90 Degree V-Twin: Firing Order of 270/450?

[Aaron D.]

If that jet plane were on a giant treadmill, would it be able to take off?   

Yup.

[John A]

I've wondered why the cylinders were numbered right to left ( from the seat) rather than the standard left to right. The answer is simple and it dawned on my thick head as I was looking at an engine on the bench: front to back, another standard.

[LowRyter]

OK,
For you engineering students.

: May 23, 2017 6:43 AM
Left cylinder fires, engine turns to the 270 degree position and #2 fires then engine turns to the 450 degree position and # 1 exhausts and starts intake, engine turns to the 270 degree position # 2 exhaust and starts intake, engine turns to 450 position on compression and fires then engine turns to the 270 degree position and fires.
These two firings are 180 degrees apart,(measured in the direction of rotation), position wise.

In engineering parlance this is what is called a 180 degree firing order.

First semester 101.

No Kirby, the firings are 270 and 450 degrees apart.

Look at your clock, start at midnight, #1 fires at 9am (270 degrees), the clock goes past noon and back around again to midnight (450 degrees) and #2 fires.  start again.

[Chuck in Indiana]

Mmmmm hushpuppies. I've gotta say that the Cedar Vale specials were the best I've ever had.

[LowRyter]

next you'll be telling me that you fry hushpuppies at 180 degrees.

I'd recommend 270, better yet 450 degrees.   

[oldbike54]

 325 degrees , just to be a contrarian 

 Dusty

[LowRyter]

yep  Dusty............45 0 is wayyyy toooo hot.

But we gotta ask Chuck.  I use his recipes for Buffalo Wings and ABTs. 

[Huzo]

325 degrees , just to be a contrarian 

 Dusty

Nobody's got their undies in a bunch (yet), but someone is RIGHT and someone is WRONG... I can understand the desire to get some water on this before it catches fire, but there are couple of luminaries here who don't have things the correct way around and on Wild Guzzi that's just not a good thing. And while we're all being schooled, can we delineate between "firing interval" and " firing order". One is a representation in degrees between successive ignition points and the other is information regarding the numerical order in which each cylinder fires, distributed around two revolutions. For example, on a standard V8 you could mess around enough with the camshaft, ignition and alter the firing 'order" but the firing "interval" will always be 90 degrees if you leave the crankshaft alone. But (as usual) I digress, back to the Guzzi. We must start at the top of the "clock" at zero degrees and only measure degrees of rotation from that fixed reference, not degrees from the last firing. Mixing the two will end in tears. Saying that #1 fires at the top of the clock at zero degrees will give a different answer to saying it fires at 3 o'clock ( or 90 degrees), this I think is where the schools of thought are diverging. BTW, the word is " you're" not "your" and where is Kev m when you need him ?

[oldbike54]

 Peter , what are you talking about 

 Dusty

[Muzz]

Did someone say bacon?   

Do I detect a trace of thread drift here?????

[PJPR01]

Definitely this thread has the potential to be Thread of the Month - perhaps a new category we can develop for the Winning Controversial thread.  Have managed to get a couple of good chuckles seeing the back and forth here...

Prescott...I just have to say you picked a nice prickly topic to divide the pilots on the board...looking forward to the ongoing debates here on Firing intervals, orders and degrees of separation on when ignition takes place!

Carry on gents!!

[Huzo]

Peter , what are you talking about 

 Dusty

PM'd

[Huzo]

Definitely this thread has the potential to be Thread of the Month - perhaps a new category we can develop for the Winning Controversial thread.  Have managed to get a couple of good chuckles seeing the back and forth here...

Prescott...I just have to say you picked a nice prickly topic to divide the pilots on the board...looking forward to the ongoing debates here on Firing intervals, orders and degrees of separation on when ignition takes place!

Carry on gents!!

It's the one about taking off on a treadmill that nearly got me ! I get sucked in every time...

[PJPR01]

 

[Huzo]

And yes.... Great thread SS

[johnr]

If that jet plane were on a giant treadmill, would it be able to take off?   

Yes. The speed of rotation of the wheels is not relevant to airspeed. Planes are not wheel driven.

[nc43bsa]

The treadmill conundrum came from another motorcycle forum.  It was mostly tongue-in-cheek, but it went on for months.

Sort of like the Durrani wheel thread, which went on for years, with dozens of thread-jacks.

[LowRyter]

this makes me wonder if they've ever done a "tw-ingle" 90/630?

