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Old 11-10-2012, 01:29 PM   #31
PhilB
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Quote:
Originally Posted by Gryphon12 View Post
I've been riding a long time now (40 years), and I'm an engineer, so I follow the technology. The V-4 motors have always been less fuel efficient (more thirsty) at all rpms than the I-4 engines, and I can't think of a reason why. In the post above, 17-18 km/l is 40-42 mpg US, is good for the VFR. Many never get above 38 mpg. Puzzling to me. The only other ST/ADV bikes that are this low are the very highly tuned motors of the KTM V-Twins. I did not think that the VFR's were that highly stressed (HP/l, HP/lb, HP curve on the dyno, richness on the fuel curve, A/F ratio). Although, the VFR-800 produces a little more specific power (HP/l) than the 'Bus - it's just a lot smaller motor.

A second post from a 'Busa owner getting between 40 and 50 mpg US is also very enlightening. Wow, that's great for that motor. The equvialent on the ZX-14 is MUCH lower - High 20's to Low 40's. The differences in how highly "stressed" the state of tune of the two motors just don't seem to be that different from my perspective (mathematically, they are very close). Is the FI tuning that different?

Many folks will say "its a motorcycle, who cares?". Well, I do. I want moderate to good economy from whatever class of motor I'm dealing with. I also want longer range for touring western States. Big tanks plus better mileage yields longer range.

Apparently, lots of experience doesn't equate to lots of knowledge or understanding. Educate me please. What is going on with the Honda V-4's? Why the economy difference between the 'Busa and the ZX-14?
Some of it is simply that a vee-type engine has more parts and more internal friction than an inline; the advantage of a vee is narrowness. That narrowness can be made into an efficiency advantage if the bike takes advantage of that by being made narrower and thus more aerodynamic, but I don't think the VFRs did that.

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Old 11-10-2012, 02:01 PM   #32
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I'd guess there are lots of variables, some that often are not mentioned. Is the bike completely stock? Intake been modified with a different air filter? Rejetted or remapped? Stock exhaust or aftermarket? Gearing? Last but not least, people ride with different "enthusiasm", that has to make a big difference.

FWIW, my Busa is bone-stock, and I usually don't twist the throttle hard all the time, in fact, rarely - only when I want to get some adrenaline flowing.
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Old 11-11-2012, 08:15 PM   #33
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I've had a '99 and '02 zx9r. Great everything bike. Comfortable enough for touring and nimble around town. Maybe the best solo alround bikes I've ever owned???

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Old 11-11-2012, 10:43 PM   #34
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That's why the Triumph Daytona 955i has been mentioned twice. A ZX-9R with an awesome Triple motor, and if you care, a SSSA. Larger tank and lower insurance. Nothing but .
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Old 11-11-2012, 11:48 PM   #35
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Originally Posted by Gryphon12 View Post
That's why the Triumph Daytona 955i has been mentioned twice. A ZX-9R with an awesome Triple motor, and if you care, a SSSA. Larger tank and lower insurance. Nothing but .
Wot he said.

Aaaand, because these old girls don't get enough exposure and any excuse will do...





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Old 11-12-2012, 11:10 AM   #36
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Originally Posted by Gryphon12 View Post
That's why the Triumph Daytona 955i has been mentioned twice. A ZX-9R with an awesome Triple motor, and if you care, a SSSA. Larger tank and lower insurance. Nothing but .
Less power & more weight plus a heat problem? Having owned a moded 1050 tiger the zx9r will smoke them triples, plus it's just a better all-rounder imho.
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Old 11-12-2012, 11:38 AM   #37
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Ok, we're splitting hairs here. If you like the I-4, go ZX-9R. If you like the Triple, go Daytona 955i.

The 2005 Daytona is only 8 lbs. heavier (478 lbs. wet) than the 2002 ZX-9R (470 lbs. wet) and it hold 5.5 gallons rather than 5.0 gallons of gas. Which means that they are almost identical with an empty tank.

I'll avoid the HP arguement regarding the last generation Daytona. The book says 147 to the ZX-9R's 144. But many said that the Triumph was over-rated. Some said only the Centennial Edition (2002) had the forged crank and pistons to support the 147 hp number, others quoted the Triumph parts manual saying that no such parts existed. The battle went on, and on, and on.

Suffice to say, they are very, very close. Only gearing would determine the difference in a sprint (smoking?), and the Daytona was geared tall for top speed. Used as a sport tourer (neither will compete against 1000cc supersports), it doesn't matter. The ZX-9R might have a better front suspension and brakes. By a bit.

The heat problems of the Tiger and Sprint RS/ST were not prevalent on the Daytona 955i.

So, they are both great bikes for this SPORT (solo) end of sport touring. Take your pick: Triple or I-4.
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Old 11-14-2012, 12:07 PM   #38
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Originally Posted by nemuro View Post
I believe I got all of the answers are needed, Thank you all for this and sorry for posting this thread in two sections. it was a mistake. See you this summer :).
Well... we're waiting!

