

Well-Known Member
HMEM Supporting Member
Joined
Mar 8, 2019
Messages
284
Reaction score
158
Location
Charlottesville, VA
Mini HV6 Diesel Injector

The Detroit Diesel HV6 injector served as an inspiration for my latest attempt at a mini diesel injector.

Here are the items that make up the injector.
The 7 items at the left end of the top row are actually from the HV6 injector nozzle. I had to fabricate the rest of the items.
HV6-Mini-1.jpg


Here is the assembled mini-HV6 injector.
HV6-Mini-2.jpg


Here is a side-by-side of the original and the mini. The original weighs 790 grams; the mini weighs 85 grams.
HV6-Mini-Compare.jpg


I have just started testing the mini-HV6 and it does work, although the atomization is not what I would like. However, there are no leaks. Some fiddling around is necessary. Some of the problem is probably that the nozzle is capable of at least ten times the volume that the model engine will need. But, at the same time, the full size nozzle is also capable of atomizing the fuel properly at idle when almost no fuel is used.
 

ajoeiam

Well-Known Member
Joined
Aug 14, 2020
Messages
597
Reaction score
174
Location
blank (like some others I've noticed)
Mini HV6 Diesel Injector

The Detroit Diesel HV6 injector served as an inspiration for my latest attempt at a mini diesel injector.

Here are the items that make up the injector.
The 7 items at the left end of the top row are actually from the HV6 injector nozzle. I had to fabricate the rest of the items.
View attachment 139750


Here is the assembled mini-HV6 injector.
View attachment 139751


Here is a side-by-side of the original and the mini. The original weighs 790 grams; the mini weighs 85 grams.
View attachment 139752


I have just started testing the mini-HV6 and it does work, although the atomization is not what I would like. However, there are no leaks. Some fiddling around is necessary. Some of the problem is probably that the nozzle is capable of at least ten times the volume that the model engine will need. But, at the same time, the full size nozzle is also capable of atomizing the fuel properly at idle when almost no fuel is used.

Very nice!!

Do you think that the parts you did use from the mini-HV6 would also be 'makeable'?
Fascinating following this thread.

thank you all
 

Lloyd-ss

Well-Known Member
HMEM Supporting Member
Joined
Mar 8, 2019
Messages
284
Reaction score
158
Location
Charlottesville, VA
Very nice!!

Do you think that the parts you did use from the mini-HV6 would also be 'makeable'?
Fascinating following this thread.

thank you all
Thank you Joe, I appreciate that.

If you had nice equipment, and the skill to use it, you might make all the parts except the tip with the spray holes. On that top row of parts, the only part I made was the plunger, and it is basically a .156 dia x 1.50 long hard dowel pin with some grinding done on it. The other parts are hardened and ground, and all the interfaces are lapped. They wring together leak-free, just like Jo blocks. In order for the pressures to build quickly and precisely enough, it seems like metal-to-metal contact is needed, with nothing that is compressible in the actual circuit. I have a few o-rings in there that are not shown, but they are really just back-up for the metal to metal interfaces. They keep any internal leakage contained.
Here is a close-up of the Yanmar tip which is used on little engines in the 300cc range. The longish tip is .272" dia, the small tip is about .070" dia, and you can barely see one spray hole. There are actually 5 spray holes around the tip and you need either good light and good eyes, or magnification to see them. The Detroit Diesel HV6 tip is very similar in size except with 6 holes. How in the heck did they do that in 1945? I have a friend who worked at a textile plant in the 70's. They had similar little "spinnerets" that made the synthetic thread. He said the spinnerets were made in a very restricted access area. I wonder why, LOL?
Lloyd
YanmarTip.jpg
 

abby

Well-Known Member
Joined
Apr 13, 2009
Messages
508
Reaction score
171
In the UK a very large textile company also made spinnerets in a restricted area , this was because they were made from platinum and liable to be stolen.
Dan.
 

ajoeiam

Well-Known Member
Joined
Aug 14, 2020
Messages
597
Reaction score
174
Location
blank (like some others I've noticed)
Thank you Joe, I appreciate that.

If you had nice equipment, and the skill to use it, you might make all the parts except the tip with the spray holes. On that top row of parts, the only part I made was the plunger, and it is basically a .156 dia x 1.50 long hard dowel pin with some grinding done on it. The other parts are hardened and ground, and all the interfaces are lapped. They wring together leak-free, just like Jo blocks. In order for the pressures to build quickly and precisely enough, it seems like metal-to-metal contact is needed, with nothing that is compressible in the actual circuit. I have a few o-rings in there that are not shown, but they are really just back-up for the metal to metal interfaces. They keep any internal leakage contained.
Here is a close-up of the Yanmar tip which is used on little engines in the 300cc range. The longish tip is .272" dia, the small tip is about .070" dia, and you can barely see one spray hole. There are actually 5 spray holes around the tip and you need either good light and good eyes, or magnification to see them. The Detroit Diesel HV6 tip is very similar in size except with 6 holes. How in the heck did they do that in 1945? I have a friend who worked at a textile plant in the 70's. They had similar little "spinnerets" that made the synthetic thread. He said the spinnerets were made in a very restricted access area. I wonder why, LOL?
Lloyd
View attachment 139760


Well - - - I do know where I can find drill bits to 0.002" dia.

Wonder what size those holes are?
Ever tried measuring them?

