Olakšavanje zamajca coupe 20vt

[martin_bravo]

Znaci zanimame kolko se dobi olaksanjem zamajca a kolko izgubi , i dali se to isplati radit na tom motoru

i zanimame dali pase zamajac sa obicnog 20v po šifri nije isti pa me zanima ako pase i dali je lakši?

[ludaman]

ne pase ti sa obicnog 20v.. olaksavanjem ces dobit bolje razvrtavanje i manji moment :) nabavi plocu 7075 aluminija i napravi ga od toga, kvalitetniji a 10 puta laksi od serijale :) makar ako imas tog materijala na lageru i mene bi interesirao takav zamajac :)

p.s. daj ugnjavi frenda da nadje motoric lera da mi ga posaljete. samo to cekam za djir :)

[gturcic]

Ne dobije se momenat, a ni snaga, samo se smanji inercija motora, tj. motor brže "nabire" i gubi okretaje. Dobitak je isključivo ovisan o brzini motora (rotacija), tako da je primjetniji na "visokoturažnm" motorima, tipa Honda typR i pri niskim brzinama (niskim prijenosnim omjerima mjenjača).

Coupe 20vt, odnosno većina turbaka, su relativno sporohodni motori (redline 6-6.5k rpm a ne 7-8k kao naturpijani atmosferci), s jakim srednjim područjem i relativno dugim prijenosnim omjerima u mjenjaču.
Po meni, mislim da se ne isplati olakÅ¡avati zamaÅ¡njak pri niskom ili srednjem nivou tuninga, pogotovo jer takav zahvat ima i negativnih efekata na voznost. TakoÄ'er, ukoliko se nestručno radi riskiraÅ¡ veliku havariju tj. mehaničku eksploziju u prednjem koÅ¡u auta!

Ne znam jesi li pročitao thread o tome,
http://fiatisti.hr/forum/index.php?topic=23995.15
u kojem ima svakakvih mišeljna i informacija.

malo ozbiljniji i detaljniji članak je postojeao na siteu www.pumaracing.co.uk, ali site-a više nema, tako da postam copy tog teksta:

When the flywheel of a car is lightened it can have a great effect on acceleration - much more than just the weight saving as a proportion of the total vehicle weight would account for. This is because rotating components store rotational energy as well as having to be accelerated in a linear direction along with the rest of the car's mass. The faster a component rotates, the greater the amount of rotational kinetic energy that ends up being stored in it. The engine turns potential energy from fuel into kinetic energy of motion when it accelerates a vehicle. Any energy that ends up being stored in rotating components is not available to accelerate the car in a linear direction - so reducing the mass (or more properly the "moment of inertia") of these components leaves more of the engine's output to accelerate the car. It can be useful to know how much weight we would need to remove from the chassis to equate to removing a given amount of weight from the flywheel (or any other rotating component). There is more than one way of solving this equation - we can work out the torque and forces acting on the various components and hence calculate the accelerations involved - also we can solve it by considering the kinetic energy of the system. The latter approach is simpler to explain so this is the one shown below. Copyright David Baker and Puma Race Engines

Let's imagine we take two identical cars - to car A we add 1 Kg of mass to the circumference of the flywheel at radius "r" from the centre. To car B we add exactly the right amount of mass to the chassis so that both cars continue to accelerate at the same rate. If we accelerate both cars for the same amount of time they will end up at the same speed and will have absorbed the same amount of kinetic energy from the engine. In other words, the additional 1 Kg in the flywheel of car A will have stored the same amount of kinetic energy as the additional M Kg of mass in the chassis of car B. To solve the problem of the size of M we need to use the following definitions:

V - the speed of either car after the period of acceleration
R - the tyre radius
G - the total gearing (i.e. the number of engine revolutions for each tyre revolution)
r - the flywheel radius (i.e. the radius at which the extra mass has been added to car A)
M - the amount of mass added to the chassis of car B

Kinetic energy is proportional to½mv² - the kinetic energy stored in the extra chassis mass in car B is therefore½MV².

The extra 1 Kg of flywheel mass in car A stores linear kinetic energy in the same way as if it were just part of the chassis. After all, every part of the car is travelling at V m/s - so it stores linear kinetic energy of½ x 1 x V² =½V².

