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The bump might be there to add turbulence near the injector to improve air/fuel mixing or to push the airflow towards the offset injector to improve air/fuel mixing.

The injector offset may be to better aim the spray of fuel in the direction that the air flows through head. The ports in the head aren't a straight shot to the valve/cylinder, they each bend right or left towards the valve.
My comment wasn’t clear. If you were to look at a round runner head on I don’t think it would matter what degree of the circle the injector fires from.
 

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Discussion Starter · #23 ·
I was wondering about these things too….
The bump might be there to add turbulence near the injector to improve air/fuel mixing or to push the airflow towards the offset injector to improve air/fuel mixing.
If this was the case, I am hoping that the modern fuel injectors and higher pump pressure provide better atomization.

The injector offset may be to better aim the spray of fuel in the direction that the air flows through head. The ports in the head aren't a straight shot to the valve/cylinder,
What is interesting is that the humps were in the middle (the divider between runners of each arm) so they are not consistently on one side or the other for a given arm
 

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Discussion Starter · #24 ·
So, here are the options that I am considering to proceed:
  1. Machine hole for injector bungs from opposite direction (from the inside from the head flange).
  2. Drill and weld the bungs into a piece of aluminum similar to original design but welded
  3. Machine slots from top using a small hand tool
  4. Cut off some of the angle / length of the runners and weld back together
  5. Cast plenum of modified design with shorter, less angled arms.
no matter the option, I figure I need to get the injector bungs all machined at the same 30 degree angle from parallel. I checked my metal bandsaw And the limit of cutting is about 52 degrees. So I designed and am 3D printing a jig to get the extra 8 degrees. So 60 degree cut from a right angle should be 30 off of parallel
 

· Detritus Maximus
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I think you are right about the bump being reinforcement for the center mounting bolt for the injector plate.
I'd say option 2...if you mess up, you just make another. If you decide to revise it...just make another.
 
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I got to thinking ( that's usually dangerous for me) and I think the reason for the fuel injectors being off set is just to have room for the fuel rail mounting.
Hopefully this picture makes sense of it..
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Discussion Starter · #28 · (Edited)
Keep in mind that the oem FI was solely focussed on economy and low emissions, with very little consideration of power. When I was configuring the 2.4 motronic FI on my 2.4, we tried out an aftermarket throttle body that was the equivalent size to the larger throttle on a 6 cylinder 3.0 liter Opel FI system. The 2.4 computer was too dumb to handle the much larger air flow, but at about mid-throttle it had rev response that was super fast, like you are trying to achieve. With a more adaptable computer, that could deal with the higher air flow, we could have made it work and gotten a faster rev'ing engine.

So, what I'm saying is: Don't get locked into the stock throttle size. I don't know how one calculates the maximum size throttle that an engine can handle, but going big on the throttle is something to consider. I'm sure there are detriments to going too big or too small.
Thank you. Could you perchance measure the diameter of the throttle body that you tried? It might be just what I am looking for, as I am going to put a flexible / programmable stand alone ECU and have started gather parts to upgrade displacement to 2.4 liter stoker.

Here is my take on throttle body sizing, mounting methods, and purchasing options under $100 after much research and pondering.
  1. I like the idea of a higher / non constrictive air flow and thus going with larger diameter throttle body as long as it doesn’t make throttle response wonky.
  2. I believe the original throttle body was 55mm? With a 60mm square bolt pattern
  3. I am targeting a 60 mm to 70 mm diameter throttle body for this build.
  4. I would get the 60mm Nissan/Infiniti throttle body, but alas I cannot find one so have moved on to other options - CANT FIND
  5. I have found a 65 mm billet throttle body that comes with a weld on flange and has the same 60 mm bolt pattern (see pic below). I like this as I could bolt it onto the Opel manifold, and have a spare weld on flange for future custom intake builds.
  6. I found a 70 mm billet throttle body I could make with a weld on plate and a little die grinder work — TOO BIG
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Just an FYI, but a 60 mm TB can easily handle 200 hp.

I’m not sure what you are building your engine up to, but 200 hp street engines are few and far between.

If you go too big on the TB, you end up with a sort of ‘on-off’ throttle response. It works with larger displacement engines but can be annoying on smaller displacements.

