SV650 Scitsu Application

[adjblade]

Does anyone use a Scitsu tacho on their minitwin, I am trying to confirm if the SV (carb model) runs a wasted spark system?

Thanks for any advice

AJ

[flymo]

cant be a wasted spark as it has two ignition coils, one for each cylinder.

I had a FZR400 race bike that did have wasted spark, two ignition coils for 4 cylinders.

So, you need a Scitsu suited to a single cylinder (only pick up from one lead) with no wasted spark.

I think thats the 'White' version tacho.

[Blue_SV650S]

I don’t know, I think it IS a wasted spark system … I think it has two coils as it would be impractical to have one, not coz they fire at different times … :scratch:

At the end of the day, there is only one pickup and it is on the flywheel (so gets triggered once per rev), not the cam (1/2 speed of crank, so 4-stroke)!!

Unless the CDI does something clever I can’t see that it is NOT a wasted spark system. But unfortunately adjblade, I too am only making an educated guess and can’t categorically confirm or deny … soory :oops:

[flymo]

I don’t know, I think it IS a wasted spark system … I think it has two coils as it would be impractical to have one, not coz they fire at different times … :scratch:

At the end of the day, there is only one pickup and it is on the flywheel (so gets triggered once per rev), not the cam (1/2 speed of crank, so 4-stroke)!!

Unless the CDI does something clever I can’t see that it is NOT a wasted spark system. But unfortunately adjblade, I too am only making an educated guess and can’t categorically confirm or deny … soory :oops:

But blue there would be no point in having two coils. The idea of wasted spark is that multiple cylinders can share a coil. On my Yam each coil had two cylinders each so that meant that one of the pair would fire a spark on the exhaust stroke, wasting it.

Some twins only have a single coil that fires both plugs at the same time, again one on the exhaust stroke for one cylinder.

On the SV I cant see any reason why there would be two coils other than to dedicate one coil to its own cylinder. :confused:

[flymo]

AdjBlade, as you know though these tacho's are expensive so probably best to call the man from Del Monte and get it from the horses mouth.

Out of interest, are you adding one for any particular reason? or just a fashion statement :-)........come on be honest.

[Blue_SV650S]

Er, I understand the concept of wasted spark … and it is there for simplicity of the electronics ;)

As there is only one pickup and it is on the crank, you are either going to have to alternate the firing between each cylinder/coil every rev, or to fire both every time and just 'waste' it … I don’t care if it is physically 2 coils, it has to be easier to simply waste it ;)

Agreed as it has 2 coils and an CDI/ECU, it could be single spark, but I am not sure having 2 coils is conclusive enough evidence to determine that.

Anyway, look in the blurb at the front of the ignition chapter in the manual, it might say as a comment in there if it is wasted spark …

[Blue_SV650S]

Oh and thinking about it, it HAS to be a wasted spark system ;)

Else how would you be able to set the cams up when rebuilding an engine .. think about it! ;)

[flymo]

Oh and thinking about it, it HAS to be a wasted spark system ;)

Else how would you be able to set the cams up when rebuilding an engine .. think about it! ;)

I'm with you dude....... :-) Having had 10 minutes to let this sink in. I think the only benefit to having a wasted spark but still retaining two coils is to keep things simple, the ignition timing can run at engine speed rather than half engine speed.

[flymo]

Er, I understand the concept of wasted spark … and it is there for simplicity of the electronics ;)


Sorry, wasnt trying to teach you to suck eggs :-), was thinking (typing) out loud

[tranx]

I have one of these on my bike, If you phone them up they will be able to tell you what tacho you need. The pick up lead runs off a single coil to get the correct reading so it will be a wasted spark design, it does also have 2 coils though. I'll go get the instructions and box tomorrow from the garage and tell you which one it is if you like.

[flymo]

"Place your bets........." :-)

[adjblade]

Thanks for the info folks, if you can confirm which type that would be great, should be a red back to it. No not a fashion statement just need a revcounter for the track and they are not too unreasonably priced. I used to have one on my supermono and it did the job ok. (Scitsu were not sure if it was wasted spark or not hence my original post)

I would also like to fit a steering damper, anybody got one out there sitting around not doing anything?

Thanks

AJ

[flymo]

I'm in the same boat with race prepping but was going to run with the stock rev counter on my K3. I'll have it on the dyno in the coming weeks so can verify the accuracy then.

[FOO]

i also need a rev counter for racing, any got a spare or a set of standard clocks for my curvy SV?????

[yorkie_chris]

At the end of the day, there is only one pickup and it is on the flywheel (so gets triggered once per rev), not the cam (1/2 speed of crank, so 4-stroke)!!


