I'm reading this book and there's a chart that says V8 is slightly smoother than a rotary. Any thoughts?


http://ecx.images-amazon.com/images/I/51vfaUwmNqL._SS500_.jpg

Depending on each engine, that could be true.

edit: what's the definition of smooth they're talking about?

prob. engine vibration to rpm ratio

edit: what's the definition of smooth they're talking about?

They just said "smoother". I assume they mean free from vibrations, friction and coarseness.

Is apple pie better than cherry pie? I say apple pie is, my girl says cherry.

Is apple pie better than cherry pie? I say apple pie is, my girl says cherry.

that post = fail. Whether they mean a smoother power deliver or overall feel of the engine vibrations in the car, it's something that can basically be measured or rated, regardless of opinion. If it was really close, you could sum it up to inaccuracies, but it's not really an opinion thing.

It depends upon the crank and firing order. Ferraris are not balanced the same way as an American V-8.

Rev that V-8 up to 9500rpm and then ask... :cool:

I guess it depends how they measure it, but I doubt in real life driving any V-8 would "feel" as smooth -- the only piston motor that is inherently balanced is the I-6 (and V-12). The V-8 configuration is not inherently balanced.

I have that book too i recommend it to everybody it tells you everything you need to know...I got very familiar with maintaining and increasing hp safely from that book...the knowledge anyway i still need the funds to actually do it :)

Rev that V-8 up to 9500rpm and then ask... :cool:

I guess it depends how they measure it, but I doubt in real life driving any V-8 would "feel" as smooth -- the only piston motor that is inherently balanced is the I-6 (and V-12). The V-8 configuration is not inherently balanced.

Drive the new m3. Redline is pretty high.

In theory an opposed action cannot be smoother than a rotary action.

Not sure why one would care if a V8 was smooth or not. With a V8 you want the roar of the motor and sheer power of the beast unlocked. That includes the trembling and vibrations from the excess power. For a rotary smooth is nice, but for a V8 no danke.

I'd wager that there are V8's that are smoother than currently available rotary engines. In theory, I would think that a rotary has more potential smoothness.

i dont think v8s were meant to be "smooth" so to speak but thtas may just be me

A well-balanced V8 is slightly smoother than a 2 rotor based on torque fluctuation.

This graph is from a Mazda technical document.
http://www.rx8club.com/attachment.php?attachmentid=151004&stc=1&d=1265058180

i dont think v8s were meant to be "smooth" so to speak but thtas may just be me

V8s are meant to have a smoother power delivery than the other engines, same applies for the v12. Then you have firing orders, cranks and whatever to throw in that could mix the cards. I think that they're talking about stock or race tuned engines, not the usual dyno queen\drag strip 200000hp rustang.
American engines in the v8 family were not "well designed" from a sports car point of view but if you take into consideration many of the european engines (smaller displacements, higher power outputs NA vs NA) then you can see that even with a high redline they have a nice smooth power band and torque curve. You could make a comparison out of a Ferrari F430 and a Rx8 to see what the torque delivery is like. The v8 in the new m3 is another good example.
We're talking in percentages though, those engines are way too different!

i dont think v8s were meant to be "smooth" so to speak but thtas may just be me

See that's the issue I'm having... what do they mean by smooth? I'm guessing the V8's in F1 cars could be considered smooth in a sense

V-8 Ferrari's are poorly balanced due to firing order and crank shaft. American V-8's are better balanced because of the reverse BUT don't rev near as high as a result.

I-6's (slant 6 included) are a very well balanced engine but they often pose packaging concerns for front wheel drive cars. Plus its hard to have a common plenum with equal length runners.

Four cylinders sucks with balancing and that is why the bigger a four cylinder is, the more vibration is inherent in the motor. Some four cylinders have counter rotating internal balance shafts to counteract vibration.

V6's are ok balanced in the 60 degree V configuration vs the 90 degree. Volkswagen has a 15 degree compromise V angle. It functions much like a straight 6 but with better under hood packaging with the slight V.

12 cylinders is the way to go with smoothness but then you have greater internal friction to overcome, particularly when cranking the motor.

V10's lots of power---Poorly balanced.

Everything is a trade off. Rotaries have smooth power delivery because of the law of physics: You don't have pistons that constantly accelerates and then deaccelerate. But, rotaries have a poor elongated shaped combustion chamber.

The advantage to the rotary really is its HP power to weight ratio. Smoothness may be a plus but a light engine allows for a light car that corners on rails. It's definitely not fuel efficient though because of the no torque because there are no con rods acting on the crank to multiply torque. And you still have the poor combustion chamber.

