Wild Dog Adventure Riding

General => General Bike Related Banter => Topic started by: Pavlovski on December 23, 2015, 09:22:25 am

Title: Why the 1200LC is not Twin Spark
Post by: Pavlovski on December 23, 2015, 09:22:25 am
So help me if I'm wrong....but ysterday I had a look at a mate of mine's 1200LC GS and noticed that it only has 2 spark plugs.

Later 1150GS models were twin spark (4 spark plugs in total) and the previous generation 1200's were also twin spark, so why would the new LC not be twin spark?

As far as I know twin spark has more to do with fuel efficiency than power...is this correct?
Title: Re: Why the 1200LC is not Twin Spark
Post by: Eendstop on December 23, 2015, 09:25:26 am
I read a version that the additional plugs got added as a way to meet emission standards.  They probably now have some cheaper alternative or maybe VW showed them the way :snorting:
Title: Re: Why the 1200LC is not Twin Spark
Post by: whitedelight on December 23, 2015, 09:50:40 am
I read about this a while back. Due to many engine changes,such as a down drought setup,they could up the the compression ratio a little. So basically the more compact combustion chamber only required a single spark.
And yes the older twin spark did help towards emission controls.
Title: Re: Why the 1200LC is not Twin Spark
Post by: gser on December 23, 2015, 10:10:42 am
I read a version that the additional plugs got added as a way to meet emission standards.  They probably now have some cheaper alternative or maybe VW showed them the way :snorting:
My gedagte loop ook so Eendstop.
 Dus, nie n werklike 2-Vonk waarby altwee vonkproppe gelyk vuur nie.
 Die tweede vonkprop vuur heelwat "later" om die onverbrande gasse te help verder verbrand om sodoende n "skoner" uitlaatgas te help verseker. Ek dink dit dien die doel mits die uitlaatstelsel standard is of indien die klankdemper 'n EU, ens. afkoop/aanvaarding het.
Die LC is van meetaf ontwerp/ontwikkel/getoets om aan 'n hoer EU-uitaatgas vereistes te voldoen waaraan die ouer enjins nie aan sou voldoen het nie.
Enjinontwerp-Evolusie in werking.
Title: Re: Why the 1200LC is not Twin Spark
Post by: Draadwerk on December 23, 2015, 10:59:13 am
My LC het 6 plugs. 😉👍
Title: Re: Why the 1200LC is not Twin Spark
Post by: gser on December 23, 2015, 11:14:54 am
Met n wyntjie daarby ! LOL
Title: Re: Why the 1200LC is not Twin Spark
Post by: Pavlovski on December 23, 2015, 11:35:59 am
So in terms of cleaner exhaust gasses.... Would the second spark plug then sort of loose its purpose if you have a free flow exhaust system? Or if you've removed the catalytic converter?
Title: Re: Why the 1200LC is not Twin Spark
Post by: whitedelight on December 23, 2015, 11:45:06 am
So in terms of cleaner exhaust gasses.... Would the second spark plug then sort of loose its purpose if you have a free flow exhaust system? Or if you've removed the catalytic converter?

The second spark was to burn unspent gas. So you would have better emissions. So a cat con would perform the same function. The free flow exhaust would just move the exhaust fumes quicker.
Now you find with all the bike manufacturers they run them a little leaner in the lower revs to help with emission tests.
Title: Re: Why the 1200LC is not Twin Spark
Post by: Leo on December 23, 2015, 11:49:03 am
If they brought the current model out as a twin spark, how/what would they upgrade 3 years from now?

They can't just add high lift footpegs, different colors and racing mirrors!!  :o

At least now they have the option of adding twin spark as well  :peepwall:
Title: Re: Why the 1200LC is not Twin Spark
Post by: gser on December 23, 2015, 07:35:58 pm
So in terms of cleaner exhaust gasses.... Would the second spark plug then sort of loose its purpose if you have a free flow exhaust system? Or if you've removed the catalytic converter?

