308 QV CIS question | FerrariChat

308 QV CIS question

Discussion in 'Technical Q&A' started by JohnMH, Feb 19, 2004.

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  1. JohnMH

    JohnMH Formula 3

    Jan 28, 2004
    Dubai / Bologna
    A simple CIS fuel injection question.

    My non-cis fuel injected ducati comes with a fuel delivery map burned onto an eprom located in the brain of the motorcycle. It is set up such that certain paramaters can change (temperature, barometric pressure, load, etc.) but some variables must be fixed (cam timing, exhaust flow). If I change the cams to a more aggressive profile, or put on a less restrictive exhaust, the computer cannot compensate. I need a new eprom.

    In comparison, my 308 QV has CIS fuel injection. If I add a tubi exhaust, or swap US spec cams for the higher lift, longer duration european cams, will the fuel injection system recognize the change and compensate? Does CIS even have a computer, like an EFI system?
  2. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    83' 308 QV has no Jetronic ECU
    84-85 QV has a Jetronic ECU mainly used for Lambda sensor and Frequency Valve.
    You didin't list your year so I put down both for you.
  3. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    "computer" is maybe too strong a description, but an '84 US version 308 QV (if that's what you've got) will have a "K-Jetronic with Lambda" Bosch CIS system which uses the voltage output from an O2 (Lambda) sensor mounted in the exhaust gas stream in a closed-loop manner to keep the A/F ratio at ~14:1 under normal driving conditions (after warm-up) -- so it should work OK with any reasonable mechanical modifications (after the open-loop A/F adjustment is reset and assuming the closed-loop stuff is working).
    Even if you have a year/version with the earlier simplier "K-Jetronic" CIS system, unless you're talking about extreme mechanical modifications, I believe it would be OKish (again assuming the open-loop A/F ratio is reset after the mods) -- there are plenty of non-US version, cat-less, K-Jetronic-equipped 308 out there.
    If you're talking about radical modifications, you should buy a 355 ;)
    Do an internet search on "K-Jetronic" and/or "K-Jetronic Lambda" -- plenty of other makes use the same system so there's a bunch of information out there.
  4. Matt Morgan, "Kermit"

    Matt Morgan, "Kermit" Formula Junior

    Nov 12, 2003
    Ferndale, WA
    Haveing spent many days in developing the 70mm Throttle Body Modifications, includeing an extensive flowbench developement workup, and in working with Frank Capo on camshafts for the motor, I would say that there should be no problem with adding slightly hotter cams, provideing you take care to set them up with as minimal overlap as possible. Excessive overlap on the Bosch system causes reversion pulses to confuse the metering in the Bocsh unit as it "fools" it into thinking that the engine is doing what it isn't. The simple vacuum activated plate that controls the flow reacts to positive pulses as though it were a low vacuum situation, similar to full throttle, and as you can see, that would cause mixture problems.
    Although my Web Site is still under construction, there is quite a section on the series of tests of the entire system from ait cleaner on thru both stock and 70mm TB's
  5. JohnMH

    JohnMH Formula 3

    Jan 28, 2004
    Dubai / Bologna
    Thanks for all the info, (I should have added that the car is an '84). The lambda sensor is the difference, as it is able to adjust for that 14:1 fuel/air ratio, withing reason. Sadly, the 355 is not an option (but having been able to take brief spin in one last weekend I understand the attraction of the suggestion).

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