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  Topic Review (Newest First)
08-17-2005 03:20 AM
2005Ninja250R
Quote:
Originally posted by Si-lo
I don't think it's the engine or the drivetrain, I think it's the ball bearings, it's all ball bearings now, ya know?
Indeed Si-lo...it's all in the ball bearings...lol
08-16-2005 10:10 PM
Si-lo I don't think it's the engine or the drivetrain, I think it's the ball bearings, it's all ball bearings now, ya know?
08-16-2005 09:44 PM
2005Ninja250R [QUOTE]Originally posted by scottland
[B]Just a forewarning, this is going to get ugly quick

1. Bring it on, Scotty.

Dude, your conclusions may be close to correct, but you reasoning is DEAD wrong. It is painfully obvious that you are just regergitating this info, and have learned none of it first hand.

2. I am not an engineer, are you perhaps? Then enlighten me please, Mr. Honda, or is it Dr. Porsche?

The valvetrain is not the most important factor with regard to engine design. It is the cylinder heads, cylinder heads, and the CYLINDER HEADS. Engines are like big air pumps, air in, air out. The more air you can get in, the more air you can get out, the more power you can make. And flow comes from the heads. The intake port flow, exhaust port flow, and equally important, the port velocity. Valvetrain is just an aftermath.

3. Beeep! Wrong Scotty. Without valves to throw in air/fuel, and evacuate exhaust, what is the reason of the head? The VALVES determine the air/fuel and exhaust movement. The VALVES determine the effeciency of the head.

Now for your 4 vavles are better than 2.
not always true. You can only can fit so much valve inside the cylinder bore, a 4" bore can only fit so much valve. so what you are forgetting is that most 4valve heads, have valves that are nearly half the size as a 2 valve head. Now given 4 valve heads do have outstanding low lift flow numbers, but as far high lift numbers go, a properly ported 2 valve head can easily surpase a 4valve head.

4. Again, as I wrote earlier, "ALL OTHER THINGS BEING EQUAL..." You need to read my former posts again. Then talk smack.

once again regergetated crap. You simply don't understand the concept of torque. Every engine builder dreams of a fat flat torque curve.

5. How else does one learn of engine design? Through osmosis perhaps? No, it is through READING, TALKING with master engine-builders, tearing down and building-up performance engines. Also, asking questions of these geniuses often helps in understanding. You might want to try it sometime.

Now is where you are starting to lose it kid, the Carrera GT is a 5.7L V10 that makes power up to 8400rpm. The Z06 makes near equal power(almost 500 to the wheels), and MORE torque at 2000rpm LESS. And the z06 costs SIX TIMES LESS and is just a pinch slower around nurburgring, not bad I would say. Considering the GT is the ONLY production car faster than the Z06.

6. I am not losing anything, and you might want to forego calling me a kid, I have served my nation in the USAF. I may be only 23, but i have seen a great many things in my time, "son".

Again, "ALL OTHER THINGS BEING EQUAL BUT VALVETRAIN..."
Two 5.7 V8s, made of the same material, with the same cylinder angles, etc...but one with DOHC and one with OHV...the DOHC one will push out more power, everytime.

See I dont disagree with your conclusions, just the resoning behind them. And the absoluteness with which you state them.

Dude, your not really tearing any argument apart, your making an ass out of yourself. You may have read magazines, and read lots of forums on the internet, but you only half know what you are talking about. Before being so arrogant, try listening, it will go along way.

7. I AM tearing arguments apart, your disagreeing with me does not change that Scotty. You are the ass, Scotty. I don't get my info from thhings as unrelaible as forums: a Chevy forum will think differently than a Honda forum, of course...

I have listened, to people who build these damn things, so shut your trap before talking smack Scotty.
08-16-2005 09:03 PM
scottland Just a forewarning, this is going to get ugly quick

Quote:
Originally posted by 2005Ninja250R

6. Beeep! Wrong! The valve train is perhaps the most important factor in engine design. Who cares if an engine will spin freely with virtually no effort, if it wheezes and has difficulty under hard acceleration? The valvetrain is second perhaps to only valve timing in importance.
Dude, your conclusions may be close to correct, but you reasoning is DEAD wrong. It is painfully obvious that you are just regergitating this info, and have learned none of it first hand.

