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post #1 of 7 (permalink) Old 11-10-2008, 08:44 PM Thread Starter
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Best Configuration....

I ask you, what would be the best 4cylinder-engine configuration be?

an inline4
is how compact the engine can be: since all the cylinders are aligned the exhaust can be placed easily on one side and the intake will also be easily placed like the exhaust on the opposite side, and the transmission can be placed behind the engine .... the only downside I can think is that inlined bikes dont make much torque.... but as I've learned with my buell: horsepower beats torque at the drag strips

a Vtwin
is the broad powerband, but I can see much else.... the configuration complicates the bike, the exhaust has to have two exit points in the back and the front; the front is the easiest one to play with but the rear exhaust has to snake its way around and not overheat anything. And as for a ducati i have no clue where the rear exhaust goes, the pros of a Ltwin is no vibration, but its such a huge angle, that it makes a void between the cylinders that makes it hard to plan a layout of the all the bike other parts.... a smaller angle saves space, but adds vibration

a V4 (the unknown challenger)
who make a competitive V4? aprilia? how have they done? i can seem to find any articles on this mysterious configuration.... I believe this configuration, if done right, will kill all the competition.... you have the 4cylinder punch, and the Vangled strengths.... the problem will be the Vtwins weakness, the placement of intake, the angle, and exhaust.... to aid the vibration I would suggest that the V4 have two cylinders from the opposite banks firing, pretty sure that will quell the vibration, but then that makes have 2'empty' strokes.... but i still think this configuration will dominate it can have great horsepower and torque either way you play with it

the never-done angled-inline ©ochoa0042
which an idea of mine that you start off with a inline4 engine, then spin the cylinders around like a spiral staircase, to have a combined angle of 45degrees or whatever number is 'suit to fit'.... you following me here? so each bank is angled 11.25degrees from the next or 'suit to fit'.... you have the simplicity of the inline setup of the header/intake which is slightly off camber and the angle from cylinder-to-cylinder can have the benifits like more torque and a strong power stroke.... though I think this engine might have a quirky character to it, but it may have great potential

© angled-inline copyright of ochoa0042

Last edited by ochoa0042; 11-10-2008 at 08:52 PM.
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post #2 of 7 (permalink) Old 11-11-2008, 05:31 AM
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You are ignoring cost and engine width.

The width is going to affect both aerodynamics and ground clearance. I4's are the worst in this regard, while twins are the best (unless you count singles).

A great deal of the strengths of configurations actually arise from their limitations. I4's can be tuned for more torque, at the expense of peak power. On the most basic level, its a function of bore vs stroke. There is a theoretical limit to how fast a piston can move up and down. The heavier the piston, the slower its max speed is. In one revolution, the piston goes up the stroke dim's and then down the same distance. Thus the longer the stroke, the faster the piston has to move at any given RPM. Or, the longer the stroke, the lower the red line is going to be. But, the longer the stroke, the farther the distance on the crank shaft, the more of a lever the connecting rod has when turning the shaft, so the more torque the engine produces. This is why sportbikes are oversquare, with bore bigger than stroke, while cruisers are undersquare, with stroke longer than bore.
Since horsepower = [email protected] * RPM you can either multiply big torque by little rpm, or little torque by lots of rpm. Since at high rpm you can take advantage of a few unique tricks, the winner always tends to be small torque by lots of rpm.
This is why you can build an inline with a good torque spec at the expense of horsepower. Now in the case of twins, you only have two cylinders, to the pistons have to be pretty big. Since they are bigger, they cannot move as fast, so the high rpm is already unreachable, therefor the designers have no choice but to tune them for more torque. If they could get them to spin faster, they would be low torque too.
Let's see, ducati's motogp bike is a v4, and yamaha makes at least one such engine. I believe the honda VFR is a v4 as well. There is also a narrow angle V, as in the honda's V5. It makes for a very compact enigne, that can sport lots of cylinders, and thus have smaller cylinders, spin faster, and make more power.
Now for the costs.
Inline4 are cheap, because there is only one head, with two shafts, and one cylinder block. Twins will be more expensive, since there are two heads to worry about (twice the shafts, bearings, cooling lines, belts/chains, etc) but at least the heads are some what simple. Ditto for the cylinder blocks. With a V4 you have two complex heads and two complex cylinder blocks, so they engine is even more expensive, but it should have the high rev's of an inline with almost the low width of a twin. Narrow angle V5 is more expensive still, but its a motogp bike, so who cares. Angled inline would be the most expensive of all of these, and the least compact.
The compactness of an engine is important, since the engine is the heaviest part of the bike. If you make it compact, you have room to move it within the frame, which greatly affects the bike's center of gravity, and handling. If the engine is large, then there is only one way it will fit, and thats all there is to work with.