You can't just stir a pot like this and then walk away without telling us what you decided on. It's not right.
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Old 11-14-2012, 01:17 PM   #39
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Some of it is simply that a vee-type engine has more parts and more internal friction than an inline;

As an (almost) engineer myself I'd like to comment that that's not true. A V-motor does not have a lower efficiency than a I-4 motor. Efficiency losses in a combustion engine because of friction are lower than 2%. Even if a V motor had more friction the differences would be very small.

Why the Honda V-4 motors are thirsty? Well not because of the V4 concept. Probably design choices. When these V4's were designed fuel consumption wasn't that big of an issue although the sport tour V4's never have been high on power or something.


the 800 v4 makes me wonder especially since the V-tec system should give quite a bit better fuel consumption on low RPM's, which is working for Honda in their car division. Somehow the V4's are just way of the sweetspot of B.SFC
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Old 11-14-2012, 04:27 PM   #40
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Originally Posted by Bugz View Post
As an (almost) engineer myself I'd like to comment that that's not true. A V-motor does not have a lower efficiency than a I-4 motor. Efficiency losses in a combustion engine because of friction are lower than 2%. Even if a V motor had more friction the differences would be very small.

Why the Honda V-4 motors are thirsty? Well not because of the V4 concept. Probably design choices. When these V4's were designed fuel consumption wasn't that big of an issue although the sport tour V4's never have been high on power or something.

the 800 v4 makes me wonder especially since the V-tec system should give quite a bit better fuel consumption on low RPM's, which is working for Honda in their car division. Somehow the V4's are just way of the sweetspot of B.SFC
A V-motor does have more moving parts, more bearings, more friction than an inline motor of the same number of cylinders. It may not be a huge factor, but it's not insignificant.

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Old 11-15-2012, 01:18 AM   #41
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A V-motor does have more moving parts, more bearings, more friction than an inline motor of the same number of cylinders. It may not be a huge factor, but it's not insignificant.

PhilB
Let me rephrase; A V-motor does not have a lower efficiency grade when compared to a inline motor. A V-motor does not burn more fuel compared to an inline motor when performing the same amount of labor.

Both engines being optimized for the job obv.
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Old 11-15-2012, 09:54 AM   #42
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Let me rephrase; A V-motor does not have a lower efficiency grade when compared to a inline motor. A V-motor does not burn more fuel compared to an inline motor when performing the same amount of labor.

Both engines being optimized for the job obv.
Okay. Never mind.

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Old 11-15-2012, 10:22 AM   #43
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Originally Posted by Bugz View Post
Let me rephrase; A V-motor does not have a lower efficiency grade when compared to a inline motor. A V-motor does not burn more fuel compared to an inline motor when performing the same amount of labor.

Both engines being optimized for the job obv.
don't forget that almost part of almost an engineer.

V engine has heavier cam drive (twice the length of camchain, more cam bearings etc).

V engines have serious packaging constraints on intake and exhaust plumbing.

V engines in motorcycle have relatively large imbalances in combustion forces, so bearings need to be built bigger and heavier to withstand the stresses, as well as the torsional fluctuations all through the drivetrain.

If you just look at each combustion chamber, sure, a cylinder is a cylinder, but if you look at the practical evidence that almost every V engine is a guzzler relative to it's single-headed counterparts, the writing is on the wall as they say. Proof in the pudding. Etc etc etc.
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Old 11-15-2012, 11:05 AM   #44
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I'm a civil engineer, not a mechanical engineer, but as a life-long gear-head, that sounds like a rational explanation to my original query. Thanks!

Also, as I've said before, most riders don't care. They find a bike that they love and they ride the wheels off of it. I just have a very bad habit of overthinking just about everything. Since I can only affort one bike at a time, my bad habit keeps me busy between bikes. And I learn a lot in the process!
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Old 11-15-2012, 11:20 AM   #45
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Originally Posted by DannyZRC View Post
don't forget that almost part of almost an engineer.

V engine has heavier cam drive (twice the length of camchain, more cam bearings etc).

V engines have serious packaging constraints on intake and exhaust plumbing.

V engines in motorcycle have relatively large imbalances in combustion forces, so bearings need to be built bigger and heavier to withstand the stresses, as well as the torsional fluctuations all through the drivetrain.

If you just look at each combustion chamber, sure, a cylinder is a cylinder, but if you look at the practical evidence that almost every V engine is a guzzler relative to it's single-headed counterparts, the writing is on the wall as they say. Proof in the pudding. Etc etc etc.
Do not take this post as me being a smartass. Just like to comment on these V4 gass guzzlers

It is not written on the wall as they say. You'll find a lot of Big V engines in the diesel industry (ships etc) and not because of their love for fuel (Not that they are more efficient compared to a inline engine...just a lot smaller because of the V design)


Even if a v4 would have TWICE as much friction losses it would still be a total of 4%. Whoop-di-doo. It's not even close as twice as much. It's not even close as 2% more friction losses. Friction losses pretty much only consist of the friction caused by the pistons which is the same for a V4 or I4 engine.

