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Cadillac Powertrain Control Module (PCM) Tuning Discussion, What is Tuning? By Definition in Cadillac Engine Technical Discussion; Originally Posted by N0DIH It is in the LS1 and 3100/3400/3800 too, Adaptive Spark Multiplier. It is in %, but ...
  1. #16
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    Re: What is Tuning? By Definition

    Quote Originally Posted by N0DIH View Post
    It is in the LS1 and 3100/3400/3800 too, Adaptive Spark Multiplier. It is in %, but it is a % between the low octane and high octane table. Contrary to most belief's the high/low octane table makes up a 3D map, and the Adaptive Spark Multiplier makes up a new "3D map", as it tries to keep towards the high octane "upper limit" and the low octane is the "lower limit" of this virtual adaptive table.

    I think Cadillac did it differently, a Calculated Octane Number IIRC. Then probably fed the ASM or it was the ASM.

    Is that what you were talking about?
    I think someone told me about these 3D maps when they had some knock on a 3800 SC

    Maybe I should think about posting that map.

  2. #17
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    Re: What is Tuning? By Definition

    AJ, For a 2002 STS VIN 9 F55 PCM are you able to add 3 - 5 degrees of basic timing advance and remove the 130 speed limiter ??

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    Re: What is Tuning? By Definition

    wonder who messes with them v6's? Most are wrong wheel drive....

    Quote Originally Posted by AJxtcman View Post
    I think someone told me about these 3D maps when they had some knock on a 3800 SC

    Maybe I should think about posting that map.

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    Re: What is Tuning? By Definition

    Quote Originally Posted by submariner409 View Post
    AJ, For a 2002 STS VIN 9 F55 PCM are you able to add 3 - 5 degrees of basic timing advance and remove the 130 speed limiter ??
    The spark has been an issue with me currently.

    When I change spark in the table it doesn't produce the same amount of effect. OK I change the spark in the low octane and the same thing happens.

    Can you tell me what TPS, MAP, MAF, RPM you would like it done at?
    I don't need all of them, but what RPM and Load are you looking at?

    This is from HPTuners web site
    Main Spark Tables
    The VCM constantly looks up both High Octane and Low Octane spark tables and interpolates a value between the two tables based on the current Knock Learn factor. If the engine has been operating for a moderate time without any Knock Retard then Knock Learn is zero and the interpolation favors the High Octane table, if Knock has been detected then the interpolation will move towards the Low Octane table. During MAF failure the Knock Learn is set to maximum and the Low Octane table is used (HP Tuners speed density enhancements allow both spark tables to function).


    Note: Excessive spark advance will cause knock (detonation, pinging) and lead to severe engine damage. Do NOT rely on knock sensors as the only source of detecting knock during tuning.




    High Octane: This is the High Octane spark advance versus RPM and Cylinder Airmass.
    Low Octane: This is the Low Octane spark advance versus RPM and Cylinder Airmass.



    High Octane vs. MAP vs. RPM: This is the High Octane spark advance versus MAP and RPM (some I4/5/6 vehicles).
    Low Octane vs. MAP vs. RPM: This is the Low Octane spark advance versus MAP and RPM (some I4/5/6 vehicles).
    High Octane vs. MAP vs. RPM (Alcohol): This is the High Octane spark advance versus MAP and RPM when running alcohol fuel (some I4/5/6 vehicles).
    Low Octane vs. MAP vs. RPM (Alcohol): This is the Low Octane spark advance versus MAP and RPM when running alcohol fuel (some I4/5/6 vehicles).



    High Octane PE Spark vs. MAP vs. RPM: This is the High Octane spark advance used during PE mode versus MAP and RPM (some I4/5/6 vehicles).
    Low Octane PE Spark vs. MAP vs. RPM: This is the Low Octane spark advance used during PE mode versus MAP and RPM (some I4/5/6 vehicles).
    High Octane PE Spark vs. MAP vs. RPM (Alcohol): This is the High Octane spark advance used during PE mode versus MAP and RPM when running alcohol fuel (some I4/5/6 vehicles).
    Low Octane PE Spark vs. MAP vs. RPM (Alcohol): This is the Low Octane spark advance used during PE mode versus MAP and RPM when running alcohol fuel (some I4/5/6 vehicles).