The valvetrain is not the most important factor with regard to engine design. It is the cylinder heads, cylinder heads, and the CYLINDER HEADS. Engines are like big air pumps, air in, air out. The more air you can get in, the more air you can get out, the more power you can make. And flow comes from the heads. The intake port flow, exhaust port flow, and equally important, the port velocity. Valvetrain is just an aftermath.

Now for your 4 vavles are better than 2.
not always true. You can only can fit so much valve inside the cylinder bore, a 4" bore can only fit so much valve. so what you are forgetting is that most 4valve heads, have valves that are nearly half the size as a 2 valve head. Now given 4 valve heads do have outstanding low lift flow numbers, but as far high lift numbers go, a properly ported 2 valve head can easily surpase a 4valve head.

Quote:
If a rider keeps the engine "on cam", or "on the boil", then the engine is in it's element. Pushrod engines are lazier, and take less effort to flog correctly. That must be why dumber people seem to like them so much. Ignorance is indeed bliss afterall.
once again regergetated crap. You simply don't understand the concept of torque. Every engine builder dreams of a fat flat torque curve.

Quote:

And another argument for pushrods. The z06 vette.

12. Fast, but still a Chevy.

13. I know pushrods are shorter on top than DOHC engines, and all is as simple as it seems. How can you compare a 5.7, with EIGHT cylinders, to a DOHC 3.8 FLAT SIX? You seem to have missed my argument: all other things (displacement, number of cylinders, engine cylinder arrangement...) being equal, a DOHC engine wins. Lets compare a 5.7 'Vette against that same car, but with a DOHC, 4 valve/cylinder engine...The results would be different.

Your argument states essentially: A ZO6 beat a DOHC Honda insight aroung the Nurburgring, so, therefore, DOHC is not as fast afterall. How laughable.
Now is where you are starting to lose it kid, the Carrera GT is a 5.7L V10 that makes power up to 8400rpm. The Z06 makes near equal power(almost 500 to the wheels), and MORE torque at 2000rpm LESS. And the z06 costs SIX TIMES LESS and is just a pinch slower around nurburgring, not bad I would say. Considering the GT is the ONLY production car faster than the Z06.


See I dont disagree with your conclusions, just the resoning behind them. And the absoluteness with which you state them.

Quote:
/b]
15. You are free to disagree with me, but I am fre to tear your argument apart, especialy when it is as presumptious as the "Vette argument. [/B]
Dude, your not really tearing any argument apart, your making an ass out of yourself. You may have read magazines, and read lots of forums on the internet, but you only half know what you are talking about. Before being so arrogant, try listening, it will go along way.
08-16-2005 08:23 PM
2005Ninja250R Strong words buddy. No need to get all defensive about it all. Its just metal.

1. Which I am very passionate about.

But abit of background to clearify my point. I'm not a supporter of pushrod design. I've never owned a pushrod engine (one SOHC, 5 DOHC) correction. I do own an f150, which is most likely pushrod. But I bought it couse it was cheap, not powerfull.

2. The newer F-150s utilize SOHC heads...

So onto engines. DOHC do allow for higher rev lines.

3. Which is great.

But not becouse of reduced friction, rather due to reduced recipocating mass.

4. Yes, but reduced friction is not an added benefit of OHC, but rather, a prerequsite of its design. Also, lower recipricating mass is better than clunky pushrods throughout the powerband, makeing an angine that "snaps open or shut" when the RPM rise and when they fall, as opposed to the slower engine braking of most all pushrod engines in production today. Those hundredths of a second matter on the track, which is why in the higest levels of motorcycle racing today, all you see is DOHC. It's not a fashion statement: it's for a legitimate reason.

Less parts have to come to a stop, change direction, accelerate, and come to a stop again. Less vibration=less stress.

5. Uh-huh.

Still the limiting factor is most often not the valve train, but rather the linear piston speed.

6. Beeep! Wrong! The valve train is perhaps the most important factor in engine design. Who cares if an engine will spin freely with virtually no effort, if it wheezes and has difficulty under hard acceleration? The valvetrain is second perhaps to only valve timing in importance.

Which is completely unaffected by valve train configuration.

7. Wrong again.

Moving on to the subject of drivability. A high revving engine produces plenty of power on the dyno, but does it work in the real world? Well in the extreme, no.

