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Location:
Newcastle
Registered:
August 2003
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4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 03:02
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Just curious of opinions.
Say a 3s compared to a 1g, or is there a better comparison?
What I am most intersted in is how they perform against each other in acceleration...
When people get cars dyno'd etc, is there a graph that maps acceleration? What is it called? May sound silly but I damn don't know!!!! All I know/hear about is the kw and nm reading outputs...
Anyone have printout for the listed engines?
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Location:
Brisbane
Registered:
July 2002
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 05:31
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| no_tofu_speed wrote on Sun, 26 December 2004 14:02 |
Just curious of opinions.
Say a 3s compared to a 1g, or is there a better comparison?
What I am most intersted in is how they perform against each other in acceleration...
When people get cars dyno'd etc, is there a graph that maps acceleration? What is it called? May sound silly but I damn don't know!!!! All I know/hear about is the kw and nm reading outputs...
Anyone have printout for the listed engines?
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id say this would be a bit hard to compare.
cause other than the same capacity they have nothing in common
1g has 2 small turbo's so that would lead you to assume it spools onto boost quicker, more cylinders so would assume produce more torque. not sure about overall power.
when comparing there are a few things i can think of to consider.
age of the engine(can find a newer less k's 3s gte)
packaging/weight(3s should be lighter by a decent ammount)
when looking at total power output, it depends what mods you plan as to which would be the better engine
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Location:
Melbourne
Registered:
March 2003
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 06:17
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just how exactly does more cylinders produce more torque when both engines are of the same displacement?
This is a common misconeception associated with engines. More cylinders does not mean more torque, it means a smoother power delivery.
The only reason i can think for more cylinders being able to produce more power would be because the stroke would be shorter, thus being able to rev higher and produce more power because power = torque x rpm.
But if the rev limitations are the same i can see now way that more cylinders would produce more power.
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Location:
Brisbane
Registered:
July 2002
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 06:22
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i actually have no idea why i said that.. lol
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Location:
Sydney, Australia
Registered:
May 2004
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On Probation
Location:
Hobart
Registered:
December 2004
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 06:54
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ARGHAGHARGHGAR u said the SR20, RB20 word, NAUGHTY BAD BAD BAD
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Registered:
September 2004
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 06:59
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^^^^^^ and he called an rb20 a 4 cyclinder 
very very naughty 
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On Probation
Location:
Hobart
Registered:
December 2004
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 07:01
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BIG Guy u also use the RB20 word... U r also very NAUGHTY AND BAD
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Location:
Brisbane
Registered:
July 2002
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 07:45
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| TRD_Supra wrote on Sun, 26 December 2004 18:01 |
BIG Guy u also use the RB20 word... U r also very NAUGHTY AND BAD
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bad naughty bad bad *raves on* ..... etc
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Location:
Brisbane
Registered:
February 2003
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 08:07
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back to the topic...
6cyl = 3 combustion events per crank rotation
4cyl = 2 combustion events per crank rotation
smoothness has to be a factor in that somewhere?
6 cyl tend to produce torque/power from an earlier point in the rev range, but unless both engine have similar head/valve/intake/exhaust design - you'll not get a useful comparison
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Location:
London
Registered:
July 2004
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 09:27
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A 6 cyl 2 litre can be made to rev higher than a 4 due to less piston/valvetrain inertia.
Power in BHP = Torque in lbft x revs/5250.
More revs = more powah
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Location:
Brisbane
Registered:
May 2002
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 09:27
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With more cylinders but the same capacity you can have a much shorter stroke  hello revie engine 
Also straight 6 cylinders are better balanced (they are naturally balanced), straight 4's on the other hand require a balance bar. This is the reason that BMW', mercs and what not are big fans of straight 6's 
Cheers
Wilbo
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Location:
Newcastle
Registered:
August 2003
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 09:50
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More cylinders = more revvy?
Hmmmm a V block with 8 cylinders isnt very revvy, and some 4age variants love to rev.......
Confused....
Hmm can anyone answer my Q on acceleration please, and how to measure.
