kav4o написа:Това,че са "скопили" 20-тина коня е много тъпо
само си помисли, че ако не бяха "скопени" тези кончета, колите щяха да са акцизни и голяма екзотика за БГ, както VR6 примерно


musura написа:kav4o написа:Това,че са "скопили" 20-тина коня е много тъпо
само си помисли, че ако не бяха "скопени" тези кончета, колите щяха да са акцизни и голяма екзотика за БГ, както VR6 примерноВажното в случая е, че лесно се "отскопяват"
до 170 кс.
DON'T (read that again DON'T) get a VW 16v. They are absolutely junk.
If you saw the insides of one, you would puke. It is a dead-player
for high performance. The exhaust valves are top-dead-center over
the combustion chamber, and make a 95 degree bend around to exit the
head. BAD!
Before the head came out, rumors were circulating as to its design
characteristics. All of us in the high performance business cringed
at what we heard. We heard that VW had designed the head with the
exhaust valves top dead center over the combustion chamber; the
intake valves cocked over about 20 degrees. We said if that was true,
the head was junk. We couldn't believe VW (read that ANYBODY) would
introduce a high performance head with such awful flow characteristics.
When I saw my first 16v head (off the motor), all my nightmares turned
into reality. Actually, it was worse than I thought. The exhaust valves
were top dead center, but the exhaust ports exceeded a 90 degree bend
to allow the gas to exit. This head was obviously not designed for
performance. The valves spacing is too close together, thus putting
in bigger valves would be near impossible. The only possibility of
obtaining higher performance was porting and polishing.
Ok lets talk about engines. Lets compare some of the best engines with the vw 16v engine.
First when i built an engine i determine the purpose of the engine and the rpm bandwith that i will need the power. How many horsepower i will need and the engine time limit.(reliability).
Reliability and power is something completly diferent.
2 things makes an engine broke : piston velocity and piston aceleration.
When an engine have long stroke the piston velocity goes higher. Typicaly 25m/sec its the limit of a normal engine. The abrasion of the piston inside the engine is very important. So a vw 2ltr engine with 92,8 stroke have 25,1m/s at 8100rpm. If we need to work this engine to higher rpms we must reduce the stroke, for example: from 92,8 to 85 (1817cm3) at 8100rpm we will have 23m/s so we can go to 9000rpm that we will have 25,5 m/s piston velocity. Some guys think that displasment is better than higher rpms. Thats stupid. I prefer an 1.670cc engine that revs 12000rpm thank a 3ltr engine that works 7500rpms. This balance is absolutely calculatable. All the mater is the actual flow of eatch engine lbs/min.Lets see an example:
3ltr engine with 8,5 comp.ratio and 7500rpm limit with volumetric efficiency 82% will gave us 62lbs/min. A 1,7ltr engine with 11 comp.ratio and 12000rpm limit with volumetric efficiency 82% will gave us 70lbs/min. The things are clear.
The other thing is the piston aceleration. Its very important the type lenght of rod / stroke ratio. The vw 2ltr engine have 159/92,8 = 1,713
1,6 - 1,7 is bad engine with rpm limit until 7000rpm max.
1,7 - 1,8 is good engine that can revs 9000rpm.
1,8 - 2,0 is very good engine that can revs 12000rpms.
So vw engine with 1,713 have 30000m/sec2 acceleration piston velocity and piston position from TDC 50000m/sec2 acceleration. When this prices reduces the best lenght to stroke ratio we have. My engine now have 2.105 length to stroke ratio and gives me the benefit to rev it until 12700rpm with no problem. For example a cosworth engine that have 90,8mm piston 76mm stroke and 130mm rod its better engine from stock 2ltr vw because have at 10000rpm 25m/sec 1,710stroke ratio. But thats only the design of the engine. Design of the engine cant give us power but can alow us to rev the engine higher. Cylinder head makes the power. Some theories tells that an cylinder head with bigger valves is better. Thats almost inacurate.
Typical its true but in real fact is mistake.Lets see the theory.
Vw 1.8ltr kr head have 117cfm inlet and 91,2cfm exsaust.
Cosworth have 122cfm inlet and 95,9cfm axsaust.
Theory tell us:
CFM x No. of Cylinders x 0.43 = BHP
Vw 117cfm x 4 x 0.43 = 201.24 bhp.
Cosworth 122cfm x 4 x 0.43 = 209.84 bhp.
Cosworth intake valve is 35mm and vw 32mm.
Typicaly the cosworth head its better BUT lets see it in action:
All the matter of power is how much mixture can pass at the same period of time.
Lets compare the 2 engines with same parts exaclty:
Vw 32mm intake valve 8000rpm limit and 10mm valve lift.
Cosworth 35mm intake valve 8000rpm limit and 10mm valve lift.
Cosworth 131,14 m/s flow mixture.
Vw 140.86 m/s flow mixture.
Thats the real benefit of the vw engine that noone knows.
The cosworth have 1005.16 mm3 valve open, vw have 942.33 mm3 but thats nothing to do with power / flow mixture per sec.
These years i am searching all the kind of engines i ve spent many many hours compare eatch other. Cosworth, Opel Vauxhall XE 16v, 3Sgte st205, Mitsubishi evo. Cosworth is the best of all the above and its more easy to tune.A good engine is more cheap to make it better but a normal engine is most expensive and dificult to make it better.I ve spent thousants of $ and private time to compare all the engines and to make the normal vw engine propably the best of all. I can write for hours but i have limited time.
sin orel C20XE написа:Както каза РАСО,главата на С20ХЕ е уникална,но и долнището не е зле.А и голямо преимущество е и че изпускателната система е отпред!
ПП:Голф 3 1.8,сега видях темата ти в Тунинга,много ревеш за килата на Астрите!
sin orel C20XE написа:Както каза РАСО,главата на С20ХЕ е уникална,но и долнището не е зле.А и голямо преимущество е и че изпускателната система е отпред!
ПП:Голф 3 1.8,сега видях темата ти в Тунинга,много ревеш за килата на Астрите!
Golf 3 1.8 написа:sin orel C20XE написа:Както каза РАСО,главата на С20ХЕ е уникална,но и долнището не е зле.А и голямо преимущество е и че изпускателната система е отпред!
ПП:Голф 3 1.8,сега видях темата ти в Тунинга,много ревеш за килата на Астрите!
Нещо ако искаш да ми кажеш ми пиши на лични а не пълни темата с тъпните ти.
sharkdata написа:Извинявам се за тъпия въпрос,незнам за опеловите двигатели много но C20XE който е атмосферка 150 коня е с предно разположен изпускателен колектор аджеба C20LET 204к.с. е същия мотор но с турбо на него каде му е изпускателния колекто отпред или отзад
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