Motorcycle ITBS on a car engine
Written on June 30th, 2024 by sudoyashi
Adapting CBR600RR ITBS to an ABA 2.0
The CBR600RR ITBS
Made with the help of Nub Autoworks
Breakdown of the ITBS
Since I’m not using the CBR fuel rail, I installed a 12mm ID x 10mm bushing.
Velocity stacks, trumpets, whatever, you want to call it
I went back and forth with how I wanted to move forward with the velocity stacks, in the end, I ended up buying the OEM velocity stacks because they just work. Manufacturing my own stacks was proving to be a materials challenge than anything. I designed and printed out several designs for the stacks and flange. While they fit well, the reality was that ABS and PLA might not withstand for long underneath the hood for proper driving. Print times are long and the Creality I have is not setup to the tee, meaning the prints aren’t 100% perfect. The design process was fun, but I think I’ll revisit this project later.
I ran into a couple issues with 3D printing the velocity stacks: durability and difficult manufacturing.
PLA and ABS aren’t the best for production, but they are great for prototyping. I’ve made a few flanges out of PLA and ABS and eventually made one that I could fill in the gap for a flange. The issue I have is with the velocity stack. I went with a lip that proved to be trouble for my 3D printer. Since the lip shape is rounded, there’s no support to hold up on the outer edges. I flipped the STL upside-down so that the lip would print first and that seemed to work better. Finally, I’d epoxy the rest of the parts together to make a completed stack. But I feel like this design won’t last.
I want it to be in one piece to account for any issues on backfire. For reinforcement, adding fins and supports to any sharp angles would help as well. However, with this much time sunk in, I still wouldn’t have a product that I could use long term. In the end, I didn’t finish this project because it was going to be impractical in the end. Instead, I went on eBay and ended up buying Honda’s velocity stacks for the car. Two actually.
Honda Velocity Stacks, I forgot they existed
To be fair, I wasn’t able to find these stacks before because I was searching for “intake” and “trumpet”, but not “velocity stacks.”
These stacks were from an 2005 CBR600RR and a 2022 CBR600RR. They are slightly different on lengths and wanted to see if the equal length intakes, or variable length would impact drivability.
Generally speaking, longer stacks help the bottom end and shorter stacks help the top end. Motorcycles were designed for higher RPMs, so consequently the stock runners are short. But for a road car, we should extend the stack. One thing to note is that when I ran the first iteration of ZX6R motorcycle carbs, the intake length was VERY short but in my opinion, drivability was not that bad and it was more dependent on having a good tune.
To get the car running, these stacks will do the job, but later down the line I will hopefully find a way to make longer stacks.