Weighing Fueling Options

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wyly
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Re: Weighing Fueling Options

Post by wyly »

You're going where no one has gone before!

The design and build process will be interesting to follow.
CBX a work in progress, still improving...GS1150EFE completed and awaiting modifications.....RD350, remnants in boxes scattered throughout the garage

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Syscrush
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Re: Weighing Fueling Options

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wyly wrote:
Tue Oct 26, 2021 2:46 pm
You're going where no one has gone before!
That's IF we can get it to actually work. If it doesn't work, then I'm going where lots of people have gone before. :lol:
The design and build process will be interesting to follow.
I think so, too. This project will mean quite a bit of new territory for me, starting with the CAD/CAM stuff. I feel good about getting my hands on Fusion 360 and getting the models made - I'm not on the clock for this, and I know I will enjoy the learning and the process, so I'm looking forward to it. I think that this project serves as a good justification for (finally) pulling the trigger on getting a 3D printer (for plastic prototypes), which is another thing I've been wanting to get into for years.
Phil in Toronto
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Syscrush
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Re: Weighing Fueling Options

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Well, boys - we got there:
PXL_20211030_172752423.jpg
We also managed to scan the carbs on the bike before pulling them, and I think the model turned out pretty well. Once I learn more about CAD I'll import the model and share some screenshots.
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Phil in Toronto
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Re: Weighing Fueling Options

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A bit about the scanning that was done on the bike:

I found an iPhone app called EM3D aka Ethan Makes 3D. It works using the "TrueDepth" 3D laser scanner that enables the Face ID feature to unlock your phone by looking at it. You can install and use the app for free, then if you like how the scans look you can unlock exporting features for $10 each or unlock everything for $27. Because it relies on the front-facing scanner hardware, it's a bit tricky to use on something like the carbs on the bike, because you have to fly blind for at least part of it - working with the screen facing away from you. If I was going to do a lot of this kind of stuff, I would connect an external display and mirror to that.

My goal with scanning on the bike was to have a reference for clearance and fitment when making the CAD models. 1-2mm accuracy is fine for that purpose. I can't say for sure at this point, but I suspect we got there with this technique using consumer-grade HW and inexpensive SW.

Here are some screenshots of the scan imported into a dedicated tool - a free product called MeshLab:
snapshot01.jpg
snapshot02.jpg
snapshot03.jpg
You can see that it's not perfect, but for $10 I'm glad to have it as an extra bit of info as I work through the design and modeling. If I wasn't willing or able to get the pro scanning done, I would instead just set up a rig with a secure phone mount, rotating table, good bright & diffuse lighting, and an external display and stick with this EM3D tool. The price for that would likely come out a bit less than having the scans done (and then cleaned up and post-processed) by the pros, and be accurate to ~1mm. The pro scan is supposed to be good for ~0.1mm. The cheap scans plus having the parts in hand with a digital caliper would be fine for my purposes, but I'm so new at all of this I want to outsource anything I can to people who know what they're doing.

So, the next step is to receive my Triumph throttle bodies and disassemble & clean them and the CBX carbs for high-res 3D scans by a professional shop. I'm not trying to fit the Triumph TB's to the CBX - I just want to use them as reference because I like how they've fitted the injectors under the "carb caps".

I am hopeful that I can use the OEM CBX carb caps (maybe modified) over those same injectors in a similar way. The Triumph setup fires the injectors into the port above and behind the throttle plate - which seems tricky to do with the OEM intake boots, but we'll see once everything is in CAD. I also intend to use the OEM CBX float bowls on the custom TBs just for camouflage.

Those who warned me of the fussiness of the cable setup were not kidding. I almost want to go with a ride-by-wire conversion just so I never have to deal with that stuff again, but that would be too much additional risk for too little reward.
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Phil in Toronto
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Pics of Perry, my '79.