To find out how much rotational kinetic energy the 1 Kg stores, we need to know the speed the flywheel circumference is travelling at. The car is travelling at the same speed as the circumference of the tyre (assuming no tyre slip of course). We know that for every revolution of the tyre, the flywheel makes G revolutions. However the flywheel is a different size to the tyre - so the speed of the circumference of the flywheel is VGr/R. The rotational kinetic energy is therefore½(VGr/R)².

Now we can put the whole equation together - the extra kinetic energy in the chassis of car B = the sum of the linear and rotational kinetic energies in the 1 Kg of flywheel mass of car A - therefore:

½MV² =½V² +½(VGr/R)² =>

Ã,½MV² =½V² +½V²(Gr/R)² => divide both sides by½V² to arrive at the final equation:

M = 1 + (Gr/R)²

That wasn't so bad then - we managed to avoid using true rotational dynamics involving radians and moments of inertia by considering the actual speed of the flywheel circumference. This did of course involve assuming that all the mass added or removed from the flywheel was at the same radius from the centre. In the real world that is not going to be the case so we need to use moments of inertia rather than mass to solve the equation. The simple equation above is useful though in getting an idea of the relative effect of lightening components provided we have a good idea of the average radius that the metal is removed from. It can be seen that gearing is an important factor in this equation. The higher the gearing the greater the effect of reducing weight - so for a real car the effect is large in 1st gear and progressively less important in the higher gears. We can also hopefully see that when r is larger, so is the effective chassis weight M. So removing mass from the outside of the flywheel is more effective than removing it from nearer the centre. Copyright David Baker and Puma Race Engines

It might at first look as though tyre diameter is important but of course it isn't for a real car - if tyre size was to change then so would gearing have to if overall mph per thousand rpm were to stay the same - the two factors would then cancel out again.

To show the sort of numbers that a real car might have, I did some calculations based on a car with average gear ratios and tyre sizes - the table below shows the number of Kg of mass that would have to be removed from the chassis to equate to 1 Kg removed from the O/D of the flywheel at a radius of 5 inches.

GEAR MASS KG
1 39
2 12
3 6
4 4
5 3

So in first and second gear this is a pretty important effect - I built an engine recently and managed to remove nearly 3 Kg from the outside of the standard flywheel - so that would be equivalent to lightening the car by over 100 Kg in 1st gear - not to be sneezed at in terms of acceleration from rest. With special steel or aluminium flywheels even more "moment of inertia" can be saved. The recent trend in racing engines to using very small and light paddle clutches and flywheels is therefore more effective in terms of the overall performance of the vehicle than it might first appear. Copyright David Baker and Puma Race Engines

There's a final consequence of the "flywheel effect" being dependent on gearing. Small highly tuned, high revving engines need to run much higher (numerically) gearing than large, low tuned engines. This means that the effect can be very pronounced on them. Bike engines are a good case in point, especially as they are now starting to be used in cars so much. A 100 bhp bike engine might only be 600cc and rev to 12,000 rpm. A 100 bhp car engine might be 2 litres and rev to 5,500 rpm. Put the bike engine in a car and you'll need to run a final drive ratio twice as high as for the car engine. As the flywheel effect is proportional to the square of gearing, it will be 4 times as high for the bike engine. You could therefore be talking about 1kg off the flywheel being equivalent to 160kg off the weight of the car. That's why bike engines have such small multiplate clutches to keep the moment of inertia down. On the other side of the coin, it's not worth spending much money lightening the flywheel of a 7 litre Chevy engine revving to under 5,000 and geared for 60 mph in first as the vehicle will be very insensitive to the reduction in weight. Copyright David Baker and Puma Race Engines

If you are going to get your standard cast iron road car flywheel lightened then be sure to take it to a proper vehicle engineer and not just your local machine shop. Take off too much material and it might be weakened so much that it explodes in use. Given that flywheels (at least in rear wheel drive cars) tend to be situated about level with your feet, it isn't worth the extra acceleration if you lose both feet when the ring gear comes out through the side of the transmission tunnel like a buzz saw at 7,000 rpm. There are plenty of ex racing drivers hobbling about on crutches who'll tell you that this can and does happen. On FWD cars the effects can even more unpleasant - a flywheel entering the cabin can give you a split personality starting from just below the waist that will put quite a crimp in your day. Also when you remove any weight from the flywheel it will need re-balancing again properly. We'll be happy to do the job for you if you don't know of an experienced engineering shop.

