Hacking an IDA 'Weber', turning it into EFI

Jasper

Supporter
you might be able to do one extruded fuel rail section per carb, and then just have one connection back onto the AN fitting coming out of the carb base.
Would be easier, but due to the staggered nature, and the inclination angle, the left and right bank of injectors interfere with each-other, and cannot use such a profile.
Due to this angle i'm getting a very low profile package though, which is what i'm after, but i'm kind of forced to plumb to each injector individualy.
Thinking about an aluminium cover plate over the injector package when all is done to hide everything even better. But that would be cherry on top.
 
Just a thought - if you have the headroom height, rather than drilling the manifold you could make blocks to go between the faux carbs and the manifold in which the injectors are held. This moderates the risk of making a machining error on one manifold inlet and ruining the manifold.

Also, might be easier to angle the injectors downward somewhat using separate blocks rather than drilling the manifold. An injector spraying horizontally right at the opposite wall of the inlet throat will affect optimal atomization and tuning ability. Better to have the injector spraying into the air flow rather than cross-wise and up against the wall of the throat.
 
angle the injectors downward somewhat using separate blocks rather than drilling the manifold. An injector spraying horizontally right at the opposite wall of the inlet throat will affect optimal atomization and tuning ability. Better to have the injector spraying into the air flow rather than cross-wise and up against the wall of the throat
Agree Cliff, it looks like its close to being aimed right at the back of the valve. I'm not sure how much better one could get it.
Ryan

 

Jasper

Supporter
Agree Cliff, it looks like its close to being aimed right at the back of the valve. I'm not sure how much better one could get it.
Your right Ryan. I understand Cliff's intent, and fully agree. It might not have come across perfectly in the photos' but indeed the injectors are shooting right in the dead center of the intake port, not at the walls. The injector bungs were drilled as low as possible, while still aiming at the dead-center of the intake. This was the key to bring the whole package down as low as possible while getting the best possible tuning and drivability.

This moderates the risk of making a machining error on one manifold inlet and ruining the manifold.
What's the fun in moderating risk.. :-D I was a bit tense, for sure, but I can now marvel at the quality of the job and the skill of the machinist looking at my intake. :cool:
 
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Clayton

Supporter
Updates coming in fast and hot.. Got the intake back from the machine shop today. They did an awesome job in aligning and tolerance fit. 0.05mm which is nice and snug.

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With the 'carbs' installed, I think I can conclude that it will actually work.. but is going to be a very tight bunch of plumbing!
Any tips on bending aluminium tubing in tight radii? Heat, no heat? i'm using a nylon 4mm rod to 'fill' the ID when bending, to prevent kinking the tubing.

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how about banjo fittings ?
 
how about banjo fittings ?
Most modern injectors wont have a provision for that as they are designed to be a push fit on both sides, clamped between the intake manifold and fuelrail.

Old skool mechanical injectors had threaded unions like Bosch K Jetronic and Lucas and Kugerfisher.

Makes me wonder, anybody ever tried Hilborn injection on their GT40?
 
As I can't edit my previous post,

Looking again at the previous pics, Ill guess with the single fuel rail per injector as it seems to be it must be possible to do so, 8 x banjo fitting to a central fuel block like the oldskool Hilborn.

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Jasper

Supporter
any chance of a picture from the valve side of the intake showing where the injector sits?
There we go: Dead center I think.

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I selected my injectors: Full cone spray, extended nose to get the fuel spray right in the air flow. 20deg spray cone angle, which I simulated with a paper cut-out. Is not hitting the walls of the intake or head, should evaporate nicely on the back of the intake valve. Looks like the right spray pattern to my inexperienced eyes.

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I've started with my first attempt at the plumbing. However, I realised I have to wait for the injectors to arrive to make sure nothing bumps into the connectors etc.
Also.. very typical. You always make a plan, then order the right AN fittings for that plan. Plan doesnt work 100%, and you end up buying the entire store supply worth of different AN fittings, returning 99% after the job is done.
Chose 90deg 1/8NPT for the injector bungs, want to use 45deg.. damn.
Chose 45deg bulkhead fittings, want to try 90deg.. damn..
etc. etc.
 

Jasper

Supporter
Update: Finally got the plumbing sorted out. Took a few weeks as I was waiting for different AN fittings a few times. Changed the 'design' a few times too, but very happy with the final routing. Tight routing, and neat as well.
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Used T-piece on the outboard injectors, than a loop-de-loop underneath, routing to the AN fitting that's hiding underneath the weber body.


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Best part is the 'total height'. hardly any higher than the intake manifold itself.

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Jasper

Supporter
If you don't like 'bling' and irrellevant and period-incorrect eye candy, please look away now!

Anyhew.. I decided to try a gold painted weber, to spice up the look of the engine bay a bit more.
Also continued with the re-assembly of the carbs.

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On the throttle shafts, the 48IDA's are quite leaky, and this impacts Idle and low load operation. There's a guy in the VW community that makes seals for this leak path, which I bought a set off and installed as well. Basically a o-ring in an aluminium retainer, and a spring to keep it all a little bit compressed.

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Jasper

Supporter
Working on the linkage this week. What a fiddly job, with a lot of interference issues on all linking elements of course. Having a crowded 'valley' also doesn't help.
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Started with a Webcon linkage kit, somewhat modified of course.
It's a very very close fit when at 'full throttle'. But hey, close is good enough!
It's such a close fit, that it looks like premeditated and well engineered.. it's not. I'm just lucky at times.

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Jasper

Supporter
Nice!! Will those fuel pipes pass enough fuel for a thirsty SBF engine?
I think it should, because each 'small fuel pipe' only feeds 2 injectors. If I compare it to the OEM fuel rail on a LS-engine making around 450-500hp, approximately 8mm ID feeds all 8 injectors. Based on that, I guestimated that a 5mm ID should be able to feed 2 injectors..
The bigger risk I see is that there is a small pressure drop between the 'first' and 'second' injector on each fuel line, where potentially the second one would flow slightly lower rates as a result. I'll compare exhaust gas temperatures on each cylinder to see if that's a noticeable difference.
 

Jasper

Supporter
Did not like the central linkage system. Single bearing was wobbly when pulled (for example by throttle cable), and very lineair which would turn the gas pedal in an on-off switch.
Bought a new bell crank /swivel that could solve all of that. Good call, much better fit, 2 bearings which can take up some eccentric loading, and the spiral shape results in a gradual opening of the throttle plates.

Closed ------------------------------> ------------------------> -------- Fully open.
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Its also a better fit for the linkage, and still clears all the injector bosses and fittings.

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Finally been doing come CAD (cardboard aided design) on my throttle position sensor. Will be a Variohm contactless sensor.
Should arrive soon, and the stainless bracket will be ready in time (I think)

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