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24v DOHC V6...

Discussion in '2005-2010 V6 Mustang Tech' started by WYLDHorses, Feb 22, 2005.

  1. 6gofast

    6gofast New Member

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    Correct me if I'm wrong, but don't the injectors spray into the short runner port?

    Wouldn't having them closed off hinder the fuel from atomizing and going into the CC correctly?

    I'll have to look at my heads tomarow after work while I'm putting the car back together.
     
  2. SpeedKills

    SpeedKills New Member

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    Both of you go look at a dyno graph that was recently posted. It showed that at 3500rpm there was a sharp drop in the torque qurve??? Why??? Because when the IMRC opened air started going through the shorter runner and there wasn't enough air velocity to create the RAM air effect that boost torque.

    IMRCs are built in to multy stage intake manifolds like that of 99+ v6 and new 05 GT and 86+ cobras. So that correct air velocity can be achived to create torque boosting ram air effect at low rpms without sacrificing top end power.

    Actually the 01+ v6s got a boost in torque and it came on much lower just because ford added the IMRCs. Check the specs.

    The reason people remove the IMRCs because the are restriction at high rpm, but the cars loose lowend torque.

    V6go, the injectors shoot in to the heads where the runners meet so weather or not IMRC are closed doesn't affect it.
     
  3. KTBug

    KTBug - Kris -

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    Quite possibly. It sounds plausible.

    I get what you are saying but at low RPMs the IMRCs don't even come in to play. They have 0 effect until they open. It's the long runners that make the extra torque, not the IMRCs. Once the IMRCs open the intake can flow through the short runners and make more hp than possible through the long runners.

    The boost in torque (5 ft/lbs) was due to the fact that the intake didn't flow through long AND short runners like the 99/00. Starting in '01 the intake only had the long runners to use for the low end. This helped intake velocity at low RPMs.

    They might lose torque but it's not real noticeable. 99/00 V6s are rated at 220 ft/lbs with no IMRCs while '01+ are rated at 225 ft/lbs with IMRCs.
     
  4. 03f1504x4

    03f1504x4 New Member

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    LOL, hey man..i know how they work and what they do. :D
     
  5. SpeedKills

    SpeedKills New Member

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    O.k lets just drop it... I can't make you understand that the reason that 01+ have more TQ and earlier that when IMRC close off the short runner.

    May be one more try. Like I said earlier cross sectinal area times air velocity equal mass air flow or volume per second. At a certain RPM and WOT, the mass air flow number is fixed. Can we agree on that???

    In order to achive ram air effect in the long runner you need to certain high air velocity in it. Thats how it works. Can we agree on that???

    When you don't have IMRCs, you have both runners open at all RPMs. Can we agree on that???

    Then your total cross sectional area is about 2X that of just the long runner alone. Agree?

    So then when one 01+, IMRCs are closed only the long runners are open, which means that the cross-sectional area is about 2X smaller then that of 99-00.
    Can we agree on that???

    Well, if we have follow previously stated rule, cross-area X air velocity = mass air flow. If mass air flow is fixed at a certain rpm and WOT, then we can manipulate the equasion so:

    Mass air flow
    ___________ = air velocity
    Cross-area

    Then if you make the Cross sectonal area 2X smaller you have:

    Mass air Flow
    ___________ = 2 X air velocity
    cross-area/2



    So as you can see you have 2 X the air velocity with closed IMRCs then without IMRCs. The 2X velocity significatly increases the ram air effect and creates it earlier, so you get the EXTRA LOWEND TORQUE!!!!

    Agreed???
     
  6. 03f1504x4

    03f1504x4 New Member

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    <lost> I understand why the newer ones had more low end tq. I'm confused as hell about that post... I dont think it was directed to me tho??
     
  7. SpeedKills

    SpeedKills New Member

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    Don't worry its just for KTBug, I was trying to explain to him why closed IMRCs make for more torque.
     
  8. 03f1504x4

    03f1504x4 New Member

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    Maybe he should take a look at the sho's.....they are the best example IMO..
     
  9. KTBug

    KTBug - Kris -

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    Eh, I guess I see your point. With only the long runners open, the velocity is greater. If both long and short were open then the short runners could possibly overwhelm the engine with a little more air than needed. Kinda like using a huge carb. You tend to lose torque with too much air unless it's rammed down the engine's throat with forced induction.

    IMRC's aren't a big deal either way. If Ford was telling the truth with their ratings then it only made 5 ft/lbs and 3 hp of difference anyway.

    So what's the deal with the SHO's?
     
  10. 03f1504x4

    03f1504x4 New Member

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    If a carb is too big....it will have problems getting air/fuel right...not necessarily make you lose torque because of it. Sho's has the best looking intake manifold on the market..and it obvious how it works, just by looking at it.
     
  11. KTBug

    KTBug - Kris -

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    Well, by "losing torque" I was mainly referring to losing throttle response which would roughly be the same thing.
     
  12. 03f1504x4

    03f1504x4 New Member

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    "Certainly, with modified or competition machines, a larger carb is often necessary to compensate for an increase in the engine’s appetite for air. But bigger is not always better... Of course, too small a carburetor will cause a restriction to the intake of air into the engine. On the flip-side though, too large carb has the detriment of decreasing the sensitivity of the venturi (the part of the carb that creates a vacuum to draw fuel up from the main jet). Imagine a venturi the diameter of a 5-gallon pail- there would be virtually no vacuum created to draw up fuel. To compensate, you’d need a main jet the size of a soda can to get the same fuel that a properly sized carb would provide. The upshot is that the ability of the carb to react to changes in airflow would be greatly desensitized. Additionally, with such a slow airflow through the carb throat, atomization of the fuel into the airstream would be difficult at best and the fuel mixture would be inconsistent at best."

    from
    http://www.off-road.com/atv/kidskorner/carburetor2.html

    I think you are in 2 different trains of thought here.
     
  13. KTBug

    KTBug - Kris -

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    I'm well aware of what you quoted. I've run carb'd V8 Mustangs for 20+ years. My example may not have been totally correct. An oversized carb will definitely make you run lean. The lean condition, or starvation for fuel, will cause a "dead spot" off idle. The engine is not realizing it's full potential because of the lack of fuel. This lack of fuel will reduce your available torque.

    Obviously this is why chips and tuners are so popular.
     
  14. 03f1504x4

    03f1504x4 New Member

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    My point is that they are completely unrelated occurences. think of it more like...a dual plane carb's intake and a single plane carb intake. The performer rpm, makes a good amount more tq because of the design..down low at least..while say the victor jr makes it tq up higher. I think you already know this stuff...
     
  15. 6gofast

    6gofast New Member

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    As far as IMRCs go, I thing we need to consider the torque and power curves in their entirety. The peak torque number may only be 5 ftlbs above the cars w/o the IMRCs, but the difference may be significantly higher at lower RPM. We'd have to see the dyno graphs to make an acurate comparison.
     
  16. KTBug

    KTBug - Kris -

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    Just so no one panics, this is purely my opinion! :D

    I would assume that since our torque curves are flatter than Kansas that the 5 ft/lbs with IMRCs would be the same at nearly every RPM before the 3500 opening point.