8. That is why Japan has produced 18,000 RPM two strokes for the street, and why Kawasaki's beloved ZX-6RR has a 16,000 RPM redline? Far beit for me, a lowly college student to tell the "Big Four" how to produce motorcycles, as I have not created my own, and never will. Drivability is only an issue because of the limits of the rider's skill. If a rider keeps the engine "on cam", or "on the boil", then the engine is in it's element. Pushrod engines are lazier, and take less effort to flog correctly. That must be why dumber people seem to like them so much. Ignorance is indeed bliss afterall.

g a jet turbine in a motorcycle. While it has been done, its little more than a novelty. The engine performs very poor in transients.
Why? becouse the energy of a recipocating (or rotating) part is 1/2mv^2. It has a great deal more to do with its speed than with its weight. So the faster the engine spins, the more reluctant its going to be when it comes time to spin faster or slower. Furthermore in a bike, it will create stronger gyro forces, which will slow down handling.

9. Yet there is still that problem of ever-rising redlines...what to do about that? Better go tell the "Big Four", they might want to know this...

Thus suzukis approach of keeping the stroke as long as possible, limiting rev's but creating an even torque curve with a great deal of ussable power and unparallel throttle responce. Compare that to yamaha's mill and their sudden lunge in the powerband.

10. It is all up to taste. Suzuki has a great powerplant, with a ceiling of 13,000 if i am not mistaken on their GSX-R 1000, and Yamaha is limited to 13,500 on their new YZF-R1, if I am not mistaken. Both great engines, but Yamaha's solutions are more elegant: 5 valves per cylinder, a higher redline, etc. All up to personal taste.

Now on to handling. Fewer powerpulses per second (becouse of a twin configuration, or a slower rev) allow the tire more time in a rest state, thus giving it more time to regain traction. The key to the magical advantage ducati's had over otherbikes for years. Thus the big bang firing order was born, which simulates a twin.

11. Um, yeah, but that can be overcome by holding in the clutch. A secret from me to you, now don't tell anyone Vash...Screw Ducati's overpriced high-maintenance bikes. Screw V-TWINkies.

And another argument for pushrods. The z06 vette.

12. Fast, but still a Chevy.

Not my favorite car, but one that demands respect non the less. It turnes out faster lap time in norimburg (a long involved course) than any porche barring to carrerra gt. The engine itself isnt really anything to be bragging about. However the lower profile of a pushrod engine does allow lower CG than a DOHC engine could. All is not as simple as it seems.

13. I know pushrods are shorter on top than DOHC engines, and all is as simple as it seems. How can you compare a 5.7, with EIGHT cylinders, to a DOHC 3.8 FLAT SIX? You seem to have missed my argument: all other things (displacement, number of cylinders, engine cylinder arrangement...) being equal, a DOHC engine wins. Lets compare a 5.7 'Vette against that same car, but with a DOHC, 4 valve/cylinder engine...The results would be different.

Your argument states essentially: A ZO6 beat a DOHC Honda insight aroung the Nurburgring, so, therefore, DOHC is not as fast afterall. How laughable.

Also the handling of the 911 series of Porsches is quite different from the handling of a conventional front-engined 'Vette.

If all other things are equal Vash...

On to honda's v-tech. A simple switch from one cam profile to another at higher revs. The idea was not to get more power, it could've been done with just sticking to a more aggressive profile. The idea was to preserve gas milage at low rpm. BTW ferrari took the same concept to a much more elegant solution by grinding multimple profiles into a single cam, and moving the cam longitudnally as the revs increase. No sharp transition there.

14. Um, yeah, did you get the memo? Honda's solution to drivability at lower revvs was VTEC, and fuel economy was a secondary concern to perfomance, as VTEC was developed from FORMULA ONE! In street applications (Type-Rs, NSXs, Integras, etc...) fuel economy became more important. Ferraris' solution was nice, but when was the last time you saw the mileage on a Ferrari exceed 100,000 successfully? Elegance at the expence of reliablity: That's Ferrari!

See I dont disagree with your conclusions, just the resoning behind them. And the absoluteness with which you state them.