I went with a 75 mm throttle body of my father’s 2.5 turbo CIH. I wanted enough flow for 550 hp. My intercooler tubes are 3” for relevance….roughly 75 mm.
 
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Discussion Starter · #30 · (Edited)
Just an FYI, but a 60 mm TB can easily handle 200 hp.

If you go too big on the TB, you end up with a sort of ‘on-off’ throttle response. It can be annoying on smaller displacements.
Thank you for the driver insight and technical perspective. I am definitely looking for a driving experience that makes me smile (not annoyed). So I’ll rule out the 70 mm.
However do you think that the 65 mm would be too binary (on/off) throttle response on a 2.4 street stroker build? It may not be ideal, but it is compelling to me, because it is: available, has the right bolt pattern, and looks good.
 

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Discussion Starter · #31 · (Edited)
So, here are a few pics of an injector bung machined to the requisite Opel 30 degree angle off of parallel. I 3D printed a holder the diameter of the injector bung with the 30 degree angle and took off 10-15 thousandths per pass in the mini mill with 1/2” end mill to get it down to the proper shape.

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· Just Some Dude in Jersey
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The throttle body in your pic is the one we used. We ended up not using it because the stock Motronic couldn't seem to handle it at low rpms, only at mid to hi. We also noticed that it had vacuum leaks at the throttle pivot holes and decided that it was too loosely machined. Basically: Cheap, Shiny, Crap. We also needed to add a 3/4"-1" spacer to clear things. It's the same size as the Opel 3.0 liter throttle body, but you can tell right away with one of those in your hand that it was machined to MUCH tighter tolerances. But the hole pattern is off a bit and won't directly bolt on to the 2.0-2.4 manifolds. Some modification needed.
 

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Discussion Starter · #33 · (Edited)
Ok, so I am back from a week long business trip. I am working on fitment of the 75 injected manifold in the GT today.

First thing I did was to remove the hood latch mechanism. I will trim it down and put it back in so that it only latches on the driver side. And I cut off the big hood hooks on the passenger side so that the hood can close.

Second thing was to grind off the back of the manifold where it hit the Opel GT heater box. I believe that perhaps a cold start valve of something of that nature mounted here. It seems that the casting had a hole there and then a machined piece was pressed in that had 3 threaded holes.

here is a picture of the end that interfered.
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then a picture after grinding some aluminum away. I just used a big belt sander with super heavy duty 60 grit sandpaper. Here we have breakthrough.
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I will TIG weld a piece of aluminum over the hole from the sanding.
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And here is a side by side (albeit inverted)
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Below you can see how much material was removed. I wanted clearance and prevent any potential bumping.
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Here I am cleaning up the ears off of the hole with my die grinder (great inexpensive tool for aluminum work)
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I had a left over aluminum slug that I had cut with a hole saw when prototyping another project. It was just the right size, so I tapped it into place. During the process, the larger disc insert ring came out. So I just tapped them both into place.
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If anyone else tries this, I recommend welding the inner disc first (lower amperage, cleaner metal, better angle). Then up the amperage for the outer thicker metal to the manifold casting, which is full of all kinds of contaminants.
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my TIG welding is not very good (just started last summer), but it should work as long ad the penetration is sufficient and I don’t have pinholes from the contaminants. I turned the AC balance up when welding the manifold for more cleaning action. Also I still have my big 1/8 tungsten in the torch from welding my other manifold. Should have taken the time to switch back to 3/32 with a nice sharp tungsten.

It cleaned up pretty nice with the belt sander.

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· Just Some Dude in Jersey
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Looking good! You seem to have done the necessary mods. How is your clearance between the manifold and the cowling? I'm using a 2.2 manifold and I had to bend the drainage channel of the cowling up about 1/4".
 

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Discussion Starter · #35 · (Edited)
How is your clearance between the manifold and the cowling?
I think that @krewzer must have modified the manifold for the cowling before sending it to me. Here is a picture of the original
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and here is the picture of the modified manifold. The yellow circled area is the part that slips under the cowling.

