EFI Interest

Minimutly · Nov 17, 2023

Racerin said: ↑

Ok. Update so far:
Btw, sit down, this would be a long post.

I thought of calling the project:
- MC Carb Substitute
- Motorcycle All-In-One Individual Throttle Body Carburetor Replacement
- Or some combination of the above.
All suggestions will be considered.

Next, I've changed the project scope for simplicity/design cost sake.
The project aims to be a platform for creating EFI All-In-One Throttle Body for motorcycles. This includes other models of Yamaha and other brands. This does not mean that one throttle body could fit on all motorcycles. It means that with consistent parts/layout/configurations/dimension relations, the throttle body design could be adapted to other vehicles and similiar/proportional tuning could be used across motorcycles. Think of the Holley EFI TBI kits for cars and trucks.
Also, the kit should be easy to install. Few modifications. An amateur should be able to put it in. Just take off the carb, mount the kit in the same manner, connect some wires, and be good to go. Pre-tuned and all. The only modification I think is required is a Wideband O2 sensor for detailed tuning. I found a kit on Amazon (https://a.co/d/5J0DNMi) that only requires drilling and clamping the bung in place for the O2 sensor to mount. It would be intimidating to drill into your exhaust but simple enough. No welding required.
Btw. The scope is subject to change.

Next, I've gone through so many design iterations.
Initially, I wanted to make a peristaltic pump (https://en.wikipedia.org/wiki/Peristaltic_pump, Google It) driven throttle body. I searched the internet and did not find such a device. I thought I was on to something, something new. I didn't want to tell anyone. But as you guessed, I gave up that plan. After weeks of research, I found out that peristatic pumps could have fuel metering issues with wear. It just would not be constant between strokes or with operation time (the time it spent running). Also, the failure of the device due to lack of maintenance could lead to catastrophic consequences. A ruptured hose could lead to a fuel leak and a fire. I didn't want to risk that, especially if other people used the design. Also, I would need to design my own firmware to run this device. I realized that it's better to piggyback off of other people's work (no, I'm not stealing).

This introduces the Speeduino (again, google it). An open-source DIY ECU that uses an Arduino Mega 2560 for processing power and control. This would be my platform for controlling the electronics and running the engine. With this, however, I would need to do modifications to the bike electronics, especially the ignitor pickup. I need to design a new Variable Reluctance (VR) circuit to send the proper signal to the Speeduino to give it a sense of engine speed. That's the most critical work to be done. I don't need to do this now but it is vital for the future if I want the throttle body to be easily swappable and non-intrusive.

There were many designs I made but I will show you a few:
Next design, PVC housing. I thought that PVC pipes were a good material to use for the substrate for mounting and modifying. I learned later that PVC is not considered safe with gasoline but that wouldn't hold me back. I could use HDPE pipe if I tried hard enough or CPVC for higher temperatures. However, the true stopper was that I could not create a reliable design to isolate the downstream from the upstream of the throttle body. I was basing my design on a barrel throttle body and the upstream is close to atmosphere while the downstream is close to the engine and is regulated by the throttle mechanism itself. I thought of o-rings to seal but they would wear-out and they are difficult to hold in position. Eventually, I abandoned the idea but if you see of a way to hold a seal/isolate the chambers, let me know. I would consider the design. Just look at the following picture, PVC looks so cooool.

Next design, Sliders.

I designed all kinda slider designs. A vertical slider as seen above, to cam profile-following slider seen below.

The main issue with the slider designs is limited space. I was creating a design to retrofit into the previous carburetor region and the sliders were limited by size constraints. Also, I found it difficult (again) to isolate the upstream from the downstream. Yes, the vacuum would help seal upon a face but what was difficult was the throttle cable. It needed to be isolated and most designs I developed required a rubber bellow (they are not standardized and I would need to make them myself) or I need to use an aftermarket throttle cable (the Yamaha XJ's hand throttle is rare enough). Abandoned. I could reduce the throttle body size but I don't want to hamper performance. I had alternative desings in my head anyhow.
The alternative, Cam-Profile. This looks cool as the cam profile moves the throttle plate from the closed position to an open position following an oblique path. Bearings would help in the follower. Again, problems as mentioned above but also, the design is susceptible to binding which is not good for when u are trying to get off throttle for the red light ahead.