    Main Spark - Intake Min, Exhaust Min: Main Spark when intake camshaft is at minimum and exhaust camshaft is at minimum.
    Main Spark - Intake Min, Exhaust Max: Main Spark when intake camshaft is at minimum and exhaust camshaft is at maximum.
    Main Spark - Intake Max, Exhaust Min: Main Spark when intake camshaft is at maximum and exhaust camshaft is at minimum.
    Main Spark - Intake Max, Exhaust Max: Main Spark when intake camshaft is at maximum and exhaust camshaft is at maximum.



    Cranking Spark: This table is used to define the spark during engine cranking.

    Main Spark Table Selects
    If either of these TPS or MPH values is exceeded the VCM will select the Main Spark tables, otherwise the Base Spark tables are used. The value minus the hysteresis is required to revert back to the Base table from the Main tables.

    TPS: This value is the Throttle Position required to disable the Main Spark tables
    TPS Hysteresis: This value is added to the value above as the threshold to activate Main Spark table in relation to TPS.
    Speed: This value is the Speed required to disable the Main Spark tables
    Speed Hysteresis: This value is added to the value above as the threshold to activate Main Spark table in relation to speed.

    Base Spark Tables


    Base Spark vs. Airflow vs. RPM Closed Throttle, In Drive: This is the base spark used predominantly at idle with selector in gear.
    Base Spark vs. Airflow vs. RPM Closed Throttle, In Park: This is the base spark used predominantly at idle with selector in Park or Neutral.

    Idle Spark Advance


    Base: This is the base spark used predominantly at idle.
    Coastdown: This is the base spark used predominantly while the vehicle in in coastdown.
    Idle Spark Adder (P/N): This adds to the current idle spark while in Park/Neutral.
    Idle Spark Adder (In Gear): This adds to the current idle spark while in Gear.
    Idle Spark Mult vs. Baro: This modifies the idle spark in relation to barometic pressure.



    Base vs. MAP: This is the base spark used predominantly at idle (some I4/5/6 vehicles).
    Base vs. MAP (Alcohol): This is the base spark used predominantly at idle when running alcohol fuel (some I4/5/6 vehicles).

    Spark Correction
    The VCM incorporates a number of corrections to the spark advance depending on current engine operating conditions.

    AFR Spark Advance Correction - Add: This table is used to modify spark advance based on the current commanded AFR value (Fuel/Air multiplier). It is used during lean cruise mode and adds to the current spark advance.
    AFR Spark Advance Correction - Mult: The multiplier table is used to proportionally enable or disable this feature in relation to MAP.
    AFR Spark Advance Correction - Gas: These values are added to the spark advance in relation to EQ Ratio. It is used in the various enrichments modes (PE, COT, etc.)
    AFR Spark Advance Correction - Alcohol: These values are added to the spark advance in relation to EQ Ratio. It is used in the various enrichments modes (PE, COT, etc.)
    AFR Spark Advance Mult vs. Fuel Composition: The multiplier table is used to modify the spark value based on fuel composition (flex fuel only).
    AFR Spark Advance Correction Mult vs. MAP: The multiplier table is used to proportionally enable or disable this feature in relation to MAP.



    IAT Spark Advance Correction - Add (Base): This table is used to modify spark advance based on inlet air temperature. It adds to the current spark advance.
    IAT Spark Advance Correction - Mult: The multiplier is used to proportionally enable or disable this feature.
    IAT Spark Advance Correction - Mult 2: The multiplier is used to proportionally enable or disable this feature.



    ECT Spark Advance Correction - Add (Base): This table is used to modify spark advance based on engine coolant temperature. It adds to the current spark advance.
    ECT Spark Advance Correction - Mult: The multiplier is used to proportionally enable or disable this feature.



    Lightoff Spark (Normal): Catalytic converter lightoff (warmup) spark table. Used to modify timing during startup to heat the cats faster.
    Lightoff Spark (Coast): Catalytic converter lightoff (warmup) spark table. Used to modify timing during startup to heat the cats faster during coastdown.
    Lightoff Spark Idle (P/N): Catalytic converter lightoff (warmup) spark table. Used to modify timing during startup to heat the cats faster during idle in Park/Neutral.
    Lightoff Spark Idle (Gear): Catalytic converter lightoff (warmup) spark table. Used to modify timing during startup to heat the cats faster during idle in Gear.



