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Variable length intake manifold

Discussion in '456/550/575' started by stephens, Apr 28, 2006.

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  1. stephens

    stephens F1 Rookie
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    #1 stephens, Apr 28, 2006
    The 550 has a variable length intake manifold which is vaccum controlled via a mechanical actuator triggered by the ECU. This is designed to optimise mid range torque without compromising top end horsepower.

    A quick explanation
    The variable length intake starts on the short setting up to 30% throttle up to 3000rpm, then it is on the short setting on 15% throttle or less upto 5640rpm, where it reverts to the short setting regardless of throttle position.
    There are only two position short or long, nothing in between.

    All of the dyno graphs I have seen of 550's have a hump in the graph just before 6000rpm as the power starts falling off before the intake changes to the short setting. This can be felt from the drivrs seat as if the car is getting a second wind asyou hit around 6Krpm.

    I did a dyno run yesterday, with the system connected and disconnected. Disconnected means that it is in the short mode permanently, which theoretically should adversely affect the midrange.
    WRONG. My car produced approx 15% more power at the wheels all the way through the midrange until approx 6500rpm where it was the same, as would be expected, with the system connected.

    The dyno operator said that the difference though the midrange was easily felt in the extra speed accelerating the rollers through the midrange, it was that noticable.
     
  2. luke9583

    luke9583 Formula 3

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    #2 luke9583, Apr 28, 2006
    Muy interesante.
     
  3. FFOUR

    FFOUR F1 Veteran

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    #3 FFOUR, Apr 29, 2006
    Interesting, I'd like to hear an explanation for this too.....where's FF?
     
  4. rmfurzeland

    rmfurzeland Formula Junior

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    #4 rmfurzeland, Apr 29, 2006
    Stephens,

    Thanks for sharing the dyno results,sorry can follow the quick explanation maybe there is a typo or the word long is missing?

    How did you disable the system? Are you now running with it disabled and how does it drive? Seems like an easy way to gain 15%. maybe I could instal an on/off dashboard switch "turbodrive".

    In my Automobilia book it says longer flow route "is to allow flow to resound, improving combustion chamber filling and engine efficiency". Doesnt quite make sense either, implies some sort of mixing effect or flow entrainment maybe? Would be interesting to compare the mpg but 550 drivers dont seem too concerned about that.

    Has anyway worked out whether the new 599 has abandoned this variable intake system?

    Ron
     
  5. stephens

    stephens F1 Rookie
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    #5 stephens, Apr 29, 2006
    I disabled the system by disconnecting the vacuum hose from the actuator that sits at the back of the intake manifold next to the firewall. This doesn't increase peak power, which isn't affected, just midrange.
     
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  6. rmfurzeland

    rmfurzeland Formula Junior

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    #6 rmfurzeland, May 2, 2006
    Amazing that no one else has spotted or reacted to this interesting piece of info. Should I try this mod for the weekend and see how it goes? Presumably I dont need to hardwire the linkage to prevent it from moving?
    Ron
     
  7. stephens

    stephens F1 Rookie
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    #7 stephens, May 3, 2006
    No, it is spring loaded to the short position. disconnecting/blocking the vacuum line just stops the actuator from changing to the long position through the midrange.
     
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  8. goldyF355

    goldyF355 Formula 3

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    #8 goldyF355, May 3, 2006
    Would there be any adverse affects to this being a permanent set up?

    I mean more in terms of engine longevity than gas milage (which aint so hot to begin with..LOL)

    I wonder why Ferrari set up the intake manifold as variable length, if a constant short profile offered no downside and comparative huge upside. Maybe emission requirements? Does this comparatively strain the engine in any appreciable way?
    Could this be an affect that only your particular engine (which I assume has at least been "somewhat" modified...) could achieve?

    Not that I doubt your word, but it seems too good to be true,...could this be the "Holy Grail" of 550 lost HP??? "The Stephens code"?!? :p
     
  9. Rifledriver

    Rifledriver Three Time F1 World Champ

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    #9 Rifledriver, May 3, 2006
    Free HP and in the middle, right where you want it. What could be better?
     
  10. Rifledriver

    Rifledriver Three Time F1 World Champ

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    #10 Rifledriver, May 3, 2006

    Any time you are making more HP you are putting more stress on the motor. But in this case it is in the middle of the power band so the total stress at that point is considerably lower than at max power and the 550's have shown they are up to that challenge. They have been very robust motors. Even so any time you increase stress you will be causing greater, more rapid wear but in this case I would be surprised if it was even quantifiable.
     
  11. stephens

    stephens F1 Rookie
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    #11 stephens, May 3, 2006
    Just looking at the shape of the dyno curve, I knew there was a benefit in reprogramming the variable intake, I just didn't realise it just wasn't needed at all.
    The fact that the 550 shares it's airboxes with the 380hp 355 and that on the 575 Ferrari increased the size of the whole intake system significantly, then on the SA with 530hp, the only modification was that the intake was further "optimised" over the 575, has always had me wondering how restricitive the whole intake was.
    I am doing some dyno runs tomorrow, with the MAF replaced by spun aluminium tubes (the car will automatically use the TPS/RPM etc to calculate fueling instead according to the manual), as they seem like the next biggest rstriction on the intake side. After that I will be trying larger throttle bodies.
     
