Instant Throttle Response??
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Cadillac Powertrain Control Module (PCM) Tuning Discussion, Instant Throttle Response?? in Cadillac Engine Technical Discussion; http://cgi.ebay.com/ebaymotors/Corve...94117661QQrdZ1 This shows a module to connect to your car via the TPS. I am assuming it is just tricking ...
  1. #1
    bigbluebrougham's Avatar
    bigbluebrougham is offline Cadillac Owners Fanatic
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    Instant Throttle Response??

    http://cgi.ebay.com/ebaymotors/Corve...94117661QQrdZ1

    This shows a module to connect to your car via the TPS. I am assuming it is just tricking the computer. Is that something you can change with tuning via your laptop?

    BBB

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    BCs71's Avatar
    BCs71 is offline Cadillac Owners Enthusiast
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    Re: Instant Throttle Response??

    I never paid much attention to this stuff but pretty sure it is the oft reappearing "snakeoil" resistor trick that is not a good idea. I forget the details but it basically sends false values to the PCM telling it that throttle is open more/less than it really is leading to PCM leaning out fuel mixture, increasing power. IIRC it doesn't help the entire powerband, either.

    Leaning out the fuel trim tables via a laptop is a much more effective and safe way to accomplish something fully and when needed, as determined by you and your specific application. GM made the stock PCM program pig rich at WOT, so adjusting the trims here is most beneficial.

  4. #3
    N0DIH's Avatar
    N0DIH is offline Cadillac Owners Master
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    Re: Instant Throttle Response??

    BCs71 is right, it is an old snakeoil trick. It did have some merit on GN Regals and other old CCC or C3I EFI cars. But not anymore.

    This was an old trick back when we had absolute readings on the TPS. It can work 1 of 2 ways. Either scale the TPS throttle position opening rate to act like it is opening faster (harder to do right) or to make over 50% throttle be WOT. So you trigger PE mode sooner, killing mpg and making the trans shift harder as it would in WOT/PE Mode.

    The stock tune for my V4P car and most all other B/D cars with the LT1 (low cool mode) is
    0 rpm to 2000 rpm, you are in PE mode at 60.2% throttle and higher,
    55% at 2400 rpm,
    50% at 2800 rpm,
    45% at 3200 rpm,
    40% at 3600 rpm,
    30% at 4000 rpm,
    20% from 4400-6400 rpm.

    So it is almost useless from the get go. A proper PCM tune will do just about anything you want with no gimicks and gadgets. The Corvette tune is actually a little harder to get into PE mode around 2400-3200, but else is the same as the B/D LT1 tuning. Even cop cars get the same as our cars do. I haven't even seen other tunes from other tuners mess with it, it really isn't needed to mess with. They changed how the TPS works, it is isn't absolute, like min throttle is not precisely 0.67v. It assumed to be the value you started the car with. WOT is anything over the throttle % seen above. So if your TPS only goes to 4v, who cares, you are at WOT by 2v anyway. The only way to flub it up is to slightly touch the gas pedal when you start it, it is off then, but I think it relearns pretty fast that "oh! idiot driver had the pedal down some when he started it, reset to new seen minimum value"

    Same with the resistor in the IAT (Intake Air Temp Sensor), don't mess with it. It just hoses up the BLM (Block Learn) or LTFT trims. Not worth it, and makes drivability worse and tuning inaccurate. My tunes are very solid for that, keep things in the stock place. I would actually like to see the MAT in the intake AFTER the throttle blades like the 4.9L Cadillac V8 was. Again, more accurate. I love how joe cool mechanic/tuner likes to think they can out-think GM PowerTrain Engineers...

  5. #4
    caddycruiser's Avatar
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    Re: Instant Throttle Response??

    Quote Originally Posted by N0DIH View Post
    I love how joe cool mechanic/tuner likes to think they can out-think GM PowerTrain Engineers...
    ^^Coming from someone who really does know, I think this sentence alone says it ALL.

  6. #5
    N0DIH's Avatar
    N0DIH is offline Cadillac Owners Master
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    Re: Instant Throttle Response??

    Although I DO think that GM PowerTrain Engineers are somewhat more conservative than I think they should be. A friend of mine insists some of it is intentional, like the HP of the 5.3L LS1 V8 in the trucks hasn't changed since 1998 and now makes upwards 35 more hp in 2006 than in 1998. According to my friend nothing has changed hardware wise, it is just software changes.

    Look at Toyota with the new Tundra 5.7. I'll bet they have let out all the tricks on that one, it isn't gonna gain jack for power in the next 5 years. GM always has more power coming year after year. I am thinking that GM's strategy sucks. Kick everyone in the nuts out of the box, don't come out being so passive.

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