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here is the under hood fit. It is tight, but fits.
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Discussion Starter · #36 · (Edited)
Just finished machining all 4 of the injector bungs to the Opel 30 degree slant. The picture below are the bungs sitting on the Opel Injection Manifold runners.
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Here is a picture of the machined fuel injector bungs mocked up with the new fuel rail.
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The next steps are:

1) Drill the fuel rail to receive the fuel injector o-rings

2) Get some injectors or at least mock up some rods shaped like the injectors to use as fixture jig to align the bungs to the fuel rail properly for welding.
 

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Discussion Starter · #37 · (Edited)
Well I though I had landed on the direction of going with Holley Terminator X for my ECU / engine management system. I downloaded the software and really like it. However. I can’t seem to find a version of the kit that would work well for my needs on the Opel. And have called them multiple times in the last few days for help. Sometimes they are helpful, but sometimes not.

Here are my criteria (in no particular order):
  1. Budget - Not much over $1000
  2. Easy to use, intuitive, and stable software
  3. Hand held controller (don’t want to have to have it hooked to laptop to get basic info (air fuel ratio) and sensor info. Plus can make simple tune changes etc
  4. Can data log and hook it to laptop to tune it
  5. Works with modern injectors (was planning USCAR EV6 plug modern LS style injectors)
  6. Works with whatever TPS, IAC etc I go with
  7. Clean looking install under
  8. Capable of controlling timing eventually

Here are my frustrations:
  1. There are Holley Terminator X kits for many different cars, but only 1 universal kit.
  2. The universal kit only comes with old style EV1 connectors (I was planning on EV6 injector connectors)
  3. The injector harness has 8 plugs. Holley said I would have to redo the harness to remove the extra plugs
  4. I found 4 cylinder injector harness when searching on my own that will plug right in (verified by Holley, see pic below), but only has EV1 injector plugs and is an extra $100
  5. Can’t figure out which main harness plugs I will need for timing control (crank and cam sensors) down the road
  6. It is pricey at $1300 and doesn’t even come with the $70 cable to plug it into the laptop

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· Just Some Dude in Jersey
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Extra wires and customizing seem to be part of the game when modding an old analog car to FI. My present car has a 1990 Motronic system and I had to eliminate half the wires. There were a lot OBD1 diagnostic wires, plus ones for controlling a modern electronically controlled auto tranny, anti-lock brakes, etc., that all had to go. If I had decided to run my oem system with an aftermarket controller, I would probably have had to cut off many, if not all, the plugs and graft them onto the new system's wiring harness.

Consider mounting your ECU and extra wiring in the passenger side footwell, which would require cutting a decent size hole in the firewall on that side. I'm customized and don't have the heater there anymore, so I have plenty of room to mount all that stuff behind the dash.

I understand your fascination with the latest, coolest, injectors, but, remember: You're rigging an old, weird, car for FI and you're making your own unproven manifold design that may or may not have the optimum injector positioning and general flow of air. Plus, you're thinking of throwing a turbo into the mix? You've got all sorts of variables going on and almost all of them are unproven. The older, larger, injectors were used for decades and nobody complained, I hardly think that the latest gee-whiz injectors would make any noticable difference. The oem FI had the injectors squirt right at the head ports, your concept has them a few inches farther away, Holley Snipers have them all the way at the beginning of the line before the throttle plates, my system will have them just after the throttle plates, carbs introduce the fuel before the throttle plates and various carbs set ups are near and far from the engine, and they all seem to work just fine.

I have also bought the Terminator X system and am awaiting it's arrival. I probably won't get to installing it until the Fall/Winter. Using only 2 injectors and 2 throttle bodies, I have concluded that I need to configure the ECU to run like a 2 barrel Holley Sniper, which have 2 injectors. I contacted Holley late last week to ask how to configure the system to run the spark and injection like a 2-barrel Holley Sniper. They said to wait 3-4 days for a response and I'm still waiting. I'll also have lots of extra injector plugs, six of them, that I'll have to bundle up out of the way or chop off. Are there knock sensors also? I don't know, that will be another hurdle to cross. Do I need or want knock sensors? Can I find those sensors and adapt them to my car? Don't know. But figuring all that stuff out is half the fun. 😀
 
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