Obrtni Moment i Ks - Nejasnoce!!!, povezanost ova dva pojma!

[shone190]

Kakva je povezanost izmedju obrtnog momenta i KS kod automobila? Tacnije vidim da se obrtni moment povezuje sa vucom automobila i osecajem "lepljenja" za sediste.
Kakva je situacija recimo kod dva automobila iste tezine koji imaju recimo po 150KS, ali je obrtni moment kod prvog 150Nm, a kod drugog 200Nm?
Koliko je to osetno pri voznji?
Takodje me interesuje jel' bolje da je maksimalni obrtni moment na nizem ili visem broju obrtaja, kada je u pitanju ubrzanje od 0-100?

Pozdrav!

[Wiz]

Sto nizi obratji to bolje,sto veci obrtni moment tim bolje,bitna je linearnost u celom rezimu rada

[shone190]

Edit 012: Ne citirati post iznad.
Sta bolje? Ubrzanje, maksimalna brzina ili nesto trece? U principu me interesuje da li je kod ubrzanja i "lepljenja" bitniji obrtni moment ili KS?
Jel' ima neko neki link ka objasnjenjima ovih pojmova ako ga smara da pise ovde?

Pozdrav!

[srle1]

Sila kojom klipovi okreću radilicu preračunata u N/m.Što veći obrtni moment potreban je niži broj obrtaja za istu snagu.Motori sa velikim obrtnim momentom dobro raspoređenih kroz ceo opseg obrtaja imaju prednost jer zahtevaju manje rada sa menjačem tj. vuku jako u svim brzinama podjednako.

[206]

Ova dva pojma su u stvari jedno te isto - odnosno kao proizvod rada motora postoji samo jedno, a to je obrtni moment. Znaci, motor proizvodi obrtni moment, a ne KS, odnosno KW.

Ono sto nazivamo snagom, je samo funkcija obrtnog momenta u odnosu na obrtaje motora, i dobija se formulom:

KS = (obrtni moment x obrtaji motora) / 5252.

Npr. 500 NM x 3000 RPM = 1.500.000 / 5252 = 285KS, - odnosno motor koji na 3000 obrtaja ima 500NM obrtnog momenta, ostvaruje ukupnu "snagu" od 285 KS. Znaci, formula 1, koja ima, sta znam, 900KS na 19.000 obrtaja, po toj formuli, proizvodi oko 250NM obrtnog momenta...smesno. Ali se vrti kao suluda, i time ti nadoknadjuje. Isto i za Honde recimo, motori im imaju mali obrtni moment, ali se jako mnogo vrte, te imaju dobru snagu, ali jako visoko.

Znaci, ono to te lepi za sediste je u stvari obrtni moment, i idealno bi bilo kada bi najveci bio na jako malim obrtajima, i ostajao dosta veliki na visokim obrtajima - sto je upravo ono sto dobijas kod dobro koncipiranih turbo motora. Atmosferci znaci slabije vuku od turbo motora na nizim obrtajima, ali se jace vrte. E sad, ne uzimajte ovo za sveto slovo, naravno da ima atmosferaca koji dobro vuku pri nizim obrtajima (varijabilni sistem razvoda ventila, itd...), i turbo motora koji slabo vuku na niskim (turbine sa velikim spool-up vremenom), ali generalno to je prica.

[tenzo RS]

...evo pogledaj malo ovde...vec se pricalo o tome...

http://hiitek.mine.nu/forums/cannonball ... c&start=20

[Nenad]

Najprostije receno, obrtni moment daje ubrzanje a KS brzinu.

S' naucne strane pogledaj ovde-

http://science.howstuffworks.com/fpte4.htm

http://science.howstuffworks.com/fpte5.htm

itd.

Kada ocenjujes kakav je auto najbolja slika je kada je maksimalni obrtni momenat ravna linija od 1500-2000 obrtaja pa do 6-6500 tj.crvenog polja U realnom zivotu ti to daju kompresori i poslednje generacije turbina sa varijabilnom geometrijom lopatica i sl.
Sto obrtni momet vise lici na strmu planinu to je losije, znaci da je iskoriscenje motora u vrlo uskom dijapazonu obrtaja.

[Black Knight]

vreme x rad = snaga









torque


The Only Thing You Really Need to Know

Repeat after me. "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*." :-)

The mass public get excited about the max HP figure. When in fact, there is a HELLA lot more to the story for an engine.

The most important performance indicator is the torque output across the entire rev range, from just off idle till redline. Manufacturers just quote the peak figures, which is fine for gearheads cuz they can quickly visualize the majority of the torque curve in their minds just by seeing where the torque peak occurs in the RPM range vs where the HP peak does (that, along with other info like # of cylinders, displacement of the engine, etc.)

What you want, is a flat torque curve, to occur as early as possible, and to last as long as possible. Look at the torque curve of small-displacement, turbo engines. Nothing...nothing...nothing...we got a heartbeat now....ah it's slightly more....BOOOM it has swelled....still going....falling off now...falling VERY fast...redline reached.

Whereas something like a large-displacement V-12 will have a very flat curve the whole way. There are many things engineers can do to affect the curve.

But in general, this is why BMW and Honda engines in particular feel so good on the road: The peak figures aren't everything: Rather, they produce nice steady torque across a good part of the RPM range. Whereas most American engines fall flat on their face once they go to the upper rpm range (Corvettes included, except for the almighty Z06).

Look at the new BMW M3 for example. It can rev to 8000 rpm. It doesn't produce much more torque over its predecessor at all (the E36 in Europe), but it can rev a LOT higher, and here's the important thing: While in that very high rpm range, its torque output is STILL at least 80% of the max it can do (around its midrange of 4-5K). That's why it pulls and pulls and pulls, hard, all the way to 8000rpm. Whereas the similarly-powered and similarly-heavy car its racing needs to stop short at say, 6000 rpm, and shift. Of course, the BMW will walk it.

Always try to look at the torque curve from idle to redline. That formula provided of HP = (T x RPM) / 5252 should be used to calculate the horsepower OR the torque (my preference, always) at any respective RPM, based on what the graph tells you.

For example, if the MDX makes 253 lb-ft at 3500rpm and 265hp@5800 rpm, it is in fact outputting the following amount of torque at that HP peak:

265 = (T x 5800) / 5252; solving for T yields 240 lb-ft @ 5800rpm.

What does this mean? Means that the MDX has impressively-flat torque output all the way to redline. Only a mere 13 lb-ft less than at its very broad mid-range!! That is very admirable. Especially since this is also true at ~2000 rpm.