TIA
 

ajoeiam

Well-Known Member
Joined
Aug 14, 2020
Messages
597
Reaction score
174
Location
blank (like some others I've noticed)
Where? Broken off inside a part? 🤬 Ouch!

I will get another close-up pic with a piece of super-fine wire next to the holes.
Joe, you always present these bothersome provocative questions, LOL. 😉

Well - - - - I would hope not - - - then you have a 'not good' part - - - chuckling.

Not meaning to be a royal pita but there are not too many different ways of making these very small holes.
And - - - as diesel injectors are sorta 'common' somebody somewhere is making lots of these holes.

I sure wouldn't want to drill a 0.002" hole using a 'sensitive' drill press.
(Sensitive drill press is one where its you feeling the drilling and exerting the pressure to get the drilling done.
Besides - - - that tiny little drill bit wants to turn at some seriously high rpm I would think.)
 

L98fiero

Well-Known Member
HMEM Supporting Member
Joined
Oct 18, 2013
Messages
325
Reaction score
124
Location
Keswick, Ontario
Well - - - - I would hope not - - - then you have a 'not good' part - - - chuckling.

Not meaning to be a royal pita but there are not too many different ways of making these very small holes.
And - - - as diesel injectors are sorta 'common' somebody somewhere is making lots of these holes.

I sure wouldn't want to drill a 0.002" hole using a 'sensitive' drill press.
(Sensitive drill press is one where its you feeling the drilling and exerting the pressure to get the drilling done.
Besides - - - that tiny little drill bit wants to turn at some seriously high rpm I would think.)
It's quite possible though, years ago I had a job that required 0.006 holes, I used a Guhring HSCo drill with a 1mm shank and about 2 mm of 0.006 drill and 1.5mm of flutes and a 17,000 rpm Dumore 16 sensitive drill. That said, we drilled thousands of holes and I could get ~10 holes from a drill but my wife sat and drilled holes, watched tv and got ~100 holes from a drill so it is possible but a 0.002 drill is 1/3 the size. From memory, I think we ran the drill around 12k rpm in C36000 yellow brass.
 

ajoeiam

Well-Known Member
Joined
Aug 14, 2020
Messages
597
Reaction score
174
Location
blank (like some others I've noticed)
It's quite possible though, years ago I had a job that required 0.006 holes, I used a Guhring HSCo drill with a 1mm shank and about 2 mm of 0.006 drill and 1.5mm of flutes and a 17,000 rpm Dumore 16 sensitive drill. That said, we drilled thousands of holes and I could get ~10 holes from a drill but my wife sat and drilled holes, watched tv and got ~100 holes from a drill so it is possible but a 0.002 drill is 1/3 the size. From memory, I think we ran the drill around 12k rpm in C36000 yellow brass.

Interesting drill press - - - thanks.
 

Lloyd-ss

Well-Known Member
HMEM Supporting Member
Joined
Mar 8, 2019
Messages
284
Reaction score
158
Location
Charlottesville, VA
It's quite possible though, years ago I had a job that required 0.006 holes, I used a Guhring HSCo drill with a 1mm shank and about 2 mm of 0.006 drill and 1.5mm of flutes and a 17,000 rpm Dumore 16 sensitive drill. That said, we drilled thousands of holes and I could get ~10 holes from a drill but my wife sat and drilled holes, watched tv and got ~100 holes from a drill so it is possible but a 0.002 drill is 1/3 the size. From memory, I think we ran the drill around 12k rpm in C36000 yellow brass.
Interesting that your wife could get such long life out of the drills. There is quite an art to knowing how far to push tools. I know we have all run across the guy who is always beaking taps and stripping out screw heads and wringing off bolts. I call it "getting greedy," but for some folks I think they just don't have the right karma, or whatever you want to call it, and maybe never will. For me, I always end up paying the price for getting greedy.

Regarding small drill presses, I have long wondered why there aren't horizontal or inverted drill presses to help the chips clear naturally. Or, at least I haven't seen any, nor have I tried to jury rig something like that when faced with a troublesome part. It just seems like it ought to help, but I don't really know. Probably any easy concept that is difficult in execution.
Lloyd
 

Lloyd-ss

Well-Known Member
HMEM Supporting Member
Joined
Mar 8, 2019
Messages
284
Reaction score
158
Location
Charlottesville, VA
Hi !
With a lot of testing, with some injectors on my engine
My conclusion is - fuel atomization : Good but not so important - if you just need the engine running
The most important thing is : The injector must be completely sealed. + The oil pump must create enough pressure to inject into the cylinder - The injection time depends on the pressure created by the pump, can inject from 45 to 22 degrees before TDC
Minh-Thanh,
I am taking everything you are saying to heart. The learning curve (hill) is steep and experienced help is always appreciated
Thanks, Lloyd
 

L98fiero

Well-Known Member
HMEM Supporting Member
Joined
Oct 18, 2013
Messages
325
Reaction score
124
Location
Keswick, Ontario
Interesting that your wife could get such long life out of the drills. There is quite an art to knowing how far to push tools. I know we have all run across the guy who is always beaking taps and stripping out screw heads and wringing off bolts. I call it "getting greedy," but for some folks I think they just don't have the right karma, or whatever you want to call it, and maybe never will. For me, I always end up paying the price for getting greedy.
Lloyd
I'm going with the idea that she had a better feel for the drill than I, her 'day job' was working in a clerical position while I was in a machine shop.
 
Top