While all of this was going on, I was learning my CAD and CAE software, Solidworks in greater detail. Better workflow, more features. Now I'm venturing into using surfaces. Might be able to create 3D files of the Yamaha XJ bikes soon (fingers crossed).

Next Design, Hinge Joint.

Ok. Most throttle bodies are butterfly flow control valves. Common alternates are barrel and slide. I introduce to you a new design. Hinge joint. Instead of having the butterfly valve shaft mid-stream, you could put the shaft at the top (or bottom) of the stream and let the 'paddle' cover or open and control the flow of air. Some folks might think, 'Wouldn't the hinge be affected by the vacuum inside the chamber in terms of forces required to open and close?'. In a sense, yes. However, these calculations I found to be minor to the other forces needed to open and close the throttle body, or maybe I'm doing the maths wrong. Anyhow. I'm going forward with this design.
Btw, if anyone is into engineering, I highly recommend the website McMaster-Carr. Holy moly. They have all kinda hardware and CAD files for them too. This helped me brainstorm my designs. From there, I got some of the components for this hinge throttle design.
The hinge design uses sheet metal (I finally gave in) as the forces on it are too high for plastic and it deforms too much (from simulations). It would require torsion retention springs like a carburetor and it would use a rubber-like seal to mate to when in a closed position. I might use a resin laminate with carbon fiber or fiberglass with a 3D print core or a cast core for the casing/body (if you know, you know). I would mount the electronics enclosure below and give it access to the manifold for the MAP sensor. I could also mount the fuel pump below (this is a whole nother story). Fuel injectors and rail on top at the intercept angle. The fuel relief valve on the fuel rail with lines running to the fuel pump enclosure. I'm considering designing a sheet metal plate to replace the petcock. This would allow for return fuel and intake. I might also just put a new in-tank fuel pump (like a car) inside and let people install the barb and such for it. Idk yet, TBD.
The fuel pump. OMG. This is scary. Either I build an enclosure for the fuel pump (who am I? the EPA?) or get some kinda compact fuel pump enclosure, OR I use an inline fuel pump. Small inline fuel pumps are expensive but I don't want my DIY fuel pump enclosure to explode. It's difficult to get material that is fuel compatable. Basically metals. Then how do I manufacture the enclosure? This is my biggest issue so far. I might give in and go with the Walbro $120 inline fuel pump. Get all the features, little headache, and move on with the project. There's a lot of work to do.

PS. 'Why didn't you use the butterfly design?'
- Well, it would require a shaft to mount to each flap and a hard cylindrical surface (pipe) to mate to when closed. I might go to it if all hope is lost but right now, I'm working with hinge throttle.

If you have any suggestions, AGAIN I'm all open ears. Read the above mess at your leisure.
TLR: I am creating an All-in-one carb replacement EFI throttle body kit for my Yamaha XJ 750 bike. It should be easy to install. I am currently in the design stage of the project and I would use a Speeduino for the ECU.
Click to expand...

Ppictures not working.

Racerin · Nov 18, 2023

Minimutly said: ↑

Ppictures not working.
Click to expand...

Sorry about my post. I will upload the respective pictures here.
1. Peristaltic Pump design

2. PVC Housing design

3. Slider Throttle Design

4.

Don't mind the glitches in the model. That's proof of the limitations.
5. Hinge throttle body. Early concept. Need to Design for manufacture.

6. Current design of hinge throttle body plates. Sheet metal work.

I thought I had to do something fancy to upload pictures. I just need to paste it from my computer.

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EFI Interest

What stop you from converting to EFI?

Cost

Complexity

Inconvenience

System Requirements too high (lol)

Don't need it.

Carbs are superior!!!

Minimutly Well-Known Member

Racerin New Member

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