    Launch Spark: Base launch spark table. Used to modify timing during cold start takeoffs.



    Piston Slap Spark: This table is used to modify spark advance to reduce piston slap (noise) during warmup.



    Startup Spark Correction: During the first 80 seconds of engine operation the VCM has the ability to modify the spark advance based on cylinder air and time. Generally this is used to assist in cold start low speed drivability. This value adds to the spark advance.
    Startup Spark Correction Mult vs. Startup ECT: The Multiplier table is used to enable and disable startup spark correction based on coolant temperature it is a proportional value between 0 and 1.



    EGR Spark Advance Correction - Add: This table is used to modify spark advance based on EGR operating conditions. It adds to the current spark advance.



    Startup Flare Control: This table is used to adjust timing to attempt to control RPM flaring during startup.
    Startup Flare Control - Mult: The multiplier table is used to proportionally enable or disable this feature in relation to ECT.




    Idle Adaptive Spark Control

    Overspeed: Amount of spark adjustment in response to an idle overspeed condition.
    Underspeed: Amount of spark adjustment in response to an idle underspeed condition.



    Overspeed (P/N): Amount of spark adjustment in response to an idle overspeed condition in Park/Neutral.
    Overspeed (Gear): Amount of spark adjustment in response to an idle overspeed condition in Gear.
    Overspeed (Coast): Amount of spark adjustment in response to an idle overspeed condition in coastdown.
    Underspeed (P/N): Amount of spark adjustment in response to an idle underspeed condition in Park/Neutral.
    Underspeed (Gear): Amount of spark adjustment in response to an idle underspeed condition in Gear.
    Underspeed (Coast): Amount of spark adjustment in response to an idle underspeed condition in coastdown.

    Mean Best Timing

    Max Torque Timing vs. RPM vs. Cyl Air: Theoretical spark advance that delivers maximum torque. PCM torque calculation routines reference this table when estimating current engine torque output relative to theoretical maximum. We do not recommend modifying this table.

    AC Torque Spark

    AC Bump Torque Spark: Enables/Disables spark adjustment when AC cycle on/off.
    AC Bump Torque Idle Spark: Enables/Disables spark adjustment when AC cycle on/off at idle if AC Bump Torque Spark is enabled.

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    Re: What is Tuning? By Definition

    Quote Originally Posted by submariner409 View Post
    AJ, For a 2002 STS VIN 9 F55 PCM are you able to add 3 - 5 degrees of basic timing advance and remove the 130 speed limiter ??
    Quote Originally Posted by AJxtcman View Post
    The spark has been an issue with me currently.

    When I change spark in the table it doesn't produce the same amount of effect. OK I change the spark in the low octane and the same thing happens.
    The short answer on the spark curve is that he can't.... and even if he could he has no idea if it will make things better.

    Let me explain. In the early days of distributors (pre 1980) the distributor used 2 inputs to determine the advance... RPM and Load (engine vacuum) it used those two things to mechanically determine the advance...

    Then around 1980 along came the CCC system, and it replaced the vacuum canister with a MAP sensor but basically it did the same thing and this resulted in the "3D spark map" that AJ was wondering about 3 or 4 posts ago... This was the "hey day" for "chipers" since you could make a change confident that you know what you were going to get and it was easy to test your results...

    The equation was simple and it was easy to measure the results...

    Then in 1985 (or so) they started to add knock sensors and speed limiters and tranny shift delay algorithms and the 3D chart became a mind blowing 9D and beyond chart. To the point were you had almost no idea what a change to the main spark table might do... Often, especially if the engine was on the edge of detonation, it would have NO effect AT ALL. Or worse a change that should add 5 or six horse power would run into some other "control variable" and the car would run a 10th slower in the quarter (and we have never seen that )

    Moving ahead with the advent of OBDII things only got worse... As AJ's quote from HP tuners shows now there are DOZENS and DOZENS of inputs that the PCM considers when it sets timing and fuel delivery.

    There is a speed table, a knock attack table, a knock retard table, a highway "constant speed" table, a egr table, a cold start table, a hot start table, a overheat table, a traction control table, a transmission protection factor, a max spark table, min spark table, bla bla bla.. There are dozens these chips started out as 1Kilo Byte babies and now they are Mega Byte monsters.

