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jake brake 2002 camaro v6

This is a discussion on jake brake 2002 camaro v6 within the External Engine forums, part of the LSx Technical Help Section category; Originally Posted by Spikito since diesels run on compression alone, the valve timing is adjusted so that compression is never ...

  1. #21
    ʢ ൧ ൨ ൩ ൪ ൫ ൬ ൭ ൮Ր Ց Ւ Փ Smittro's Avatar
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    Quote Originally Posted by Spikito View Post
    since diesels run on compression alone, the valve timing is adjusted so that compression is never allowed to build, resulting in no compression, if the same were done in a gasoline engine, the spark plug would still fire, and combustion would still occur, it would just all blow out the exhaust
    I know how a diesel works I've been a heavy hauler mechanic and that is not exactly how a "jake" brake works but close. That distinctive rapping sound is really the compressed charge being released (through the use of electrical solenoids) on the compression stroke. Before any fuel has been added, the charge is under very high pressure and is being allowed to escape only through a very small hole, causing that rapping sound. Without compression in a gasoline engine combustion would likely not accure and the plug would likely be fouled. I can't comment on smaller diesels as I've never worked on one like in cars and pickups.

    The point is this has nothing to do with this thread or the issue the poster is having.
    Last edited by Smittro; 11-30-2012 at 04:50 AM. Reason: Added to

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    Moderator Firebirdjones's Avatar
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    Quote Originally Posted by Smittro View Post
    Curious FBJ. Is this the same for the throttle by wire cars? Because that is what the 2002 3800 is? My 2001 throttle by wire never acted in this way.
    Yes sir, my 2004 6.0 is drive-by-wire and it also has the DFCO tables in the tune.
    Smittro likes this.

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    Quote Originally Posted by Firebirdjones View Post
    Yes sir, my 2004 6.0 is drive-by-wire and it also has the DFCO tables in the tune.
    Thanks! I always wondered how different they really are.

  4. #24
    Junior Member bipolar420's Avatar
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    After driving around last night. I looked at the rpms to see when it goes into the normal coast at 30. The rpms are at 1100 when the normal coast sets in and the engine brake stops or at least when the loud _ _ _ noise stops like what we were talking about. Dont know how to tell when it sets in. Any clues to look, hear, or feel when the engine brake sets in? Kinda made people mad at 2am playing with my car lol.

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    Moderator Firebirdjones's Avatar
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    Quote Originally Posted by bipolar420 View Post
    After driving around last night. I looked at the rpms to see when it goes into the normal coast at 30. The rpms are at 1100 when the normal coast sets in and the engine brake stops or at least when the loud _ _ _ noise stops like what we were talking about. Dont know how to tell when it sets in. Any clues to look, hear, or feel when the engine brake sets in? Kinda made people mad at 2am playing with my car lol.
    If you are feeling it kick off at about 1100 rpm, that's about right. That's about as low as I set mine, if you get that setting too low then you sometimes run into idle surge when coming to a stop, because the fuel is shut off, trying to come back on, and you are too close to idle speed etc...

    As far as telling when it comes on, no way to feel it, you just reach a certain rpm to activate while going down the road. Once past that rpm, DFCO is set to come on the next time you let off the gas. Only way to know what that rpm setting is, is to go into the tune and see. On some cars (all of my LS cars) the setting is so high, you never see DFCO. You aren't having that problem though it seems.

    DFCO is also deactivated if you touch the clutch pedal on a standard shift car. So while you are deccelerating next time, just lightly touch the clutch pedal enough to activate the switch while slowing down. You'll feel the car kick out of DFCO, but if you keep coasting down, you'll feel DFCO come back on, providing you are still above the activation rpm.

    An issue I had while driving around town was that I like to rest my foot on the clutch pedal ever so slightly (just above where you feel pressure) so when I'm ready to shift, I'm there. Problem though was when I let off the gas to slow down, DFCO wasn't coming on. I have to make myself take my foot off the clutch pedal completely.

