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Inline six. Torque monster? How come?

Discussion in 'The Hokey Ass Message Board' started by BeatnikPirate, May 22, 2010.

  1. BeatnikPirate
    Joined: May 21, 2006
    Posts: 1,384

    BeatnikPirate
    Member
    from Media, Pa.

    Last evening at a cruise-in a discussion came up about inline six cylinder engines (like the Chevy 292 and Ford 300) having a reputation for being "torque monsters". It was also noted that inline sixes were often the engine of choice for big trucks because of their torque characteristics.
    So here's my question: is the higher torque attributed to inline sixes due to the fact that their generally vertical configuration allowes for a longer stroke? Or is there some other factor inherent in the design (such as degrees of crankshaft rotation between cylinder firing, breathing characteristics, or something else that encourages higher torque?
    It's been said that Henry Ford hated six cylinder engines. Anybody know if there was a rational (i.e. engineering) reason for this? Personally I just think they're cool.
    Anyway, all things being equal, does the number of cylinders and the engine configuration ,in itself, have a significant effect on engine torque?
    Thanks for sheding some light on this.
     
  2. madgrinder
    Joined: Feb 5, 2005
    Posts: 324

    madgrinder
    Member

    Torque is directly proportional to rotating mass... the long crank has more rotating mass.
     
  3. The Hitch Hiker
    Joined: Apr 12, 2010
    Posts: 72

    The Hitch Hiker
    Member

    Whilst I am no expert on the chevy I6's I believe a part of it may be due to the Stroke ratio. For example the 225 slant six is massivley undersquare and gives diesel like performance with power low down in the Rev band. I would imagine the I6's have a similar design feature to 'adapt' gassers to drive more like a derv given that they where used in alot of truck applications.

    Imagine undersquare engines as having more leverage on the crank, a bit like a breaker bar on a stuck nut, there is more torque at the cost of less speed undoing the nut compared to a over square engine with little torque and high speed at undoing the nut with a small ratchet. A rough illustration to the principle.... Not perfect.

    http://en.wikipedia.org/wiki/Stroke_ratio


    Also, I'd recommend picking up a copy of 'Performance tuning in theory and practice' by Graham Bell.
     
  4. R Pope
    Joined: Jan 23, 2006
    Posts: 2,974

    R Pope
    Member

    Guys call 'em torque monsters to hide the fact that they got no horsepower! Haha!
    A stroker engine makes more torque by having the expansion of the combustion gases acting on the crankshaft for a longer period of time, due to the longer moment arm of the crank. The same thing limits horsepower at higher RPM. The piston speed actually gets ahead of the expansion rate, especially halfway down the firing stroke, and increasingly at higher revs.
    They also come apart sooner at revs! Haha again!
     
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  5. Heo
    Joined: Jan 8, 2010
    Posts: 530

    Heo
    Member

    monster.....naaaa but got torquey caracteristics
    at low rpm due to the long stroke. Rotating mass
    have nothing to do with torque. Only stored energi
    when you let up the clutch and big rotating mass
    give slower trottle respons
     
  6. gas pumper
    Joined: Aug 13, 2007
    Posts: 2,786

    gas pumper
    Member

    it's true. more torque for the same configuration, but how can you compare? apples to apples? everything the same?

    The big difference you will see if you can find a v and an inline with the same bore and stroke is that the con rod is a lot longer on the inline.

    And it don't take much increase on rod lenght to make a difference.

    I read that one of Henery's objection to the six was the crank lenght.
     
  7. Heo
    Joined: Jan 8, 2010
    Posts: 530

    Heo
    Member

    and if you compare numbers a 302 ford V8 got 310 lb ft
    a 300 i6 got 260lb ft?? so torque monster i just a rumor
    spread by those trying to cover up the lack of hp
    and a chevy 292 got 215 lb ft so the tq mosters are
    just bs
     
    Last edited: May 22, 2010
  8. Truckedup
    Joined: Jul 25, 2006
    Posts: 3,353

    Truckedup
    Member

    Yeah,the inline low speed torque,cause that's all they got is low speed,stock ones anyways.When modified an inline 6 can loose it's low speed torque and be lumpy like a modified V engine.
    I've driven a few later model 300 inline Ford PU's with fuel injection.They ran good,maybe like a 302 V-8 more or less.Torque monster? No more than any V-8.
     
  9. Road America
    Joined: Sep 23, 2009
    Posts: 76

    Road America
    Member

    Beatnik, you pretty much said it right in your question, it's easier to get a long stroke in an upright design. Torque is just leverage, a long stroke puts the "push" further from the center of the crank. Just like a long wrench or prybar compared to a short one.
    I think the main reason Henry didn't like 6's is because Chevy and Plymouth had them!
     
