cadebytiger
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| posted on 21/7/06 at 01:04 PM |
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Bike engines
Having a pinto lump in my car i know very little about bike engines.
What is is about them that allows them to rev so high. Are they all steel? Is it that the bits are lighter or what?
Is there any reason why a pinto could not be built to rev to similar levels? provided all the bits were steel?
Sorry for prob. a stupid question
Rupert
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Pezza
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| posted on 21/7/06 at 01:17 PM |
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Yeah a pinto could probably be made to rev almost that high, cost you around 15 grand thoughat least 
You couldn't pwn your way out of a wet paper bag, with "PWN ME!!" written on it, from the "pwned take-away" which originally contained one
portion of chicken tikka pwnsala and the obligatory free pwnpadom.
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angus.d
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| posted on 21/7/06 at 01:30 PM |
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Rupert
My understanding is that bike engines (particularly modern sports 4 cylinder 4 stroke versions) have over the years become shorter stroke in
comparison to the bore of the engine - probably to accomodate multi valve heads and larger valve head diameter for better engine breathing. Usually
the shorter the stroke the higher the engine revs.
Yes I believe the Japanese bike engines (certainly the ones which are high revving) have steel cranks (as opposed to cast iron ones). In addition the
parts are probably designed to closer tolerances and therefore are better matched and balanced than say a Ford Pinto engine. It would also add
tremendous cost to manufacture Ford Pinto engines from standard with steel cranks etc.
I'm not sure that the Pinto would be able to be built to rev to a similar level as I believe two of the critical criteria for all the moving
parts are that they are light as well as being in balance. When you think of a piston thundering down a cylinder (or a cylinder head valve opening)
the heavier that part is, the more difficult it is going to be to slow down that momentum and reverse its direction (ie to make the piston come back
up cylinder or for the valve to close).
Usually these 4 cylinder bike engines are fitted to a sports bike so you want this high revving nature to go with the bikes purpose. There are other
bike engines which are designed the other way for example a Harley Davidson has a slow revving long stroke motor as this has the characteristics
better suited to relaxed cruising.
Cheers
Angus.
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smart51
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| posted on 21/7/06 at 01:33 PM |
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Bike engines are all alloy, often with pieces made from magnesium because aluminiums is just so heavy.
They rev high because they have a large bore and small stroke, so that the piston speed isn't too high.
Big bike engines also have high compression ratios, lots of valves (the R1 is 5 per cylinder) high revving cams and 1 carb (or throttle body) per
cylinder. Think of them like a car engine that has had all the work done on them for performance, except done by a big quality focused Japanese
company rather than a back street race tuners.
The down sides are that they don't have much low rev pull and have to be revved a lot at high speed. Peak torque on mine is 9500 RPM rather
than 3500 on a typical car engine.
The plusses are phenominal acceleration and a glorious sound track at full throttle.
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02GF74
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| posted on 21/7/06 at 01:41 PM |
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quote:
Originally posted by cadebytiger
Is there any reason why a pinto could not be built to rev to similar levels? provided all the bits were steel?
steel pistons,  that'll be good, they'd rev up to the same level, maybe once, as you sit back and watch the internals fly out through
your bonnet 
... serioulsy though, doesn't torque come into it? you need more of it when moving a heavier object, cars engines acheive this by heavier
flywheels and longer stroke.
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cadebytiger
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| posted on 21/7/06 at 02:20 PM |
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Thanks chap i understand a little better now.
So what gearboxes do you mate a bike engine to?
Are the only differences between BECs and standards the engine? I guess you have a semiautobox do you?
Also if these engines are already at full tune do you have to do any further tuning?
Quite fancy building a BEC at some point they sound like fun!
Rupert
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Hellfire
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| posted on 21/7/06 at 02:33 PM |
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Bike engines run as a complete unit through the engine to a gearbox and then to output shaft which is where you connect the prop via an adapter.
Basically take the engine/gearbox from a bike and fit it into a car... sounds easy and I guess it is as most weigh less than 75Kg's - a two man
job to lift engine/gearbox
Clutch's on most motorbikes are wet as they use mostly multi-cork pads on 13-14 alloy rings between steel porous disc's. When you let out
the clutch the oil squeezes into the ring allowing smooth take up's. You then do not need a heavy flywheel and other stuff.
FTR - magnesium cast parts are not magnesium it's misleading. They are high percentage magnesium/aluminium alloy. Most aluminium castparts are
just that. The reason is pure Magnesium will spontaneoulsy combust when it gets hot and hits ignition temperatures ie when it is machined or cut.
The only part I know which used to be made from almost pure Magnesium is the body of the WACCA - a reciprocating wacker plate used to tamp down road
surfaces. They closed the factory in Austria because of fire risk... I believe they are now made from a more friendly aluminium/magnesium
composite.
Steve
[Edited on 21-7-06 by Hellfire]
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cadebytiger
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| posted on 21/7/06 at 02:37 PM |
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MAgnesium burns at silly temperatures and emits a very bright light. You may have done this at school.
They make you look through a darkened glass plate
Rupert
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cadebytiger
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| posted on 21/7/06 at 02:39 PM |
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So in that case does it make them quite easy to fit to the car?
A couple of engine mounts a new prop and a new exhaust?
How does their oil system work? Are they all dry sumps?
Rupert
quote:
Originally posted by Hellfire
Bike engines run as a complete unit through the engine to a gearbox and then to output shaft which is where you connect the prop via an adapter.
Basically take the engine/gearbox from a bike and fit it into a car... sounds easy and I guess it is as most weigh less than 75Kg's - a two man
job to lift engine/gearbox
Clutch's on most motorbikes are wet as they use mostly multi-cork pads on 13-14 alloy rings between steel porous disc's. When you let out
the clutch the oil squeezes into the ring allowing smooth take up's. You then do not need a heavy flywheel and other stuff.
FTR - magnesium cast parts are not magnesium it's misleading. They are high percentage magnesium/aluminium alloy. Most aluminium castparts are
just that. The reason is pure Magnesium will spontaneoulsy combust when it gets hot and hits ignition temperatures ie when it is machined or cut.
The only part I know which used to be made from almost pure Magnesium is the body of the WACCA - a reciprocating wacker plate used to tamp down road
surfaces. They closed the factory in Austria because of fire risk... I believe they are now made from a more friendly aluminium/magnesium
composite.
Steve
[Edited on 21-7-06 by Hellfire]
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mandbsheldon
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| posted on 21/7/06 at 02:39 PM |
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