[Huzo]

this makes me wonder if they've ever done a "tw-ingle" 90/630?

That's a good graphic

[jacksonracingcomau]

That's a good graphic

I like it too, means V twin Guzzis have a 360 crank, dunnit ?
Just the barrels are on funny

[LowRyter]

I like it too, means V twin Guzzis have a 360 crank, dunnit ?
Just the barrels are on funny

Unlike V style engines, parallel inline engines can have individual pistons firing independently from all the others.  (Although GM brought out a like of 90 degree V6 engines with an off set crank that made them fire like a smooth 60 degree engine.)

I don't understand how a 90 degree V twin can have a 360 crank since there is always a 90 separation from the two cylinders...... I can only figure 270/450 or 90/630

[LowRyter]

http://www.cycleworld.com/2016/02/01/motorcycle-v-twin-and-parallel-twin-and-flat-twin-engine-tech-sound-insights

Let's go crazy: Kevin Cameron knows it all.  And to complete the circle for Kirby:

Another way to build V-twins is with Honda’s “offset dual-pin crankshaft.” Normally, the only way to balance a single crankpin V-twin is by giving it a 90-degree V-angle, as described above. But Honda found that by using two crankpins instead of one, and by offsetting them by the correct angle, a self-balancing V-twin could be built with any cylinder V-angle–without need of any balance shaft. To get this effect in a given engine, we subtract twice the V-angle from 180-degrees to find the correct crankpin offset angle. Thus, in a 90-degree V-twin (Ducati, Guzzi) this is 180 – (2 X 90) = 0 (no crankpin offset, which is what Ducatis and Guzzis have). If we want to balance a 45-deg V-twin, the numbers become 180 – (2 X 45) = 90-degree crankpin offset.
Carrying this out requires a rather wide crankcase, as there has to be some way of connecting two crankpins spaced 90 degrees apart at its center. This takes the form of a 3rd flywheel disc.

[PJPR01]

So...I just have one question for Prescott now.  Is this as clear as mud or does it make sense to you now, or would a long ride from Dallas to Datil be necessary in order to work out the firing order while on the road!  One thing we haven't injected here into the discussion is how do spark plugs feel when you are not sparking...do they feel left out or jealous while the other plug is getting its chance at being sparkly?

:)

[Phang]

One thing we haven't injected here into the discussion is how do spark plugs feel when you are not sparking...do they feel left out or jealous while the other plug is getting its chance at being sparkly?

:)

ahh... now I know why the spark plugs of the BMW boxer look  happier, they get fired equally amount of time by the waste spark ignition system...

also, should we factor in the timing advance when we discuss the firing angles?  I don't think guzzi engine will run with usable power if the spark plug really fire exactly at 270/450

[SmithSwede]

Phang, yes, I know for certain that a BMW airhead has a wasted spark system.

And Paul, I now understand this to my satisfaction, but I was apparently correct that this is quite confusing.   

And you are correct---when the spark plugs on my small block are not firing at all, that would be a "0/0" firing order.

[SmithSwede]

Now I'm really curious about the concept of a 90/630 V twin. 

As I understand a "twingle," that's a two cylinder engine set up so that both cylinders are firing at the same time.  So it's just like a single cylinder thumper, except that there are two cylinders firing, not just one.

But a Guzzi 90/630 V twin would not really be a "twingle," since the firing strokes would be 90 degrees off, not simultaneous.

Maybe we should call the 90/630 a Guzzi Quasi-Twingle.

[oldbike54]

 You never want to ride a twingled Brit Vert twin , like Kirby said "ugly vibration" . Yes it was done specifically for traction on dirt tracks . I actually owned a 500 CC BSA framer way back when , shook worse than a Victor  Damn , my hands just started hurting from the memory 

 Dusty

[rodekyll]

Mmmmm hushpuppies. I've gotta say that the Cedar Vale specials were the best I've ever had.

And I can say with equal conviction that the cedar vale hushpuppies were the FIRST ones I ever had.

but this thread is about BACON!   

[kidneb]

I don't think guzzi engine will run with usable power if the spark plug really fire exactly at 270/450

You don`t ?
Even if the firing point of #1 cylinder has been point zero, throughout this thread ?

[oldbike54]

You don`t ?
Even if the firing point of #1 cylinder has been point zero, throughout this thread ?

 Ben , I think Phang is referencing ignition lead .

 Dusty