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Carb to TBI

Discussion in 'Performance' started by AeaRy, Oct 30, 2021.

  1. AeaRy

    AeaRy New Member

    Hey Guys, I am new to Kei-trucks but have been a wrench turner most of my life. Gotta be honest though, my KS3 Sambar is the first carbureted motor that I have ever had to work on. Seems that upgrades would go much easier if there was a way to convert from carbed to TBI. Has anyone attempted or succeeded in this?
     
  2. fletcher0780

    fletcher0780 New Member

    I converted my Hijet to EFI, works pretty well.
     
  3. AeaRy

    AeaRy New Member

    Yeah, I am thinking more TBI (Throttle Body Injection) which is a type of mechanical fuel injection vs a full re-wire + ECM/ECU addition to go full EFI. It's a nice middle ground that would allow for a turbocharger setup and intake modification.
     
  4. Limestone

    Limestone Well-Known Member

    fletch,
    Please Tell us more what you did, with pics and details!
    I don't remember past posts on this.
    Limestone
     
  5. fletcher0780

    fletcher0780 New Member

    You're going to have a hell of a time with boost enrichment and boost timing retard if you're relying on a rudimentary control system. Don't be afraid of a few

    Here you go, it was actually quite simple. I have $855 into the conversion and have full spark and fuel control.

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    And all the crap left over:
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    My next step will be a little turbo with a goal of about 75hp, lets see where the weak link is in these engines. I know I can keep my timing and AFR safe, it's just a matter of what those little bitty rods can handle.
     
    AeaRy and Limestone like this.
  6. AeaRy

    AeaRy New Member

    Man...that does seem pretty easy. My normal subie tuner at MZM here in Austin was recommending a Garrett GT06 or RHB31 for a turbo setup. I guess worst case, if I screw it up I can re-use the Microsquirt on the EN07Y I'll end up replacing the carbed engine with and go SC/TC on it...lol
     
  7. bc_

    bc_ New Member

    @fletcher0780 How's your build doing? I was planning on doing a similar setup with a turbo. What's your duty cycle on the stock injector at the top end? It looks like that Honda throttle body only has a 240cc injector stock which I would think you'd be getting pretty close to the limits on, especially if you try and add a turbo. I see that you can get a 550cc aftermarket from DeatschWerks intended for the CRF450R that uses the same injector as the throttle body you have.

    Calculators say for 3 bar fuel, the 240cc is good for about 40hp and the 550cc would be ~75hp.
     
    Last edited: May 5, 2022
  8. AeaRy

    AeaRy New Member

  9. AeaRy

    AeaRy New Member

    Jigs-n-fixtures likes this.
  10. bc_

    bc_ New Member

    That looks like it comes with a 100lb/hr (1050cc/min) injector, that should be plenty. That's not a bad setup either.
     
  11. AeaRy

    AeaRy New Member

    Thanks
     
  12. bc_

    bc_ New Member

    That Holley is interesting, are you using it for ignition? You're 4 cyl, but it also only shows setting it up with 4, 6, or 8 cyl, with the Daihatsu 3 cyl we could probably set it up as a V6 and just treat 4,5,6 as wasted spark I would think. The throttle looks interesting on it as well, I see in your picture you have what looks like a bent aluminum bar for a cable mount and an opposing spring connected to something on the IM?

    Just thinking about options, still leaning microsquirt, but I like how it simplifies a lot of things. Significantly less wiring, includes wideband and display out of the box, no 4 wire iacv controller, etc. But I also don't quite understand how it would work with the factory position sensors/timing yet for ignition.
     
  13. AeaRy

    AeaRy New Member

    No, still using OEM coil/distributer for ignition. Spliced into OEM coil/tach signal for timing. Yes, return spring connected to static position on intake manifold just to ensure no stuck throttle. Unsure about a 3 cylinder utilization; would probably reach out to Holley for that particular question if you went that route.
     
  14. Latka

    Latka New Member Supporting Member

    Hey @fletcher0780, did you end up chucking a hair dryer on your setup? Would love to hear how that part went!
     
  15. fletcher0780

    fletcher0780 New Member

    The injector is 400cc, I haven't seen more than about 60% DC at 6500RPM and 100 kpa. I ended up buying an AMR300 supercharger that I have yet to install, but am going to aim for 10psi. The truck has been running solid on MS and the Honda TBI for over a year though, I don't miss the carb one bit.
     
  16. bc_

    bc_ New Member

    That's excellent news, I've been collecting parts and slowly getting other projects done. I have the throttle body and a few related items, but lately been building bumpers, installing lift, and just driving it. My stock carb is still happy as can be, but it won't be with boost. A little boost would definitely wake this engine up I'd think. I don't need it to be a rocket ship, but some of the hills around here are painful.
     

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