Interesting debate how a Vulcan V-twin is different than a HD V-twin

[ubernomad]

I'm a very curious sole. I love to learn about things. One of the things I've been digging into lately is why/how the unique sounding Harley Davidson V-twin engine sounds so much different compared to the sea of Japanese "metric" V-twin engines. Google searches turned up all kinds of info, correct or not, but I stumbled across this discussion which had me thinking about how the 1500/1600 Vulcan engine operates compared to the Harley Davidson engine. Both are single pin cranks. Both are fuel injected. Both a narrow angle V-twins.

So, for those who care to share.....why doesn't the Vulcan V-twin engine sound anything like a similar H-D v-twin?

http://www.justanswer.com/motorcycle...ato-thing.html

It's not the potato potato thing that makes me curious. That's a simple explanation.

My question is -- and no one has ever been able to provide a really good answer:

The HD V-Twin, while at idle, has a noticeable 'miss' or a 'pause' every few cycles.

We love the idle sound and cadence. We agree it's unique. Other single pin crank V Twin bikes don't have the HD cadence at idle. We don't understand why.

Whatever you want to call it: Skip. Misfire. Pause. Lope. Cadence.
Why does it do it.
And HOW does it do it.

If it is a "designed-in" random idle misfire to get that cadence - how does HD get away with it.

Listen to any Harley at idle. Carb, FI, stock or custom pipes, doesn't matter. At idle, every few rpms, it "skips" a beat, sounds irregular. I'm not talking about the natural uneven firing rythm due to the single throw crank. I'm referring to the "SKIP". The resulting rolling sound is wonderful.

What causes it. I can understand sloppy carbueration on the older models, an occasional 'hiccup' at idle.

Even the modern Harley FI motors, the ones supposedly so carefully computer controlled... how can they have that idle 'skip' or hiccup. To me, seems impossible. Or implausable.
My 2011 103" Street Glide is fuel injected, yet idles like an old carbuerated model. I love it. But with modern fuel injection, just don't understand how it can happen. Properly running fuel injected engines simply don't misfire at idle.

But mine does, and so does every other Harley on the planet.

A designed-in idle misfire? To create the unique rolling idle sound with the occasional skip?
Just can't see any way an idle misfire could sneak past EPA. The HC ('unburned') emissions would blow off the scale.

I grow weary of tired old explanations like "it's the pushrods" or "the unique HD valve angle", it's all a bunch of nonsense. Those things by themselves don't make an engine occasionally miss a beat at idle. It has to be something associated with fuel and or ignition delivery at IDLE, maybe combined with some weird cam overlap profiles, to produce the irregular sound. Something is causing the engine to skp a beat, to produce the Harley stutter step idle quality. So, what is it.

Answer according to the "expert":

the cause of the miss at idle....and occasionally when riding....is the result of the way the entire engine is designed, not just the common crank pin.

the problem comes from the "siamesed" intake system. this does two things. first, it causes the front cylinder to run leaner than the rear and occasionally results in an upset of the air flow to the rear cylinder, resulting in a lean mis-fire.

it causes the front cylinder to run leaner than the rear due to a combination of the valve timing. it was designed this way to account for the front cylinder receiving fresh cooling airflow and the rear cylinder receiving warmer airflow off the font cylinder. most people mistakenly assume the rear cylinder runs hotter than the front on a Harley. it does not. it was designed to run cooler.
the issue exists in fuel injected bikes, but is controlled by the ability of the fuel injection to offer a different air/fuel mixture to each cylinder.

the lean mis-fire will always exist in 4 degree V twin Harleys. even fuel injection cannot compensate for the occasional air flow disturbance to the rear cylinder.
basically....the air is drawn into the common intake and then must either go right or left, in uneven intervals and, during valve overlap there is another airflow component which is exhaust from front to rear or rear to front. occasionally, the airflow to the rear cylinder stalls.
the fuel injection can only provide a fuel injector pulse for the anticipated air flow when the intake valve opens, but it cannot compensate when the airflow gets disturbed at that moment and only for a fraction of a second.
this effect is more evident on older models with points triggered ignitions idling at about 600 rpm. an added affect in that system is that when the cylinders fire, the crank is accelerated and the advance flyweights open up and advance the ignition, then the flywheels coast down to the next power pulse and the flyweights pull in, retarding the spark.
the issue, although still prevalent with electronic ignitions, is less noticeable due to a constant advance input at idle and by setting the idle rpm to 1,000 rpm.

I'm trying to wrap my head around how these engines operate from a engineering/design standpoint.

[Sparks500]

I still think Harley engines started out as scrap air compressors........