    A good place to start is with this:
    http://www.geocities.com/ecmguy.geo/bruce/prog_101.html

    And that was for a PCM from 19 years AGO... We have come along way from there.

    The PCM takes inputs from all over the car and engine, adds some, subtracts some, compares some, truncates a few and based on over a dozen or so inputs it determines fuel requirements and spark advance.

    To tune a PCM you need to know and understand two things
    1) the location of each and every table, AND just as important,
    2) the logic the PCM uses to manipulate those tables to calculate the final spark advance.

    If you don't know both of those...and I mean REALLY know them...
    Then you are basically forced to make a change, run the car, see if the change made things better and the move on from there... Of course this becomes more and more difficult as the change could (and usually does) have undesirable side effects.... Or as we have seen has no change what so ever.

    If you are unwilling to do the enormous effort of test, run, repeat, repeat, repeat and repeat some more... Then you are forced to just take a stock PCM that you know works the best and swap that in...

    Which is not at all bad... lots of tuners do that... You take a stock tune from the best motor the they made in your family of motors and you build a motor like that one (custom tunes are useless without custom engine work) and then you use that tune... GM created a ton of excitement for example with the ZZ4 chips the offered with the HO350 swap kit they sold for 82-86 Camaro's... Lots of guys used that tune to swap 350's into EVERYTHING. and have the motor run as well as the ZZ4 in the Camaro swap... Of course running the ZZ4 Chip in a LG4 305 Camaro had a car that ran WAY too rich and produced less power, bad millage and even worse emissions.

    What is tuning?
    That would be building a custom PCM that matches the CUSTOM ENGINE MODIFICATIONS that you have done...
    If your car is stock, it will work best with a stock PCM.

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    Re: What is Tuning? By Definition

    That is not what this thread is about.

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    Re: What is Tuning? By Definition

    Actually, Ur7x' reply is exactly what this thread is about. TUNING. I knew full well before I posted my "basic timing advance" question that there is no way on earth to perform a PCM tweak similar to twisting a distributor 2 degrees + or -. I shudder to think how many basic Delco points and HEI distributors I have assembled over the years.....hundreds. Fun and games, and with a handful of springs and weights and an old Sun machine you can dial in any advance curve you want. Adjustable vacuum cans were another luxury. Pertronix and Mallory were another yet...

    Not so in our Northstar 2000 - 2004 world. Watching the PCM advance/retard performance while driving bears no relation to "the old days". If I think I have a handle on a particular load/advance reading, that observation is impossible to duplicate under what should be the same conditions. It's as HPT and Ur7x state: There are so many variables in the stew pot that meaningful ignition tuning is damn near impossible in the 2000 - 2004 series of GM PCM's. The ultimate trick would be to leave the existing PCM to run the body and transmission and adapt a stand-alone ICM to the engine.

  8. #23
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    Re: What is Tuning? By Definition

    Sub I typed out a long post and then Deleted it. I was going to post it in the Tuning thread, but decided not to.

    This thread is ment to clear up what Tuning IS!
    I didn't want to cluter it up. OK?

    I will post over in the Tuning thread in a few days on your question.


    Quote Originally Posted by submariner409 View Post
    Actually, Ur7x' reply is exactly what this thread is about. TUNING. I knew full well before I posted my "basic timing advance" question that there is no way on earth to perform a PCM tweak similar to twisting a distributor 2 degrees + or -. I shudder to think how many basic Delco points and HEI distributors I have assembled over the years.....hundreds. Fun and games, and with a handful of springs and weights and an old Sun machine you can dial in any advance curve you want. Adjustable vacuum cans were another luxury. Pertronix and Mallory were another yet...

    Not so in our Northstar 2000 - 2004 world. Watching the PCM advance/retard performance while driving bears no relation to "the old days". If I think I have a handle on a particular load/advance reading, that observation is impossible to duplicate under what should be the same conditions. It's as HPT and Ur7x state: There are so many variables in the stew pot that meaningful ignition tuning is damn near impossible in the 2000 - 2004 series of GM PCM's. The ultimate trick would be to leave the existing PCM to run the body and transmission and adapt a stand-alone ICM to the engine.