Addenda (May 2002). A friend, Garry, told me an interesting story the other day which relates to my warning above about lightening flywheels properly. He was at the local engine reconditioners chatting to the proprietor about having a cylinder head skimmed. At the back of the workshop, one of the lads who worked there was lightening a flywheel on the lathe. Suddenly there was an almighty bang and a lot of swearing so Garry and the owner went back to see what had happened. The lad had been removing material from the centre of the flywheel, just outboard of where the 6 crankshaft bolt holes are. For starters this is a stupid place to remove material because it is a highly stressed area and also much less effective in terms of the reduction in inertia than removing material from the rim of the flywheel. Anyway, to cut a long story short this idiot had machined right through the flywheel leaving the centre attached to the chuck of the lathe and the rest had flown off and bounced across the workshop. It made me wonder what would have happened if he'd stopped just short of machining right through, say with only 1mm thickness of material left, without realising how thin and weak he'd made it. It would then have failed in the car, maybe at high rpm, and done the sort of damage I describe above. The moral is clear. Get critical work like this done by someone who knows what they are doing.

[martin_bravo]

Mislio sam  olaksat samo vanski rub ali nikakvo pretjerivanje , znaci cisto malo da se dobi na razvrtavanju motora , e sad dali se gubi moment ?  po meni se nebi smjelo gubit osim onog pocetnog momenta pri kretanju ??

Ima neko da je probo olaksat zamajac?

[gturcic]

Mislio sam  olaksat samo vanski rub ali nikakvo pretjerivanje , znaci cisto malo da se dobi na razvrtavanju motora , e sad dali se gubi moment ?  po meni se nebi smjelo gubit osim onog pocetnog momenta pri kretanju ??

Ima neko da je probo olaksat zamajac?

Moment se ne gubi, u smislu Nm koje mjeriš na valjcima, tj. moment sile, M=F*d.

Moment se gubi, u smislu momenta "inercije", tj. kinetička energija, E=mv^2 (smanjio si m, masu, a time i energiju koju ti ta masa, jednom ubrzana, "vraća").

Pročitaj prethodni post u kurzivu.

Gubit ćeš u kretanju, a dobit ćeš u odazivu na gas. Bit će ti teže krenut, i teže brzo krenut (ne ugušit motor niti provrtjet u prazno); teže točno promijenit brzinu (tj. pogodit okretaje, pogotovo iz više u nižu). Sve ovo vrijedi ako si prosječan vozač, ako si natprosječan, bit ćeš oduševljen većom kontrolom i življim motorom.

Tvornički zamašnjak je optimum performanse/elastičnost po mišljenju tvornice; kao pri svakom tuningu možeš promijeti taj omjer, ali što dobiješ na jednoj strani izgubiš na drugoj.

[martin_bravo]

Malo sam cito ovu temu sta si satvio ,i to je to , odlucio sam ga olakšat , e sad nezelim pretjerivat znaci neka zlatna sredina , sta preporucujete znaci nikakvo pretjerivanje mislio sam oko 20-25% kolko cu uopce dobit s tako malim olaksavanjem ?

E sad sto se tice balansiranja je dovolno samo njega balansirat ili i radilicu s njim bez obzira sta se samo on olaksava
I zanimame ako neko zna kolko je na tom autu cc tezak seriski zamajac , cinio mi se dosta tezak kad sam ga bio skidao , puno tezi nego na nekom 1.6 motoru

[alfaomega]

Kak ti je kolega rekel samo taj dio ti je neisolativ omjer utrošenog i dobivenog ti je minus. A ako si toliko napel treba balansirat skupa sa radilicom.

[bax145Q4]

Olaksaj ga cim vise i bolje ce ti auto izlazit iz turbo rupe, osjeti se razlika, nemoj trosit na aluminijski zamasnjak bespotrebno ti je to