number of cylinders has nothing to do with the bore stroke ratio ...
I-4
I-6
V-6
V-8
Box 4
Box 6
Don't know
Enthusiast
number of cylinders has nothing to do with the bore stroke ratio ...
Enthusiast
no not directly but I was looking at the actual width and length of potential bore and stroke values to achieve 1:1 on a 4, 6 and 8 cylinder engine if they all must be 2L. The 4 cylinder engines need roughly 86mm bore and stroke. the 6 cylinder engines need roughly 75mm bore and stroke and the 8 cylinder engines need only 68mm for bore and stroke. From this you can see that 8 cylinder engines are too small and only increase internal weight, inertia, and friction. A 4 cylinder configuration is also not optimal becuase it is too unstable and has too high vibration losses. So the 6 cylinder configurations are the ones to choose. Next you have to choose whether you want the boxer 6 or inline 6 and this is answered quickly by noting that the boxer 6 has greater valvetrain losses (because you have 2 seperate heads) and the inline 6 stands out as the best. Of course if packaging is an issue go for a VR6.Originally Posted by KnifeEdge_2K1
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.
Novice
the V8 will run the smoothest except maybe the I6, and breathe easier than any other option given. Air pump. thats all a motor is.
~Couch
Enthusiast
v8's are inhenrently unballanced, just like I4's they need ballancer shafts
the I6 and V12 will run the smoothest along with any horizontally opposed engine
Enthusiast
Yes and you don't want the V12 because that has too much internal friction and the pistons are too small (if they all have to be 2L) and you don't want the flat engines because they weigh more and have higher mechanical losses through the valvetrain.
Inline 6 is the best in this case.
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.
Member
i6 produces most power for a given milage range, to have 8 little cylinders only increases surface area to loose heat.
v8 technically has more horse power per cubic inch but if you ask me i would go for i6 turbo.
Once fanboyism infects you it impares all your judgement.
It's like being drunk, you lack common sense and everyone laughs at you.
Member
nobody brought up yet that the more cylinders u have the more power strokes per revolution of the crank you are going to get, and we cant forget the cylinder(s) on their power stroke are the only ones making power (duh).
My rides:
1999 Mustang GT
1974 Ford Country Squire (for sale!)
1991 Jeep Cherokee
1970 Shelby GT500
Enthusiast
But cross plane V8s effectively get the balance shaft for free. The ideal cross plane V8 balance shaft should spin at the same speed and direction as the crankshaft. So add some weights to the crank and you have an inherently balanced system. Combine that with what Juggs said about more pots being more power pulses per rev and a V8 can be very smooth and theoretically smoother than an I6.
As for the general question answered in VERY general terms:
More cylinders allow for more power for a given displacement. Generally smaller cylinders can rev higher. Higher revs bring more power. So if peak power is my goal I will generally want more cylinders. This was the logic that lead to the H16 1.5L BRM racing motor.
More cylinders generally will hurt fuel economy. Basically you have more parts that drag over each other. If we assume the drag of a piston moving in a cylinder is proportional to the diameter of the piston (ie each inch of piston ring causes the same drag force regardless of the piston size) then 12 small pistons end up having more drag than 4 large ones. This means the motor's parasitic drag will be lower thus it's efficiency will be higher.
Note that the above generalizations look only at number of cylinders. It says nothing about layout. Layout is more about packaging and to some degree smoothness. Consider that almost all 4 cylinder motors are I4s. Yes, there have been V4s in cars (and in commonly in bikes) and Subaru uses boxer 4s but almost all 4s are I4s because that configuration packages well.
6 cylinder motors are mostly V6s again for packaging reasons. A V6 is significantly shorter than an I6 yet not as wide as an H6. H6 motors can also make service more difficult. However I6s aren't so long as to make them impractical for common use. So in the 6 cylinder engine range we actually have several common configurations used by more than one manufacture. This is something we don't see in other cylinder counts.
Eight and twelve cylinder engines are basically all V configurations these days. It's been a long time since any manufacture produced a straight 8. Ferrari has produced some H12s but they are effectively 180 degree V12s. They are not boxer engines.
In general after selecting the number of cylinders the layout of the motor is largely set.
Engine displacement is basically larger yields more power. Yes, that is a generalization. However, it is not always practical to just go larger. In many countries tax laws create a disincentive to creating larger displacement motors. Also to some degree the exterior size of a motor is driven by it's displacement. In that sense more displacement yields a larger motor. HOWEVER, changes to the fundamental engine architecture can change that. So while a 2.5L Ford Duratec DOHC V6 is smaller than a 3L Duratec (the 2.5L motor has slightly shorter cylinders and a lower deck height) the difference is small. Also changing the valve train can make a significant difference in engine size. As a rule pushrod motors are significantly more compact than OHC motors. This is because the pushrod heads are lower in profile.
Again all of the above information is based on generalizations. Like any generalization there will be cases where it doesn't hold true. Deal with it.
Rookie
it's depend.the more cylinder the more power you get ,and the higher the engine revs.i would say the V8.it will be oversquare engine and because of that it can rev higher than otheres ,and when you can rev higher you will make more power.it will have bigger valves and pistons as well.
Last edited by mehrshadvr4; 09-17-2006 at 02:09 PM.
Novice
Production in-line sixes,
Have proven to not only be seriously fuel efficient, but also make higher torque per litre and hence a higher B.M.E.P. than any other configuration.
They also sound good too.
Novice
to put it simple the V8 has the most power and the 4 has the best fuel economy
Enthusiast
That is an overly generalised statement, and no it is easyier to get more power from a 12 than and 8. the secand half is ussually true, but not always the case. There is no simple answer.
Enthusiast
Assuming it has more CI. Theres no replacement for displacement.
UCP biggest mustang lover
Supporting Member
a turbo....
"I find the whole business of religion profoundly interesting, but it does mystify me that otherwise intelligent people take it seriously." Douglas Adams
Enthusiast
So your saying a 1.8 litre at 20lbs of boost will make more then a 6 Litre LS2 at 20lbs? A engine will still make more horsepower with more ci no matter if its n/a or FI.
UCP biggest mustang lover
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