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For the last few years I've run a home built itb setup using late model CBR600rr throttle bodies. It's worked better than ever expected and made my completely stock 185k old d16y7 a lot more fun to drive. I get 27-36mpg depending on how I drive and the car still has great street manners.
I wanted something a lot cleaner but couldn't justify something like a jenvey or kinsler setup on my car. So I started designing my own...
after a million iterations I came up with this. It accepts the 08+ CBR1000rr boots that use a flanged surface with an o-ring to seal. Coolant bypass hose clearance is tight but doable. I purposely kept runner length really short so that the setup could accept a plenum for boost or use longer velocity stacks for tuning.
Last week the foundry finished the sample part!
it's rough as hell but dimensionally within .3mm of the designed part. Good enough to run and will allow for a finishing machine pass on all sides. I'm going to produce a few of these and probably never do it again. DM me in the next week if you're interested.
It was more design time than I'd like to admit to. Didn't show a great deal of the process. Took a year to get to the point that I could take a pattern to the foundry.
In my case the pattern is two pieces on match plates and four core boxes to create the voids for the runners. Up next is fixturing the cast part in a small cnc mill for facing, drilling, and a finishing pass around the edge of both flanges.
The factory honda bike stuff is really great and honestly a better option for middle ground builds than the really wild stuff out there and 200% more reliable than the obx stuff. Throttle plates are only 44mm so really this is maxed out at 175hp or so.
This is awesome, youre the only person Ive seen to do the DIY ITBs using the Honda flange boots.
I spent a nuch of time trying to figureout the best way to do CBR1000RR throttles on my B series, and came to the same conclusion that the boots are the tidiest way to do it. Im amazed how many people dont do anything to accomodate the inner bore of the throttle body being offset from the outside diameter.
I was initially thinking of making this complex flange, which would account for the offset, and use a captured o-ring to seal it up. But it requires something to hold the throttle in compression with the flange, and there wasnt much there to work with.
Ended up with this. Although I never got aroung to welding it up, and now Im doing a K swap. lol
Being compared to Kinsler is a big compliment. Thanks!
That captured o-ring business is trick! I'd considered something like this previously, but once I saw the late model OEM boots I knew it was easiest way. The stuff that no one talks about is how to make the idle circuit work. I've 3d printed a hose barb adapter for mine and also printed tpu re-route gaskets. How were you planning on idle control? I may just remove it all entirely, my car has very little control over its idle as is.
I've actually started working on a b-series version for someone! These are definitely for a very specific type of build. On the d-series its harder to achieve enough flow to outrun the 44mm throttle plates. On a b-series this will definitely be doable. What you will get is monstrous mid-range and response. My manifold should make for an incredibly fun street car.
Thanks! I'm actually considering doing one for a personal project! Duratec swap in a 4wd converted early 80's b2000!
Right now I'm working on a b-series version of this. Anything specific about a b-series version that would be beneficial? I have no firsthand experience with the B motor.
Being compared to Kinsler is a big compliment. Thanks!
That captured o-ring business is trick! I'd considered something like this previously, but once I saw the late model OEM boots I knew it was easiest way. The stuff that no one talks about is how to make the idle circuit work. I've 3d printed a hose barb adapter for mine and also printed tpu re-route gaskets. How were you planning on idle control? I may just remove it all entirely, my car has very little control over its idle as is.
I've actually started working on a b-series version for someone! These are definitely for a very specific type of build. On the d-series its harder to achieve enough flow to outrun the 44mm throttle plates. On a b-series this will definitely be doable. What you will get is monstrous mid-range and response. My manifold should make for an incredibly fun street car.
I was planning on having a little manifold block that connected to each runner, that had the honda IACV on it. You could get away with not having it though. Ive run cars without them, its usually just accepting the idle will be a little high when warm and a little low when cold.
I agree that even the 1000 throttles are a bit small for a B series. I started the project with a B16, thinking it wouldnt be too much of an issue, but ended up doing a B20 vtec later. I still wanted to complete the project just for fun, and to get some experience tuning ITBs with alpha-n.
I learned more about tuning my ITB car that I did with any of the turbo cars I've worked on in the past. Do it! To do it right you really have to tune with the goal of ultimate drivability. Anyone can tune for WOT. I'd also recommend HTS for tuning. Hondata and Neptune lack a couple features that I feel are critical to a well running ITB setup. I wouldn't be surprised if I end up running some kind of standalone in the future because of this. The end goal is to run ITB's and boost.
I'm currently running a blended map setup with the crossover happening at 30% throttle opening. I give up sport-bike like response at really low rpms, but have better cruising drivability and mileage. My 272 cam doesn't really come to life until 3k, so the low low response is really unneeded. Also, my injectors are about 8" away from the backs of the valves!
DBW would open up so many doors for getting the drivability awesome, but the actuation is still cost prohibitive for a street or hobby build. Idle control, proper soft limiters, downshift blips, etc. But otherwise yeah, having the ability to blend tables is pretty key for a cable setup. Link does up to 6-d blending and has a plug-in box for older Hondas.
Originally Posted by flatblackdime
Thanks! I'm actually considering doing one for a personal project! Duratec swap in a 4wd converted early 80's b2000!
Right now I'm working on a b-series version of this. Anything specific about a b-series version that would be beneficial? I have no firsthand experience with the B motor.
Three different flanges to deal with (if you include non vtec). With some creativity you could make a flange that works for all three. Skunk2 Ultra already fits both P72 & PR3 heads, you can look at one of those for an idea of how to pull it off. PR3 & P72 have slightly different entry angles, you could probably split the difference if you wanted to make it work well for both.
You'd hate to see my chicken scratch drill press and welded manifold I got for my CBR1k ITBs. Thought of doing another manifold using the factory CBR sealing right after I put the ITBs on the car the other day, glad to know i wasn't the only one. Currently trying to get my setup to idle worth a hell, have a stock D15Z1 and it's a struggle to get this thing to idle below 2k unless i just lean it out to nothing almost.
Got my manifold and 1000rr itbs on and tuned. Took two dyno sessions to get it sorted. I'll have a 3rd session to dial in runner length before printing custom velocity stacks.
New setup:
D16Y7 bottom end
D15B head - mild port (bowl blend, divider straightening, slight roof raise), .040" milled, d16y7 rockers + 272 camCBR 1000rr 44mm itbseBay header, 2.5" exhaust
New setup is a night and day difference. Torque is everywhere now and comes on 500rpm sooner. The consensus is that my header is restricting me over 6k. Going to hack up a b series tri-y when I can pick one up cheap enough.
If you didn't know already, the unequal length stacks on the CBR were to broaden the torque curve at the expense of peak power. Will be interesting to see how your torque changes, if at all, with equal stacks.
Edit: Someone else has already played with this idea on the dyno and posted it to the tubes to share with all of us. His example is a bit extreme.
05-02-2021, 06:56 AM
D series itb shenanigans