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post #3 of 7 (permalink) Old 11-11-2008, 03:58 PM Thread Starter
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im glad that your pointed out the width factor.... and cost aside because as manufacturing progresses its get cheaper....

I was wondering.... why dont car makers like ferarri, lambo, or even ford, and such build a supercar with a huge bore and a short stroke? whats holding them back?

Last edited by ochoa0042; 11-11-2008 at 04:00 PM.
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post #4 of 7 (permalink) Old 11-11-2008, 04:07 PM
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Ever heard an F1 car? How oversquare does that engine need to be to get to 20-30k rpm?

Mostly its that cars are heavy, so they need the low end power to get moving.
Then there is the fact that they are not as constrained by engine size (or price). They can add cylinders and displacement getting the same power out of a large engine that spins slow as one could with a small engine that spins fast

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post #5 of 7 (permalink) Old 11-11-2008, 04:16 PM Thread Starter
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yea but F1 cars only have a displacement of 2800cc (2.8L) or less, and torque isnt much of a factor because they are feather lite.... and a smaller engine with a big bore will have less weight and more HP, and HP beats torque.... and conciderably, an angled-inline will actually have a smaller width because the cylinders can somewhat hide behind the next one....
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post #6 of 7 (permalink) Old 11-11-2008, 08:52 PM Thread Starter
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what if they made a inline4 HEMI? that would sell
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post #7 of 7 (permalink) Old 11-12-2008, 06:34 AM
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a short stroke/big bore engine will have tons of HP, but only at the high end. The low end may well end up pretty pitifull. On the other hand, a long stroke engine will have good low end, but will redline so soon, it won't reach the really high rpm (like a diesel engine).
Look at it this way. Your average literbike engine makes about 170-190hp, which is enough for a sedan (somewhat underpowered by today's standards, but not too bad). So you take this engine and you cram it into a 4,000lbs car, and you gotta drive it. Can you imagine how easy it would be to stall it? How much you will have to feather the clutch on every start? It would be absurd.
There are a few other factors. All things being equal, and engine that spends most of its life spinning at 3k rpm will last a whole lot longer than one that spins at 10k rpm. Nowhere is it more obvious than in the lifters. Fast spinning engines use solid lifters, instead of the usual hydraulic ones, to control their much faster moving valves. Solid lifters call for adjustment every 14kmiles. Can you imagine having to do that for a car? Or look at it this way. A bike with 100k miles is getting up in age, while a car with that many miles still has some of the new in it.

Now the hemi is an absolutely absurd concept. Way back in the day, when cars still had spoked wheels and such, the head had a completely different design. The head actually had a chamber, that was bigger than the cylinder bore. The valves were beside the cylinder, pointing up into this larger chamber. This simplified some of the mechanical linkages. The problem was that even with the piston all the way up, there was still considerable volume in the cylinder, which meant that the compression was really low. So you had 6 liter engines making 30hp. The hemi was an obvious improvement, not bacause of its shape, but simply because it moved the valves, making the combustion chamber much smaller. However, the piston can only go to the begining of hemi radius, still leading to fairly low compression ratio's by todays standards. Modern engines are of a pentaroof design, allowing the high compressin ratio's we are familuar with.

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