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 Post subject: Nozzle Positions
PostPosted: Sat Dec 29, 2012 11:45 am 
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Hello,

I am currently trying to fit an LPG kit to my 2004 Kia Sportage and I have a question regarding the inlet manifold and where to drill for the injector nozzles.

I am thinking about drilling the hold approximately 3.5" back from the petrol injectors (space near the injectors is very tight) - do you think this will be OK? I have seen people mention Bi-directional nozzles or ones with tubes, would they be needed for this distance to help minimise spread?

The photo below shows the whole inlet manifold (goes up and over the engine):
Image

This photo shows the top half removed and where I am planning to drill:
Image

Stuart


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 Post subject: Re: Nozzle Positions
PostPosted: Sat Dec 29, 2012 1:50 pm 
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they need to be closer than that. If that is as close as you get it then you will need straws.

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 Post subject: Re: Nozzle Positions
PostPosted: Sat Dec 29, 2012 2:31 pm 
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Have you not got clearance on the underside of the manifold?? looks like you could get directly opposite the petrol injectors


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 Post subject: Re: Nozzle Positions
PostPosted: Sat Dec 29, 2012 5:08 pm 
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Ive seen a kia done with the spuds half way up the plenm above the join to the inlet. And it did run. But somewhat hesitant :lol:
The proposed placement is quite a bit away. And maybe you should have a look at putting the spuds either below the manifold underneath or use straws. Depends what kit you are fitting as to how fast the injectors react. You may get away with it, may not.


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 Post subject: Re: Nozzle Positions
PostPosted: Sat Dec 29, 2012 7:24 pm 
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It does look like you should be able to get in from the underside and even room to mount the injectors there.

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 Post subject: Re: Nozzle Positions
PostPosted: Sat Dec 29, 2012 9:53 pm 
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Normally, having injection points a way back like that wouldn't matter much.
BUT
On your manifold, the petrol injectors are air-shrouded; idle air bypasses the regular manifold tract and is delivered through the petrol injector mount itself.
http://www.northcarolinakia.com/pics/sp ... ctors2.JPG
You need to get to get your gas injection stream intersecting that airflow, or you'll get stumbles and stalls at idle and in transition to/from idle.
You might be able to get nozzles right "in the corner" just inboard of the air shroud nozzle and on a similar line; else you'll have to use straws.

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 Post subject: Re: Nozzle Positions
PostPosted: Sun Dec 30, 2012 3:23 pm 
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Thanks for the reply's. :)

Just had another look at the manifold and I can see the air-shroud setup (never seen one of these before).

Would this be the area to drill?? (does not look a lot of room there)
Image

If it was just short of the of the air shroud nozzle would that still cause issues?

Thanks,
Stuart


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 Post subject: Re: Nozzle Positions
PostPosted: Tue Jan 01, 2013 5:38 pm 
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Hi all,

I hesitate to offer opinion in this expert company, but would rather raise the question & be corrected!

Never come across this "air shrouded" injector thing before, but it seems to be about improving atomisation at the injector, especially at idle. I don't see why this would cause a problem for the gas injectors, as long as there's still plenty of air going past the LPG injectors. In which case it would all depend rather on where the "shrouding" air actually comes from, and what % of the airstream comes that way.

The problem with the "idle control valve" system used by e.g. BMW (and discussed elsewhere on this forum) is that at idle (almost) none of the air travels down the main manifold runners, instead being delivered directly to the head just before the valves via a separate set of runners. As Ross mentions this is an issue because any reasonable placement of injector spuds is therefore not in the idle air flow (hence need for straws or other strategies to get the LPG reliably into the cylinder).

However it's not clear (to me) that such a problem exists here - no separate idle air paths (that I can see). I could be missing it but from the pics it looks like the air shrouding the injector comes from the same runner. In this case all the air will always go past the OP's (originally) proposed spud location - in which case surely there's no problem? Even if not and the shrouding air somes from somewhere else, this should only be a problem for the OP if *all* the idle air goes this route, and the main throttle is completely closed at idle.

I'm just questioning this 'cos I wouldn't want the OP to go to additional trouble if not necessary; though I would of course defer to greater experience than mine (just one conversion!)

On the OP's original question on spud placement, when I converted I was careful to get the spuds as close as poss to the cylinders. However I'm no longer convinced that's as important as I thought (assuming they're not too close to funky resonance chambers etc like we've seen on supercharged jags on this forum). The reason, as rehearsed on a lengthy thread on here a while back (by Ross?), is that each "gulp" of the cylinder (>500cc here I assume) should easily empty 3.5" of intake runner - and more!