The second spark was to burn unspent gas. So you would have better emissions. So a cat con would perform the same function. The free flow exhaust would just move the exhaust fumes quicker.
Now you find with all the bike manufacturers they run them a little leaner in the lower revs to help with emission tests.

The cat con can only convert a % of "bad" combustion, the "good" combustion" should in the total combustion cycle of the total efficiency
 of the whole combustion cycle to set requirements in the users/client design inputs to conform to EU standards in an engine. It starts with " to spec fuel " to be converted into automotive motion. For a starter, in a laboratory-dyno. eg. a EU test lab, the fuel that is used is to a calibrated EU fuel specification. ETC . .
It is a "repeatable science" that can be tjippoded, the test procedures for the dyno/lab test can be downloaded. 

 
Title: Re: Why the 1200LC is not Twin Spark
Post by: T Rex on December 23, 2015, 08:36:10 pm
The old LC's won't work as aircraft engines then ....???
Title: Re: Why the 1200LC is not Twin Spark
Post by: hedleyj on December 23, 2015, 08:40:26 pm
Advances in induction systems have progressed in leaps and bounds over the years.

One of the more significant of those is Striated injection mapping. Which feeds fuel in as the combustion requires it. Hence far more accurate mixtures and leaner/cleaner emissions
Title: Re: Why the 1200LC is not Twin Spark
Post by: 2StrokeDan on December 23, 2015, 09:23:38 pm
The addition of water jackets in the head is possibly a cause for having to drop the 2nd spark plug. No space for it.
Title: Re: Why the 1200LC is not Twin Spark
Post by: OomD on December 23, 2015, 09:39:12 pm
The addition of water jackets in the head is possibly a cause for having to drop the 2nd spark plug. No space for it.
As far as I know the water never goes near the head, but only flows around the base of the sleeve.

But then, I've been wrong before. Once. I thought I was wrong, but I was mistaken...
Title: Re: Why the 1200LC is not Twin Spark
Post by: 2StrokeDan on December 23, 2015, 09:47:07 pm
The addition of water jackets in the head is possibly a cause for having to drop the 2nd spark plug. No space for it.
As far as I know the water never goes near the head, but only flows around the base of the sleeve.

But then, I've been wrong before. Once. I thought I was wrong, but I was mistaken...

 :imaposer:
Mine was also only a guess.
Title: Re: Why the 1200LC is not Twin Spark
Post by: Wes on December 29, 2015, 09:13:14 am
These days i am sure 99.99% of cars run a single spark plug , second plug is not neccesary on modern engins .
Honda 1.4 jazz 2007 i know has twin sparkl plugs per cylinder
Title: Re: Why the 1200LC is not Twin Spark
Post by: TheBear on December 29, 2015, 09:30:33 am
These days i am sure 99.99% of cars run a single spark plug , second plug is not neccesary on modern engins .
Honda 1.4 jazz 2007 i know has twin sparkl plugs per cylinder

I think, all through history 99,99% of cars were single spark.  So were bikes.  Twin spark became a bit of a hit in the late 90's when combustion gasses became a bigger issue.  With more modern technology, twin spark seems to be on the way out again.
Title: Re: Why the 1200LC is not Twin Spark
Post by: jaybiker on December 29, 2015, 11:02:15 am
I thought it was because the designers were really concerned to bring down the cost and complexity of DIY maintenance.

And then the missus thumped me and said "Are you going to doze there all bloody day?"  :imaposer:
Title: Re: Why the 1200LC is not Twin Spark
Post by: alanB on December 29, 2015, 11:42:24 am
Twin spark ignition is normally used in cars to maximise the amount of air/fuel mix burned before the exhaust valve opens.  Because the flame front begins at two different points at once in the combustion chamber, the combined flame front can reach further in the same time.

This has benefits for high compression engines to reduce knock, because more/all of the fuel can be burned before the remaining mixture auto-ignites due to high pressure.

It also will improve fuel efficiency and emissions because less of the fuel air mixture is wasted.