And 1g and 3s were just base examples I know u have the twin turbo or supercharger for the 1g and the 3s were just NA or single CT26 or that other one on the newer ones lol
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Registered:
October 2003
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 10:12
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the thing to look for when you want to know how revvy an engine is the bore to stroke ratio, having a higer bore and less stroke leads to a oversquare engine which revs much more easily. as for v8 engines the usual strokes are still big as heck due to the large displacements they had. if the same despacement would be placed in a v12 same piston bore less stroke it would rev better. im not quite sure but i think you can produce more torque with a longer stroke and mroe hp with a larger bore, so a balance must be met when making an engine
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Location:
townsville NQLD
Registered:
February 2004
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 11:22
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most diesel engines that are designed to produce torque, ie generators, have a really long stroke and just choonkachoonkachoonka at really low rpm's all day long
but on the hand a yamaha WR426 have a huge diameter piston and a really short stroke and revo out to infinite  and have lots of power
thats what im led to belive anyway, correct me if im rong
brett
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Location:
London
Registered:
July 2004
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 11:26
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| no_tofu_speed wrote on Sun, 26 December 2004 20:50 |
More cylinders = more revvy?
Hmmmm a V block with 8 cylinders isnt very revvy, and some 4age variants love to rev.......
Confused....
Hmm can anyone answer my Q on acceleration please, and how to measure.
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Ok, you're being very obtuse here. I presume you're refering to big Holden/Ford V8s. These engines have capacities in excess of 5 litres (big and heavy pistons,valves,etc), and the POS in the Holden uses pushrods. These motors are therefore not inclined to rev.
Catheram have just produced a prototype 2 litre V8, made using Yamaha motorbike heads. It makes 340bhp at 10,250 rpm and 190lb ft from 7000 - 7800 rpm. It can rev to 15,000 rpm but they decided that 340bbhp was enough.
Now, this is a lot of power (170 bhp per litre, compared to a 3sge's 70 bhp per litre), but it's produced at very high revs. You couldn't simply put this V8 into a car the size of a celica and expect it to be practical - you'd have to rev it's tits off to get anywhere.
Catheram can get away with it 'cos their car is very light and doesn't require a lot of bottom end torque to get it moving.
The 3sge doesn't produce the same amount of power, but it makes a lot more torque where it counts for lugging around a 1000+ kg car.
What a rant. Am I way off topic? Too much beer.
P.S.
Can you clarify acceleration q?
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I Supported Toymods
Location:
south Melbourne/KL
Registered:
June 2004
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 11:55
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back to the 1st question, ill say that I4 is better than I6.
ppl have been playin with rb20 and sr20 for long long time. in most cases the sr20s r faster.
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Location:
Newcastle
Registered:
August 2003
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 12:08
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Ahhh, lots of input.
Clarifying the acceleration question.
One question was, is there a dyno graph of some sort that records this (the following question) if so what is it called.
........ Just after passage I typed of rambing (and erased) and thinking. The acceleration I was thinking of as an engine in a car, is more reliant on gear changes transmision ratio etc.
All in all, ignoring the small weight difference, and forced induction type... Was thinkin on which had quicker acceleration, as in from zero and climbing.... a straight 4 or 6.
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Location:
townsville NQLD
Registered:
February 2004
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Location:
Newcastle
Registered:
August 2003
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 13:58
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Yea I meant in my first post, when people tlak about a cars stats from dyno testing, the output in form of kw and torque in nm is usually given but not its acelerating ability.
Anyways bleh forget all my ramblings........
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Location:
Melbourne
Registered:
March 2003
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 15:08
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The KW graph or HP graph shows you where the car makes power correct?
newtons laws, force = mass x acceleration
so basicly where the car makes the most power is where it will accelerate the greatest
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Location:
Melbourne
Registered:
November 2003
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 17:34
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When you talk about a car having good torque, what you really mean is it has good low down power, as torque only rotates the crankshaft and power is what moves your car. A road car needs low down power to make it useable. I mean where do most people spend all their time? Up to about 3000rpm? That's why VTEC, VVT-i and other variable timing/advance/lift methods are popular. You can have a car tuned for low RPM, and high RPM.
