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Old 9th October 2005, 13:48   #1
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Post I got a few questions for you motorheads...

Guys, I have a few questions that I would like you guys to answer as they weren't cleared by our Mechanical lecturer:
1) Why do we use an oil and fuel mixture only in 2-Stroke vehicles and not in 4-stroke vehicles?
2) What does the angle of an engine have to do with its performance?(like...we have got 60 degree V's, 90 degree V's, etc.)

I'll keep asking questions as and when they are not clarified...please try and use simple words while explaining...I aint too good at HI-FI words...car related words...you can use.
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Old 9th October 2005, 14:22   #2
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Quote:
Originally Posted by Sid Schumacher
1) Why do we use an oil and fuel mixture only in 2-Stroke vehicles and not in 4-stroke vehicles?
To put things VERY simply: 4 stroke engines require lubrication on the valves and other parts of the engine that are not INSIDE the cumbustion chamber, whereas 2 strokes require lubrication only for the Crank, piston and connecting rod, all of which are part of the cumbustion chamber. The cumbustion cycle of the two strokes include the crankcase.

4 Strokes therefore require a lubrication system that takes oil to these points outside the cumbustion chamber (like the thin chrome pipes you see very clearly on the Bullet's engine, which takes the oil to the valve heads).

This is a very high-level explanation, but there are plenty of sites online to explain things in detail.

Nice example here: http://www.k-wz.de/vmotor/z_omotore.html
you can see how the petrol-oil mix goes through the crank case and then to the cylinder, lubricating the cycle.

Last edited by Steeroid : 9th October 2005 at 14:41.
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Old 9th October 2005, 14:48   #3
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Hey Sid all I know about V engine configurations is it makes the engine more compact if it has more no of cylinder as compared to in line configutration but it gives less centre of gravity.
Detailed info on this can be found in this site - How Stuff Works
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Old 10th October 2005, 05:29   #4
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Who is teaching you mech? I remember that our mech teacher told us that Fiats run with a oil-reserve system, that feeds oil when necessary into the combustion chamber, a la RDs. Saving grace: he was nice enough to accept he could be wrong.
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Old 10th October 2005, 13:11   #5
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yes as Steer said 4 strokes have oil sumps (reservoir at the bottom where the lube is put) which then is circulated thru out the engine for lubrication. The same is done via the petrol/oil mixture in 2 strokes.

As far as Vee angles, higher the V angle flatter (if you visualise) the engine hence lower its CG (center of gravity)...hence more compact and can fit lower in the engine compartment...of course all this is in relation to hi-perf cars like F1 where aerodynamics of engine cover etc is very important.

But there is an optimum V angle for most engine configurations , e,g 3 L V10s (in F1) have that as 72 degrees, but some engine makers do change it..

Renault had a radical 111 degree V10 coupla years back just for the sake of lowering the CG, but it was prone to vibrations and a bit low on power.
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Old 13th October 2005, 15:43   #6
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Thanks guys...Steeroid,Sridhar24,Abhay...not you v1p3r...you went outa topic...but thanks anyway.LOL
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