The most likely reasons why BMW neglected it in later models are IMO:
1) Not enough space
2) Not enough benefit to warrant the extra cost and complexity
 
Title: Re: Why the 1200LC is not Twin Spark
Post by: Welsh on December 29, 2015, 01:56:36 pm
My view is the previous ones were engineered around a moving emissions target, later one have a target to engineer to, until they move the posts.
Title: Re: Why the 1200LC is not Twin Spark
Post by: Pullaway on December 30, 2015, 09:58:45 am
Seems that the new BMW has lost its spark. :imaposer:
Title: Re: Why the 1200LC is not Twin Spark
Post by: TheBear on December 31, 2015, 08:33:05 am
Seems that the new BMW has lost its spark. :imaposer:

 :laughing4:
Title: Re: Why the 1200LC is not Twin Spark
Post by: Ou Krokkedil on December 31, 2015, 08:43:15 am
Why put to spark plugs, why cant the one just fire 2 times? I am sure with the right computer you can have one spark plug and have 2 sparks from one spark plug.

you will probably have to change the plug every 20k and not 50k but it will be more cost effective

Title: Re: Why the 1200LC is not Twin Spark
Post by: TheBear on December 31, 2015, 08:49:10 am
Why put to spark plugs, why cant the one just fire 2 times? I am sure with the right computer you can have one spark plug and have 2 sparks from one spark plug.

you will probably have to change the plug every 20k and not 50k but it will be more cost effective



If my understanding is correct, it is not so much about the number of sparks but rather the positioning.
Title: Re: Why the 1200LC is not Twin Spark
Post by: alanB on December 31, 2015, 12:10:00 pm
Why put to spark plugs, why cant the one just fire 2 times? I am sure with the right computer you can have one spark plug and have 2 sparks from one spark plug.

you will probably have to change the plug every 20k and not 50k but it will be more cost effective



If my understanding is correct, it is not so much about the number of sparks but rather the positioning.

Ja thats right.  Firing the same spark plug twice is useless.  There will be nothing left to burn in the vicinity of the spark at that point.

The problem is that before ignition, the combustion chamber is full of fuel/air mixture - the objective is to burn as much of that mixture as possible during the piston's power stroke, without the mixture all simultaneously self detonating/exploding (which is knock).

Its a complex problem because the mixture ignites at the position of the spark plug and then burns outwards from that in a 3D flame front the spreads throughout the chamber.  That flame front travels at a speed defined by the properties of the fuel used.

Depending on the shape of the chamber, the flame front may or may not reach all the crannies during the piston's power stroke.

The hemispherical head was designed to for this reason, where the spark plug is positioned in the centre of the hemisphere.

Using two spark plugs helps because then the flame front starts in two places simultaneously. and thus the combined flame front can reach further in the same time.

Another thing which makes this quite complex is auto ignition delay.  The unburned mixture in front of the flame front is being compressed by the rapidly expanding  flame front.  All fuel air mixtures have a pressure/temp curve above which the mixture simply all self detonates/explodes which is called knock, and which can destroy an engine.  The mixture in front of the flame front can often be compressed above this self detonating pressure/temp threshold, but there is a delay before it actually explodes, so as long as the flame front reaches all the unburned mixture before then, you will not experience knock even though the auto ignition press/temp was exceeded.  High performance engines all work in this mode and thus are susceptible to knock in some situations.  Twin spark designs are sometimes used to avoid this problem.
Title: Re: Why the 1200LC is not Twin Spark
Post by: OomD on December 31, 2015, 05:00:59 pm
Why put to spark plugs, why cant the one just fire 2 times? I am sure with the right computer you can have one spark plug and have 2 sparks from one spark plug.

you will probably have to change the plug every 20k and not 50k but it will be more cost effective



If my understanding is correct, it is not so much about the number of sparks but rather the positioning.

Ja thats right.  Firing the same spark plug twice is useless.  There will be nothing left to burn in the vicinity of the spark at that point.

