Author Topic: Fuel injection systems  (Read 75321 times)

Offline Admiral_dk

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Re: Fuel injection systems
« Reply #360 on: October 07, 2021, 10:56:41 PM »
I really like your idea about using the bush - as down in those very small dimensions every detail counts  :ThumbsUp:

No way in Hell I could achieve your results (I might be able to learn to do it, but ...).

Crossing fingers that you will be satisfied with the result when you test them  :cheers:

Offline Minh Thanh

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Re: Fuel injection systems
« Reply #361 on: October 08, 2021, 05:17:55 AM »
Hi Roger !
Your injector parts are great

Offline Roger B

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Re: Fuel injection systems
« Reply #362 on: October 09, 2021, 08:57:31 PM »
Maybe not so great  :(  I milled the flats on the nozzle and then checked the pieces together. I had mixed up two different drawings of the needles and the thinned down part was 5mm too long  :facepalm:

Start again with another piece of 2mm silver steel  ::) This time all looks ok and both needles have been lapped with 5 micron diamond paste  :) Looking at the finish after turning I decided that the grinding and polishing step may not be needed. I will see what happens with the test rig  :thinking:
Best regards

Roger

Offline Roger B

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Re: Fuel injection systems
« Reply #363 on: October 10, 2021, 10:40:09 AM »
It looks like the grinding and polishing steps may be necessary  ::) Both the new injectors gave a similar almost sideways spray pattern  :( It was difficult to capture but there is a sort of spray at 45░downwards.


It may be that the needle extends further on the new builds as the diameter has not been reduced by grinding or it may be a surface finish effect  :thinking:  :headscratch:

After my mistake reading the drawing for the needles I have produced a new drawing with only the current parts on it to reduce my confusion  :old: It is attached as ACad R12 and PDF
Best regards

Roger

Offline Roger B

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Re: Fuel injection systems
« Reply #364 on: October 12, 2021, 06:51:54 PM »
As usual I made the mistake of changing two things at the same time  ::) I didn't grind and polish the cones and I went from 1 micron to 5 micron diamond paste. I could feel a distinct ridge on the new needles, whether this was due to removing the machining marks or the 5 micron paste I don't know, but it would cause the sideways spray. I ground and polished both the needles in the same way as before and lapped them with 1 micron paste so I can see if I can repeat the previous result  :thinking:

I also received what I hope is the solution to the delivery valve problem. I ordered two 3mm diamond charged lapping balls from a firm in the US. As these were custom they were not cheap but I will see how they can improve the valve seatings  ::)
Best regards

Roger

Offline RReid

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Re: Fuel injection systems
« Reply #365 on: October 12, 2021, 08:25:13 PM »
Roger, your perseverance and attention to detail just boggles my mind! :ThumbsUp:
Regards,
Ron

Offline bent

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Re: Fuel injection systems
« Reply #366 on: October 13, 2021, 06:44:45 PM »
Still following.  :popcorn:

Also agree with RReid, admiring your persistence.  Ah well, back to work.  We have finally found a supplier for hydraulic controls who isn't using Covid as an excuse for  :censored: all of our purchase orders.

Offline Zephyrin

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Re: Fuel injection systems
« Reply #367 on: October 14, 2021, 10:53:12 AM »

the delicate point to obtain a regular spray could be related to the volume of the filling chamber behind the nozzle, I wonder if this chamber is not filled, the fuel does not form a ring around the rod and will give a tilted jet and not in cone?

Offline Admiral_dk

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Re: Fuel injection systems
« Reply #368 on: October 14, 2021, 12:02:46 PM »
Interesting point Zephyrin - but as air is compresable and the liquid isn't - would that mean that when the pressure finally is high enough to open the Injector, that the air will be escaping too ...?

That said - there might be a very valid point about the internal shape behind the valve.

Still crossing my fingers for your succes Roger and may it happen sooner than later.
« Last Edit: October 15, 2021, 11:13:57 AM by Admiral_dk »

Offline Roger B

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Re: Fuel injection systems
« Reply #369 on: October 14, 2021, 02:14:04 PM »
Thank you all for your interest  :) The problem was due to me changing the way I made the needles. Having ground and polished the cones as usual I got good results.

The old nozzle with a new needle:


And the new assembly fitted with a weaker (about half the force) spring. The pattern is still good but it doesn't give the characteristic buzz.

Best regards

Roger

Offline Admiral_dk

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Re: Fuel injection systems
« Reply #370 on: October 14, 2021, 04:45:23 PM »
I like the look of the latter, but honnestly (and please do not use me as a reason for buying this) I could use a fast recording camera and slow-mo playback, to really detailed see the pattern / mist :-[

Offline Roger B

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Re: Fuel injection systems
« Reply #371 on: October 14, 2021, 05:05:56 PM »
Thank you Per  :ThumbsUp:

The second one is intended for petrol/Benzine/gas manifold injection. The first one is just a copy of the previous diesel ones to see if they are reproducible.

Nest step sort out the delivery valves  :thinking:
Best regards

Roger

Offline 90LX_Notch

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Re: Fuel injection systems
« Reply #372 on: October 15, 2021, 12:49:49 AM »
Great work Roger, stay at it.

-Bob
Proud Member of MEM

My Engine Videos on YouTube-
http://www.youtube.com/user/Notch90usa/videos

Offline Minh Thanh

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Re: Fuel injection systems
« Reply #373 on: October 15, 2021, 07:12:12 AM »
Roger !
How much diameter pump are you using ?

Offline Roger B

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Re: Fuel injection systems
« Reply #374 on: October 15, 2021, 09:42:31 AM »
Hi Minh,

I am using a 2mm diameter plunger. I calculated the theoretical stroke for full power from a 20cc engine as follows:

The density of air is around 1.2kg/m3 so 20 cc of air is around 0.024g. Taking a fuel air ration of 14-1 this would require 0.0017g of diesel fuel. The density of diesel fuel  is around 0.8kg /dm3 so at full output around 2mm3 of fuel would be required. This could be achieved with a plunger of 2mm diameter and a stroke of 1.5mm (plus a bit to allow for leakage).

I have seen the thread on HMEM and am happy for you to quote this.

I have designed the pumps to give 2mm of stroke after the inlet port closes, a total of 3mm. The working stroke is adjusted by the helix which makes it hard to determine what it is in reality. Test measurements have shown the output ranging from less than 1mm3 to 5mm3.
Best regards

Roger