15. You are free to disagree with me, but I am fre to tear your argument apart, especialy when it is as presumptious as the "Vette argument.
08-16-2005 02:10 PM
Mike08 Wellcome from Spain

Nice Bike, enyoy it with health

Vsssssssss
08-16-2005 12:12 PM
Vash Strong words buddy. No need to get all defensive about it all. Its just metal.
But abit of background to clearify my point. I'm not a supporter of pushrod design. I've never owned a pushrod engine (one SOHC, 5 DOHC) correction. I do own an f150, which is most likely pushrod. But I bought it couse it was cheap, not powerfull.

So onto engines. DOHC do allow for higher rev lines. But not becouse of reduced friction, rather due to reduced recipocating mass. Less parts have to come to a stop, change direction, accelerate, and come to a stop again. Less vibration=less stress.
Still the limiting factor is most often not the valve train, but rather the linear piston speed. Which is completely unaffected by valve train configuration.
Moving on to the subject of drivability. A high revving engine produces plenty of power on the dyno, but does it work in the real world? Well in the extreme, no. Consider putting a jet turbine in a motorcycle. While it has been done, its little more than a novelty. The engine performs very poor in transients.
Why? becouse the energy of a recipocating (or rotating) part is 1/2mv^2. It has a great deal more to do with its speed than with its weight. So the faster the engine spins, the more reluctant its going to be when it comes time to spin faster or slower. Furthermore in a bike, it will create stronger gyro forces, which will slow down handling. Thus suzukis approach of keeping the stroke as long as possible, limiting rev's but creating an even torque curve with a great deal of ussable power and unparallel throttle responce. Compare that to yamaha's mill and their sudden lunge in the powerband.
Now on to handling. Fewer powerpulses per second (becouse of a twin configuration, or a slower rev) allow the tire more time in a rest state, thus giving it more time to regain traction. The key to the magical advantage ducati's had over otherbikes for years. Thus the big bang firing order was born, which simulates a twin.

And another argument for pushrods. The z06 vette. Not my favorite car, but one that demands respect non the less. It turnes out faster lap time in norimburg (a long involved course) than any porche barring to carrerra gt. The engine itself isnt really anything to be bragging about. However the lower profile of a pushrod engine does allow lower CG than a DOHC engine could. All is not as simple as it seems.
On to honda's v-tech. A simple switch from one cam profile to another at higher revs. The idea was not to get more power, it could've been done with just sticking to a more aggressive profile. The idea was to preserve gas milage at low rpm. BTW ferrari took the same concept to a much more elegant solution by grinding multimple profiles into a single cam, and moving the cam longitudnally as the revs increase. No sharp transition there.

See I dont disagree with your conclusions, just the resoning behind them. And the absoluteness with which you state them.



08-16-2005 11:26 AM
2005Ninja250R
Quote:
Originally posted by Vash
If you're going to subject everyone to these few bits of knowledge, you might want to check up on them a tad.
I have "subjected" no one to anything. If you don't like it Vash, don't read it. No one has a gun to your head, Mr. Stampede. lol

And I HAVE checked up on them myself. DOHC is superior for fast-spinning, high-revving, lower internalfriction, high-compression engines. That is why COMPOTENT, MODERN companies (Ferrari, Porsche, BMW, Mercedes, Lotus, Toyota, Honda, Nissan, Suzuki, Yamaha, Kawasaki, etc, etc, etc...) lean towards those designs (for HIGH PERFORMANCE), and away from pushrod and flathead designs.

Sorry if it offends the clunky old Chevelle in your garage. Not to say that a Chevelle is slow, it is just that it is about as effecient as a shotgun, when a long-range Draganov sniper rifle is more approproiate for the job at hand. Need me to clarify more?

LIFE IS NOT IN A STRAIGHT LINE.

Let's not even get into how most US manufacturers do not understand what low weight, aerodynamics, all-independent suspension, and a lower center of gravity can do for a performance vehicle...with two wheels, of twice that.

I will agree that eight cylinders has more performance potential, than, say, a single lung engine, a "thumper" if you will. But, for the same displacement...a DOHC 3.0 V12 4 valve/cylinder engine with absolutely RAPE a pushrod 3.0 2 valve/cylinder V12 engine.

Why is this?

