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Retrofitting CIS

Discussion in 'Technical Q&A' started by TommyA, Mar 12, 2005.

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  1. TommyA

    TommyA Formula Junior

    Oct 7, 2002
    549
    Atlanta
    Full Name:
    Tommy A
    #1 TommyA, Mar 12, 2005
    This is an issue that has been discussed many times and concerns many of us with the aging CIS. The high cost has kept most of us from retrofitting.
    Modern vehicles (SMFI) are adjusting the air fuel ratio based on information provided to the ECM by various sensors such as Oxygen, MAF, TPS and others.
    If an ECM was used in our vehicles from a compatible V8 vehicle, is there a reason that it will not work if it was attached to the same kind of sensors?
    I do realize that the prom in the factory ECM has limited capabilities that might limit it from reaching a near perfect ratio. This can always be addressed by changing the prom with an after market for a very reasonable amount of $$.
    Any suggestions or ideas will be greatly appreciated.
    Tommy A
     
  2. Auraraptor

    Auraraptor F1 World Champ
    Lifetime Rossa Owner

    Sep 25, 2002
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    Omar
    #2 Auraraptor, Mar 12, 2005
    This has been done before with a complete aftermarket setup. If I recall the net gain was greater then 20 horsepower.

    I do not know any further details, it is in the achieves somewhere though.

    Incidentally this on a 328 in conjunction with a freer flowing exhaust in theory can make it as fast as an early 348.
     
  3. DGS

    DGS Seven Time F1 World Champ
    Rossa Subscribed

    May 27, 2003
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    DGS
    #3 DGS, Mar 13, 2005
    Much of the cost in retrofitting CIS is in the hardware: modified intake manifolds, new EFI injectors, fuel rails regulators etc., cam position sensors, and the basic ECU computer.

    I think you'd find that a complete ECU computer from a modern V8 would cost as much as an aftermarket computer.

    And ECUs are designed for specific vehicles. A modern OEM computer will also contain OBD diagnostics for a specific car, based on specific sensors. Without the sensors, many modern computers revert to "limp mode" which gives poor performance (but is intended only to get you back to the dealer).

    An aftermarket computer comes with an adjustable map that can be adjusted for a variety of different engines, so you can configure it to work on your engine. (But most aftermarket ECUs don't then monitor the health of the engine ... at least, not without plugging a laptop back into it.)

    I don't think getting, say, a Chrysler ECU would be either functional or much cheaper.

    If you want to do the homework to save money, check the web for the diy-efi program and the "Mega-Squirt" computer. You'll still need intake manifolds revamped to take the EFI injectors, etc.

    Theoretically, you might mung up some kind of electronically controlled CIS system that would use the same injectors, but would replace the fuel distributor with computer controlled differential pressure valves. I'm not sure that would be much cheaper, as the only diff valves I've seen were a bit large for the application, and you'd need eight of them.

    One advantage of an e-CIS (sic) would be that you wouldn't need to know the cam position -- but you could get that from an aftermarket "double-tap" EFI port injection system (half charge on every rev).
     

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