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  12. rmfurzeland

    rmfurzeland Formula Junior

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    #12 rmfurzeland, May 3, 2006
    Keep us posted on the dyno results, scanned graphs of the midrange would be greatly appreciated,
    "maximize the area under the curve"
    Thanks,
    Ron
     
  13. goldyF355

    goldyF355 Formula 3

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    #13 goldyF355, May 3, 2006
    Please keep us appraised of your progress in this area...sounds very, very promising!

    Imagine,..... toss in some high-flow airfilters, install an X-pipe variant , disconect the vacuum line on the intake mainfold .....and voila....gain yourself close to 100 hp on a standard 550!

    Amazing!! Makes the 550 sound like the Toyota Supra of the Ferrari line...
     
  14. stephens

    stephens F1 Rookie
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    #14 stephens, May 3, 2006
    Just to clarify, disconnecting the vacuum line gains NO peak power at all, just midrange. My results are based on a car with airfilters and X pipe. It MAY not be the same on a completely standard car.
    My goal is an additional 100hp over standard. Dyno results from tomorrow will clarify how realistic this is, but requires more than the filters and X pipe.
     
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  15. gougoul

    gougoul Formula 3

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    #15 gougoul, May 4, 2006
    It is very interesting indeed ! Can't wait to read more on that !
     
  16. stephens

    stephens F1 Rookie
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    #16 stephens, May 4, 2006
    Ron
    I didn't bother with a printout as the improvement was so obvious. It was a quick dyno run 1/2 hour in and out to test my theory, so I wasn't interested in what the actual numbers were.
     
  17. rmfurzeland

    rmfurzeland Formula Junior

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    #17 rmfurzeland, May 7, 2006
    Dear Stephens,
    Brainstorm idea, since we are now no longer using the upper central plenum, we could do the opposite and leave the butterflies open then apply compressed air from the upper plenum i.e. supercharge !
    Probably not allowed in your racing regulations.
    Just an idea.
    Regards,
    Ron
     
  18. bostonmini

    bostonmini Formula 3

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    #18 bostonmini, May 8, 2006

    stephens, any idea what you are up to power wise @ the moment??? have u considered a stroker kit etc, like on the 550 GTC (6.0 no?)...anyhow, this is very exciting to make the 550 compete with the 599, but better looking...
     
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  19. Harmonyautosport

    Harmonyautosport Formula Junior

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    #19 Harmonyautosport, May 8, 2006
    I wonder if the same is true on the 360 since its a similar setup.
     
  20. ferrarifixer

    ferrarifixer F1 Veteran
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    #20 ferrarifixer, May 9, 2006
    It should be remembered that stephens car has CDA airboxes, thus removing the massive restriction the 550 intake usually suffers from.

    Also the lack of back pressure from his car having no cats or centre silencer COULD be effecting the engine response to changes in the intake lengths..

    The only way to test for sure is to put a std car on the dyno, and pull the vacuum line off the actuator.

    For 360... well, Michelotto have run locked open intakes for ages, and only say to release them in the wet.

    I tried it in a dry test at Shanghai last week. The data and driver showed no gain, and the straights are quite long at Shanghai.
     
  21. stephens

    stephens F1 Rookie
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    #21 stephens, May 9, 2006
    Unfortunately it was B&M's dyno giving bodgy readings again. Did these comparisons and more (with printouts this time) at Dynomotive. Nice repeatable results, clearly show benefits of variable intake between 3500 and 5500rpm. As much as 25kw and an average of 15kw at the wheels, so ignore my original post.
     
  22. Harmonyautosport

    Harmonyautosport Formula Junior

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    #22 Harmonyautosport, May 9, 2006
    What do you mean by running them locked open? If you can please explain this more and how its done. Very interesting to see what teams are playing with.
     
  23. ferrarifixer

    ferrarifixer F1 Veteran
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    #23 ferrarifixer, May 9, 2006
    errr. it means they are opened, and then locked that way.....

    Put your finger down the gap between 2-3 or 6-7 intake runners, grab the linkage, pull it open, tie it open to the little bracket that holds the fuel pipe.

    Michelotto 360 engines are (mostly) like this.

    I tried it on 360C, can't say it made a difference.
     
  24. Harmonyautosport

    Harmonyautosport Formula Junior

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    #24 Harmonyautosport, May 9, 2006
    Thank you for explaing that. What other modifications do they do to the engine to gain power? Any links to write ups on this>?
     
  25. ferrarifixer

    ferrarifixer F1 Veteran
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    #25 ferrarifixer, May 9, 2006
    I prefer to be careful to a degree, as I'm a Michelotto agent, but I gave away a bit here....

    http://www.ferrarichat.com/forum/showthread.php?t=6088

    I have another source of go fast parts too.

    edit

    BTW, the first "speciale" engine I built (in fact the whole car) is for sale. The engine can be had separately, as the spare can be put back in easily. PM if interested.
     
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