Because an inherent flaw in overhead valve "OHV" or pushrod designs is that they use pushrods for valve actuation, which limits the speedthe valves can open and close to admit the air/fuel mixture and push out the spent exhaust gasses. Pushrods are great for slower engines for industrial applications (tractors, tugboats, heavy duty trucks, very old tanks, etc...). However, for, say, competing in the Isle of Man TT in the year 2005, more blunt, or, shall I say, "direct" valve actuation is required to slash hundredths of a second off of lap times. Because overhead cam "OHC", and better still, dual overhaed cam "DOHC" engines have their valve actuation systems directly on top of the valves, their is less power lost, and no long pushrod "middleman" to rob the engine of power through friction, added heat, etc. Therefore, the potential for engine speed is much higher, and the only affordable, non-experimental internal combustion engine design in production with more potential for power per cc, and higher rpm, is the rotary engine. Which has only been mastered and made reliable by Mazda of Japan, formerly known as Toyo Kogyo. For future refernece, check out their mid to late 90s RX-7 turbo sportscar, it is pretty trick.

Also, note that DOHC engines breathe better because of MORE VALVES, which mean more air can be shoved in and out, as opposed to what only two large valves can do. Don't believe me? Next time you have five minutes Vash, draw two identical circles, let's say, 4 inches in diameter. Place them side by side with a stencil, or a handy Coke can perhaps. Then fit four small circles, two on each side at opposite ends of the first large circle (Circle A). Then, fit the two largest circles that you can inside the other circle (Circle B), of course, leaving room for the sparkplug in the center of both circle A abd B. REMEMBER: Make the "small" circles as large as you can without overrunning the edges of the largest circles (A and B).

Done now?

See how the four smaller circles (in Circle A) fill MORE surface area, how matter how large the two other circles (in Circle B) are? All of that area (Within Circle B) is left wasted.

It is simple geometry, and circles are the most effecient valve shape, and wear the best, so they must be utilized. Since a circles diameter is limited by the space it is inside (Circles A and B), the MORE "little" circles , or valves you can fit into the larger one, the more air you can move in and out.

Do you think Honda created VTEC just to show off? No. Honda created VTEC, which was copied subesquently by Porsche, BMW, Toyota, Nissan, etc, because it was more effecient at higher RPM...which just so happens to be where an engine makes most of it's power! Wow, really, 2005Ninja250R? The only way to spin one of these engines faster is by utilizing the holy grail of vavle timing: electronic valve timing "EVT", a technology rumored to be in development for decades, but it has never emerged, even as a technolgy demonstrator form a manufacturer. But if it ever surfaces, it will change everything: again. Think about it...literbikes, with 25,000 RPM redlines for under 15,000. I don't know about any of you, but the future is looking very nice. screw the harley "potato-potato", give my not the modern bliss of vroom-vroom, but zooom-zooom!!!

Really.

This principle also applies to jet engines: the faster the blades spin, and the more fuel is compressed and lit inside of the combustion chamber, the faster the F/A-22 will go. This is, of course, limited my metalurgy, and the wear and limits of the engine installed. It is not slow radial piston aero engines that are state-of-the-art! It is the fast-spinning jet engines.

That is, not to say that propeller aero engines have no future. I mean, look at Cessna from crying out loud! But look at what a Cessna is limited to. Then look at the most modern fighters...name one with an "old", slow-spinning design. I thought not.

I may not be an engineer, but I have torn apart a few engines, and know a few guys who build these things, and I feel they are even more qualified to validate what I have typed here.

So Vash, I hope the next time you ride your awesome Kawasaki, know this: Your DOHC engine, and it is ONLY that design, makes your affordable high-performance sportbike possible. Don't count on weak-lunged pushrod engines to do it for you. You have invested in DOHC, like it or not. OHV is a dinosaur in the throws of it's death, accept it.

I hope I have made my point.

Here are some sources to get you started Vash, baby.


http://www.datsuns.com/Tech/ohv_vs_ohc.htm

http://www.allpar.com/eek/cams.html

http://www.canadiandriver.com/articles/jk/040421.htm

http://www.canadiandriver.com/articles/jk/050713.htm
08-16-2005 05:36 AM
Vash If you're going to subject everyone to these few bits of knowledge, you might want to check up on them a tad.



08-16-2005 01:39 AM
2005Ninja250R
Quote:
Originally posted by Vash
Just out of interest where do you come up with the info for your sigs?
From talking to engineers, and reading car and bike mags since I was 16...I am 23 now.

Oh yeah, and personal experience.
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