The problem is that before ignition, the combustion chamber is full of fuel/air mixture - the objective is to burn as much of that mixture as possible during the piston's power stroke, without the mixture all simultaneously self detonating/exploding (which is knock).

Its a complex problem because the mixture ignites at the position of the spark plug and then burns outwards from that in a 3D flame front the spreads throughout the chamber.  That flame front travels at a speed defined by the properties of the fuel used.

Depending on the shape of the chamber, the flame front may or may not reach all the crannies during the piston's power stroke.

The hemispherical head was designed to for this reason, where the spark plug is positioned in the centre of the hemisphere.

Using two spark plugs helps because then the flame front starts in two places simultaneously. and thus the combined flame front can reach further in the same time.

Another thing which makes this quite complex is auto ignition delay.  The unburned mixture in front of the flame front is being compressed by the rapidly expanding  flame front.  All fuel air mixtures have a pressure/temp curve above which the mixture simply all self detonates/explodes which is called knock, and which can destroy an engine.  The mixture in front of the flame front can often be compressed above this self detonating pressure/temp threshold, but there is a delay before it actually explodes, so as long as the flame front reaches all the unburned mixture before then, you will not experience knock even though the auto ignition press/temp was exceeded.  High performance engines all work in this mode and thus are susceptible to knock in some situations.  Twin spark designs are sometimes used to avoid this problem.

Nice and quite informative. Thanks! :thumleft:
Title: Re: Why the 1200LC is not Twin Spark
Post by: Master Beerkie on January 01, 2016, 07:37:58 am
Useless info twin spark technology was used for the first time in a Alfa Romeo Grand Prix car in 1914
Title: Re: Why the 1200LC is not Twin Spark
Post by: jaybiker on January 01, 2016, 08:20:54 am
That doesn't make the info useless. Many forum readers weren't around in 1914. That even includes me, I didn't learn about ignition and combustion chamber technology until the early 1960's, and it's still new stuff to some who weren't around even then.
But if BMW, or any other manufacturer can revert from twin to single spark through advances in cooling or cylinder head design, or any other research and still achieve efficient engine running, then it's something to be glad about.
Even if their primary concern wasn't easier, less costly maintenance for DIY owners! :snorting:
Title: Re: Why the 1200LC is not Twin Spark
Post by: TheBear on January 01, 2016, 10:43:26 am
Even if their primary concern wasn't easier, less costly maintenance for DIY owners! :snorting:

If the cost of two extra spark plugs every 10000 or so km's is a costly problem, that particular owner should perhaps go for another make of vehicle?  Something like this:

 :lol8:

(http://www.ecovelo.info/images/hercules-carrier.jpg)

I have to say, the cost of the two extra plugs does become an issue when you are charged for 4 plugs after a service.  Conversation that followed:

Me:  "I see four plugs on te invoice here?"

Workshop Manager: "That is correct, Sir.  4 plugs"

Me: "But this bike is a 2-cylinder!"

WM (rather condescending): "Yes Sir.  It is because of the twin spark setup of the bike."

Me:  "Really?  This bike is a twin spark?"

WM:  "Yes.  All of these models are twin spark"

Me: "Why did you only replace 2 plugs at the previous service?"

WM: "Uhm ... er .... ahem ... aaah ... impossible!"

Me (rather condescending): "No Sir, this is a DL1000.  It is NOT a twin spark like the DL650.  How are we going to go about the refund?"

WM:  "Uhm ... er ... ahem .... aaah ... hmmm ...."
Title: Re: Why the 1200LC is not Twin Spark
Post by: 2StrokeDan on January 01, 2016, 11:25:18 am
Watercooling would have nothing to do with having to have 1 or 2 sparkplugs per cylinder. Cylinder head design and combustion chamber size would.

So, what have changed inside the GS1200 combustion chamber in the evolution from air/oil to watercooling? Where's the Beemer engine boffins?

Either there was a dramatic change, or the twinspark was a sales "foofy".
Title: Re: Why the 1200LC is not Twin Spark
Post by: TheBear on January 01, 2016, 11:27:21 am
Watercooling would have nothing to do with having to have 1 or 2 sparkplugs per cylinder. Cylinder head design and combustion chamber size would.