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    Automatics don't have a clutch peddle FBJ lol jk.. Again my auto 3800 never did this. As soon as you came off the gas the car would coast but not as if it was in neutral there was still some "drag" as the rpms would carry slightly till you came to a complete stop. I never had it give a feeling of deceleration for a few seconds then release.
    Last edited by Smittro; 11-30-2012 at 12:15 PM.

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    Here's some info I grabbed from Tech.

    Deacceleration fuel cut Off

    From reading the HPTuners help section on DFCO (see below), you may not want this while tuning since it'll give some abnormal readings when it is on (essentially bad data).

    Re-enable it when you are done tuning to save gas.

    Fuel Cutoff, DFCO


    The Fuel Cutoff and DFCO Tab contains parameters related to fuel cutoff and limiters as well as Deceleration Fuel Cutoff parameters.


    Deceleration Fuel Cutoff (DFCO)
    DFCO can be broken down into 5 main modes of operation.

    Qualifications to consider (Enable)
    Spark threshold/ ramp down values and enable Qualification hysteresis values while getting to fuel cut point. (Entering)
    Spark values while in fuel cutoff (In)
    Qualifications to stay in fuel cutoff (Exit)
    Spark ramp up values to exit fuel cutoff (Exiting)


    DFCO Qualification
    DFCO must pass a series of enable tests to even be considered. If any of the tests are not passed, the DFCO process will not be started. (Fuel is still on)
    Fuel Tab - DFCO Enable Normal Section:

    Temp: Engine Coolant temperature must exceed this value.
    Enable Speed vs. Baro: The vehicle speed must exceed this value.
    RPM vs. Gear Entry: must exceed table value.
    TPS vs. RPM: Throttle position must be below this table value.
    Map vs. Baro Entry: Map must be below this table value.


    Fuel Tab - DFCO Enable Clutch Transition Section: (Not used on all models)
    These values over ride ANY of the DFCO Enable Normal Section qualifications (Enable, Entering, Exit) if recent clutch activity has been detected.
    These values will remain active for a short time period before reverting back to the normal qualifications.


    Temp: Engine Coolant temperature must exceed this value.
    Speed: The speed must exceed this value.
    RPM: Engine RPM must exceed table value.
    TPS: Alternate VCM %Throttle position Change must be below this table value.
    Map: Map must be below this table value.
    TPS Hyst: Adds to Alternate VCM %Throttle position Change value.


    DFCO Entry:
    Enable tests passed, VCM selects spark threshold/ ramp down values and Enable Qualification hysteresis values while getting to fuel cut. (DFCO is considered active and Fuel is still on)
    Spark Tab - DFCO Entry, Active, Exit Spark Section:

    Entry Threshold vs. RPM: This is the degree spark advance that must be reached to turn the fuel off.
    Entry Blending vs. RPM: This is the spark ramp out rate to reach the Entry Threshold vs. RPM spark value.
    Spark is removed at a rate of 12.5msec at the Entry Blending multiplier value. If your current spark advance is 20 degrees @3000 rpm, your Entry threshold is 5 degrees, and your removal rate is 0.010, the VCM will remove .2 degrees (20 x 0.010) of spark every 12.5 milliseconds until the Entry Threshold of 5 degrees is reached.
    Fuel Tab - DFCO Enable Normal Section:
    Speed Hyst: Subtracts from Enable Speed vs. Baro table value.
    RPM Hyst: Subtracts from RPM vs. Gear Entry table value.
    TPS: Adds to TPS vs. RPM table value.
    Map Hyst: Adds to Map vs. Baro table value.


    In DFCO:
    All of the qualifications have been met, Spark Cut Threshold has been reached and the fuel has been turned off. VCM sets the spark advance and looks for a reason to exit DFCO.
    Spark Tab - DFCO Entry, Active, Exit Spark Section:

    Active Advance vs. RPM A: This is the degree of spark advance while the fuel is turned off.
    Min TPS for Table A: TPS must exceed this value to use table A.
    Active Advance vs. RPM B: This is the degree of spark advance while the fuel is turned off.
    Max TPS for Table B: TPS must be under this value to use table B.
    Fuel Tab - DFCO Enable Normal Section:
    Enable Speed vs. Baro: The vehicle speed must exceed this value.
    RPM vs. Gear Exit: Engine RPM must exceed table value.
    TPS vs. RPM: position must be below this table value.
    Map vs. Baro Exit: Map must be below this table value.


