Author Topic: Fuel injection systems  (Read 43020 times)

Online Roger B

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Re: Fuel injection systems
« Reply #195 on: August 31, 2018, 07:58:45 PM »
I received some (expensive) reinforced shank 0.2 mm drills. The first attempt at a holder was made in brass as before, but it broke at the end of the 1mm hole. The 0.2mm wall thickness was not enough  :(  I then tried again with silver steel. I wasn't sure about drilling a 1mm hole 15mm deep but it was ok. I had made a trial nozzle to check the diameter and for polishing I supported the bore with a reversed 1mm drill in the tailstock drill chuck. OK so far  :)
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Roger

Online Roger B

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Re: Fuel injection systems
« Reply #196 on: September 01, 2018, 06:49:32 PM »
Having made the drill I then tried to make the nozzle. The blank was 27.3mm long so it was drilled 1.3mm dia 26mm deep, reamed 1.45mm 25 mm deep and then finished with the D bit to 26.8mm. I then pecked with the 0.2mm drill until the resistance went and luckily the point was still there  :)

I had bought some stronger springs for the injector but they had a smaller bore so I had to turn down the adjuster and the needle cap. I normally use ER collets but the thin needle cap was a good use for the Hobbymat spring collets.
Best regards

Roger

Offline Admiral_dk

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Re: Fuel injection systems
« Reply #197 on: September 01, 2018, 09:19:20 PM »
Looks very good Roger  :ThumbsUp:

I really hope this one works to your satisfaction  :cheers:

Online Roger B

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Re: Fuel injection systems
« Reply #198 on: September 04, 2018, 10:31:13 AM »
Thank you Per  :ThumbsUp: The stronger spring certainly made a difference (video is in the diesel thread) but I need to lap the bore on the 0.2mm nozzle before I can try it.
« Last Edit: October 07, 2018, 08:11:42 AM by Roger B »
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Roger

Online Roger B

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Re: Fuel injection systems
« Reply #199 on: October 07, 2018, 08:10:07 AM »
When I tried the 0.2mm nozzle in the engine I had problems with fuel leaking from the injector union which I couldn't solve at the time. This are was not really designed, just made up as I went along so I decided to revisit it.

The original injection piping was 1mm bore 2mm od copper pipe sleeved into a commercial 3mm union at the delivery valve end with a home made nipple and nut at the injector end. The connection into the injector nozzle was via a cone made with a 0.8mm tip 3.15mm od centre drill.

Since this time I found some 2mm unions from Regner with the same M5 x 0.5 threads. They appear compatible with the original ones from Holzapfel Dampfmaschinen but I need to check the cone angles.

Looking at the original pipework the nipple at the delivery valve end seems quite distorted and the nipple at the injector end has a noticeable ring. I think that the Regner type nipple will be better at the delivery valve end. The problem at the nozzle end is that the nipple is 4mm diameter and the centre drill used was 3.15mm diameter so if the cone is drilled too deep it won't seal. I check the dimensions around that part of the nozzle and I can use a 4mm diameter 1.6mm tip centre drill which should resolve the problem. I will need to make a 4mm bore guide nut for the drilling operation. Previously I used the actual union nut. Some means of depth control will also be required.
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Roger

Offline Vixen

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Re: Fuel injection systems
« Reply #200 on: October 07, 2018, 12:03:26 PM »
Hello Roger,

Is there anything to be gained by hard soldering (use silver solder) a short length of pipe to the injector body and having a standard (bought in) union joint a little way away from the injector. That way you may be able to divorce the injector design from the union problems.

Just a thought

Mike
It is the journey that matters, not the destination

Online Roger B

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Re: Fuel injection systems
« Reply #201 on: October 07, 2018, 02:42:20 PM »
Hi Mike, the problem joint is between the injector body and the nozzle. This is why I have tried to make a cone fitting at that point. If I move the fuel connection to the body I would probably have to lap the nozzle into the body to gain an adequate seal. O rings are too elastic for the high pressures and small volumes. A variation on your thought is to combine the nozzle and the lower half of the body and then screw the spring assembly on top. This would allow me to silver solder the fuel connection to the nozzle and move the union away. I may move to this when I have the design more fixed but currently a new nozzle is a short length of 8mm brass rod and an evenings work.

I have attached a PDF of the current state of the injector design.
« Last Edit: October 07, 2018, 08:27:27 PM by Roger B »
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Roger

Online Roger B

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Re: Fuel injection systems
« Reply #202 on: October 20, 2018, 07:58:53 PM »
I moved on with this making a new union nut and a guide bush for the larger centre drill. The Proxxon drill makes it quite easy to set the depth using a drill of the appropriate diameter. I also used a drill shank to check the depth of the union nut.
Best regards

Roger

Online Roger B

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Re: Fuel injection systems
« Reply #203 on: October 20, 2018, 08:03:38 PM »
I shortened a Regner nut to match the delivery valve and then silver soldered both ends on the pipe using my small Portosol torch rather than the big blowlamp.
Best regards

Roger

Offline Admiral_dk

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Re: Fuel injection systems
« Reply #204 on: October 21, 2018, 08:41:43 PM »
Looks nice - have you pressure tested them after soldering ?

Online Roger B

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Re: Fuel injection systems
« Reply #205 on: November 05, 2018, 08:29:11 PM »
Thank you Per  :ThumbsUp:  I can only test them by assembling the system, maybe I need to build a test fixture using something other than diesel oil.
Best regards

Roger

Offline Vixen

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Re: Fuel injection systems
« Reply #206 on: November 05, 2018, 08:52:22 PM »
Keep a close eye on the pipework, every injection pulse creates a shockwave which can fatigue the pipe joints.

I even had it happen with one of our companies cars. I was miles from home when one of the injection pipes fractured and the engine went on to three cylinders. I did not wish to be stranded, so limped slowly back to base. The engine sounded really rough and stank of the diesel oil which was being squirted all over the engine. Arrived back at base leaving an oil slick under the car.

Mike
« Last Edit: November 05, 2018, 09:19:26 PM by Vixen »
It is the journey that matters, not the destination