Page 3 of 3 FirstFirst 123
Results 31 to 40 of 40

Thread: Naturally aspirated manifold positive pressure

  1. #31
    Join Date
    Sep 2006
    Location
    why would I tell you?
    Posts
    108
    The longer trumpet is for low end torque because it increases the velocity of the air before the valve. The shorter trumpet is for horsepower because it is the shortest possible path from atmo to the cylinder.

    Bikes are starting to use that technology IIRC. Most of what has been spoken of is stuff i'm familiar with. I haven't taken many classes on mechanical engineering but I read a lot.

    I just thought that there might be something a bit more exotic to this that i wasn't thinking of.

  2. #32
    Join Date
    Oct 2006
    Posts
    10,227
    What causes the peaks and troughs mentioned earlier with turbos?

  3. #33
    Join Date
    Nov 2005
    Location
    Norway
    Posts
    260
    Quote Originally Posted by CapnBoost View Post
    The longer trumpet is for low end torque because it increases the velocity of the air before the valve. The shorter trumpet is for horsepower because it is the shortest possible path from atmo to the cylinder.

    Bikes are starting to use that technology IIRC. Most of what has been spoken of is stuff i'm familiar with. I haven't taken many classes on mechanical engineering but I read a lot.

    I just thought that there might be something a bit more exotic to this that i wasn't thinking of.
    Yes. If you look at the Yamaha R6 you see the moveable intake duct
    Nulla tenaci invia est via

  4. #34
    Join Date
    Nov 2005
    Location
    Norway
    Posts
    260
    And the ramming occurs at higher speed.
    Lets say you have a 2L straight four with an inlet duct of 40mm diameter in the plenum. The velocity in the duct is then 28 m/s at 7000 rpm. Using Bernoulli at 250 km/h=70 m/s gives an increase in pressure in the plenum of 0.5*rho*(70-28)^2=1kPa.
    -> An increase in pressure of 1%. And ~an increase of 1% VE. Not to much
    Nulla tenaci invia est via

  5. #35
    Join Date
    Dec 2005
    Posts
    1,200
    ...Contrary to popular belief I am not banned ...

    Anyways...

    Quote Originally Posted by CapnBoost
    The longer trumpet is for low end torque because it increases the velocity of the air before the valve. The shorter trumpet is for horsepower because it is the shortest possible path from atmo to the cylinder.
    The reason for having longer and shorter intake paths (or variable length manifolds) is to time the returning pressure pulse so that the intake valves open when the pressure wave is as close to the valves as possible.

    So you need a longer intake trumpet at low RPM and a shorter trumpet at higher RPM.

    The reason being that the speed of sound (thats how fast the pressure waves travel) is relatively constant, and the main variable is engine RPM. At low RPM there is a long time between when the intake valves close and when they need to open up again, and because the pressure waves travel at a relatively constant speed the way you time them is by controling how far they travel. The longer the intake trumpet the longer it is going to take the pressure pulse to get to the open end, reflect, and get back to the valves.

    Quote Originally Posted by Kitdy
    What causes the peaks and troughs mentioned earlier with turbos?
    The peaks and troughs are caused by the timing of the pressure pulses in the intake manifold. This still happens even in turbocharged or supercharged engines.
    Power, whether measured as HP, PS, or KW is what accelerates cars and gets it up to top speed. Power also determines how far you take a wall when you hit it
    Engine torque is an illusion.

  6. #36
    Join Date
    Dec 2008
    Posts
    5
    I have a racing carburetor builder coming to speak to my students on Wednesday of next week, I'll show him the various posts and try to get a response. It may not be the last word on the topic, but it should be interesting.

  7. #37
    Join Date
    Nov 2005
    Location
    Norway
    Posts
    260
    Quote Originally Posted by LeonOfTheDead View Post
    believe me that magazine is rubbish.
    btw, music...I don't listen to Italian music either, too girly and it all sounds the same. for as regards movies, I could recommend "Io non ho paura" and "Mediterraneo" by Gabriele Salvatores, or the recent "Gomorra" by Matteo Garrone. The problem is that movies (and music too) contain a lot of "slang", that's to say "dialetti", different languages developed behind Italian in each part of Italy. and when I say part, I mean very small area. the "dialetto" that is spoken at my place is slightly different in the near town, at 20 km...
    Just saw Gomorra. Beautiful movie. Very hard to understand the talking, but was able to follow because of subtitles. Picked up some phrases and expressions for tomorrows exam aswell
    Nulla tenaci invia est via

  8. #38
    Join Date
    Sep 2006
    Location
    why would I tell you?
    Posts
    108
    Quote Originally Posted by MrPete View Post
    I have a racing carburetor builder coming to speak to my students on Wednesday of next week, I'll show him the various posts and try to get a response. It may not be the last word on the topic, but it should be interesting.
    I appreciate it.

  9. #39
    Join Date
    Oct 2007
    Location
    Modena
    Posts
    9,826
    Quote Originally Posted by Knuto View Post
    Just saw Gomorra. Beautiful movie. Very hard to understand the talking, but was able to follow because of subtitles. Picked up some phrases and expressions for tomorrows exam aswell
    Nice to hear that, and good luck!
    KFL Racing Enterprises - Kicking your ass since 2008

    *cough* http://theitalianjunkyard.blogspot.com/ *cough*

  10. #40
    Join Date
    Feb 2008
    Location
    UK
    Posts
    75
    Damn, posted that bloody long winded response in the wrong thread by the looks of it. Trust me to reply to the dead thread from 2004... pish.

    Anyway, looks like most you guys know the score with this stuff anyway, so my response would have probably seemed fairly basic, even Hightower is on the mark for once!

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. increasing power of a naturally aspirated engine
    By KnifeEdge_2K1 in forum Technical forums
    Replies: 75
    Last Post: 02-24-2006, 12:31 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •