Why dont we get smaller displacement V8's etc
Discussion
Lefty Guns said:
Dave^ said:
Defcon5 said:
Pretty sure mazda did a 1.8 V6
yup, they did....in the MX3....
sounded quite well up near the redline too....
But I suppose that back then ('92?) that wasn't a bad output from an 1800cc....
Huff said:
More likely - cost/complexity and dreadful fuel economy; the losses from (1) all the extra combustion chamber area lose energy before it even makes it to the crank, and (2) lots more internal friction are significant.
You say the economy would be dreadful, say for example you had a 2.0 v8 that was "basically" 2x 1000cc bike engines. Maybe it could make in the region of 300bhp. Edited by Huff on Friday 25th September 13:56
Would the economy be any worse than a 4.0 v8 that made 300bhp?
Lefty Guns said:
Huff said:
More likely - cost/complexity and dreadful fuel economy; the losses from (1) all the extra combustion chamber area lose energy before it even makes it to the crank, and (2) lots more internal friction are significant.
You say the economy would be dreadful, say for example you had a 2.0 v8 that was "basically" 2x 1000cc bike engines. Maybe it could make in the region of 300bhp. Edited by Huff on Friday 25th September 13:56
Would the economy be any worse than a 4.0 v8 that made 300bhp?
could be wrong tho.... I usually am....
Lefty Guns said:
You say the economy would be dreadful, say for example you had a 2.0 v8 that was "basically" 2x 1000cc bike engines. Maybe it could make in the region of 300bhp.
Would the economy be any worse than a 4.0 v8 that made 300bhp?
If you are simply comparing a 2.0L and a 4.0L engine producing 300bhp, both naturally aspirated, then the 2.0L engine isn't likely to have the kind of road manners that many people would find acceptable.Would the economy be any worse than a 4.0 v8 that made 300bhp?
However, I thought the point of the thread is why not have similar sized engines with more cylinders, i.e. a 2.0L V8 against a 2.0L i4. In this case the V8 will very likely give worse economy and emissions performance. More moving parts gives more friction, and surface area/volume of the cylinders becomes less favourable. It will require more complex/expensive exhaust and inlet manifolds. Manufacturing, running and servicing costs will be significantly higher and the resulting engine will be less compact than the equivalent i4.
Marketing.
Cylinders are seen as prestigous so you pay more for more of them. The last thing a car maker wants is to errode the market value of its more profiable products. So they put four cylinder engines in all the cheap cars.
Parts count is virtually irrelevent to the cost of an engine. For any given design you will need:
A factory
Design
Testing
Tooling
A workforce
The above are needed just as much for a V16 as for a straight four.
The time taken to assemble the engine is how long it takes massive robots to feed in the parts. Some parts, such as the block and crank for example are required in the same quantity regardless of engine design.
All of this is why doubling the cylinder count does not double the cost of an engine.
Cylinders are seen as prestigous so you pay more for more of them. The last thing a car maker wants is to errode the market value of its more profiable products. So they put four cylinder engines in all the cheap cars.
Parts count is virtually irrelevent to the cost of an engine. For any given design you will need:
A factory
Design
Testing
Tooling
A workforce
The above are needed just as much for a V16 as for a straight four.
The time taken to assemble the engine is how long it takes massive robots to feed in the parts. Some parts, such as the block and crank for example are required in the same quantity regardless of engine design.
All of this is why doubling the cylinder count does not double the cost of an engine.
Small engines need to run at high rpms to give power, (the more bangs, rather than bigger bang) and it's higher rpms that take the economy down as there is a lot of fast moving bits changing directions.
As for V6 and V8's, engines like that cost more to make with 2 cylinder heads, 4 cams.
V6's are good for their size, 3 and a half cyl long, and quite a squarish footprint, so they tend to be picked for large capacity engines that need to be compact.
I wonder if it's time to have the 4cyl, 6 cyl, v6 v8 v12 debate!
As for V6 and V8's, engines like that cost more to make with 2 cylinder heads, 4 cams.
V6's are good for their size, 3 and a half cyl long, and quite a squarish footprint, so they tend to be picked for large capacity engines that need to be compact.
I wonder if it's time to have the 4cyl, 6 cyl, v6 v8 v12 debate!
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