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Looking for a Small Mechanical Injector

Elden DuRand

In Memory Of
Age
78
Last Subscription Date
12/22/2017
I apologize for being not quite on topic but need to pick some brains out there.

I'm designing a small (prox 3 c.i.) true Diesel engine. So far, I've come up with a pump but, since I've got to fit the injector between the valves in a 1.125” bore, I'm well over my head in the smallness I can machine and, unless I can come up with something, I will have to go with an existing part.

My question is......can someone recommend a ready-made mechanical injector for a small Diesel engine like a Lombardi, Yanmar, etc?

All help will be appreciated.

Thanks!
 

PFT

Sponsor
Last Subscription Date
02/07/2020
Re: Looking for a small mechanical injector

If all you need is a small injector nozzle, the infamous Olds 350 diesel used a simple one no bigger than a spark plug. Might be worth a look if you haven't already.
PT
 

dalmatiangirl61

Subscriber
Last Subscription Date
07/10/2019
Re: Looking for a small mechanical injector

You might look at Petters and Ruggerini too, but even their smallest engines were larger than 3 cu/in, so not sure how you would cut the delivery.
 

enginenut2

Registered
Age
78
Re: Looking for a small mechanical injector

What were the smallest diameter tip of the Roosa-Master "pencil" injector which I think the early OLds engine used or the ones used in the 3208 Cat? And actually the entire nozzle tip doesn't have to protrude into the combustion chamber and then there's the possible use of a pre-combustion chamber with small opening into the main.
 

Nathan K.

Subscriber
Last Subscription Date
03/24/2019
Re: Looking for a small mechanical injector

Hi Elden,
As mentioned the roosa master Pencil injectors are the smallest? with a body ~3/8" od. but length is still a bit over 4" if you can make that work. There are cheap after market ones on ebay, I look forward to seeing the new model!.
Nathan.
Note, they seal in a reamed hole with a teflon band on the shaft and are held in with an offset 5/16" bolt/stacked spring clamp(some models come with springs) so are easy to mount.
 

Elden DuRand

In Memory Of
Age
78
Last Subscription Date
12/22/2017
Re: Looking for a small mechanical injector

It's been a long time since I saw an Olds 350 injector and forgot how small they are. They are a good possibility, although with their length, they would look a bit odd. Also, since they are for a much larger displacement, it could be hard to get them to spray at such low deliveries.

Would anyone have part numbers for the small engine injectors? My search has found a couple but, since there were no mfg. part numbers, searching places like Ebay and Alibaba is useless.

Thanks for the help!
 

PFT

Sponsor
Last Subscription Date
02/07/2020
Eldon, the injectors I referenced are the later style, not the long pencil style. There are some on ebay now if you want to see what they look like.
Item number:
221431074239
 

ronm

Subscriber
Last Subscription Date
07/10/2019
The Yanmar & Kubota injectors are huge things for the size of the engines...big ol' precup injectors.
Somewhere I have seen a variety of the Roosie pencils that was not as long as the JD's, maybe 2-21/2", but I can't think what application they were for.
I really don't know of any injector smaller than the poppet style GM 350 ones.
This will be an interesting project, I have done some research on model Diesels, & there's a point where the relative surface area of the combustion chamber causes too much heat loss in compression, & you can't get enough heat to ignite fuel...
But, if anyone can do it, you can! :salute:
 

Heins

Subscriber
Last Subscription Date
01/02/2020
I have a three cylinder Cat diesel in my side by side and each cylinder is 14.4 cu in, I thought that is a small engine. PFT has heard it run, the injectors are large about the size of spark plugs. Ronm is correct that you will have trouble building enough heat by compression to ignite the fuel, a hot tube may help with that, not a glow plug.

Elden, I could send you an old pencil injector that isn't any good to see if you could shorten it and make it work.
 

dalmatiangirl61

Subscriber
Last Subscription Date
07/10/2019
What are you going to do for a pump? I have 1 nos injector pump from a generac diesel (not sure actual engine mfr), it is a standard cam driven pump, not sure if it would be too large dimensionaly for such a small motor, but if you want it, and it is where I think it is, I'd be happy to send it to you.
 

kwfiggatt

Registered
Re: Looking for a small mechanical injector

Search ebay for L170F injector. This is the designation for the chinese copy of the L48AE Yanmar, which is a 4HP air cooled, direct injected engine. Here's a link to an aliexpress ad showing these injectors. It looks like it is approx 87 mm long, or 3.425"

]I did some googling on the Olds 350 injector and it appears to be a CAV Microjector. These injectors are designed to screw right into a 14mm threaded hole, similar to a spark plug. I found a link with a description and a cross sectional drawing of the injector here --> link

This injector uses an outward opening poppet valve, and has helical slots between the valve head and body to create fuel swirl, according to the link. Now, that's cool! Wonder how this would work on a modern common rail setup? :cool:
 

enginenut2

Registered
Age
78
Elden, I thought you might go with an air blast system, then the injector could be simple to make--of course there would be a compressor, a timing valve with cams and drive and maybe an accumulator with other accessories. Just think how that would stir the public opinion.
 

Elden DuRand

In Memory Of
Age
78
Last Subscription Date
12/22/2017
Eldon, the injectors I referenced are the later style, not the long pencil style. There are some on ebay now if you want to see what they look like.
Item number:
221431074239
PFT:
Thanks for the link. I'm still looking. 14mm is a bit large for center injection but may work for side if I use a pre-combustion chamber. They are a possibility, although with the tiny fuel volume, getting a good pattern would be problematic.

