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So, quick background: I'm building a custom aluminum intake for a RWD k24a1. I'm working on machining the injector bungs, and I was wondering if I can safely mill off the plastic from the end of the stock injectors. It's the part that normally carries the O-ring and inlets for the cold idle circuit, but I'm not going to be using that system. I would be cutting at the red line here, and milling/sanding down to the face of the metal diffuser shown in the second pic:

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I noticed most aftermarket injectors don't seem to have this nose piece at all, but I'm wondering if it would affect the spray pattern on the stock ones. And on the same topic, are most aftermarket injectors designed for the stock holes/length, or do they need extension caps? There's so many choices that I've had trouble finding a good answer 馃
 

Arouse the DAMPFHAMMER!
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So, quick background: I'm building a custom aluminum intake for a RWD k24a1. I'm working on machining the injector bungs, and I was wondering if I can safely mill off the plastic from the end of the stock injectors.
I would pull that added cab off, it is not needed for normal operation. It has an effect on the spray pattern, but more or less a positive one (depending on your injector bung outlet design).



It is recommendable to buy a maintenance kit for the RDX injectors and use the black rubber caps at the nozzle (s. above's picture). They seal to the air and prevent mud collection there (blowby mud and evtl. dust from atmosphere). Like this here:


Must be the dimensions similar to the stock injectors. Please check it out.

...are most aftermarket injectors designed for the stock holes/length, or do they need extension caps?
You need just the stock length between the O-Rings and OD of the O-Rings to select the right injectors. See pic above.
 

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Discussion Starter #3
Thanks for the info Lotus. I ended up milling them off to look similar to that first pic you had and I think they'll work much better like this.
 

Arouse the DAMPFHAMMER!
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Thanks for the info Lotus. I ended up milling them off to look similar to that first pic you had and I think they'll work much better like this.
I am curious, would you like to share a picture of your injectors?
 

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Discussion Starter #5
I am curious, would you like to share a picture of your injectors?
Sure, here's what I ended up with after milling. Luckily the top of the injector is metal so I was able to chuck it in my lathe:

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Also for reference, this is the injector port design I ended up using, moved up the runner slightly as I have no way to machine the flange like the stock manifolds are. Been a while since I welded aluminum:

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I would have liked to keep the injector aiming further toward the intake valve, but I had to strike a balance between function and being able to weld in the narrow angle at the front. Considering starting a build thread for this, as long as people don't mind a few of my "that looks pretty good" measurements :LOL:
 

Arouse the DAMPFHAMMER!
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Sure, here's what I ended up with after milling. Luckily the top of the injector is metal so I was able to chuck it in my lathe
Thanks for the picture 馃啓. Are you going to use the end caps to reduce the oil mist on the injector?

Also for reference, this is the injector port design I ended up using, moved up the runner slightly as I have no way to machine the flange like the stock manifolds are. Been a while since I welded aluminum
If I remember right from my IM the injectors where pointing in a 45掳 angle roughly at the divider. Your injector points a bit more above from that. If that make issues at idle you still can find BOSCH injectors with an slightly upwards directed angle to compensate this.

...Considering starting a build thread for this, as long as people don't mind a few of my "that looks pretty good" measurements :LOL:
Do it, I would much appreciate it!
 

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Discussion Starter #7
Are you going to use the end caps to reduce the oil mist on the injector?
Eh, I probably wont go through the trouble. I saw the kits you mentioned, but this is going on a (mostly) show truck that probably wont see a thousand miles before I change over to better injectors, so I'm not super worried about it

Your injector points a bit more above from that. If that make issues at idle you still can find BOSCH injectors with an slightly upwards directed angle to compensate this.
I really wanted them to be angled down more than they are, but I found that with a larger angle I couldn't weld easily around that narrow bottom seam without burning through the side of the port. I might give it another try though since its kinda been bothering me :rolleyes:

I was wondering if you had any advice one injector depth? I.e. are they meant to protrude past the wall of the runner by a few millimeters? Stay short of it? Even with it? I haven't really been able to find information on that part. Also, what category would be best to start a build thread in?
 

Arouse the DAMPFHAMMER!
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Eh, I probably wont go through the trouble. I saw the kits you mentioned, but this is going on a (mostly) show truck that probably wont see a thousand miles before I change over to better injectors, so I'm not super worried about it
Yes, I see your point.

...I was wondering if you had any advice one injector depth? I.e. are they meant to protrude past the wall of the runner by a few millimeters? Stay short of it? Even with it? I haven't really been able to find information on that part. Also, what category would be best to start a build thread in?
I can check it by tomorrow on my 3D drawing I did for the DAMPFHAMMER IM (s. below)

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Discussion Starter #9
That would be great. Is that a cast mani with a second set of bungs added then? Looks pretty well done (y)
 

Arouse the DAMPFHAMMER!
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That would be great. Is that a cast mani with a second set of bungs added then? Looks pretty well done (y)
It's a CNC plus weld job IM, designed for producing the highest and widest torque band possible. Made 202 flywheel ftlb's at 5250 rpm on my 2 Liter NA engine, before transmission stock during my tuning session.

The injector bungs have following depths:
  • O-Ring ramp up to O-Ring sealing ID = 2.8 mm
  • 10 mm from top to the upper edge of the phase which narrows the OD of the injector nozzle
  • further 5 mm to the final ID of the injector nozzle
  • the injector should not touch the streamlines of the air, set it back by a few mm, otherwise the spray nozzles will get dirty
The O-Ring ramp is introduced by a dedicated radius not to cut or scratch the O-Ring. The O-Ring OD is 7.52x3.53 mm, the ID-bore is 14 mm. The injector nozzle ID (around 9.8 mm) has to have a certain clearance and is not allow to stick the nozzle under all conditions.
 

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Discussion Starter #11
The injector bungs have following depths:
Thanks for the info, mine actually ended up within a millimeter of those measurements 馃槅. I'm going to start a build thread in the Welding and Fabrication section soon. I thought about putting it in engine building, but Fabrication seemed more appropriate. I can tag you in it once it's up if you'd like
 

Arouse the DAMPFHAMMER!
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Thanks for the info, mine actually ended up within a millimeter of those measurements 馃槅. I'm going to start a build thread in the Welding and Fabrication section soon. I thought about putting it in engine building, but Fabrication seemed more appropriate. I can tag you in it once it's up if you'd like
Very good man.
Yeah, I would appreciate a built and fabricate thread of your project!
 
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