Even if it was twice as much...What does your regular I4 1000cc return for fuel economy? 40ies mpg? Now according to your theory the V4 would get economy of 39.2 mpg because of being a v4.

Pretty sure that the RCV V4 honda in MotoGP is a gas guzzler compared to the rest of the field. Man that bike is slow. Fair enough. The thing has pneumatic valves

A V engine does not have large imbalances in combustion force. When properly designed it doesn't need a balance shaft where a I4 does need one to cancel out all vibrations. Even if it had harmonic vibrations it doesn't mean it can't be fuel efficient though obv. some energy will be lost because of those vibrations.

I'm not really sure of your point mentioned about the intake and exhaust valves. Do you have any information on this since I really can't find any about it in my books.

Where honda get's it wrong (regarding fuel consumption....their V4 engines are a gem regarding driving charasteristics) is with the B.SFC

If you want to know what actually determines fuel consumption regarding a ICE I'd say look at this posted a few weeks ago;

My post from the Honda NC 700 thread. This will give you information about SFC or specific fuel consumption. As I said before, I'm dutch and I might use some words which arn't technical correct. You should be able to understand though.
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Hello lads,

I'm just a lurker on this forum pretty much. Really like the website but somehow I don't post very often here though I do like to get involved in this ungoing fuel consumption discussion! (I'm dutch. my dutchized english isn't THAT good).

I'd like to start with efficiency of engines and specific fuel consumption.

Most people do know that the thermal efficiency of a normal petrol engine is about 30% whereas the thermal efficiency of a diesel engine is about 40%. We're talking about car / motorcycle engines here. Industrial diesels found in ships and energy plants can go up to 50% currently.

What most people do not know is that the efficiency of a combustion engine is far from constant. It is about as variable as it gets (variable as in running conditions, not because the stars don't allign that well on mondays). The easiest way of 'seeing' the different thermal efficiencies of an engine is by using a SPF diagram (Specific Fuel Consumption Diagram). Let's use one I found on wikipedia from a VW 3 cylinder 1.5. diesel engine found below;


On the x-axle there is RPM and on the Y-axle there is the effective pressure of the engine. For the sake of simplicity the Y-axle can be read as a form of power output. The red lines are the working borders of the engine. It will nut run above those conditions.

SPC (Specific Fuel Consumption) is how much fuel you need to get a certain power output. SFC is defined as SFC = r / Pe where r = gramms of fuel (weight) en Pe is effective power of the crankshaft. In other words; The higher the SFC the higher the efficiency of anengine is. In the above diagram we see that the ultimate sweet spot of 206 kilogram / kilowatthour with regards fuel consumption of this engine is at about 15 Pe and 2300 RPM. For maximum fuel efficiency one would have to create driving conditions to get this.

The reality with modern cars and motorcycles is that it is near impossible to achieve these running conditions. Running on a 80% load with modern cars will end you up flying way above the speed limit! Our engines in cars and motorcycles are incredibly overpowered with regards what they have to do; My estimate is that most cars / motorcycles will be running on an engine load of around 25% (and that's for european cars, not the american supermarktet V6 / V8 / V12 SUV's. They will do much worse). You can see in the SFC diagram that an engine load is way below the optimum SFC. If we take an estimated 250% load of an engine at 2500 RPM (highway conditions) we can see that the SFC is 260ish. You need 260 - 206 = 54 gramms of fuel extra just because of how we design our cars / motorcycles. You don't need 150 BHP to get a car in motion. 40 HP is more that sufficient to get you op to 85 mph.

I think the main reason for manufactures is that people don't really want these cars yet. People want a car / motorcycle that's responsive to their foot / wrist which means we want pretty low end gearings (I think most motorcycles go above 6000 RPM on the highway @ 85 mph) and want power.

Now back to Honda's claim. I'm very willingly to believe it will achieve 60ish mpg figures under highway conditions. It's build in a way it will obtain a high engine load since it has such long gears / low maximum RPM, and I think even the NC is still quite a bit away from maximum efficiency! It's not that a Honda fireblade doesn't have a sweet spot, it's just nowhere near normal driving conditions.

Don't get me wrong. do not know anything about building or constructing engines. I just have a good understanding of operating principles and efficiency regarding combustion engines. If anyone sees major flaws in what I've written feel free to correct me.

I do not know exactly what causes the sweetspot (apart from that it obvious has to to with pressure ) and I do know that engineers can build engines to suit their operating conditions (a racecar will have a sfc sweetspot around it's maximum RPM under full load, since that's the place it will be running during a race) but engineers cannot peform miracles. You cannot build a sportbike to suit maximum economy if the engine has 180 bhp on tap.



Some reading stuff;

SPC on wiki; http://en.wikipedia.org/wiki/File:Br...onsumption.svg

http://autospeed.com/cms/title_Brake...6/article.html

http://www.heat2power.net/en__wasteheat_in_ices.php
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Feel free to educate me. I love to get it all wrong.
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