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Offline dflowers0122

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CCs and HP
on: April 23, 2021, 02:12:51 PM
Hello there,

I have a few newb questions. I am the one who just got an endorsement, had no prior riding experience, and went out and bought a Z9 all within a week and a half  :001:

(1) Can someone define for me CC's and HP in PRACTICAL terms. I'm looking for something more than the text book definition (i.e. something more than 550lbs-1ft/engine's work capacity or engine's size/cylinder volume). Because, Lord knows, those aren't helpful for a newbie like me. Get very practical, please.

(2) How does CCs and HP relates? Is it as simple as the more CC's the more HP? I don't want to complicate things.


If you are not going to answer the questions at some point, please reserve your comments for another post. In my last post I had guys making comments just to see themselves type. Heh...just to see themselves type...that's a good one!

Offline KawaJagz

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Re: CCs and HP
Reply #1 on: April 23, 2021, 06:01:21 PM
CC is the Cubic Capacity of the engine in centimetres cubed (metric) arrived at by multiplying the diameter of the bore with the length of the stroke, then multiplying by 4 (the number of cylinders)

All other things being equal, the more CC you have the more power you will get.
However not everything is normally equal hence why engines of the same capacity from different manufacturers produce different amounts of power.

There are so many variables, even between the same manufacturer, such as valve lift, bore and stroke differences, rev limit, number of cylinders etc. that mean there is not a simple answer to this.
I used to be indecisive, but now I'm not so sure!

Offline Its about speed

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Re: CCs and HP
Reply #2 on: April 23, 2021, 06:40:30 PM
More cc's can produce more hp IF you tune for that.  More hp doesn't require more cc's.

Our modern motorcycles, like the z900, are tuned-up, but there's quite a bit left in the OEM setup.

I like the z900 for sport canyon carving in north California.  Brakes are super, throttle can scare you, throw down your inside shoulder and let the bike turn, it's so fluid and controllable.

Offline mininsx

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Re: CCs and HP
Reply #3 on: April 23, 2021, 09:00:37 PM
There is way more to displacement/horsepower than just more displacement=more horsepower. Engine design (V-twin, inline twin, V-four, inline four) just to name a few, and the type of valve train, and camshaft lift and duration, all affect what kind of horsepower you'll get. For instance, large displacement Harley engines make very little horsepower for the size of the engine, but loads of torque. I used to have a 900cc Vulcan cruiser (V-twin) that made around 55 hp, and a typical Z900 makes around 125. Same size but huge difference in hp.

Offline DFW_Z

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Re: CCs and HP
Reply #4 on: April 24, 2021, 05:03:25 AM
@mininsx draws a great example. I have a 2020 Z900 and an Indian scout, which is 1,133 CC motor making about 100 HP. Two different beasts. I will let my older children ride the scout but wont let them anywhere near the Z. If you are not sure and controlled with your throttle hand, it will try to kill you.
And what do we say to the God of Death? Oh, you again?

2020 Candy Plasma Blue/Metallic Matte Fusion Silver z900; 2019 Indian Scout Icon; 2019 Ninja 400; 2015 Vulcan 650 S

Offline zed9

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Re: CCs and HP
Reply #5 on: April 24, 2021, 01:54:12 PM
Dflowers.. It all depends on its state of tune. The z900 has a mild tune, not the most HP/CC but it's reliability/longevity will be higher than bikes where they squeeze every ounce of horsepower out of the engine.

To get more power out of an engine you increase its compression ratio to get the biggest bang out of its air/fuel charge, install more aggressive cams which will open the valves more and hold them open longer, and smooth out the intake/exhaust runners to get the mixture there quicker and directly.
To take advantage of the cams you now need larger throttle bodies which will flow more mixture and you need a less restrictive air filter to let more air in and you need a less restrictive exhaust system to let it all out.
And to handle all this power the internal parts are stronger so they can spin up to higher RPM.
These high performance bikes get less mpg because they're using more to make the extra power. No freebies there.
And all of this, for most riders, is just to go as fast on the road as you with your z900 and it's paltry 115 hp.

I've glossed over the facts and nothing is in order. What I said is just a generalization. If you're really interested, pick up a copy of Kevin Cameron's book "Sportbike Performance Handbook". It's a little dated but the basics are all there. Kevin can spend several pages just describing the flame front initiated by one spark of one power stroke. A very interesting read.

