Hacking an IDA 'Weber', turning it into EFI

I always hated the fact that the Borla's sprayed directly onto the butterfly plate.. can't be good for fuelling accuracy.
Jasper, I believe you are thinking of the old (+6 yrs ago) TWM now Borla system? The later version has located the injectors below the throttle plate and they are angled directly at the intake port, thus the fuel rails run along the centerline between the throttle bodies. They have been using a cast-in plenum chamber for the MAP sensor and the Idle Air Control for quite sometime, which I believe they pioneered and Roush used their stack system on their "IR" engines. Good luck with your hack.
 

Jasper

Supporter
Thanks Tom, do you have any pictures on the 'new' system you could share? I havent been able to find any meaningful information about what you're describing. (w.r.t cast plenum or injector rails now being part of the 'Borla' system?)
 

Randy V

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What manifold is this Randy? There's plenty of space for injectors too there! :)
I don’t really know as the manifold has been surface sanded and polished so any mfgr markings are gone. I bought it this way
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Randy V

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I don’t think I would build something with the injectors down in the lifter valley. That is an extremely harsh environment. Not only is everything bathed in oil that’s 250° or more, but the vapors can be blow-by gasses that can be 400-500° F degrees at times. I wuold put everything down low as I could and put a heat shield or turkey pan above it. Imagine trying to diagnose an intermittent injector problem with everything buried under the intake in the lifter valley...
 

Jasper

Supporter
Your absolutely right Randy, and the temperatures/heat is also part of my concern. However, please note that this 'plenum chamber' is sealed and covered 100% air tight though, as it functions as a vaccum MAP chamber in this design.
I do agree that it is so far out of the way that packaging and troubleshooting is pretty much impossible. Temperatures will be a warm 200-250F (90-100degC) I think.

So the quest for tiny injectors, and sleek injector mounts are not in vain. I'm leaning 90% to installing these on the outside, and also there space is limited. So i've ordered a few different mounting options, two chinesium Webers, and the manifold. Will share pictures when I receive them, but will be a good few weeks i'm guessing.
 
Thanks Tom, do you have any pictures on the 'new' system you could share? I havent been able to find any meaningful information about what you're describing. (w.r.t cast plenum or injector rails now being part of the 'Borla' system?)
I had to dig up some of my old build pics. But here are a few pics that should answer your question. I just saw that Borla Induction has another system out. Mine works pretty well as-is. You can see the smaller plenum is for the IAC, the larger plenum is the vacuum manifold and the MAP sensor resides on top next to the capstan. All sensors, with the exception of the upgrade Penny-Giles Hall-Effect TPS, are GM sensors so not proprietary and easy to replace, if ever needed.

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Jasper

Supporter
Thanks Tom.. This looks like a well engineered manifold to integrate all these tricks into it. Love the IAC integration there, I think I'll have to resort to remote mounting an IAC valve somewhere (hidden).
I didn't recognise this as the Borla 8-stack, but I now realise the confusion. This is the 'normal' EFI 8-stack that Borla sells, but not the Weber IDA look-alike EFI stack. Up untill now, I still believe the Borla is selling these with the injector spraying right on top of the throttle plate. Can't see how they would be able to change that.

Thanks for the pics, very informative.
 

Jasper

Supporter
Some progress: I have 2 Chinesium webers stripped, and got all my parts in. (except manifold, massive Corona delays getting parts from the USA due to overloaded freight forwarder).

There's an AN 4 line for fuel, going to each injector. Using these 'billet speed' injector bracket, and aluminium hard piping fittings.
I think I found a way to use the normal banjo fitting connection for the high pressure fuel, and in the fuel bowl a link is made between the T-piece and the banjo connector. This way I can even use the 'original' fuel routing.

To be continued!

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Randy V

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The quality of those castings looks amazing! I don’t think the Italian carbs look any better or worse!
 

Jasper

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Yeah I was surprised about that as well. Its difficult for me to point you to the differences, as I've never stripped a 'real' one before though.
The only thing that concerns me at this stage is the tightness of the throttle plates.
I can actually see some light shining through the fully closed plates, and i'm concerned it might lead me to a poor vaccuum and/or high idle conditon.

What does 'good' look like? No light whatsoever? Can you re-bore the hole 0.1mm over at a top-shop to get it 100% circular?
I already tried losening the throttle plate and re-center, but no sigar. Still some small light streaks. The plate touches on one point before the whole circumferance seals it seems. I could try a polishing dremel and work at it that way too.. ?

Manifold should be arriving early next week i've been told, so we can keep some momentum.
 

