Forced Induction Honda CR-X boosting help

Discussion in 'Classics & Heritage' started by swampyjason, Wednesday 11th May, 2016.

  1. swampyjason Junior Member ☆ ☆ ☆ ☆ ☆

    Hello everyone.

    My CR-X currently has the JDM D15b Dual Carb engine which uses a Mechanical Fuel Pump. I would like to eventually boost it after an engine rebuild and I was just wondering if it's possible to boost a car with a Mechanical Fuel Pump and Carbs or will I have to convert to EFI and Electric Fuel Pump?

    I'm also on the fence about keeping the D15b Non-VTEC head or doing the Mini-Me D16 VTEC Head Swap - in which case I will have to convert to EFI anyway.

    Any help on the main question would be great.

    Thanks.
     
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  2. Ichiban Founder Staff Team

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    @tviracing this is right up your street. would say the carb will need jetting and fuel pressure may also , how are you boosting the car ?
     
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  3. swampyjason Junior Member ☆ ☆ ☆ ☆ ☆

    That does sounds like a good plan yes. I assume Carb Jetting is where you increase the size of the jets etc?
     
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  4. Ichiban Founder Staff Team

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    Yes jetting is an art and will need dyno and a lot of tweaking to get right otherwise you will leaning your engine out. If you can't get jets then aftermarket Webber carbs are your route.,
     
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  5. swampyjason Junior Member ☆ ☆ ☆ ☆ ☆

    Thanks, I thought that would be it.

    Does sound like the best route to go though since a mechanical FP isn't really adjustable etc.

    I only plan to run a T3 Turbo anyway. Not after huge gains, just a nice bit of 'fun' shall we say.
     
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  6. Zebster Expert Advisor ★ ★ ★ ★ ★

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    If you're fitting a turbo then you'll probably need larger bore carbs, or more carbs. Simply fitting larger jets will make the AFR too low. Carbs are horrible, why not convert to injection?
     
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  7. swampyjason Junior Member ☆ ☆ ☆ ☆ ☆

    Thanks for the reply.

    Yeah I figured that too but since there's bigger jets, wouldn't the forced induction air compensate for the increase in fuel flow?

    I would convert to EFI but on my car it's a lot of work with it having a mechanical fuel pump etc; tons to do haha. I need to get a second car ideally so I can get this indoors
     
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  8. Ichiban Founder Staff Team

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    Carbs are horrible really what a load of tosh they don't have no rev limiters
     
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  9. Bo_ Club Member ★ ☆ ☆ ☆ ☆

    Wouldn't be easier to get B or K-series engine instead of trying to boost D? It would involve change of wiring and maybe some different engine fixings, but in overall you will gain engine with much more potential than you will ever get out of D-series.. :peace:
     
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  10. Zebster Expert Advisor ★ ★ ★ ★ ★

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    The rev limiter would be on the ignition system, not on the method of introducing fuel.
     
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  11. Ichiban Founder Staff Team

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    Which carb set up don't as they are simple.
     
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  12. Zebster Expert Advisor ★ ★ ★ ★ ★

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    The carb bodies would act as a limit to the air flow and could become a serious restriction, depending on how much you intend to boost. The flow of air through the carb pulls fuel from the jets using the venturi effect, so the increased flow would simply draw more fuel. But if the pressure inside the carb drops too low, then the suction will draw too much fuel... the carb body diameter needs to properly match the flow range to ensure the fuel delivery remains within the correct limits. An FI system would do this far more accurately
    Balancing carbs is time-consuming and then they drift out of sync.

    I have a good deal of experience (albeit over 30 years ago, ahem) balancing a pair of Weber 40 DCOE carbs on a Ford/Lotus 1558cc engine used in an 2nd Generation Escort stock car. That's 4 individual carbs, in effect... I still have fond memories of my improvised u-tube manometer and how the 'perfect' balance I finally achieved would 'all go a bit Pete Tong' after the first race. Happy days...
     
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  13. Ichiban Founder Staff Team

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    Yes they get out of sync but easy to put right they always need TLC to keep them sweet.
     
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  14. jimjams Expert Advisor ★ ★ ★ ★ ★

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    The Citroen SM (early 1970's with V6 Maserati engine) came with either EFI or triple carbs, the latter was the preferred version, and still is when buying one of these today.

    Carbs are just as good as EFI, EFI only became ubiquitous because of catalytic converters. It also depends on the carb, Weber were/are mainstream, dellorto were/are known to be better in every way.
     
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  15. swampyjason Junior Member ☆ ☆ ☆ ☆ ☆

    Thanks everyone for your replies. And for once, they all do make sense to me!

    It does sound like a big job and a lot of tinkering and perfecting but even still, I'm curious on what the effect would be if it was set up perfectly.

    I guess after all the parts have been fitted and the carb diameter has been sorted, it's just a case of professionally fine tuning and keeping on top of it.

    Iv never heard of this been done before on a Honda engine but there's a first time for anything and anything is possible I suppose!

    Will need to give this some full/long thought.

    Thanks again guys
     
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    SpeedyGee likes this.