Offline hazy

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Re: CCs and HP
Reply #6 on: April 28, 2021, 10:33:05 PM
CC's = cubic centimeters - the displacement of your motor.

Displacement equals the size of the cylinders, measured in bore (diameter of the cylinder) and stroke (length of piston travel)

Horsepower can have a correlation with engine size, but often does not due to the designs in motors.  Horsepower is calculated as a derivative of Torque, which is a measurement of "work"

the reason HP can't be determined solely by engine size is due to many things, but often boils down to the design of the engine itself, as well as the design of the top end components (heads/cams/etc)

VERY generally speaking here, but given the same cylinder size, the a longer stroke will generate more torque, and a shorter stroke will generate more high-revving horsepower

Horsepower = torque * RPM/5252

this is why, when you look at a dyno chart, hp and tq curves cross that that RPM. 

A good example is comparing an LS7 motor (GM's 427 from the c6 z06) to an Italian exotic v12.  The GM motor has a large bore and a large stroke, relative to the v12 which has a shorter stroke AND smaller bore diameter to allow for higher revs. This limits the LS7 to a lower max RPM, but generates gobs of torque, whereas the v12, you'll see a pile of horsepower, and a much lower (relatively) amount of torque due to the MUCH higher rev range.

Another thing of note - the LS7 displaces 427 cubic inches (7.0L) whereas the v12 in the Ferrari 812 Superfast "only" displaces 6.5L - factory specs on these two motors:

LS7 - 505hp/475tq
812 Superfast engine - 789hp/530tq

Notice how the tq figures are fairly close, but the HP number is SIGNIFICANTLY higher in the 812?  That's because RPMs!!  The 812 revs to something like 9k rpms, where the LS7 goes to (I believe) 6800. 

So in the ferrari it took 4 extra cylinders to get a moderate increase in torque, but a massive increase in power.  Smaller cylinders, shorter stroke, allow it to rev higher and faster due to less stress on the rotating assembly.  Let's compare bore/stroke between the two:

LS7 - 4.125" bore, 4" stroke
812 - 3.7" bore, 3.07" stroke

Imagine the numbers a 12cyl motor would put out if it kept the same bore/stroke as the LS7 (if you ask me, that would be bonkers and I love it)

that shorter stroke creates less (relative) torque, but allows the motor to run higher, thus the higher HP figures.

Compression also figures into it, but I'll leave that be, as you were asking more directly about CC (engine displacement) and how to judge horsepower via that.  Compression is more like Chapter 4 in this book hahahahaha

The real answer to your question is probably best served by just reading as much as you can about engines in general.  There are quite literally a zillion different books on the topic, and what I've typed above is pretty elementary vs the actual facts, but it's generally in the right direction with regards to your question.

So.....to answer your question....hopefully a short answer?  There is no direct correlation between displacement and horsepower.  Sometimes, the larger motor will have more HP than the smaller motor, but remember - HP is a function of both Torque and RPM, so if you can't rev out that huge motor, you're not going to get much horsepower, but you'll often get a very torquey motor in place of the "lost" horsepower

Have I sufficiently confused you enough?

Offline Balbino

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Re: CCs and HP
Reply #7 on: May 17, 2021, 08:12:57 PM
There is a saying that there is no replacement for displacement. In many ways this is not true.
Two engines with the same displacement (cc's) here is a list of things that greatly affect HP regardless of displacement.

1. Compression ratio.   (more compression = more heat, power and more need for better cooling like liquid cooling)
2. RPM.   spinning the engine faster will cycle more air and fuel through the engine regardless of displacement.
3. Valve capacity. (or flow rate of valves and number of valves 2 vs 3 or 4 (or even 5 if your into old Yamahas.)
4. Forced induction. ( Turbo, supercharger)

In summary if you are looking at 2 engine with the same displacement and one is Air cooled, 2 valves per piston and redlines at 5000 rpm. and the other is liquid cooled 4 valves and redlines at 14,000. You can imagine there would be a huge difference in HP. And then there is the whole issue of where your HP is on the RPM range for rideability issues.

Offline broderp

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Re: CCs and HP
Reply #8 on: May 18, 2021, 02:33:29 AM
A lot of the answers here are not the simple answer you are asking for...so I will keep it simple: Its complicated.  Morse so than what your looking for.  :084:

I'll just go watch myself type.... :164:
Last Edit: May 18, 2021, 02:34:55 AM by broderp