[glwilson]

This is directly from Wikipedia; and is as an accurate description of why the sound is produced as one can explain. It is all here...
The classic Harley-Davidson engines are V-twin engines, each with a 45° angle between the cylinders. The crankshaft has a single pin, and both pistons are connected to this pin through their connecting rods.[9]

This 45° angle is covered under several United States patents and is an engineering tradeoff that allows a large, high-torque engine in a relatively small space. It causes the cylinders to fire at uneven intervals and produces the choppy "potato-potato" sound so strongly linked to the Harley-Davidson brand.

To simplify the engine and reduce costs, the V-twin ignition was designed to operate with a single set of points and no distributor. This is known as a dual fire ignition system, causing both spark plugs to fire regardless of which cylinder was on its compression stroke, with the other spark plug firing on its cylinder's exhaust stroke, effectively "wasting a spark". The exhaust note is basically a throaty growling sound with some popping. The 45° design of the engine thus creates a plug firing sequencing as such: The first cylinder fires, the second (rear) cylinder fires 315° later, then there is a 405° gap until the first cylinder fires again, giving the engine its unique sound.[102]

Harley-Davidson has used various ignition systems throughout its history – be it the early points and condenser system, (Big Twin up to 1978 and Sportsters up to 1978), magneto ignition system used on some 1958 to 1969 Sportsters, early electronic with centrifugal mechanical advance weights, (all models 1978 and a half to 1979), or the late electronic with transistorized ignition control module, more familiarly known as the black box or the brain, (all models 1980 to present).

Starting in 1995, the company introduced Electronic Fuel Injection (EFI) as an option for the 30th anniversary edition Electra Glide.[103] EFI became standard on all Harley-Davidson motorcycles, including Sportsters, upon the introduction of the 2007 product line.[104]

In 1991, Harley-Davidson began to participate in the Sound Quality Working Group, founded by Orfield Labs, Bruel and Kjaer, TEAC, Yamaha, Sennheiser, SMS and Cortex. This was the nation's first group to share research on psychological acoustics. Later that year, Harley-Davidson participated in a series of sound quality studies at Orfield Labs, based on recordings taken at the Talladega Superspeedway, with the objective to lower the sound level for EU standards while analytically capturing the "Harley Sound."[citation needed] This research resulted in the bikes that were introduced in compliance with EU standards for 1998.

On February 1, 1994, the company filed a sound trademark application for the distinctive sound of the Harley-Davidson motorcycle engine: "The mark consists of the exhaust sound of applicant's motorcycles, produced by V-twin, common crankpin motorcycle engines when the goods are in use". Nine of Harley-Davidson's competitors filed comments opposing the application, arguing that cruiser-style motorcycles of various brands use a single-crankpin V-twin engine which produce a similar sound.[105] These objections were followed by litigation. In June 2000, the company dropped efforts to federally register its trademark.[106][107]

[glwilson]

Originally Posted by Sparks500

I still think Harley engines started out as scrap air compressors........

No they let the Metrics do that...

[ubernomad]

Originally Posted by Sparks500

I still think Harley engines started out as scrap air compressors........

My Vulcan 1600 sounds a lot like my v-twin 23 HP riding lawn mower.


It's weird because my father just bought a 2014 HD Dyna Low Rider. He was over yesterday and we were comparing how my bike and his bike sound soooo much different. You definitely notice the "bang-bang...pause...bang-bang...pause" sound of his engine. The VN1600 has a much more even sounding bang-bang-bang-bang sound at idle (when it does idle). Very even firing order. The HD engine has a very pronounced "miss" as everyone puts it.

Does anyone have any technical info on the engine dynamics for the Kawasaki engine?

[HwyRider]

52 degree v-twin

[ubernomad]

Originally Posted by glwilson

This is directly from Wikipedia; and is as an accurate description of why the sound is produced as one can explain. It is all here...
The classic Harley-Davidson engines are V-twin engines, each with a 45° angle between the cylinders. The crankshaft has a single pin, and both pistons are connected to this pin through their connecting rods.[9]

This 45° angle is covered under several United States patents and is an engineering tradeoff that allows a large, high-torque engine in a relatively small space. It causes the cylinders to fire at uneven intervals and produces the choppy "potato-potato" sound so strongly linked to the Harley-Davidson brand.

To simplify the engine and reduce costs, the V-twin ignition was designed to operate with a single set of points and no distributor. This is known as a dual fire ignition system, causing both spark plugs to fire regardless of which cylinder was on its compression stroke, with the other spark plug firing on its cylinder's exhaust stroke, effectively "wasting a spark". The exhaust note is basically a throaty growling sound with some popping. The 45° design of the engine thus creates a plug firing sequencing as such: The first cylinder fires, the second (rear) cylinder fires 315° later, then there is a 405° gap until the first cylinder fires again, giving the engine its unique sound.[102]

But correct me if I'm wrong isn't the Vulcan V-twin basically the same engine configuration? Single pin crankshaft. "Wasted" spark system. very close to 45 degree V angle (I think the Vulcan engine is something like 46 degrees??). Seems to me the Vulcan engine would have the same plug firing sequence with a slight difference due to the angle "V" being a little more than HD.