If you got a 2000cc 4 cyl engine, then get another one and attached 2 extra cylinders then reduced the stroke to 2000ccs again, the engines should produce the same power. The 6 would be smoother, but the 4 would have better power to weight as it's lighter (And thusly giving a better front/rear weight balance for your car). If you then however, re-adjusted the redline on the 6 cylinder, you should find it can rev out a little higher now, and thusly will make more power, and so you should re-design the head and crankshaft for this, thusly making the two engines totally different again. All things being equal, the 6 cylinder should make more power, similar torque, and rev higher, while the 4s advantage will be weight.
Look at engines like the Ferrari 3.6 liter V8 that makes it's max power of 294kw at a heady 8500 rpm. It achieves this by having a bore of 85mm and stroke of 79mm, not to mention a whole host of technology such as variable valve timing and strong internals to take the high RPM. To compare, a SR20 has a bore x stroke of 86 x 86, as does the 2JZ and 3S, and a 4A-GE has 81 x 77.
Anyway, that's a pretty high RPM to be having your power band, but it still has good drivability, as it's max torque is 373nm at 4750rpm which is equal to 185kw at 4750rpm. All that pushes only 1350kg of car. Once again, to compare a R33 Skyline GTS-T has 183kw and weighs in at 1360kg. Similar power to weight figures, however the Ferrari makes it at max torque, then goes on to make a shit load more power.
A dyno shows you power figures of the engine, not how well the whole car performs. There is a test that can be done to show acceleration. Go to the track and whip out some Quarter Mile times. That's a good test of acceleration.
End rant.
Edited: Damned Word and it's not using standard apostrophe characters.
[Updated on: Sun, 26 December 2004 17:36]
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Location:
Brisbane / Gold Coast
Registered:
May 2002
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 18:13
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As probably mentioned above, if the heads are much the same and everything - apart from the number of cylinders - is the same, then the engines will make very much the same power.
However, this isn't likely in the real world as the six will likely have smaller bores and so smaller valves, etc.
There's generally a benefit in having a bigger bore/shorter stroke, so that may tend to favour the four.
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Location:
sunny coast, qld
Registered:
October 2002
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 21:55
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and the test you speak of that tests acceleration is called the quarter mile
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Location:
Sydney, Australia
Registered:
May 2004
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Re: 4cyl Vs 6 cyl (same displacement)
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Sun, 26 December 2004 22:04
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From HSC Calculus, I recall that Accelleration is measured by
(d^2)x/(dt)^2
so just punch that into ure calculator while ure driving
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Registered:
September 2004
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Re: 4cyl Vs 6 cyl (same displacement)
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Mon, 27 December 2004 13:44
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hmm...i get so confused wit this stuff!!!!!
is it power or torque u neeed to "win" drags (not in a drag car terms but as in street car
wots the go??
sorry if it a bit off topic
cheers
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Location:
Melbourne
Registered:
November 2003
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Re: 4cyl Vs 6 cyl (same displacement)
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Tue, 28 December 2004 03:33
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| BIG guy wrote on Tue, 28 December 2004 00:44 |
hmm...i get so confused wit this stuff!!!!!
is it power or torque u neeed to "win" drags (not in a drag car terms but as in street car
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Both. Low torque (ie, lots of torque at low RPM) will give you a good launch, but once your into your power band, the car with the better power/weight will catch up. Depends how fast you wanna get to. A Honda Integra may not launch as well as a VN Commodore, but it should catch up by end of second gear (just guessing here, so don't jump down my throat if I'm wrong). Then it would blow passed by end of 3rd.
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Location:
Campbelltown
Registered:
November 2003
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Re: 4cyl Vs 6 cyl (same displacement)
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Tue, 28 December 2004 04:20
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low torque will not necessarily give you a good launch too much of it will see you having poor traction and not being able to launch the car at full throttle unless you have the desire to sit there wheelspinning that is. And if your racing, you would just bring teh revs up to the desired rpm in whatever car you are in and dump the clutch.
Also around the high end of third gear I'd tip the commodore to start actually catching the integra as its higher amount of torque makes it easier to overcome the effects of wind resistance etc.
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Location:
toowoomba qld
Registered:
March 2004
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