I'm sure somebody will come by and say I'm an idiot spouting half truths but okay, whatever, just add to the dialogue and save the insults.

Ferrari's are poorly balanced due to firing order and crank shaft. American V-8's are better balanced BUT don't rev as high.

Yep, but if you take the average torque into consideration from idle to redline then you have a smooth power delivery :)
The firing order and crank shaft designs are a pretty needed trade-off when you consider that those cars should be driven in their appropriate rpm range, when you start driving them then they're smooth... another thing is if you buy one to attend your cool happy hours and dinners ;)

It would be cool to make the same comparison between a 20b and a v8 or a v12 to see how the added rotor behaves.

No disagreements. Everything is a trade off. I wish the rotary had more torque but it doesn't and never will.

After the edit your comment is much more complete and i like it even if it is a bit generic. The thread is generic too so that's fine.
Rotaries with higher torque numbers are possible but changing the e-shaft's eccentricity and housing depths means huge investiments. There's another problem that's displacement related too.
Will a new generation rotary be as smooth as a v8? we shall wait and see.

Anyway i think that part of the problem is also created by the weight of the rotors. Spinning them around at low speed requires a bit of effort while a piston has got what you call "torque multipliers", the rods. Dunno if you understand what i mean though.

At least that paper didn't take boxer engines into consideration!

Drive the new m3. Redline is pretty high.

I know.... it's not 9500rpm.

I know.... it's not 9500rpm.

Neither is the RX-8. The redline on the 8 is 9k. The rev limiter on the other hand, is slightly higher. I'm not sure if it quite goes to 9500 stock though. The tach lags a bit so it's typically a couple hundred rpms lower than what it looks like. Either way, it doesn't matter since you have less power in the 9k range. You can rev to 9k+ (and it's still fun), but not very useful as far as power goes. The 8 is best shifted at 8700 rpm. The m3 has peak power at its redline (8300 rpm) and a rather flat torque curve up until that point as well. My point is, the redline means nothing. I realize the point of this discussion is smoothness, but the thing about the V8 redline is that it's most likely making significantly higher power at that redline. How many renesis engines are putting down more power than the M3? What rpm do they stop making power at?

Well... if you drive luxuray cars all the time....

I would say the rotary is smoother in normal operting driving conditions.

http://www.mazda.com/mazdaspirit/rotary/story/p6.html
While the dual-rotor rotary engine was as smooth as an inline six-cylinder reciprocating engine, the triple-rotor rotary engine could outdo a V8; and nearly match the smoothness of a V12 engine. However, there were a few technical problems with multi-rotor engines Mazda first had to overcome.

that post = fail. Whether they mean a smoother power deliver or overall feel of the engine vibrations in the car, it's something that can basically be measured or rated, regardless of opinion. If it was really close, you could sum it up to inaccuracies, but it's not really an opinion thing.

Sorry but to ask which is "smoother" a V8 or Rotary is very vague. Are we talking about power delivery? Engine vibrations? What V8 are we talking about, there are literally 1000's. Too many variable's to very basic question.
smooth (sm)
adj. smooth·er, smooth·est
1. Having a surface free from irregularities, roughness, or projections; even. See Synonyms at level.
2. Having a fine texture: a smooth fabric.
3.
a. Free from hair, whiskers, or stubble: felt his smooth cheek after the close shave.
b. Having a short dense flat coat. Used of dogs.
4. Having an even consistency: a smooth pudding.
5. Having an even or gentle motion or movement: a smooth ride.
6. Having no obstructions or difficulties: a smooth operation.
7. Serene: a smooth temperament.
8. Bland: a smooth wine.
9. Ingratiatingly polite and agreeable.
10. Having no grossness or coarseness in dress or manner.
v. smoothed, smooth·ing, smoothes
v.tr.
1. To make (something) even, level, or unwrinkled.
2. To rid of obstructions, hindrances, or difficulties.
3. To soothe or tranquilize; make calm.
4. To make less harsh or crude; refine.

Mazda says...

V6 < 13b < V8 < 20b < V12

Mazda says...

V6 < 13b < V8 < 20b < V12

I added the inline 6 which is equivalent in smoothness (torque fluctuation) to a 2 rotor.

I4 < V6 < I6 ≡ R2 < V8 < R3 < V12

I'm curious to know where the H4 and H6 fall in this arrangement.

V10 is inherently unbalanced, so I'm guessing it falls between V8 and R3.

why isnt a 1 rotor in that example? or a 3cyl?

