Weighing Fueling Options

[Syscrush]

On the weekend I met with Rob aka Andrew11 on this forum. As I've noted before, he's done a very cool conversion to EFI on a Pro-Link bike and a MicroSquirt system, and he has been very generous with his time and insight. He added to that generosity by lending me a spare cylinder head that he keeps for fixturing purposes. I will never cease to be amazed at the kindness and support of the community here.

I wanted that head to have a look at and measure/model the intake ports to help finalize my decision about if the injectors should be on the top or bottom of the throttle bodies.

I haven't done any detailed measuring or modeling, but it doesn't take a lot of inspection of that head to see that trying to fire the injectors at the intake valves in throttle bodies that look/fit like the OEM carbs is a fool's errand. If the head was ported and there were 3 separate TB designs created with the express purpose of spraying directly onto the intake valves, it would probably be possible, but for my plan and design, it will not be possible.

So, I'll be updating the design to put the injectors on the bottom. I will reuse the OEM carb caps on my custom throttle bodies, which will help retain something close to the OEM looks. I really like what mlynch001 did on his bike - replacing the float bowls with aluminum blocks machined to take the injectors and fuel rails. I also really like the fuel rail he built, which has its supply and return lines on the rear face instead of hanging off the side.

I don't know about the fuel rail details yet, but I will also position the injectors so that they're not hanging out into the flow as much as in the current design.

[Syscrush]

Well, friends. This thread almost made it to one year of sitting idle, but not quite. It's been another hectic and problematic year, but stuff is happening for me again.

Here's the quick update, with more to come before too long:

1. I am the proud owner of a new Bambu Labs X1 Carbon Combo. This is a very capable and easy-to-use "prosumer" level 3D printer. I'm new to printing - the 3D printing world is full of people for whom the printer itself is almost like having a pet or a musical instrument. They take (well-deserved) pride in understanding the intricate details of how the printing hardware and software work, and spend a lot of time and energy in getting the results that they want. They're a bit like Linux people, and for this stuff, I wanna be like an iPhone person. The sophistication of this setup goes towards ease of use - so far I've been very impressed at the ability to just press "Print" and get the results I want with my test prints.
2. From the research I've done so far, I've come to the conclusion that it should actually be possible to print the throttle bodies directly with my current printer using some of the semi-exotic "engineering filaments" that are now available. The material will be either nylon or polycarbonate - chosen for stiffness, fuel resistance, and temperature range. Whether I go with nylon or polycarbonate, it will be reinforced with 25% carbon fiber by weight. I'm actually printing my first ever PA-CF test part right now. I expect this choice to be contentious, but I feel good about the chances of success and will share everything I learn about the successes and failures of that approach.
3. Once I've finalized the models, I will open-source this project, so that others can leverage and build on this work. I've benefitted so much from the free and open sharing of information, the patient sharing of hard-won advice from my friends here, that I hope sharing ALL of my results (including the print-ready throttle body models) will help someone else the way that I've been helped.

[Syscrush]

Please keep on coming with the updates what you are doing is fascinating stuff

I'm quoting this because it'll give heli_madken a notification - I want to say thanks to you for your initial suggestion that plastic throttle bodies could be viable at least for initial running and debugging before proceeding to the finalized aluminum parts. That one suggestion kicked open a door to a broad and deep area for research and learning.

I can't be certain yet that it will work, but from what I've seen so far I am at least certain that it's worth a try.

[NobleHops]

That is awesome, Phil. Glad to see you back at it.

[Syscrush]

Thanks, Nils. I'm so pumped about getting going on all of this again.

BTW - I ordered a set of 6 used K1600GT injectors (all came off the same low-mileage bike), and I chose a set that came with the fuel rails. I doubt I'll be able to reuse them, but I want to have them for reference in modeling my own custom rail solution. Looking at the pics I saw this:



Yup, not only is that fuel rail plastic, it's made of glass fiber reinforced nylon. The PA6 is the type of nylon and the GF30 means 30% by weight glass fiber. I'm pretty confident that 3D printed fuel rails made of nylon with 25% carbon fiber will hold up just fine - I am planning to design mine with double the wall thickness of this part for some extra safety.