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Re: Weighing Fueling Options

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They're here, they're here! Bonnie TBs turned up today. I'm looking forward to getting them broken down and cleaned up - but looking at them lined up with the CBX carbs, it seems like the dimensions aren't wildly different. This makes me hopeful that my plan to use the Bonnie TB design as a reference for the new custom TBs has a decent chance of working out. Here are some quick photos of the Bonnie TBs together with the CBX carbs:
Bonnie TBs on their own:
PXL_20211102_194446946_2.jpg
Sorry, the Bonnie TBs here are upside-down compared to the CBX carbs in this photo. But you can see that while the spacing is very different, the TBs themselves are superficially close in width.
PXL_20211102_194533788.jpg
Here we can see that the Bonnie TBs have different vertical proportions and are a bit taller overall. They have a shorter cap, longer body, and probably deeper "float bowl" - but not worlds apart.
PXL_20211102_194612882_2.jpg
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Phil in Toronto
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Re: Weighing Fueling Options

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I couldn't conceive attempting this, seeing the tbs you're starting with it's hard to picture the finished product.
CBX a work in progress, still improving...GS1150EFE completed and awaiting modifications.....RD350, remnants in boxes scattered throughout the garage

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Re: Weighing Fueling Options

Post by Andrew11 »

Looks interesting, have you decided on which ecu you want to use?

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Re: Weighing Fueling Options

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Andrew11 wrote:
Sun Nov 14, 2021 10:10 am
Looks interesting
Thanks.
have you decided on which ecu you want to use?
I haven't decided. I consider the MS3 Pro the front-runner, because there's such a huge community of support for it around tuning, etc. Also, if I end up wanting or needing to do something more sophisticated than just dialing in the maps I have that option with the MS3 - although I prefer to not write/debug software outside of office hours.

However, it's hard to ignore the ECUMaster EMU Black these days. Great value for money, and it seems like there's more and more support for it.

The dark horse is something from AEM - basically because they're a big name and I expect really excellent support from the vendor.
Phil in Toronto
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Re: Weighing Fueling Options

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Today I partially disassembled and cleaned the OEM Honda CBX carbs and the OEM Triumph Bonneville throttle bodies. It was a very interesting experience. Both are made by Keihin, and the outer diameter of the inlets are almost identical. Of course, the Honda has a bunch of circuits, jets, and mechanisms that aren't required for the Triumph setup, namely:
  1. Choke butterflies.
  2. Vacuum-operated slides.
  3. Many passages and jets.
  4. Float, needle & seat.
  5. Accelerator pump.
The Triumph has a couple of things that the Honda doens't:
  1. "Choke" plunger (really an air bypass valve that admits more air for faster idle when cold) - but it looks exactly like a choke plunger from the outside.
  2. Mounting bosses for the injector, and a port for spraying the fuel downstream of the throttle plate.
  3. There is a full, removable float bowl, but it's empty.
On top of this, the throttle bores are different diameters: Honda is 32mm, while the Triumph is 36mm. I haven't decided what bore size I will use for my custom setup, but I am leaning towards 32-34mm.

Here are some photos of the parts that show the points of interest:
Image
Inlets match up almost perfectly.

Image
Outlets are VERY different diameters

Image
Here we see why the Triumph TB outlet is so much bigger than the CBX's carb outlet. There's a lot of additional material there to make & hide the port for the fuel injector. Both pieces are shown here upside-down as they sit better on the bench that way. Fitting an injector port between the throttle plate and the outlet in a way that still fits in the OEM rubber boot on the head is going to be the single biggest challenge of this project.

Image
This shows the (bent) "choke" plunger in the upper left, and the mounting boss for the injector. This all gets covered by the stamped cap.

Having looked at both assemblies pretty carefully, I'm confident that this is doable. I said it above but will repeat for emphasis: Fitting an injector port between the throttle plate and the outlet in a way that still fits in the OEM rubber boot on the head is going to be the single biggest challenge of this project. This will be made easier if I can cheat the throttle shaft & butterflies upstream a bit to make more room.

I am giving serious consideration to eliminating the synchronizing linkages between the carbs and having just 2 throttle shafts with 3 butterflies each. I'd add bleed screws for balancing if I go that way. The only reason I'm thinking of that approach is to make things simpler while making something with 100% new parts. Related to that, I would like to replace the throttle shaft bushings with sealed bearings like what's used on Weber carbs.

