Are I4s really that different than parallel twins?

[Juan1]

Aren't the rev-happy characteristics of I4s just due to the way the engine is tuned (usually based off of a race engine)?  Isn't the low RPM torque of a v-twin just the result of a longer stroke and smaller bore?  My point is we throw around statements like I4s need RPMs to produce power, but isn't that the result of the way the bikes are tuned, rather than some innate engine characteristic.

One thing is certain.  My GPZ750 (I4 from 1982) is a torque beast that produces most of its power down low.  Meanwhile my GS500 loves to rev.

[mister]

Aren't the rev-happy characteristics of I4s just due to the way the engine is tuned (usually based off of a race engine)?  Isn't the low RPM torque of a v-twin just the result of a longer stroke and smaller bore?  My point is we throw around statements like I4s need RPMs to produce power, but isn't that the result of the way the bikes are tuned, rather than some innate engine characteristic.

One thing is certain.  My GPZ750 (I4 from 1982) is a torque beast that produces most of its power down low.  Meanwhile my GS500 loves to rev.

Thank you, Juan1.

This is what I have been trying to say for ages. To STOOP spreading the Myth of I4s being revvy. As I point out, my GS500 revs higher than my 919 in any gear at the same speed. The I4 may sound like it is revving more but it isn't necessarily. And as for "where the power is" it is still outpowering the GS500 at lower revs than the GS500.

Michael

[mysterious_rider]

I noticed my gs500 with a stock end can would put all its power out at the top. This got sorted when I fitted an aftermarket can, all my power comes in at 6k or so now.    It absolutely trashes my friends 600s off the line up to 45mph, and she's restricted to 33bhp! 

inline fours make their power at the top of the rev range, it's when you hit speeds like 50-60mph do they start to overtake.

[comradeiggy]

Your friends must be terrified of the throttle if you're beating their 600's on your gs500. It shouldn't even be a contest tbh.

[BaltimoreGS]

inline fours make their power at the top of the rev range, it's when you hit speeds like 50-60mph do they start to overtake.

I think you are missing the point of this thread.  Your statement is true of race replica I-4 sport bikes because the engines are designed to make power high up in the RPM range but the OP's point is that an I-4 doesn't necessarily have to be that way.  Bikes like the Honda 919, 599 and Suzuki Bandit are inline 4's that are designed to make their power in lower RPM's.  Which brings me to another gripe, I hate the word "de-tuned" being applied to those bikes.  It has a negative connotation.  I prefer re-tuned   

-Jessie

[SAFE-T]

Over time as advances in design and manufacturing allowed engineers to increase the rpm limits of motors, they found you could also make more power. So their engines came to be designed around making power at higher rpm. Thus you get a 1986 Yamaha YX600J Radian with an air-cooled I4 and a strong midrange but mostly more noise from 9,000 to its 10,500 rpm redline. Later you get a 2008 Yamaha YZF-R6 with a liquid-cooled I4 that makes its best power starting at 10,500 rpm up to its 15,000 rpm redline. At the same time there is the 2009 Yamaha FZ6R, which uses a motor from the 2003 Yamaha YZF-R6 but with different cam timing which is more like riding the Radian, albeit with about 50% more power overall.

[SAFE-T]

Parallel twins and V-twins have entirely different characteristics, given that the same displacement divided amongst 2 or 4 cylinders is going to give you different results. But generally twins tend to feel a little more 'torquey' because you don't have to rev them as hard to make power (and in some cases you can't), whereas the higher performance I4 motors (sometimes) need to be revved up to make the most power.

If you did a side-by-side comparison between bikes like the CBR900RR and the 919 Hornet you would find the 919 probably bests the 900 up to about 7500 rpm, after which the 900 would start to pull away. Same motor, different tuning, different results.

Put a Ducati Panigale up against a Suzuki GSXR1000 and you would probably see similar results if you used a distance great enough to allow the two bikes to reach their terminal speeds. Ducati actually tried designing a v-twin for MotoGP based on their Superbike motor, but couldn't make enough power up top to be competitive and switched to a V4. Today all the bikes in MotoGP use V4 motors, or in Yamaha's case an I4 designed to emulate the firing order of a V4.   

[SAFE-T]

If you want to read a more technically correct version of this, Google 'Kevin Cameron', a regular contributor of magazine articles about motorcycle engineering and technology.

[Phil B]

Aren't the rev-happy characteristics of I4s just due to the way the engine is tuned (usually based off of a race engine)?  Isn't the low RPM torque of a v-twin just the result of a longer stroke and smaller bore?  My point is we throw around statements like I4s need RPMs to produce power, but isn't that the result of the way the bikes are tuned, rather than some innate engine characteristic.

One thing is certain.  My GPZ750 (I4 from 1982) is a torque beast that produces most of its power down low.  Meanwhile my GS500 loves to rev.

To summarise the other replies:
While what you said is correct at a technical level... at a *practical level*, almost every modern I4 motorbike is tuned "that way", so the more common "I4's need high revs for power", is mostly correct at a practical level.

The only modern exception I am aware of, is the FZ6R. Which is a shame, because I personally would love to see more choices in this area.
It's surprising to me that the appropriately tuned I4 in the FZ6R actually gets milage almost comparable to our 2cyl gs500.

What would be REALLY nice, is if it were possible to somehow take "engine maps" or whatever, and turn a lightweight gsx600, into a low-end torque machine like the FZ6R, with nothing more than what is effectively a "software tweak".
(the 6R is *heavy* !)

