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2008-2013 Cadillac CTS General Discussion Discussion, What's the difference between DI and normal fuel injection? in Cadillac CTS Second Generation Forum - 2008-2013; Originally Posted by 928S It seems that everyone wants to believe that DI is more fuel efficient, but contrary to ...
  1. #16
    yatesd's Avatar
    yatesd is offline Cadillac Owners Enthusiast
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    Re: What's the difference between DI and normal fuel injection?

    Quote Originally Posted by 928S View Post
    It seems that everyone wants to believe that DI is more fuel efficient, but contrary to what you've read here and elsewhere (I've seen the same misinformation on other websites and in print magazines) GM says...

    http://www.cadillac.com/cadillacjsp/model/po_specification.jsp?model=cts&year=2009&section=Powertrain

    EPA Estimated 18 MPG City and 26 MPG Highway (RWD 3.6L non-DI Auto model)
    EPA Estimated 17 MPG City and 26 MPG Highway (RWD 3.6L DI Auto model)

    Note: DI is estimated to have a 1 mpg advantage for AWD, Highway only.
    GM says the DI engine is 3% more efficient than the non-DI version. Whether transmission ratios or EPA mileage cycles reflect this fact is another matter.


    Direct-Injection technology

    The 3.6L Direct Injection engine is the premium engine option for the 2008 Cadillac CTS. This technology on the 3.6L VVT engine contributes greatly to a 15-percent increase in horsepower; 8-percent increase in torque, and 3-percent improvement in fuel consumption. Additionally, the application of direct injection reduces cold-start hydrocarbon emissions by 25 percent and it is designed to operate with regular unleaded gasoline.


    BTW I own the AWD DI so my EPA numbers also reflect some of this efficiency.

  2. #17
    AlanJS is offline Cadillac Owners Member
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    Re: What's the difference between DI and normal fuel injection?

    Is there a down side to direct fuel injection?
    Perhaps. I have a 3.6 L performance ATS which makes rattling or clicking noice under the hood while accelerating. Not heard while idling. No noticeable vibration. Brought it in to dealer for evaluation and engine was found to be specs by technician.
    When I complained to my service advisor he stated that I was hearing the "direct" fuel injectors under higher pressure than normal fuel injected auto.

    My wife's Infiniti G37 uses premium gas and gets going pretty damn fast without that noise.
    Maybe the downside of using regular unleaded to achieve 321 horses is valve noise in the ATS.
    BTW the loaner was a 2013 XTS and the big "tank" did not make any similar sound while accelerating as it has standard EFI engine.
    Anyone else hear the valves tapping along?

  3. #18
    like2drive's Avatar
    like2drive is offline Cadillac Owners Fanatic
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    Re: What's the difference between DI and normal fuel injection?

    Quote Originally Posted by AlanJS View Post
    BTW the loaner was a 2013 XTS and the big "tank" did not make any similar sound while accelerating as it has standard EFI engine.
    Anyone else hear the valves tapping along?
    Wrong, the 2013 XTS also has the DI 3.6L. It makes 304hp in the XTS.

  4. #19
    AlanJS is offline Cadillac Owners Member
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    Re: What's the difference between DI and normal fuel injection?

    Quote Originally Posted by like2drive View Post
    Wrong, the 2013 XTS also has the DI 3.6L. It makes 304hp in the XTS.
    then the service advisor indicated differently. Glad to hear from you.

  5. #20
    gohawks63's Avatar
    gohawks63 is offline Cadillac Owners Connoisseur
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    Quote Originally Posted by AlanJS
    then the service advisor indicated differently. Glad to hear from you.
    It's scary when the service advisor doesn't have a clue on what engines are in the cars they service.

  6. #21
    JackB is offline Cadillac Owners Fanatic
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    Re: What's the difference between DI and normal fuel injection?

    What about the carbon build up on valves and all the photos of same we have seen on the forum with suggestions to install a catch can?

  7. #22
    gohawks63's Avatar
    gohawks63 is offline Cadillac Owners Connoisseur
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    Quote Originally Posted by JackB
    What about the carbon build up on valves and all the photos of same we have seen on the forum with suggestions to install a catch can?
    That is true. While DI has it's benefits, one of the drawbacks is that the intake valves aren't kept clean by fuel passing over the valves.

    BTW, I installed a catch can and I was surprised how much oil I emptied after only 1,200 miles.

  8. #23
    JackB is offline Cadillac Owners Fanatic
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    Re: What's the difference between DI and normal fuel injection?

    Since a catch can seems like such a simple thing to do why didn't GM engineers install one?

  9. #24
    arw1510 is offline Cadillac Owners Enthusiast
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    Quote Originally Posted by JackB
    Since a catch can seems like such a simple thing to do why didn't GM engineers install one?
    Since the majority of people who buy the cars don't know what it is and would never empty it, causing more damage than it would good

  10. #25
    gohawks63's Avatar
    gohawks63 is offline Cadillac Owners Connoisseur
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    Quote Originally Posted by arw1510

    Since the majority of people who buy the cars don't know what it is and would never empty it, causing more damage than it would good
    Actually I'm not sure what harm it would do if not emptied. The oil would just get reintroduced and ingested into the engine like how how it would be stock.

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