    Exiting DFCO:
    VCM has found a reason to turn the on and start the spark exiting process.
    Spark Tab - DFCO Entry, Active, Exit Spark Section:

    Exit Blending vs. TPS: Spark is added at a rate of 12.5msec at the Exit Blending value. If your current spark advance (Main spark table, not Active Advance vs. RPM A/B) is 20 degrees @3000 rpm, and your add rate is 0.286, the VCM will add .286 degrees of spark every 12.5 milliseconds until the main spark table value is reached.
    Exit Blending CT (Clutch Transition): This value over rides the Exit Blending vs. TPS table if clutch activity has been detected.
    Stall RPM: This is the lower RPM limit for DFCO fuel cut.
    Last edited by Smittro; 11-30-2012 at 12:24 PM.

  8. #28
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    Here's the link..Hopefully it's allowed..

    DFCO disabled to tune...why re-enable it?? - LS1TECH

  9. #29
    Moderator Firebirdjones's Avatar
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    Quote Originally Posted by Smittro View Post
    Automatics don't have a clutch peddle FBJ lol jk.. Again my auto 3800 never did this. As soon as you came off the gas the car would coast but not as if it was in neutral there was still some "drag" as the rpms would carry slightly till you came to a complete stop. I never had it give a feeling of deceleration for a few seconds then release.
    I would guess your car was capable of DFCO, but possibly (like all my LS cars have been) the activation rpm was just set too high to reach during normal driving conditions.

  10. #30
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    Quote Originally Posted by Firebirdjones View Post
    I would guess your car was capable of DFCO, but possibly (like all my LS cars have been) the activation rpm was just set too high to reach during normal driving conditions.
    Maybe when I had the transmission reprogramed for firmer shifts maybe they made changes I was unaware of. The trany in that car was never quite right though.

  11. #31
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    if your car never done this before you put on the muffler. then it is the muffler that is causing the problem. the stutter feel is gasses building up inside the muffler. the inside of the muffler hotter that the pipe so the gasses ignite and cause the rumbling sound or pop. in return that popping sound will cause your car to slow down, as a minimal amount of back pressure is created. therefore the engine will slow down more when that occurs. my 04 gto does the same thing when the exhaust starts popping after the rpm's have came down, and it has done this for about 50000 miles. just drive your car and enjoy...

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    I agree.....I think you're just hearing the exhaust and not used to it. I'm not familiar with how the tranny settings look in the tune on a v6 but I'm wondering if that's about where your converter unlocks therefore making it seem like it's stopping there....it's just the converter unlocking and taking load off the engine. Nothing you're describing sounds out of the ordinary to me.

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    if it was the torqconverter it would have done this before the muffler exchange.

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    Quote Originally Posted by 04yellowjacket View Post
    if it was the torqconverter it would have done this before the muffler exchange.
    the torque converter was doing it before the muffler change.....he just couldn't hear it like he can now. In the tranny tune there's a mph lock/unlock flag versus throttle %. When you're coasting down the converter will stay locked until x mph then it will unlock....up until that point there's a tad bit of engine braking going on due to the converter being locked which creates a small load on the engine. Think of it like this....in a standard you down gear to say 2nd gear when slowing down with open exhaust. The exhaust is popping and raising all kinds of hell. Now push the clutch in and it goes away and drops to idle. Kind of the same principle only with a converter clutch.

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    i have rebuilt my share of auto transmissions and engines. and yes the converter will do that to an extent. but no where like to stop your car. even when the tranny downshifts like you are talking about. that is not enough to start stopping the car as was mentioned. i do have a 6sp in my gto. and yes if i press in the clutch, yes the rumble will go away. but if i leave it in gear when the rumble of the unburned gasses ignite it will slow down quicker. auto or stick will do that.

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