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Old 05-22-2010, 06:14 AM   #1
BeatnikPirate
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Default Inline six. Torque monster? How come?

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.
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Old 05-22-2010, 06:34 AM   #2
madgrinder
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Default Re: Inline six. Torque monster? How come?

Torque is directly proportional to rotating mass... the long crank has more rotating mass.
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Old 05-22-2010, 06:34 AM   #3
The Hitch Hiker
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Default Re: Inline six. Torque monster? How come?

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.
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Old 05-22-2010, 07:35 AM   #4
R Pope
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Default Re: Inline six. Torque monster? How come?

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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Old 05-22-2010, 08:02 AM   #5
Heo
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Default Re: Inline six. Torque monster? How come?

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
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Old 05-22-2010, 08:21 AM   #6
gas pumper
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Default Re: Inline six. Torque monster? How come?

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.
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Old 05-22-2010, 08:33 AM   #7
Heo
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Default Re: Inline six. Torque monster? How come?

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 by Heo; 05-22-2010 at 08:39 AM.
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Old 05-22-2010, 08:40 AM   #8
Truckedup
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Default Re: Inline six. Torque monster? How come?

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.
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Old 05-22-2010, 08:51 AM   #9
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Default Re: Inline six. Torque monster? How come?

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!
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Old 05-22-2010, 08:56 AM   #10
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Default Re: Inline six. Torque monster? How come?

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
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Old 05-22-2010, 08:59 AM   #11
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Default Re: Inline six. Torque monster? How come?

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.
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Old 05-22-2010, 09:30 AM   #12
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Default Re: Inline six. Torque monster? How come?

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.
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Old 05-22-2010, 10:30 AM   #13
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Default Re: Inline six. Torque monster? How come?

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.
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Old 05-22-2010, 10:35 AM   #14
Larry T
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Default Re: Inline six. Torque monster? How come?

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.
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Old 05-22-2010, 11:15 AM   #15
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Default Re: Inline six. Torque monster? How come?

Quote:
Originally Posted by Larry T View Post
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
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...and_torque.htm
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Old 05-22-2010, 11:18 AM   #16
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Default Re: Inline six. Torque monster? How come?

Quote:
Originally Posted by Larry T View Post
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
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!
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Old 05-22-2010, 12:54 PM   #17
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Default Re: Inline six. Torque monster? How come?

Quote:
Originally Posted by r pope View Post
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!
be nice! Can't we all just get along?
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Old 05-22-2010, 01:30 PM   #18
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Default Re: Inline six. Torque monster? How come?

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
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Old 05-22-2010, 01:34 PM   #19
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Default Re: Inline six. Torque monster? How come?

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.

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Old 05-22-2010, 01:45 PM   #20
Larry T
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Default Re: Inline six. Torque monster? How come?

Quote:
Originally Posted by Chuck R View Post
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...and_torque.htm
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)
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Last edited by Larry T; 05-22-2010 at 01:54 PM.
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