Else how would you be able to set the cams up when rebuilding an engine .. think about it! ;)

+1

Heard from zadar (iirc) a while ago that the SV can be set up as big bang if you put the cams in wrong, this says to me that it has to be wasted spark.

Wasted spark simplifies overall design, can put all the engine electronics in one place then instead of needing a 1/2 rpm pickup.
Also I have a feeling that a spark on exhaust could help with emissions?

[tranx]

Ok the tacho is a red backed one.

[adjblade]

Great, many thanks :D

[chunkytfg]

+1

Heard from zadar (iirc) a while ago that the SV can be set up as big bang if you put the cams in wrong, this says to me that it has to be wasted spark.

Wasted spark simplifies overall design, can put all the engine electronics in one place then instead of needing a 1/2 rpm pickup.
Also I have a feeling that a spark on exhaust could help with emissions?


Huh?

I thought the theory behind big bang was to change the firing timeing of a IL4 to simulate a V-twin thus giving it the same characteristics?

[tranx]

Maybe he means that you end up turning it into a single?

[chazzyb]

Heard from zadar (iirc) a while ago that the SV can be set up as big bang if you put the cams in wrong, this says to me that it has to be wasted spark.


I can't see how you can do big bang on a V-twin unless it's got two crankpins, offset by 90 degrees (in the SV case), to emulate a 360 degree crank (British parallel twin stylee). I'm convinced the SV has only a single crankpin but not a forked con-rod, a-la HD. I have an idea that the Deauville may have offset crank pins, giving evenly spaced power pulses. So it's not a real V-twin at all. ;-)

I know some of the V4 racers (Duke?) configure their bikes for big bang, but that will be both pots in one bank firing, not a pot from each bank.

[yorkie_chris]

OK I put that badly, you can turn it into a big-bang ISH motor :D. I think you'd advance one cylinders cams by 360 deg of crank rotation, but I'm not sure.

[chazzyb]

OK I put that badly, you can turn it into a big-bang ISH motor :D. I think you'd advance one cylinders cams by 360 deg of crank rotation, but I'm not sure.

Hmm, as the engine already goes bang-turns 90-bang-turns 270 and the crankpin is fixed, I can't see how it can be changed to any great degree. ;)

[yorkie_chris]

You're not changing the crank at all, just which stroke the valves are opening on, i.e it's not it's normal firing stroke, it fires on the next one instead

I think this can be done, I read a post from zadar about it a while ago when someone was setting their timing up because the same question of wasted spark came up. Why you'd want to do it is another thing, though it would probably sound very different

[Blue_SV650S]

It'd just sound like a big single ... 1 BANG (technically 2 smaller bangs making one big bang) every 2 revvs as opposed to one every rev as they are as stock ...

It'd sound well 'lazy'!! :-# :D

[chazzyb]

It'd just sound like a big single ... 1 BANG (technically 2 smaller bangs making one big bang) every 2 revvs as opposed to one every rev as they are as stock ...

It'd sound well 'lazy'!! :-# :D

OK, I've just twigged. While you can't have both pots firing at once, you can have them firing within 90 degrees of each other - they don't normally. I managed to overlook a fundmental that a 4-stroke only fires every two revolutions, so the usual firing intervals between SV pots are 270 and 450 degrees.

Now, what was the question again?

[pipey]

So I,am a bit late on with this but .......

An Sv has two coils both firing at the same time. Each cylinder fires (bang) independantly of the other 90deg I believe is quoted else were.

You can time the cams 180 deg I think out thus making the bike run like a single ? I know this as my bike was like this when I bought it !:(

I thought there was a problem as she only made 61bhp on a dyno pro dyno.
I then fitted injected cams to the same locations as those removed.
This made 5 odd bhp difference and I thought it was the best thing since sliced bread.
That was until on track with a friends bike that I also fitted injected cams into. His was way stronger.
A trip to SDC on the dyno showed that I was down around 6bhp to my friends bike. Everything was checked out as ok so we checked the cam timing as they reconed many dealers time them wrong by mistake.
The rear cylinder was 180deg out, timed correctly and she is back up were she belongs around the class limit :)

[yorkie_chris]

Yup that's about the sum of it. As I said earlier on, not big bang, but pretty close.

Anyway the original big-bang 4 pot 2 strokes all fired within 70 degrees or so of each other. Didn't work, they were still highside happy.

To apply this to the general point of the thread... the ICU doesn't know whether either cylinder is on compression or exhaust stroke so "wastes" a spark" So each coil is firing once per revolution.

[zadar]

not really single but close together.firing order is 270 degree apart.if you set cams on both cylinders at same crank rotation firing order will be 90 degree apart.
pick up for spark is on flywheel and it reads it once per revolution.but since it takes two crank revolutions to turn cams one revolution you get spark on both strokes.
cams determine what stroke it is.