comparing motorcycle engine power outputs

[Anonymous]

Anyone offer suggestions where I can read or look-up HP or torque of various stock engines across the years. My bike is a 78 GS750 C. I'm particularly interested in how the old 4's compare to the endless supply of V-twin cruisers around these days. I've always thought that the current popular frenzy over v-twins was based on how they sound over their power output. Any comments?

[mark m]

Any comments?

Lots of 'em.

You are correct in your assessment. The twins are popular right now because of their feel and look. This is just another fashion trend and will eventually be replaced by the latest thing that is "cool" at the moment. A twin will always be inferior to a 4 in terms of power potential, simply because of the difference in valve area. The current "power cruisers" tend to make a lot of torque because they are big displacement engines, but they do not rev enough to make serious horsepower. They can be entertaining to ride because of all that torque, however. But they will never be truly fast because of the aforementioned limitations. To my mind, a true power cruiser is a V-Max - looks super mean and has the balls to back it up....


Mark

[flyingace]

Try www.suzukicycles.com

They have some stats on most older Suzuki bikes.

As to why V-twin popularity - sound is part of it. By and large, it comes down to something called 'image'. Why else would folks ride around on heavy, shaking, underpowered bikes with lots of chrome? This happens when motorcycles aren't used primarily for transportation.

Ace.

[first timer]

what about the modern twins like a duccati or a sv 1000 or the rc51 , how do they stack up to a 4, they must have some close numbers as well as good and bad trade off's , like with a twin they are a lot narrower so that helps with handeling


-ryan

[Anonymous]

A twin will always be inferior to a 4 in terms of power potential

Generally true but certain twins have been very effective at beating the 4 cylinders. Ducati and MV Agusta to name a couple.

[flyingace]

Maybe we should be more specific and refer to them as V-twin 'cruiser' engines.

[focus frenzy]

A twin will always be inferior to a 4 in terms of power potential

Generally true but certain twins have been very effective at beating the 4 cylinders. Ducati and MV Agusta to name a couple.

MV agusta is a multi not a twin, Aprillia is a twin.

[Anonymous]

Thanks for the opinions everyone. I found an interesting site explaining in simple terms the basic differences between torque and hp. I knew some of this stuff but the eye opener for me was the torque at higher rpm RULES rule.
torque primer: http://vettenet.org/torquehp.html

Meanwhile I will look and see if this high torque at low rpm fits the "v-twin cruiser" engine profile. Interesting!

[mark m]

Generally true but certain twins have been very effective at beating the 4 cylinders. Ducati and MV Agusta to name a couple.

Ducati's do not win when there is rules parity between the 4's and the twins. Note the last couple of years in the AMA, even with handicaps the 1000cc 4's are smoking the twins. Also, this year in WSB the 4's have dominated. Ducati have been competitive at some tracks, but are generally struggling (they do have excellent handling and a lot of years of development on that bike). Given total rules parity between the two types, the 4's will leave the twins in the dust. It is simply physics that dictates this.

what about the modern twins like a duccati or a sv 1000 or the rc51 , how do they stack up to a 4, they must have some close numbers as well as good and bad trade off's , like with a twin they are a lot narrower so that helps with handeling

The modern twins are very good (and a lot of fun), but they will never post comparable power numbers to 4's (TL/RC/SV, etc. make around 120rwhp, GSXR1000 makes 160rwhp). The width is not an issue relating to handling, but it does affect top speed. Twins generally have smoother powerbands and are more tractable, making it easier to ride them fast. As things are tuned higher and higher some of this is changing, though. I recall a few years ago the head of Ducati's engine development said that as they tuned it for more and more power it became very difficult to keep the smooth power characteristics and the bike was getting hard to ride with the very sudden, hard hit of power. They homologated a new frame mid-season a couple of years ago that greatly improved handling, but not because of any geometry changes - the new frame allowed use of a bigger airbox, which smoothed the power significantly and made corner exits easier on the riders.

That said, I wouldn't turn away a free 999 for my garage...


Mark

[Anonymous]

MV agusta is a multi not a twin, Aprillia is a twin.

Oops, that's what I meant

[gasisontheright]

https://www.suzukicycles.org

[ptm]

Here is Cycle World's take on the pros and cons of v-twins vs. inline fours...

http://www.cycleworld.com/index.cfm?siteaction=OnlineUpdate&id=46

[Dink]

Thanks for the opinions everyone. I found an interesting site explaining in simple terms the basic differences between torque and hp. I knew some of this stuff but the eye opener for me was the torque at higher rpm RULES rule.
torque primer: http://vettenet.org/torquehp.html

Meanwhile I will look and see if this high torque at low rpm fits the "v-twin cruiser" engine profile. Interesting!

Horsepower DOES NOT exist, it is actually a "calculated" figure, a Dyno actually measures torque. Horsepower is then calculated as a product of torque X RPM X a factor I cannot recall at present= HP,if two motors, regardless of configuration (i.e. Twin,Triple,Four etc)if the two motors make exactly the same amount of peak torque, but one motor is turning faster it will make more horsepower.
Dink

[mark m]

Horsepower is then calculated as a product of torque X RPM X a factor I cannot recall at present= HP

Hey Dink,

That would be:

HP = (Torque x RPM) / 5252

Torque in ft-lb, that is.

The 5252 factor is why the torque and hp curves always cross at 5252rpm on a dyno chart.

but one motor is turning faster it will make more horsepower.

This is correct. Brake Mean Effective Pressure (BMEP) is a measure of how efficiently an engine is filling its cylinders. There are practical limits to BMEP on a naturally aspirated motor and all modern sport bike motors (twins and fours) are very close to the same BMEP numbers (meaning they all breathe about as well). The difference is the rpm they turn at those BMEP figures. The twins redline around 10,000-11,000rpm and the fours are turning 12,000+rpm. The other advantage that the fours have is more valve area, so they have the capacity to flow more air at higher rpm. Combine higher airflow and higher rpm and you have the power winner.

Just to note, current 1000cc 4's are actually quite mildly tuned and could easily make 190+rwhp (stock, that is) if designed for all-out power. I bet that scares the safety nazi/insurance groups all to death...


Mark