.................. snip

This will be an interesting project, I have done some research on model Diesels, & there's a point where the relative surface area of the combustion chamber causes too much heat loss in compression, & you can't get enough heat to ignite fuel...
But, if anyone can do it, you can! :salute:
Ron:

Thanks for your confidence! I did do the Hvid and it is a great running engine with a 2" X 4" bore and stroke.

..............snip................
Elden, I could send you an old pencil injector that isn't any good to see if you could shorten it and make it work.
Thanks - PM sent!

kwfiggatt:
One link is bad but the others work but, unfortunately, all I see are too big.

Thanks!

What are you going to do for a pump? I have 1 nos injector pump from a generac diesel (not sure actual engine mfr), it is a standard cam driven pump, not sure if it would be too large dimensionaly for such a small motor, but if you want it, and it is where I think it is, I'd be happy to send it to you.
Girl:

I think I'm capable of making the pump itself but control of fuel volume is complicated (see my web page on the subject). If what you have is something you don't mind parting with, I'd be happy to have it and I will reimburse you for the postage.

P.M. sent with thanks!

Elden, I thought you might go with an air blast system, then the injector could be simple to make--of course there would be a compressor, a timing valve with cams and drive and maybe an accumulator with other accessories. Just think how that would stir the public opinion.
Air blast??!! I don't think so! Just think of the possibility of the loss of life or limb from a 2,500 psi air injection system! Thank you Herr Diesel but that one needs to stay in the past.:)
 

Thaumaturge

In Memory Of
Age
68
Last Subscription Date
07/12/2019
Eldon: You could maybe duplicate a scaled down version of injector used on my Lombardini LD435 (9hp). Uses a two stage (3 actually) injector system. Regular diaphram pump feeds high pressure pump driven off cam, which in turn feeds a really high pressure nozzle which isn't all that large, but uses fuel impulses from high pressure pump to up pressure even higher. I'll poke around and see if I can't locate my Lombardini manual for you. Has good diagram of inside final high pressure injector. If I can locate manual I'll put it on my gdrive and post link.
Doc

Link to folder (stuck in with Kohler manuals. Lombardini should be first three, most likely second one is one you want.)... Whoops, link scrambled them. Next to last is one you want....
https://drive.google.com/folderview?id=0B1p7xJAXmwbWSDZraVJ2Q0hsZWM
 
Last edited:

Heins

Subscriber
Last Subscription Date
01/02/2020
I will send you an old injector that isn't any good to see if you can make it work. If you can make it work, let me know and I will send you a better one.
 

Elden DuRand

In Memory Of
Age
78
Last Subscription Date
12/22/2017
Now all I gotta do is wait for the postman.

One of the guys who follows my web page sent me a broken WD-40 pump barrel and plunger and an injector tip. Unfortunately, they are too big but give an idea about how to make one. I'm still uncomfortable with the thought of working that small and accurate.

The same viewer suggested a single valve Diesel design (I did one for spark ignition and it runs fine). That would give more room for the injector. He added that hit and miss configuration would make for a simpler pump and the pump and injector could be then set for maximum fuel delivery.

Of course, the complication there is how to latch-out the pump but that should be easily solved with a bit of cogitation.

If at all possible, though, I would like it to be "throttle governed". Hit and miss is relatively easier than getting a throttle governed engine to run well at varying speeds and loads.

I really appreciate the help, gang. Where I live, there are no old engine or model people within range so I am left to my own devices and sometimes those devices are defective. Input is always good.:)
 

ronm

Subscriber
Last Subscription Date
07/10/2019
Some of the old pumps, & I can't remember which, used a tapered wedge between the tappet & plunger, the wedge was controlled by the governor moving it in or out, thus controlling the effective stroke of the plunger. That would be easier to engineer on a small scale than the rotating plunger, I think invented by Bosch, most systems use now.
I've seen pictures of what I'm talking about, but haven't found one on the Net yet...

A rough, oversimplified idea, used in a common rail system, but you get the idea:

Edit: OK, well hell, I should have looked at your webpage first...
 

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dalmatiangirl61

Subscriber
Last Subscription Date
07/10/2019
Elden
I went looking for that little injector pump today, but did not find it. Found the boxes of generac electrical controls, but not the pump (they came in together). Not sure if it ended up in a "misc" box, ended up on shelf in Tx, or if it is in one of the boxes that got packed but not loaded into trailer:shrug:. I'll keep a lookout for it, trying to get some inventory done.
 

Elden DuRand

In Memory Of
Age
78
Last Subscription Date
12/22/2017
Girl:

It would be great if you can come up with the small pump. That would solve the problem of varying the fuel volume.

A hit and miss idea was advanced by one of my web page viewers. It includes a single valve for both intake and exhaust (I have built a successful one valve spark ignition engine so it is doable). Only having a single valve will make room for the injector.

With hit and miss, fuel delivery is always set for maximum power, so the pump is simplified. Probably smoky, though.

Ron:

The problem with the wedge is, when fuel delivery is reduced, injection timing is retarded. I went to a lot of trouble drawing up a pump with a wedge then discovered the “clod in the churn”.

I do have a pump design worked out that keeps start of delivery at the same point and changes fuel volume by changing the timing of the end of delivery.

I could use the unit pushrod operated pump/injector idea if I change to hit and miss.

I'm getting some good input here. Keep it coming!
 
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