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Dumb questions someone else might answer


#82

No they don’t, if they would, cylinders 1 & 2 will go to the right at the same time and 3 & 4 to the left at the same time as well.

Some boxers also had an uneven header design AFAIK


#83

FFS, look at ALL the pistons…the closer pair on the boxer moves “down” at the same time,
and the other pair moves “up”. The I4 has an outer pair and an inner pair.
If you only show the pistons and the combustion chamber there is NO difference.
Both engines fire 180 deg between each cylinder.
Even when individual throttles (Webers, usually) is used, they sound very different.


#84

Part of the reason they sound so different is header design.

An H4 with equal length headers sounds somewhat similar to an I4.

And since most H4s have unequal length headers because they are cheaper to make, most H4s have the characteristic boxer rumble.

If you find videos of the engine sound from a stock GT86, that car comes with equal length headers from factory.


#85

Why do people’s voices sound different? We’re all people. Some even believe that we’re all equal.
Same thing with engines. Even if all the major factors including firing order, intake manifolds, and exhaust manifolds (didn’t mention at first because OP specifically said “ignoring exhaust packaging.”) are the same; different engines will sound differently.


#86

You need to take into account the vectors, not just the total sum of the net forces

Excuse the draft, but I’m at work. I have a resource about this, I’ll share it later

And as it was said

Also explained on the video I share above.


#87

Then why do BMW boxer and Triumph/Norton sound so different. They have equal length exhaust.
Don’t know if they just use independent exhaust per cylinder or if there is a crossover pipe also.


#88

Aren’t those two cylinder engines?

If so, it’s pretty normal they sound fairly different vs your typical 4 cylinder boxer.


#89

BMW Boxer engine for motorbikes. R series, twins, never have BMW done a 4 cyl boxer.


#90

Rob, see my post. When i get home i will explain further


#91

Misread your earlier post sorry.


#92

Both engine types have; individual throttle (singel carb x2), individual exhaust x2,
and the ignition sequence is the same. Still not the same sound.


#93

well is the character of the sound similiar?
why do we know that some engine has a unique sound characteristic? even if it’s basically the same basic design?

afaik, an engine config will usually have a certain special sound characteristic that may or may not be able to be altered, but no matter how, it will retain some of the sound characteristic particular of that engine config to some degree.
the rest is a byproduct of engineering designs. valve port angle, cam profile, airflow characteristic, or just about any minute detail decisions made while engineering the engine.


#94

Because you do not do your homework

The British twins use a 90° crank on the inline engine.
pop-270-pop-90-miss-270-miss

While BMW uses a 180° crank on a 180° engine.
pop-360-pop-360-pop-360-pop

Before you drag the Japs into this, most of the inline twins from japan use a 180° crank.


#95

How about you do YOUR homework? I’m of course are talking about the CLASSIC Triumph/Norton engines.
Triumph 500cc Speed Twin Crankshaft. by Brixton Morris


#96

I would like to know, which BMW twin you are talking about exactly?

The engine in the R series bikes is more than twice the size of the engine from which the crank you posted comes from. That would very probably have some effect on the noise coming from the engine.

And most R series bikes have only one exhaust muffler.


#97

You failed to specify a year. Now let us continue.

Triumph T120 Circa 1969 380° crank. 650cc displacement. Triumphs are known for their bad balancing.

BMW R-60/2 Circa 60’s 180° Crank 180° Bank, well balanced, and shaft driven.

They sound ‘similar’ but the difference in the exhaust, and drive type results in different noises. If we put the SAME exhaust system on both engines, they would sound even more similar with small mechanical differences between the BMW having twice the chain in the engine, and the Triumph having a poorly balanced crankshaft.


#100

Let’s ask something stupid! Hurrah
Is having high ignition timing bad and if so, why?


#101

Afaik there’s nothing bad about it, just different engines in Automation interact differently with the ignition timing setting (I have no idea what that depends on though) and it’s often not worth it over a higher compression.

Engineering Explained did a pretty good video on ignition timing:


#102

Thanks, ill check the video now!


#103

This one is really stupid… why do tyres only last a short period of time at high speeds? I have a vague understanding of this and would love any clarification.