Also, here's an automotive throttle body made from injection-molded plastic. The material that's made from is Ultem - a high-temp plastic also used in 3D printing. 3D printing that material requires commercial/industrial equipment, so I don't intend to go that way. I may add an aluminum insert in the throat where the butterfly contacts it to prevent wear, but I think I'll set up a test rig to open and close the throttle of an all-plastic TB a bunch of times first to see what happens.

[Rick Pope]

Fascinating road you're traveling here. I wish you success.

[Syscrush]

Fascinating road you're traveling here. I wish you success.

Thanks a lot, Rick.

My 2 biggest concerns are:

1. Getting them seated into the intake rubbers without cracking or otherwise damaging them. I'm less worried about that now that I've had a simple PA-CF part in my hand.
2. Doing all of this work and then finding out that it's still impossible to tune around some kind of weird resonances in my exhaust. If that happens, I'll have no choice but to replace the exhaust.

[Syscrush]

Another idea I'm giving serious consideration to is supporting flex fuel. I don't have any particular desire to run ethanol - especially since it hurts fuel consumption and the bike's range is already limited by fuel capacity. However, it gets harder and harder to find gasoline that doesn't contain at least 10% ethanol. Since part of the intent of this conversion is to try to future-proof the bike a bit, I think that planning for flex fuel from the start makes sense. It also means that I'd worry less about taking the bike on trips where I may end up having to fill with whatever I can find locally.

This requires a small amount of additional hardware (a $100 flex fuel sensor), and a comparatively modest amount of additional tuning. Doing this would mean that the bike would run as well as possible regardless of what fuel is in the tank.

Since the entirety of the fuel system will be new, I don't think there are any concerns with the injectors, pump, regulator, lines, or fuel rail having bad reactions to the ethanol. The tank is steel and won't swell from ethanol like a plastic tank can.

We don't have anything higher than E15 readily available around here currently, but that may change. The trend is clearly away from ethanol-free fuels.

[Syscrush]

So, I've also decided that I'll document this whole project via public channels that I manage myself instead of spreading info and progress across this forum, tuning forums, Reddit, emails, etc. The banner for all of this will be the name/handle/address retro-efi. I was surprised that I was able to snag the url retro-efi.com and the YouTube handle retro-efi.

Because I love you all, I'm premiering my first ever video for this project here on this very forum:



I know it's mega amateurish and should have been tightened up in editing - maybe those skills will come with time, maybe I'll continue making crap videos until this is done. Time will tell.

[Syscrush]

Another idea I'm giving serious consideration to is supporting flex fuel.

Having done some more investigation on this, there's no real need/benefit. If stuff like E25 or E50 becomes the norm, the bike can be tuned at that time via laptop. Unless there's an intent to run E85 periodically for some reason, the flex fuel tune is not necessary.

[Rick Pope]

I think you're on track with that logic. Simple is good.

As for the ethanol reacting with some plastics, I have a Moto Guzzi with a plastic tank. The tank swells to the point that if you remove it from the frame, it probably won't fit back in place. Unfortunately, there's a hose on the internal fuel pump that's a common failure point. Folks on the Griso forum were constantly wailing and gnashing their teeth about the evils of ethanol. Eventually, I pointed out that ethanol has been a common fuel additive since 1975, and the first model year for the Griso was 2005. MG had 30 years to find a suitable tank material, and failed.

It seems you are doing a much better job of planning ahead than MG.

[Syscrush]

Same with the plastic tank on my wife's Monster 620. It is beautiful but the swelling is a real problem.

[Syscrush]

Angelis Racing has converted a CBX and they say that their throttle body arrangement can be made to fit the stock airbox with modifications - not clear on if that's modifications to the airbox, the TBs, or both. They went with simple, functional TBs that have the injectors and fuel rail on top, and the throttle cables connect on the right side. You can see a short video of it here:

https://www.facebook.com/reel/573410633582761

If you belong to the CBX Past & Present video, this link might also work for you - it has more photos of the TBs being fabricated and test fit to the head:

https://www.facebook.com/groups/5984126 ... 105536546/

Anyone interested in what I'm doing might want to also check them out - to me this looks like a good option for many applications.