where to put injectors (holes in manifold)

[joshnosh]

right its time to drill and tap my manifold

my tinley tech Manuel says they need to be in the middle off the pipe. is this true?

since i can get the holes right next to the petrol injectors like 8mm away but they will be coming in at an angle

this is for an astra g 1.8

iv seen someone tap a 1.6 manifold right next to the injectors and i think it worked but i cant find it now

obv some pictures will be better so ill do that when i get home if no one can help.

some internet pictures:



my manifold with proposed area:

[rossko]

Point the nozzle at the middle of the manifold air channel.
I'd be inclined to come back away before the petrol injectors, where there is no risk of interfering with petrol pattern or gasket or directing gas all into one valve.

[Tubbs]

Its not critical to get that close to be honest. As ross says, above the petrol injector take some pics later.

[Taught2BeCautious]

I would suggest that you drill a little further up, where the metal is a bit thinner and less likely to friction-weld itself to the drill (as I have seen someone do in the past!)

Its so much better if you can get the manifold off the car - otherwise, use a Vax type vacuum cleaner whilst drilling, and plenty of grease on the tap, to catch the swarf.

A lot of sources say that you need to angle the jets at 45 degrees towards the cylinder, but this isn't essential.

[joshnosh]

ok cheers guys. ill go take a video now as its easyer!

[joshnosh]

http://www.youtube.com/watch?v=-gslRy_GDE4

watch me!

[Taught2BeCautious]

I would drill just above the flange (where the manifold connects to the cylinder head) to one side of the petrol injector housing, but at 90 degrees to the metal so the LPG hoses are underneath the fuel rail.

I would prefer to drill where the metal is a bit thinner so that more of the LPG nozzle protrudes into the airstream, and you can still tighten them with a socket or ring spanner.

There's nothing technically wrong with it, but I think that if you drill where you marked in the first picture, you would have trouble tightening the nozzles and getting a good seal in a corner of that shape - or you would have trouble removing one if you found you needed to enlarge it, or had stripped the threads trying to fit it in the first place!

[Tubbs]

You are over thinking it. A bit higher up, and slightly to the right of the injectors will be absolutely fine. I had loads of hassle from a v8 BMW once. Got the injectors too close to the petrol injectors. The fuel trims where all over the place. In the end I lengthened the gas injector pipes considerably and all was well. Lesson learned.

[joshnosh]

that's interesting. from the information i had, the closer the better lol ill give it a go tonight then
iv got metal drill bits and a machine tap so shouldn't be too hard really

[Taught2BeCautious]

In this case, 'close' means within 6 inches

If you care to do the maths, work out how much air is flowing through the manifold and at what speed - a couple of inches won't make a difference that can be felt or measured!

Nor does it matter if you go centre, left or right of the petrol injector - just drill where you can get proper access and a good seal.

[joshnosh]

fair enough. ill drill and tap to the left off the ducts
is there any bennifit at all to tilting the nozzles towards the air flow direction to create more vacume. like 20deg or something?

[rossko]

Depends what you mean. Never ever point upstream. Going in at 90 degrees to airflow is good, you want to puff the gas out where it gets evenly mixed. Going in at a really shallow angle so the gas stream is stuck to the side is bad, no mixing. It follows that an angle slightly with the airflow is acceptable, I would say 45-90 degrees to airflow. You're not injecting liquid, so you have no reason to copy what liquid injectors (petrol) do.

Before you drill all-on-the-left or whatever, plan how you are going to lead the hoses away to your injector rail. Very often a sort of fan arrangement works well.

[Tubbs]

I think that point from ross really sums it up. Your not injecting liquid, so have no reason to try and copy liquid injection.
So if you are right over the top of the valves then it would be critical to be bang in the middle of the valves. Further up the gas has a chance to mix with the air flow and introduce the gas over both.

[Taught2BeCautious]

Also, because the LPG Injectors are a lot closer together than the Petrol Injectors, and that you may not be able to mount them centrally, just concentrate on mounting them in the most convenient location where the outlet nozzles on the LPG rail can point downwards, and so thet the vapor filter can be positioned lower than the rail if possible.

Measure-off the low-pressure hose to suit the longest run between the LPG rail and the corresponding nozzle in the manifold, (it's either going to be No. 1 or 4) and cut the other 3 the same length.

It probably doesn't make a massive difference, it's just to keep the science right

[joshnosh]

yep that all makes sence

im trying to do this 100% as best as i can possibly do it so if theres anything thats going to make a difrence to performance even a little bit i want to know about it lol
is it important to drill all the holes the same leanth up the tract?


cheers guys

[Taught2BeCautious]

im trying to do this 100% as best as i can possibly do it so if theres anything thats going to make a difrence to performance even a little bit i want to know about it lol

If you get the basics right from the start, any performance issues will be a lot easier to track down later. Safety is more important at this stage, followed closely by checking and double checking the installation procedure.

Make sure the nozzles are the correct size for your engine - and if they are going to be hard to get at when the manifold is bolted back in place, use Loctite Sealer on the threads (I use Loctite 577), clip the hoses securely, and number the other ends of the hoses if you can't see which one is which afterwards.

is it important to drill all the holes the same leanth up the tract?

i can't see that being a problem from the pictures, you should be able to find a height that suits all of the nozzles, within a few mm - but make sure you allow enough space for the hoses, when they are fitted, so that they aren't kinked, near to something too hot, or rubbing on anything. Angle them downwards if necessary.

They don't all need to be on the same side of the petrol injectors either - just check how much room you have to play with when the hoses are in place for each cylinder, and base your judgement on that.

[joshnosh]

I think iv cocked it up a bit. Im not sure im happy with it.
The pipes fit but there a bit close and there pressing against each other. Not sure if it will effect the gas flow at all though :/

[joshnosh]

[joshnosh]

So yeah they fit but not sure if its ok or not

[Tubbs]

Well yes, it has to be said you have 'cocked' it up a bit. Personally i would have gone a bit further up. Judging by the pics it looks salvageable. So your options are these :-
Firstly get the clips on.
If you really arnet happy about the pipes touching each other then either you put an m6 bolt in to blank off the holes and drill further up.
Your other option would be to put some split conduit over the top of one of the pipes and then cable tie them together so they cant move.
Its easily done by the way, a lot of people dont take the pipe into account when drilling the holes , and how far the spuds stick out etc. But dont worry, its not ghostbusters, crossing the streams wont cause any issues
Oh and dont go cutting off that pipe willy nilly...its at a premuim always if you want to use it for the vac hose as well.
A word from the wise.