So, what have changed inside the GS1200 combustion chamber in the evolution from air/oil to watercooling? Where's the Beemer engine boffins?

Either there was a dramatic change, or the twinspark was a sales "foofy".

My guess is that, since they did a complete redesign of the engine, they also did the cylinder heads and combustion chambers.

Title: Re: Why the 1200LC is not Twin Spark
Post by: jaybiker on January 01, 2016, 07:23:20 pm
They have actually made a considerable change in the head design, in that the induction/exhaust 'flow' is now 'vertically' across the combustion chamber. Possibly that contributes to more complete and efficient combustion. Also the liquid cooling, may have a bearing on the consistency of combustion chamber cooling even though it doesn't actually circulate through the head.
In any case I doubt whether the engine overall is designed to run any cooler than an air or air/oil design, because the optimum running temperature remains pretty much the same for any gasoline fueled engine. Rather, the objective is to reduce the tendency toward 'localised' hot spots.

Agreed, the additional cost of a couple of extra plugs every 20,000 km isn't such a big issue, although it does seem that the type of plug used in twin spark designs are often a damn sight more costly than the 'cheap, simple ' plugs used in single spark engines. Why should that be? They also tend to be more inaccessible, making access to the plugs a pain in the ass.
But really, my comments are more of a tongue in cheek dig at my perception that bike designers have very little regard to the concerns of the old school home spannerman. >:(


Oh and who was the daft bugger who put the wheels in that bike at the wrong ends? don't they know that for dirt riding the larger wheel goes in front?   :imaposer:
Title: Re: Why the 1200LC is not Twin Spark
Post by: Pullaway on January 02, 2016, 08:27:12 am
The plugs with the resistor in are the more expensive one's. They last much longer and often have to be changed after 60 000km - often less accessible, because you don't need to get to them so often. Good idea to check if you got the plugs with the resistor if you do long intervals between plug changes. With NGK, they got n R before the numbers.
Title: Re: Why the 1200LC is not Twin Spark
Post by: TheBear on January 02, 2016, 08:32:05 am
But really, my comments are more of a tongue in cheek dig at my perception that bike designers have very little regard to the concerns of the old school home spannerman. >:(



No!  Don't be >:( .  I was just taking a tongue-in-cheek dig at your tongue-in-cheek perception.  :thumleft:
Title: Re: Why the 1200LC is not Twin Spark
Post by: 2StrokeDan on January 02, 2016, 08:49:23 am
The "R" symbol stands for a spark plug with a certain resistance value, as some ignition designs need to run with resisitor spark plugs.

The expensive ones are 1. the iridium centre/nickel ground electrode ones, which is good for around 80-100 000kms, and 2. the iridium centre/platinum ground electrode
ones, which last considerably longer.

To leave a spark plug in it's thread undisturbed for these amounts of kilometres is potentially asking for trouble, because the threads could "seize' into the cylinder head.
Good to remove them every 30 000kms or so to lubricate the thread.
So, while long life spark plugs are not more expensive over their lifespan than normal ones regarding purchase price, the removal/refitting would add to cost.
Title: Re: Why the 1200LC is not Twin Spark
Post by: TheBear on January 02, 2016, 05:19:11 pm
The "R" symbol stands for a spark plug with a certain resistance value, as some ignition designs need to run with resisitor spark plugs.

The expensive ones are 1. the iridium centre/nickel ground electrode ones, which is good for around 80-100 000kms, and 2. the iridium centre/platinum ground electrode
ones, which last considerably longer.

To leave a spark plug in it's thread undisturbed for these amounts of kilometres is potentially asking for trouble, because the threads could "seize' into the cylinder head.
Good to remove them every 30 000kms or so to lubricate the thread.
So, while long life spark plugs are not more expensive over their lifespan than normal ones regarding purchase price, the removal/refitting would add to cost.

+1.