3v VCT pwm controller

Discussion in 'SN95 4.6L Mustang Tech' started by billfisher, Sep 27, 2005.


  1. billfisher

    billfisher Active Member

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  2. Mustangl3

    Mustangl3 New Member

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    whats the VCT?
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  3. DBMSTNG

    DBMSTNG I fantasize about it being BIG! Founding Member

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    variable cam timing.
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  4. hotmustang331

    hotmustang331 New Member

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    Cool...but i stil dont understand how it adjusts the cam timing :shrug: . But I dont think that will do much...you could degree in a cam and essentially get the same result...just that it wont move lol. Maybe 5RWHP at best. This VCT could be a problem when you change the cam though...could cause PTV contact that may not hit until a certain RPM or load. Maybe.
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  5. billfisher

    billfisher Active Member

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    it varies stuff


    phase the cam is worth at least 20 hp. i am basing it on the single tooth retard done in mmff. phasing the cam to -10 degrees is worth a bunch of hp. if a cam fades at 5000 retarding it will keep it working for an extra 1000 rpm's or more.

    how it works is a long explaination:


    there are two orifices or passages ford uses for advancing and reatarding the cams. 50 degrees is the total movement. with no signal to the solenoid the orifice used is the advance. the oil pump on vct motors is very large volume. enough to supply the motor and enough to supply hydraulic oil flow to VCT. if there is a solenoid electrical failure the solenoid extends fully, opening the oil flow to advance the cams.

    at the other end, the solenoid at some point while energized opens the spool to the point that it allows oil flow to the retard orifice. this pressurizes a cylinder that actuates hellical cut channels on the cam gear to retard the cam.

    duty cycle control:

    the solenoids operate on DC only. think of a sine wave. let the bottom of the sine wave be 0vdc, and the top 12vdc. now make it a square wave form. with perfectly spaced 0v and 12v sections this is 50% duty. the wave is on 50% and off 50%. if you switch the signal at 10 times a second you will observe the solenoid oscillating up and down without completely seating and without completely extending. the avaerage position is dead center, but you can obviously see it moving. if you connect a spool with and orifice dead center the oil flow will flow at rate 'X'.

    if you now oscillate it at 2200 hz the solenoid appears to sit still in the middle. the oil flow will still be about 'X'(slightly higher). the two duty cycles are identical but the precision of centering the solenoid is exactly a function of frequency.

    i can vary the duty cycle to 25% and the solenoid will sit at 25% retracted.
    75% retracted 75%.


    i can vary the timing from full advance to full retard with extreme precision. purchase a pregram called desktop dyno. advance and retard a cam and you will see as much as 50 hp. or more difference. i can get away with a mismatched intake and still produce some bottom end torque.

    the best of all worlds. bottom and top varied with rpm's. i can precisely control phasing with rpm's. it will kill the same motor without it. i can't just throw it away.
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  6. billfisher

    billfisher Active Member

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    by the way... i don't have it all figure out yet. hitting the valves is a concern. i am going to take the vct off and look at it.

    1. if the cylinder bleeds oil out, controlling will be a breeze.
    2. if cylinder holds pressure i have a problem.
    3. possible solution is drilling very small relief hole to bleed cylinders. pwm can be controlled to flow tiny amounts of oil.
    4. i have read the patent papers the designers filed. this system seem typical so far.
    5. servo like control when used with feedback.
    6. i can't read ffedback. it would require a plc to control. plc's are expensive.

    i am hoping the engineers designed the spool to pressurize and bleed. really hoping.
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  7. StratGT

    StratGT Founding Member

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    Correct me if I'm wrong, but, the only Mustang that comes with VCT is the '05 and newer 3v GT's so this product would not apply to a 2v car. Am I correct?
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  8. hotmustang331

    hotmustang331 New Member

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    WOW, your right...didnt think about the other effects...was only thinking of peak power. Thats exactly why the 05s can carry over to 6500RPMs without really loosing any HP. I really wish there was a way to do this in the 2Vs or the 302 based motors. VERY good concept, and thanks ALOT for the info man.
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  9. billfisher

    billfisher Active Member

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    3v only

    right 3v only. i have a 5.4 3v. also i have discovered another tech problem:

    oil viscosity changes with temperature. 20w50 = pours like 20 weight when hot 50 weight when cold. (i can't remember which way). but the orifice is a fixed size, it will flow different volume at different temps. the vct retard will be more when cold less when hot.


    solution:
    1. use 5w30 and change oil filter frequently.
    2. tweak values periodically using oscilloscope.
    a) read both camshafts as 2 inputs.
    b) phase cam1 at 3000 rpm's (phasing starts there) and compare to reading of cam2
    c) read as actual degrees limit to -8 degrees.
    d) switch cams and repeat.
    3. this motor comes from the factory with oil cooler.
    4. optimize oil temps with cooler.



    also: spring pressure returns camshaft to full advance so;

    simple to control. $4 per chip.
    chip requires MOSFET high power output to actually run solenoids.
    i will design and publish circuit after running motor for a while.
    it consists of trigger circuit to set impedence to controller for descrete levels.
    i have decided that full analog continuous control is not realistic.
    instead i will set maybe 4 levels of voltage triggering to set controller input impedence. impedence controls duty cycle in this chip. i could use voltage control but impedence is easier. i can use one controller and two 12v 4 amp MOSFETS. also low level voltage output increases life of chips. also circuit boards will be inside vehicle. 150C limit for shut off. i can't afford under hood temps tripping chips. chips have indicator for tripping.

    i will probably disable system except at track or if i feel froggy.

    this motor is perfectly capable of 11.50's with forged internals with stock parts without VCT. if you consider retardin the cam 1 tooth and shifting at 6800 the rpm's will not drop into lower powerband.
    #9
  10. hotmustang331

    hotmustang331 New Member

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    11.50s are pushing it. Would need a trap of near 120. that would require over 400RWHP. Ill guess low 12s....Thats providing its N/A.
    #10

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