Never heard of this being done, though


And what makes me doubtful, is that the FZ6R doesnt just have "lower revs" in general. It has a lower "redline".
If it was just fine keeping the original bike/engine spinning at 13k, but it is now somehow "bad" to keep an FZ6R spinning at even 12k, that makes me think there are probably mechanical changes to the engine as well. Internal gearing as well as sprockets, presumably.

[tt_four]

My old triumph speed four, had a ton of midrange. The low and midrange power was comparable to my XB9, but the triumph had way more power up top, despite having almost 400cc less engine. The Buell definitely had more power off of idle though.

I think one advantage that I4s have on top end and high revving engines is the outright smoothness. Any engine can have a counter balancer, but the more cylinders you have the more you can even out the engine vibrations. There are some I4s you ride where you literally can't even feel the engine running, unlike the GS an most other bikes I've had, where you can feel the engine chugging along when you twist the throttle.

[yamahonkawazuki]

inline fours make their power at the top of the rev range, it's when you hit speeds like 50-60mph do they start to overtake.

the single crankpin vtwin of my harley even with its supercharger  , made iots power down low. just the way its designed. most i4's are rev happy. sopme however are biult to make it lower, and tbh those scare me more than hte hirevvers
I think you are missing the point of this thread.  Your statement is true of race replica I-4 sport bikes because the engines are designed to make power high up in the RPM range but the OP's point is that an I-4 doesn't necessarily have to be that way.  Bikes like the Honda 919, 599 and Suzuki Bandit are inline 4's that are designed to make their power in lower RPM's.  Which brings me to another gripe, I hate the word "de-tuned" being applied to those bikes.  It has a negative connotation.  I prefer re-tuned   

-Jessie

[SAFE-T]

The motor in the FZ6R comes from the 2003 YZF-R6, which is why it has a lower rev limit, although that motor in the FZ6 had a limit of around 13,500 rpm.

The next generation R6 has a 16,500 rev limit although it was originally advertised as 17,500...the motor actually starts to cut ignition around 16,000-16,200 rpm.

My favorite is this quote regarding the Motorcycle USA "First Ride" review of the then-new 2009 FZ6R and the response in the  Sportbikes.net forum:

Motorcycle USA review:

"...allowing the engine to rev to a screaming 10,000 rpm...
the feel is very electric and lacks character. Not much goes on sub-5,000 rpm, at which time it climes smooth and seamlessly to the 10,000 rpm redline; the problem being it's a bit too smooth...
Tossing the foot lever from gear to gear is nearly effortless.... A trade off of this silky action is a bit of feel, as the machine never makes a solid clunk or notch to let you know you are fully into the next gear."

So let me get this straight.
FZ6: panned for low 13.5k red line FZ6R: screaming 10k redline
FZ6: panned for peaky powerband FZ6R: peaky powerband gone, but boring, electric feel to motor
FZ6: panned for being buzzy FZ6R: panned for being too smooth
FZ6: panned for clunky shifts FZ6R: panned for not having clunky shifts

Yet another cliche-filled, adjective-dripping, nit-picking, copy-cat-sounds-just-like-every-bike-review-for-the-past-five-years waste of space.

[yamahonkawazuki]

hell my goped revs to near 15k lol. course its only 25.6cc, until i get a larger engine. trying to stick to an rc engine. they rev to 14k+ versus a mere 12,500 lol

[Unsane]

Shorter stroke = less torque at low revs but capable of higher revs due to lower weight
Longer stroke = more torque at low revs but less capable of higher revs due to higher weight

At a set capacity of 500cc, each cylinder in a twin will have 250cc of combustion mixture, in a triple will have 166cc of combustion mixture and in a four will have 125cc of combustion mixture - so less cylinders will give you more energy per combustion cycle... but the weight of the rotating mass, bore & stroke characteristics will determine the rate and RPMs at which power & torque are delivered.

Tuning will simply be the fuel & ignition to suit capacity a cam profile. Many 4 cylinders like the FZ6R, GSR750, Z1000, etc share engines from high revving sportsbikes but its the cam and EFI programming that makes them more punchy to ride and less revvy. These bikes will usually have revised gearbox ratios to make the most of the improved low-to-midrange performance and less reliant on peak power at peak revs

[Juan1]

So let me get this straight.
FZ6: panned for low 13.5k red line FZ6R: screaming 10k redline
FZ6: panned for peaky powerband FZ6R: peaky powerband gone, but boring, electric feel to motor
FZ6: panned for being buzzy FZ6R: panned for being too smooth
FZ6: panned for clunky shifts FZ6R: panned for not having clunky shifts

Yet another cliche-filled, adjective-dripping, nit-picking, copy-cat-sounds-just-like-every-bike-review-for-the-past-five-years waste of space.

I couldn't agree with you more.  It seems like now there are only two types of reviews.  The first type of review is from the publication that is clearly in the pocket of the manufacturer.  These are noted by have in reviews that range from 3.5/5 to 5/5.  Then there are the reviews where the reviewers rate every bike against their preferred Super Sport.  The FZ6 needs to rev, but never puts down R6 acceleration, while the FZ6R has a redline that is far too low compared to the R6.

[Twisted]

There are some I4s you ride where you literally can't even feel the engine running, unlike the GS an most other bikes I've had, where you can feel the engine chugging along when you twist the throttle.

This is what I like about the twins. I like the rawness of the engine that you feel when you twist the throttle.