:O HUH HUH WHY

Hey don't forget my Geo Metro!

Revised after a bit of reading:
I4 < H4? ≡ V6 < H6? < I6 ≡ R2 < V8 < V10 < R3 < V12

Added the V10 and the flat engines, based on torque fluctuation.

I know.... it's not 9500rpm.

So you'd rather have an extra 1100 rpm's that completely fall off on power than nearly triple the horsepower, scraping the bottom of the bowl?

Nevermind, saw you're last couple posts, you're a ball of positive energy. :wavey:

So you'd rather have an extra 1100 rpm's that completely fall off on power than nearly triple the horsepower, scraping the bottom of the bowl?

As for me, it all depends on throttle control, irrespective of horsepower or RPM. The higher the horsepower, the finer the precision of throttle control should become. I think the high redline helps in granting a finer degree of throttle control, kind of like a micro-surgery movement scaler(?).

I added the inline 6 which is equivalent in smoothness (torque fluctuation) to a 2 rotor.

I4 < V6 < I6 ≡ R2 < V8 < R3 < V12

I'm curious to know where the H4 and H6 fall in this arrangement.

I4 < V6 < I6 < 2 rotor < V8 < 3 rotor < V10 =/< W10 < V12 =/< W12 < 26B < W16?

I4 < V6 < I6 < 2 rotor < V8 < 3 rotor < V10 =/< W10 < V12 =/< W12 < 26B < W16?

Since a V10 is rough compared to a V12, and mazda says that a 3-rotor is "almost as smooth as a V12" That the 3-rotor would be smoother than the V10.

Yes. I think so. V10 is inherently unbalanced. So an R3 would be smoother. V12 is supposed to be as smooth as they come.

Plus a v12 is the sexiest layout anyway. The only reason any person drives a non v12 car is because of cost. 12 is always the best for everything. No one wants a v6, or even a v8. v12 is what it's all about.

v8s should not be smooth. at least not at idle.

:)

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What about SOHC and DOHC lol

The DEVIL Z it haunts me.

http://zdriver.com/gallery/data/500/286yamaokakazuhiro-img600x450-1043061708nanamemae.jpg

http://www.youtube.com/watch?v=4EwE15wZT7M
Came up to me on a fwy here in Vegas. Pure evil.

Neither is the RX-8. The redline on the 8 is 9k. The rev limiter on the other hand, is slightly higher. I'm not sure if it quite goes to 9500 stock though. The tach lags a bit so it's typically a couple hundred rpms lower than what it looks like. Either way, it doesn't matter since you have less power in the 9k range. You can rev to 9k+ (and it's still fun), but not very useful as far as power goes. The 8 is best shifted at 8700 rpm. The m3 has peak power at its redline (8300 rpm) and a rather flat torque curve up until that point as well. My point is, the redline means nothing. I realize the point of this discussion is smoothness, but the thing about the V8 redline is that it's most likely making significantly higher power at that redline. How many renesis engines are putting down more power than the M3? What rpm do they stop making power at?

I'm not sure what peak power has to do with this. Look around this forum and you'll find post from people admitting that they were cruising in 4th on the expressway, mistakenly thinking they were in 6th for a while before realizing their mistake. I don't think you'll ever see anyone claiming that about any V-8 engine.



Nevermind, saw you're last couple posts, you're a ball of positive energy. :wavey:
Sweet, I've got my very own stalker on the forum now. :uhh:

I'm not sure what peak power has to do with this. Look around this forum and you'll find post from people admitting that they were cruising in 4th on the expressway, mistakenly thinking they were in 6th for a while before realizing their mistake. I don't think you'll ever see anyone claiming that about any V-8 engine.

I'm not sure what the point of that post is. That's just as much about gearing as it is about rpms. If we're still talking smoothness, I'd imagine there is a V8 that is just as smooth as a rotary throughout the rpm range. The point still stands, the redline means nothing without an equal amount of power when compared to another car. If 2 cars have the exact same power curve over different rpm ranges, then yes, the car with a higher redline will be faster.

I'm not sure what the point of that post is. That's just as much about gearing as it is about rpms. If we're still talking smoothness, I'd imagine there is a V8 that is just as smooth as a rotary throughout the rpm range. The point still stands, the redline means nothing without an equal amount of power when compared to another car. If 2 cars have the exact same power curve over different rpm ranges, then yes, the car with a higher redline will be faster.

Name one V-8 that's as smooth as a rotary at 9000rpm.