Randy V

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I’ve been building carbs for roughly 50 years. The butterfly carbs such as these were never perfectly precise in terms of the fitment of the throttle plate, although, those made in the 50’s and early 60’s were far more precise that those made a couple decades later. But then, that’s a familiar story when talking about manufacturing quality. The more precise carbs were those with slide valves. SU, Solex, Stromberg, etc..
I don’t think you’re going to find enough leakage to give you idle problems. Trying to fit the valves tighter may end up causing you more trouble in attaining synchronization..
Soldier on - the thread is fascinating!
 
. . . I don’t think you’re going to find enough leakage to give you idle problems .. . .
Randy
I disagree with your comment. I had a 1st Gen Borla EightStack system that was very similar to this. Could not get a low idle (wanted to stay at 1500rpm) and it was caused by poor-fitting throttle plates. Borla reworked the system for me and was able to get the idle down into the low 900 range. And it is all caused by poor-fitting plates. It is amazing how much air is pulled thru those openings.

In a perfect world, they would seal 100%, you would hold them open ever so slightly with the idle stop screw and your Idle Air Valve would vary the makeup air to have a low, smooth idle. Reality, that's not going to happen. I purchased a compound used on Porsche & Honda systems to the openings even more however it is a royal PIA to apply and make work. Not sure if I will tackle that or just be happy with a 950 rpm idle. Back in the day, there were similar issues with GM tripower and they used a product to 'seal' the throttle plates. Same issue - you're trying to stop the airflow.

Look at the edges of the throttle plates. Are they tapered to match the wall of the bore? If not, that's your first issue. Snapping the plates open/closed repeatedly will begin to show the high spots - but you need to be real careful if you try to take some off. You could be making it worse. Scraping the point may help, using any type of a power tool is a disaster in the making. The fit is really that close.

Use google and search the terms "seal throttle plates' and you'll find a lot of references to this. Here is a link to wet your appetite: DAG-213

Keep searching, you'll get there

Paul
 

Jasper

Supporter
Thanks all of you for the input. And thanks Paul for giving me some pointers to a new world of information. Never knew these throttle plate fit could be made tighter with dry lubricant film, but I can see how and why that would work.
Throttle plates are tapered, yes. 78deg as per the 'norm'as I been told.

Love the forum, and helps me get the confidence to take on these kind of special projects. Will keep you updated.

Jasper
 

Randy V

Admin
Lifetime Supporter
Randy
I disagree with your comment. I had a 1st Gen Borla EightStack system that was very similar to this. Could not get a low idle (wanted to stay at 1500rpm) and it was caused by poor-fitting throttle plates. Borla reworked the system for me and was able to get the idle down into the low 900 range. And it is all caused by poor-fitting plates. It is amazing how much air is pulled thru those openings.

In a perfect world, they would seal 100%, you would hold them open ever so slightly with the idle stop screw and your Idle Air Valve would vary the makeup air to have a low, smooth idle. Reality, that's not going to happen. I purchased a compound used on Porsche & Honda systems to the openings even more however it is a royal PIA to apply and make work. Not sure if I will tackle that or just be happy with a 950 rpm idle. Back in the day, there were similar issues with GM tripower and they used a product to 'seal' the throttle plates. Same issue - you're trying to stop the airflow.

Look at the edges of the throttle plates. Are they tapered to match the wall of the bore? If not, that's your first issue. Snapping the plates open/closed repeatedly will begin to show the high spots - but you need to be real careful if you try to take some off. You could be making it worse. Scraping the point may help, using any type of a power tool is a disaster in the making. The fit is really that close.

Use google and search the terms "seal throttle plates' and you'll find a lot of references to this. Here is a link to wet your appetite: DAG-213

Keep searching, you'll get there

Paul
Yes there certainly are some aftermarket carbs and throttle bodies that do not have very good fitment of the throttle plates - most that I have seen were caused by a misalignment during assembly - usually pretty easy to address. You will not get an airtight seal under normal conditions and you must remember the expansion rates of the materials used lest you run into a binding issue when hot. Some Holley carbs use exceptionally thin throttle plates that are not milled to match the bore taper.
A couple other conditions that causes idle issues are
1) twisted throttle shafts - caused by lack of throttle stops and wide open throttle where the shaft is being twisted beyond the fully open point.
2) Worn throttle shafts caused by excessive throttle return spring pressures. Additional Throttle return springs should not be connected to the throttle arm, but to the linkage or cable itself.
3) Carbon buildup on the backside of the throttle plates. The more camshaft overlap and reversion, the worse the problem. IAC air contamination is another.
 

Jasper

Supporter
So the manifold has arrived. The intended routing of the fuel (inside the 'carb' body) works very well, the AN fittings exit in a very inconspicuous location and perfectly placed for the injectors.
Next up is putting some lovely big holes into the new (and expensive) intake manifold for the injector housings. Kind of crucial of course, as it determines where the fuel is spraying towards (or onto). Probably going to end up on someone's mill, not going to do this by hand i'm thinking.

Any tips on this? I'm assuming aiming for the dead center of the intake port is about right?

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