  10. Heo
    Joined: Jan 8, 2010
    Posts: 530

    Heo
    Member

    one reason some belive they have
    much torque is they have lower
    gears.Low first and low rearend gear
    I think its time to end this false rumor
     
  11. A guy I knew had a late seventies Ford 3/4 4x4 pickup with a 300ci six in it, He would take his family on vacation, load the 12ft camper on it then hook up his 21 ft boat. Add wife, kids and gear then he was on his way. That truck would cruise up the hills fully loaded with no problem, but it wasn't the fastest thing on the road.
     
  12. AnimalAin
    Joined: Jul 20, 2002
    Posts: 3,383

    AnimalAin
    Member

    In large part, it is about the tuning. Factory six cylinders are tuned for maximum efficiency in the range you usually drive. The fat part of the torque curve is right where you need it. The eight cylinder has a higher torque value, but it happens at a higher rpm, so the six seems to have more torque.
     
  13. gwhite
    Joined: Sep 1, 2007
    Posts: 2,286

    gwhite
    SUPER MODERATOR
    1. Period-correct Hot Rods of the 30's & 40's
    from TEXAS!
    Staff Member

    Just to add fuel to the fire;

    1950 Ford 239 V8 - 100 hp @ 3600 RPM, 181 ft-lbs @ 2000 RPM
    1950 Dodge 230 I6 - 103 hp @ 3600 RPM, 190 ft-lbs @ 1200 RPM
    1950 Plymouth 217.8 I6 - 97 HP @ 3600 RPM, 170 ft-lbs @ 1200 RPM

    Ford flathead V8 produced .418 hp and .757 ft-lbs for every 1 cubic inch
    Dodge 230 produced .448 hp and .826 ft-lbs for every 1 cubic inch
    Plymouth 217.8 produced .445 hp and .781 ft-lbs for every 1 cubic inch

    Bore x Stroke
    Ford 239 - 3.1875 x 3.75
    Dodge 230 - 3.25 x 4.625
    Plymouth 218 - 3.25 x 4.375

    1951 Hudson "Twin H-Power" 308 I6 - 160 hp @ 3800 RPM, 260 ft-lbs @ 1800 RPM
    1951 Olds 'Rocket' 303 V8 - 135 hp @ 3600 RPM, 253 ft-lbs @ 1800 RPM

    Hudson 308 produced .519 hp and .844 ft-lb per cubic inch
    Olds 303 produced .446 hp and .835 ft-lb per cubic inch

    Bore x Stroke
    Hudson 308 - 3.81 x 4.5
    Olds 303 - 3.75 x 3.4375

    Seems clear enough that in these cases the inline configuration produced more peak torque AND HP per cubic inch than the comparable V8. I believe the reason probably has more to do with the fact that, in each case, RPMs for the power ratings were fairly low (which we would expect for a stock street application), playing to the strength of the inline...remember, the inline compensates for a lack of additional cylinders with a significantly longer stroke - and we all recognize that a longer stroke usually produces power at a lower RPM. It would be interesting to compare average power across the entire RPM range...I have a suspicion the V8s would really begin to come alive in the 3000+ RPM range, where the undersquare inlines would begin to fall flat.
     
    Last edited: May 22, 2010
  14. Larry T
    Joined: Nov 24, 2004
    Posts: 5,729

    Larry T
    Member

    Really peak torque and horsepower don't really tell the whole story. It's the complete curve that kinda tells you how and where an engine is gonna work.
    I've never understood the torque vs HP deal since they are figured off of each other. Measure torque, throw in rpms, and you have horsepower figures.
    Larry T
     
  15. Chuck R
    Joined: Dec 23, 2001
    Posts: 1,335

    Chuck R
    Member

    The one constant is that at 5252 rpm torque and horsepower are always the same. Weird but true. Every torque vs hp curve chart has them cross at that spot. I noticed this when I was about 12 while reading hot Rod magazine, but none of my friends believed me. I had to research at the library to prove my point. I have included a link that may help explain it.
    chuck
    http://www.epi-eng.com/piston_engine_technology/power_and_torque.htm
     
  16. gwhite
    Joined: Sep 1, 2007
    Posts: 2,286

    gwhite
    SUPER MODERATOR
    1. Period-correct Hot Rods of the 30's & 40's
    from TEXAS!
    Staff Member

    I agree. Horsepower is the product of RPM and torque...the question "do inlines produce more torque than V engines" sets up a false dichotomy. At a given RPM an inline (typically undersquare) may or may not produce more or less torque than a V (typically oversquare) configuration. It depends on the bore-stroke ratio and thus the RPM range in question. In most cases, the inline will produce its torque at lower RPMs by virtue of a longer stroke. At higher RPMs I expect that the shorter stroke will produce more power and torque. Short strokes also produce less friction than long strokes, making them more efficient, especially as RPMs increase, so really it becomes a question of bore x stroke ratio rather than 'inline vs. V' as 'The Hitch Hiker' pointed out.

    I would expect a V6 with a 4" bore and 4" stroke to perform similarly to an I6 with a 4" bore and 4" stroke, all other things being equal...I doubt there is much difference in leverage between the force applied to a 'V' crankshaft and the force applied to an inline crankshaft (bore x stroke being the same), although inline 6's tend to be slightly more balanced than Vs, they typically have a heavier and weaker (torsionally) crank due to the added length.