[hayes]

The original hd was made from a 10 cylinder plane engine. You get that sound because the crank is still based of ten cylinders. You get fire on 1 then 2 but then you have 8 missing fires. That's the "hesitation" you're hearing.

I was told that by a Harley historian and it made sense. I have no idea if it's true, but I believe it...

[ubernomad]

Originally Posted by HwyRider

52 degree v-twin

Wikipedia says the 1600 engine is 50 degree V-twin. 1700 and 2000 series are 52 degree.


So, would that slight difference in V angle cause the firing order to be more "even" considering it is still a single pin crankshaft?

[dabull]

seems to me its the aftermarket pipes that make it sound like a HD.... most stock HDs sound nothing like the potato potaatoo .....

[ubernomad]

Originally Posted by hayes

The original hd was made from a 10 cylinder plane engine. You get that sound because the crank is still based of ten cylinders. You get fire on 1 then 2 but then you have 8 missing fires. That's the "hesitation" you're hearing.

I was told that by a Harley historian and it made sense. I have no idea if it's true, but I believe it...

That makes no sense to me. It's a 4-stroke engine. You wouldn't have 8 missing firings unless they purposely skip power strokes by disabling spark or fuel.

[ubernomad]

Originally Posted by dabull

seems to me its the aftermarket pipes that make it sound like a HD.... most stock HDs sound nothing like the potato potaatoo .....

I've got VH baggers on my Nomad and it sound NOTHING like a Harley v-twin regardless of speed. Mine has a very even pop-pop-pop-pop sound while his Dyna Low Rider has a more uneven sound. It does sound like it is designed to miss a power stroke firing where the Vulcan engine fires on ever power stroke.

[glwilson]

Originally Posted by ubernomad

But correct me if I'm wrong isn't the Vulcan V-twin basically the same engine configuration? Single pin crankshaft. "Wasted" spark system. very close to 45 degree V angle (I think the Vulcan engine is something like 46 degrees??). Seems to me the Vulcan engine would have the same plug firing sequence with a slight difference due to the angle "V" being a little more than HD.

No.. Re-read all that's there. HD has a patent on their firing-sequence/timing of their engines. (This is not to be confused with their feeble attempt to patent the sound of their engines. This refers to the firing sequence. It is mentioned in the material on Wikipedia.)

Kaw is not the same despite it being a V-Twin. The V-Twin is just about all that is comparable between the two.

There are issues such as HD's 405 degree firing-gap occurring on the stroke cycle causing some of what you are referring to; along with a few other factors -- but the most noticeable is the firing-sequence with their engines is what you are hearing.

Older carbed engines are more often adjusted to a low-idle where you hear the stutter-step of the timing more so than the fuel-injected models. My previous and current FI HDs only slightly provide that sound when at idle. They simple do not idle slow enough for it to be noticeable.

Too bad Mac doesn't respond to this. He would be someone who could tell you what the Kaw V-Twin does in comparison.

[hayes]

Originally Posted by ubernomad

That makes no sense to me. It's a 4-stroke engine. You wouldn't have 8 missing firings unless they purposely skip power strokes by disabling spark or fuel.

It's easier to explain if I can show you with my hands. It's not actually missing but there is a longer distance between cylinder 2 and 1 then there is between 1 and 2 (in order of fire). You can make that happen with a 4 stroke. It's not actually missing.

Like I said. Could be hogwash. Makes sense to me though.

[glwilson]

This 45° angle is covered under several United States patents and is an engineering tradeoff that allows a large, high-torque engine in a relatively small space. It causes the cylinders to fire at uneven intervals and produces the choppy "potato-potato" sound so strongly linked to the Harley-Davidson brand.

To simplify the engine and reduce costs, the V-twin ignition was designed to operate with a single set of points and no distributor. This is known as a dual fire ignition system, causing both spark plugs to fire regardless of which cylinder was on its compression stroke, with the other spark plug firing on its cylinder's exhaust stroke, effectively "wasting a spark". The exhaust note is basically a throaty growling sound with some popping. The 45° design of the engine thus creates a plug firing sequencing as such: The first cylinder fires, the second (rear) cylinder fires 315° later, then there is a 405° gap until the first cylinder fires again, giving the engine its unique sound.