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Thread: Spittybug - Designs for converting stock setup to EFI

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    "Former Delorean owning Guru" Spittybug's Avatar
    Join Date:  Jun 2011

    Location:  Hill Country, TX

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    Spittybug - Designs for converting stock setup to EFI

    I pulled my old manifold assembly (with all the K-Jet pieces attached like some kind of morbid stuffed animal back from the taxidermist) out of the cabinet I now store it in and plunked it down onto my workbench to stare at it. I'm chewing on just how one could possibly modify it to EFI with minimal intrusion and reversibility. I'm sure more mechanically competent minds than mine have tried, but then again I have a stubborn streak in me.

    My "rules" for such a mod would be that it had to be reversible, be more reliable than K-Jet, not required a new manifold, must be safe, perform at least as well as a functional K-Jet, be doable by the average Delorean owner (with some good instructions) and cost under $1000 all in.

    Ideas being kicked around:

    • Our stock injectors (always open) could conceivably be used in this mod by feeding them with a fuel line that is modulated just like a modern fuel injector being opened and closed. Megasquirt opens/closes each bank of injectors at the same time or sequentially and I've not been able to notice a real difference in performance between the two. As Opethmike pointed out, ours are constantly open anyway.
    • Alternatively, the W pipe might present a place to insert one or two large injectors, thus turning our manifolds "wet" and obsoleting our current injectors. Those holes can simply be plugged with a long bolt as several of us do. Large volume injectors are <$100 apiece items and could be plumbed via fuel hose rather than rail. The modification to the W pipe would involve drilling holes for the injector and some form of bracket to hold the injector in place. Whether this could be done at the very opening of the W pipe, under the access cover or not (one big injector), I don't know. It may need to be in the sharp radius which would required a bit more work to reverse if desired. The benefit of doing it in the W pipe would be maximum air flow for uniformity and owners could easily mail in a W pipe for a modification rather than say a whole manifold.
    • If one of the two above could work, there would be no need to find new manifolds, change the stock throttle body or throttle cable or build fuel rails. A pressure regulator would need to go inline, but other than that, the fuel system could remain pretty much intact.
    • Idle air would be an issue. I think the best solution for that would be to machine a small aluminum block into which a standard GM worm gear idle air valve (<$100) would fit. This could be mounted pretty easily in the above mentioned beginning of the W pipe if the injectors were in the elbows. It wouldn't be very big and could be made to screw into the cover plate holes to hold it down.
    • Replace narrow band 02 with wide band. Add in an intake air temperature sensor (could be put into the back side of the stock air filter housing with just a small drill hole), re purpose the water temp sensor in the Y pipe, remove the air deflector plate or block it open, and done. If spark control were desired, the mechanical advance in the dizzy must be locked in place (need to see if that can be done without the little tack weld I used).
    • Megasquirt would then control the system. Wiring into our cars would be comparable to what is in my write up earlier in this thread.

    A user could then remove a lot of the hoses and K-Jet components to clean the engine bay up if they wanted to, but wouldn't have to if they wanted to leave it looking essentially stock.

    The success of a mod like this would appear to depend entirely on the aerodynamics of our stock manifolds and whether throttle body injection rather than port injection would be good enough. If it weren't, I'm sure that we have sufficient brain power in this group to come up with the "master" fuel injectors that could be installed upstream of our existing injectors (sounds like frequency valves or 60 lb/hr fuel injectors minus their spray nozzles) to keep our port injection system.

    Calling all fabricators and tinkers!
    Last edited by Spittybug; 09-24-2011 at 11:28 AM.
    Owen
    I.Brew.Beer.

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