I ran a representative sample of parts out to the 3D scanning shop today. The scanning tech (also the owner of the business) is excited about the project and says that the parts will scan very well. He said that my planned approach to use the scans in CAD as a reference while modeling more easily-machined new parts is a good one. Those scans should be done before the end of next week.
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Re: Weighing Fueling Options

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Scanning tech is also the owner of the company, and it seems he was pretty excited to get cracking on this. He sent me these at 9:00 last night...

Image

Image
Phil in Toronto
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Re: Weighing Fueling Options

Post by heli_madken »

Remarkable what a 3D scan can produce now, shouldn't be too difficult from there to map out the internal passageways if you wanted to produce a complete model.

Are you going to import the model into a CAD package for further work?

Loving this thread so far keep at it really interesting what you are doing, way way over my head mechanically but watching with interest

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Re: Weighing Fueling Options

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heli_madken wrote:
Tue Nov 16, 2021 1:30 pm
Remarkable what a 3D scan can produce now, shouldn't be too difficult from there to map out the internal passageways if you wanted to produce a complete model.
Agreed. But I don't want a complete model - I want a simple model that looks OEM-ish from the outside and that has the barest, simplest internals that can make an EFI system work. Taking the Triumph TB apart and examining it was a great reinforcement of my understanding that an EFI TB is worlds simpler than a working carb.
Are you going to import the model into a CAD package for further work?
Yes. I'm new to CAD but overall technically proficient and have worked professionally on 3D medical imaging systems, so I am hopeful that I'll be able to pick it up without having to bash my head against the desk too much...
Loving this thread so far keep at it really interesting what you are doing, way way over my head mechanically but watching with interest
Thanks!
Phil in Toronto
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Re: Weighing Fueling Options

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Today I was going back over this whole thread to remind myself of what my thought process has been so far, and this photo really struck my eye:
Syscrush wrote:
Fri Nov 24, 2017 10:37 am
Image
At the time when I went to see this in person, I thought I was looking at hardware store plumbing adapters on the intake there, but now I recognize that those intake boots are 4-ply silicone transition couplings from Vibrant Performance. They're about $20 each from Summit Racing in a variety of sizes. If I decide that I want or need to make a larger outlet like the Triumph one in order to accommodate the injector port, it's very likely doable along with this style of adapter, which is purpose-built for this kind of environment & use case.

But looking at the scans of the carbs on the bike, I think that I should have the freedom to move the throttle plates 1-2 cm upstream, which also might be enough to give me the space I need. I'm looking forward to getting comfortable with CAD so I can start working out the details on this.
Phil in Toronto
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Re: Weighing Fueling Options

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Yesterday I had a very edifying discussion with Rob aka Andrew11. He hasn't really posted details of his experience here, but he was involved in the EFI conversion of a CBX, and he's been very generous with his time: sharing his experiences and insights from having been through this mill once already. After our chat yesterday, I'm seriously rethinking my plan to put the injectors under the carb caps, above the TBs. Here's how the pros and cons weigh out:

Injectors above TB:
  1. They're easily accessible for service. The fewer reasons there are to ever remove the rack from the bike again, the happier I'll be.
  2. I'm not an aerodynamicist, but I expect better light-throttle atomization in the upper part of the inlet tract because of the orientation of the throttle plate - it looks like you'd get nice smooth, fast, low-pressure air there, but possibly some stalling & turbulence in the lower part. Just a hunch. It probably doesn't much matter by the time the intake valve closes.
Injectors below TB:
  1. There's much more room underneath, including running a fuel rail across both banks without interfering with the center-mounted throttle linkage.
  2. Plumbing and fuel rail hidden within the float bowl area is probably less visible than up among the carb caps.
  3. The orientation of the throttle plates means more room for the injector port on the lower side of the TB outlet than the upper side.
It's worth noting that one of my early inspirations on this project was Michael Lynch's bike, which also went with the injectors below approach. If I get good enough at CAD, I'll probably model it both ways then decide.
Phil in Toronto
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Re: Weighing Fueling Options

Post by Syscrush »

Another note: increasing power is not a goal of this project, but looking hard at the OEM carbs, I do believe we can pick up some power pretty easily by the improvements in flow that come with the simpler and more streamlined design of EFI throttle bodies vs. carbs.
Phil in Toronto
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