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    Re: What is Tuning? By Definition

    Quote Originally Posted by AJxtcman View Post
    This thread is ment to clear up what Tuning IS!
    I didn't want to cluter it up. OK?
    Let me repost the last three lines of my cluter...

    Quote Originally Posted by Ur7x
    What is tuning?
    That would be building a custom PCM that matches the CUSTOM ENGINE MODIFICATIONS that you have done...
    If your car is stock, it will work best with a stock PCM.
    I could not make it more clear.

    BTW the cluter nicely documents how hard this is and why most "tuned chips" on stock motors yeild so-so results...

    There is no magic bullet, there is no quick fix..

  10. #25
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    Re: What is Tuning? By Definition

    Quote:Originally Posted by Ur7x
    "What is tuning?
    That would be building a custom PCM that matches the CUSTOM ENGINE MODIFICATIONS that you have done...
    If your car is stock, it will work best with a stock PCM.

    I could not make it more clear.

    BTW the cluter nicely documents how hard this is and why most "tuned chips" on stock motors yeild so-so results...

    There is no magic bullet, there is no quick fix.."
    End Quote: by Ur7x

    =======================================
    I'm new here, so first let me mention that I am an analog/digital/systems hardware engineer with an emphasis on computers, and communications systems. I'm also mechanically inclined and have worked on cars since I was a kid.

    Let me draw an analogy. In electronics when we do a chip design we build in margin so that nearly every chip off the line that does not have a gross defect works in the system. We call it PVT margin for process, voltage, and temperature. The chemical processes used to fabricate chips are not exact, they vary causing speed, voltage threshold shifts etc., the supply voltage is not exact, nothing is, so we allow for 5% variation, 10% often for Military designs. Temperature - depending on ambient, and how hard the system is working we have a very wide range of junction temperature - speed and thresholds are also dependent on temperature. I take it you all have heard of overclocking PCs? These are the main reasons why it works - not that I recommend it for the average user.

    I would expect the stock PCM program to be _very_ conservative with a lot of margin, when properly designed - meaning bug free, to allow for aging of the engine parts, poor maintenance habits, etc. Many here seem to want to take old cars and get more performance, unfortunately - I think we are loosing margin in an old engine, but there is probably room for significant gains in a newer engine. I would think that the top end of the Norhstar could easily do 7500 RPM when new, without vavle float and probably with good breathing. But I doubt if the average Cadillac customer wants to hear their motor reving to 7500 RPM. It currently rev limits, might not have the fuel supply or timing to provide increased horsepower up to those revs, but this would be the simple way to get significantly more power from the stock motor. It would not be recommended, obviously for an old motor with weak valve springs and who knows what else that is near end of life.

    Obviously, we want some margin on the rev limit, does anyone know where the valves float, or lifters pump up, on a stock new Northstar? Anyone know the design margin on the rev limit for the Northstar? How about the bottom end, at what RPM does it blow up? You want to look at linear piston velocity versus RPM. Is there a technical paper on the Northstar design with some of these parameters?

    I would think that pushing the rev limit up by say 500 RPM for a mild performance tune, and 1000 for a hot tune would be doable. New fuel, and timing curves would be required. However, as has been stated extensive testing would be required to be sure that everything was right. I would probably limit these higher states of tune to kick in only under optimum conditions; this is an advantage of having PCM control - you don't have to provide the gain when the car is misused and so you can fall back on the factory program. If I was an independent doing such tuning, I'd say use it at your own risk.

    More RPM is the way to power with an engine that breathes and does not have the capacity like a 6+ liter motor.

    Pete

  11. #26
    Pete1996 is offline Cadillac Owners Fanatic
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    Re: What is Tuning? By Definition

    Quote Originally Posted by submariner409 View Post
    Actually, Ur7x' reply is exactly what this thread is about. TUNING. I knew full well before I posted my "basic timing advance" question that there is no way on earth to perform a PCM tweak similar to twisting a distributor 2 degrees + or -. I shudder to think how many basic Delco points and HEI distributors I have assembled over the years.....hundreds. Fun and games, and with a handful of springs and weights and an old Sun machine you can dial in any advance curve you want. Adjustable vacuum cans were another luxury. Pertronix and Mallory were another yet...