    Gas Pumper's statement on con rod length also holds some water, as rod length has implications on dynamic compression...that's a discussion in/of itself!
     
    Last edited: May 22, 2010
  17. LIL.TIMMYUser Name
    Joined: Jan 30, 2009
    Posts: 743

    LIL.TIMMYUser Name
    Member

    be nice! Can't we all just get along?
     

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  18. RichFox
    Joined: Dec 3, 2006
    Posts: 6,618

    RichFox
    ALLIANCE MEMBER

    If you look at gwhite's compairason of the Ford V8 and Plymouth and Dodge torque you can see that the MoPars bracket the Ford. But at 800 rpm lower. Or at the speed where you will most notice it. Pulling away from a dead stop. Bottom end torque is very satisfing for normal driving. High end horsepower is very nice rolling past the 4 and headed toward the 5
     
  19. Hnstray
    Joined: Aug 23, 2009
    Posts: 5,616

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    Basically, I think it comes down to the illustrated fact that the inlines have their peak torque in the usuable rpm range as some else mentioned. It's especially noticable with stick shift vehicles.........the engine with greater low end torque keeps pulling under load and doesn't need a downshift...........whereas a V8, that may produce more torque, but at a significantly higher rpm, needs the downshift.....because......at that moment it ISN"T producing that torque.........it has to rev higher to get to it's peak torque range. There is no "bad guy" here...........just different characteristics that are more suitable for some purposes than others and vice versa.

    Ray
     
  20. Larry T
    Joined: Nov 24, 2004
    Posts: 5,729

    Larry T
    Member

    It's not weird, it's math.
    HP = torque X rpm / 5252
    So at 5252 rpms, everything cancels out and HP = torque.
    Larry T

    Whoops, I didn't click your link. I see that you know that. (G)
     
    Last edited: May 22, 2010

  21. So adding weight to any crankshaft increases torque ? Wow. :eek:

    Since HP is Torque x RPM, how much weight do I
    have to add to the crank on my Prius to get 500 hp ?
     
  22. bobscogin
    Joined: Feb 8, 2007
    Posts: 1,654

    bobscogin
    Member

    More correctly, the rotating assemby's kinetic energy is directly proportional to rotating mass. Cylinder configuration, such as inline, V, or opposed have no direct bearing on torque output. Torque is a function of combustion mean effective pressure applied to the area of the piston and acting through a lever arm known as crank rod journal offset. The dyno neither knows nor cares about the weight of rotating components when measuring torque as they don't figure into the calculations

    Bob
     
  23. Heo
    Joined: Jan 8, 2010
    Posts: 530

    Heo
    Member

    about 123.6347 lb acording to my calculations
    Ian
     
  24. nofin
    Joined: Jan 7, 2010
    Posts: 325

    nofin
    Member
    from australia

    A little OT but horsepower as a unit of measurement was only initially figured out by James Watt, one of the early steam engine guys, as a marketing tool to explain the power of his engines in a way the public could understand. As they say, torque wins races; horsepower sells cars.
     
  25. Chuck R
    Joined: Dec 23, 2001
    Posts: 1,335

    Chuck R
    Member

    Always made perfect sense to me, but some gearheads struggled with the concept. When presented to them they were always looking for some other way to explain why these two numbers crossed, Thats why I posted the link so everyone could read and see the formula.
     

  26. Excellent, thank you. [​IMG]
     
  27. bobscogin
    Joined: Feb 8, 2007
    Posts: 1,654

    bobscogin
    Member

    I've never understood why people say that. Torque is a measure of instantaneous force, and has no time component. To win a race requires the engine to do work at a specific rate measured in horsepower. I guess what they mean is that comparing engines of equal power, the one that's tuned to produce it's power down low, is more user friendly than a highly tuned engine with a narrow powerband. In the end, though, it's horsepower that wins races.

    Bob
     
  28. OldBuzzard
    Joined: Mar 8, 2008
    Posts: 777

    OldBuzzard
    Member
    from MA.

    Except in a drag race when the inline 6 gets off the line quicker than a v-8 still trying to wind up to where it makes some power. He who gets there first wins, not always the highest speed.
     
  29. bobscogin
    Joined: Feb 8, 2007
    Posts: 1,654

    bobscogin
    Member

    I guess that's why inline 6 cylinders are lot more popular than V8s in drag racing, eh? :D
     
  30. OldBuzzard
    Joined: Mar 8, 2008
    Posts: 777

    OldBuzzard
    Member
    from MA.

    I guess these days things are different. But, in the late '50's & early '60's there was a local guy that ran a 261 Chevy in a Fiat coupe. Usually won his class. When time for Eliminator came he could usually show everything up to, and sometimes including, C dragster the way through the lights at the end. No other 6's involved. In that same time frame the truck in my avatar had a GMC 270. I used to have fun at the stoplights. Maybe I'm not supposed to say that here.
     

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