Cheers,

M (preparing to eat humble pie just in case)


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 Post subject: Re: Nozzle Positions
PostPosted: Tue Jan 01, 2013 7:37 pm 
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matty wrote:

On the OP's original question on spud placement, when I converted I was careful to get the spuds as close as poss to the cylinders. However I'm no longer convinced that's as important as I thought (assuming they're not too close to funky resonance chambers etc like we've seen on supercharged jags on this forum). The reason, as rehearsed on a lengthy thread on here a while back (by Ross?), is that each "gulp" of the cylinder (>500cc here I assume) should easily empty 3.5" of intake runner - and more!

Cheers,

M (preparing to eat humble pie just in case)


Injector nozzle position is very critical for getting the right amount of fuel at the right time. Don't forget that a typical spark ignition engine will no where near fill the cylinder at low throttle opening and at full throttle can even over fill the cylinder.

The pipe length is not so critical form teh injector to teh nozzle. If you think of the injector pipe as a hose pipe and the manifold runner as a big drain pipe. The hose pipe will be shooting the water out at hiogh speed but in the drain pipe taht same amount of water will only be a trickle.

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 Post subject: Re: Nozzle Positions
PostPosted: Tue Jan 01, 2013 7:40 pm 
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matty wrote:

Never come across this "air shrouded" injector thing before, but it seems to be about improving atomisation at the injector, especially at idle. I don't see why this would cause a problem for the gas injectors, as long as there's still plenty of air going past the LPG injectors. In which case it would all depend rather on where the "shrouding" air actually comes from, and what % of the airstream comes that way.

The problem with the "idle control valve" system used by e.g. BMW (and discussed elsewhere on this forum) is that at idle (almost) none of the air travels down the main manifold runners, instead being delivered directly to the head just before the valves via a separate set of runners. As Ross mentions this is an issue because any reasonable placement of injector spuds is therefore not in the idle air flow (hence need for straws or other strategies to get the LPG reliably into the cylinder).

However it's not clear (to me) that such a problem exists here - no separate idle air paths (that I can see). I could be missing it but from the pics it looks like the air shrouding the injector comes from the same runner. In this case all the air will always go past the OP's (originally) proposed spud location - in which case surely there's no problem? Even if not and the shrouding air somes from somewhere else, this should only be a problem for the OP if *all* the idle air goes this route, and the main throttle is completely closed at idle.



You are right that it will not be anywhere near the same problem as found with the positive pressure BMW system but even so something to be awar of. To get the nozzles into a sensible position is not going to be that hard so well worth doing teh job right first time rather than taking any short cuts. The original suggest position was to far away regardles of teh air shrouding

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 Post subject: Re: Nozzle Positions
PostPosted: Wed Jan 02, 2013 4:10 pm 
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matty wrote:
no separate idle air paths (that I can see). I could be missing it but from the pics it looks like the air shrouding the injector comes from the same runner.

We cannot see; but I do think there is a cast in crossways runner to supply the shrouds with idle air. Needs someone to physically look.
The only similar thing I've looked at in depth was a Honda (? I think) arrangement, fed from a crossways channel in the manifold mounting face - which became a runner when assembled. Caught me out because there were no external pipes to give the game away like here.

classicswede wrote:
Don't forget that a typical spark ignition engine will no where near fill the cylinder at low throttle opening

I'll differ on that one ... it will fill with 500cc of air from the manifold every time. The pressure of that air will vary a lot, so you'll get different mass of air - but as an approximation, how long a column of air it pulls in by volume is much the same at all throttles.

Would get really complicated when you've got things like these shrouds bleeding in air continuously, air must flow backwards up the main branch between pulses before reversing ... ekk, figure that out ... but certainly bad for gas injection upstream

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 Post subject: Re: Nozzle Positions
PostPosted: Wed Jan 02, 2013 8:54 pm 
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Not quite evry time

http://www.popularhotrodding.com/tech/0 ... ewall.html

Have a read on the Dynamic CR section there.

Back on topic,

With the way the air pipes work on that I would fit the injector adaptors

Like these but not so expensive http://www.ebay.com.au/itm/Set-4-x-4-O- ... 1005032344

That way the air flow would be working just as per petrol

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