    Not so in our Northstar 2000 - 2004 world. Watching the PCM advance/retard performance while driving bears no relation to "the old days". If I think I have a handle on a particular load/advance reading, that observation is impossible to duplicate under what should be the same conditions. It's as HPT and Ur7x state: There are so many variables in the stew pot that meaningful ignition tuning is damn near impossible in the 2000 - 2004 series of GM PCM's. The ultimate trick would be to leave the existing PCM to run the body and transmission and adapt a stand-alone ICM to the engine.

    The real question is why would you want this? Let's assume you want it for a primative old style racing engine. You'd take the base normal operating table and copy it into all the others after adding your advance. Then no matter which table the adaptive control tried to switch to, you'd get an emulation of your old dumb distributor with a single curve. You asked for it - that is one way to get it, not exactly sure why you would want it. It demonstrates the power of table driven software, consider the alternative, a single base table with algorithmic adaptation, you'd have to understand all the algorithms and their interactions. We have learned that often the designer can't keep track of the complexity, and what if the person leaves the project? Tables are easy, what you get is what you put in the table.

    Another solution to your question, make the crankshaft position sensor lie (alter the cal table), who knows what else that would screw up, lol!

    Pete

    I don't know why several here seem to assume that it is impossible for this to be done. Yes, obviously it is not easy.
    Yes there might be bugs, or mistakes, but AJxtcman is getting there and making progress so let the man do his work.

  12. #27
    Pete1996 is offline Cadillac Owners Fanatic
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    Re: What is Tuning? By Definition

    Found the Northstar Overview for the second generation engine and noticed that the valves have some sort of electronic control for the lifters - have no idea how that might impact the rev limit. The paper does not discuss margin in the design.

    Pete

  13. #28
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    Re: What is Tuning? By Definition

    Pete, My post - your quote in #26 - was rhetorically aimed specifically at those who believe there is some magical way to tune a late Northstar FWD PCM for significant gains in power and "speed".

    How many times have you answered a question in here or another forum, an answer based on experience and study, and been told "You're full of crap ! I know better !" If the OP "knows better", then why was the question asked in the first place? Because the OP is looking for reinforcement for an idea that has not or will not work to give him the magic power gains he "knows" have been hidden by devious engineers. Black magic.

    We fully understand that modern PCM spark tables are a constantly changing dynamic and therefore a "tuning" regression to load/mechanical ignition control is going back to 1930. 55 years of engine building and racing have taught me that there's more to "tuning" than black magic (although sometimes it helps........).

  14. #29
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    Re: What is Tuning? By Definition

    Actually I have been thinking about PE mode more and more.

    Think about this SUB.

    PE (Power Enrichment) has several parameters. Some are delays and some are adders.

    Lets go back a few years.
    What throttle angle would you like your secondaries to kick in at?

    I have found 80% on some of these!

    I think 40% to 50% would be just fine. for the most part if you are in the throttle 40% you want to go.

    Now for the delay or quadrabog
    This is the length of delay before PE kicks in.
    5 seconds is a long time

    The second part of the Delay is RPM. LS1's used 1 RPM setting. Like 5000, so below 5000 has delay before it kick in and above skips over the delay time.

    Now the Northstars have a table for delay RPM vs TPS

  15. #30
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    Re: What is Tuning? By Definition

    This is from a Northstar PCM. Not the LS1 PCM setup.
    Code:
    Power Enrich Enable Delay Time Vs. TPS   
    TPS   Seconds
    0%       5.00
    5%       5.00
    10%     5.00
    15%     5.00
    20%     5.00
    25%     5.00
    30%     5.00
    35%     5.00
    40%     5.00
    45%     5.00
    50%     5.00
    55%     5.00
    60%     5.00
    65%     5.00
    70%     5.00
    75%     5.00
    80%     3.00
    85%     1.00
    90%     0.00
    95%     0.00
    100%   0.00

    Code:
    Power Enrich Enable % TPS Vs RPM   
    RPM         TPS %
    0%          75.00       
    400         75.00 
    800         75.00
    1200       75.00
    1600       75.00
    2000       75.00
    2400       75.00
    2800       67.50
    3200       60.00
    3600       60.00
    4000       60.00
    4400       60.00
    4800       60.00
    5200       60.00
    5600       60.00
    6000       60.00
    6400       60.00

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