Yics Box

[Lucky]

From the Yamaha service manual:
YICS

To increase fuel economy through more efficent combustion, the engine is equiped with the patented Yamaha Induction Control System (YICS). In this configuration, the YICS consists of a chamber linked to the intake manifold by a tube.  Upon intake, the vacuume in the manifold creates a vacuume in the chamber; when the itake valve closes, the chamber draws in some air fuel mixture. when the intake valve reopens, the mixture in the chamber shoots back out throug an nangled tube into the cylinder, mixing with, and swirling the main intake charge.  The swirling charge is then compressed and ignited, burning more completely and producing more power than that of a coventional engine.

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hooking the hoses together connects the intakes together (physicly, in the head, but still in the intake portion of the fuel system)

If you sit & think about how the valves open & close in relation to ft vs rear, you'll see that what you've done by hooking them together is akin to creating a vacuume leak. the flow of fuel mixture in the hose will be a back & fourth situation, and the result is less mix being injected back into the cylinder.

also, there is some relationship between when intakes are opening & closing between ft & rear that could be causing a situation where all the spent fuel is not being completely evacuated (intake 'overlap' is designed in)

I would say off hand, that if you have the 2 ports directly connected, with no obstruction in the middle, and still have good performance, that your carb settings may be way out of the customary range for this bike.

I haven't investigated this in any depth, and i'm sure someone will respond that their settings are 'normal'.  my own quick test with a properly tuned set of carbs was to connect the 2 ports with ordinary fuel line & run the bike.  throttle response was just 'ok', and it took probably an extra revolution to start.

gather from this what you will.

--Lucky

[silicon_toad2000]

excellent Lucky, aside from quoting from the yamaha manual but i guess you have to start somewhere.

spot on with the back and forth comment, I hadn't thought about that. given the velocity of the gasses in the linkd tube, once one cylinder has sucked through the air/fuel an the other cylinder starts sucking, the air/fuel flow has to stop and turn around, by the time it does that it may just be too late.
I wouldn't say it is akin to a vacuum leak as it is supplying metered fuel and air, usually a vacuum leak is just air which is why it screws things up.

Good call on the valve overlap screwing things up, it crossed my mind a few times but i didn't think out the order of the 4 strokes. When I did i realised there will be a time where one piston is at the top of the exhaust stroke and the inlet valve will be open and the other piston will be at the bottom of the intake stroke and have the intake valve open.

but as far as normal settings... I beleive that anyone who leaves their machine (car or bike) with the factory settings and equipment should be taking the bus (unless its something historic like a model t ford or an old indian...)

sorry about the long wided post, just wanted to get the thoughts down before i got myself confused. thanks for your patience and the exchange of ideas!

[jasonm.]

Hey Al,
 ?I'm Here in CT. ...Torrington. I'll meet you anytime...any Sunday when the roads get cleaned up. Also I guess you need a bracket to hang that billet YICS.

Jason

[CH3NO2]

Jason
    Sounds like a plan. Send me a message when it thaws out and we'll hook up. Mybe we could get a few other New Englanders together.

Al

P.S. I've got the bracket all planned out.

[Rick G]

I try Jasons trick on every YIKES box I do , but as yet  it wont work for me !! I wish I lived closer to him , I'd like a personal lessom from him. LOL

[Glyn Pickering]

It seems to be that the YICS is important for decent performance on the XZ. I wonder why this model and some others (as mentioned) have a YICS whereas the majority of twins don't? Is it as a result of the poor vacumn effect of the downdaft carbs not swirling the mixture enough? Wouldn't alot of twins therefore benefit from a YICS?

I've done away with the YICS since I put a Weber on the bike. I wonder if I should put one back on? How would you tell if it was worth it ? a dyno test?

 ???

Regards
Glyn

[Extent]

I read once that someone with an SV650 was adapting a YICS to their bike, I've no idea how that came along tho.

Reading just what the service manual says about it it dosen't sound like the shape of the chamber at all has an effect on what it's doing, and all the swirling happens when the engine pulls in the intake charge and sucks the air out of the YICS at an angle because of the return tube.  I would think that the ideal size of the YICS would then be just large enough to last during an entire intake stroke, too small and it won't swirl the intake as much, too large ..... well I can't think exactly what would happen if the chamber was too big.  But that description of the system does make me think more that the material of the YICS dosen't make a difference, since all it is is a holding chamber, all the mixing happens in the cylinder.

[Walt_M.]

That is pretty much it! The YICS is there to provide some turbulence to the intake charge so the lean mixture will be easier to ignite and burn. Since everything on the bike is about cost/performance, the YICS is probably optimum size. Smaller won't work as well and larger probably wouldn't be noticeable. As some people have found, the bike can be jetted to run well without it but it probably would not pass an emissions test if it was required.

[silicon_toad2000]

I think on the dyno, with the YICS in place you would see a slight fattening of the torque curve at lower revs provided the bike is tuned that way.
The YICS would allow the bike to run leaner while still getting a good mixture given that it swirls the air/fuel flow. without a YICS you could just tune the bike a bit richer.
Once I get some of my other problems sorted out I'll be looking on the swap shop for a YICS

[ozian]

One back fire seems to destroy YIKS box sealing properly
What about a couple of highly polished copper or brass 2" pipe with ends silver soldered on with similar vol as factory
Might take a bit to keep them polished but done neatly it would look ok
Ian

[Extent]

I just made a 1 piece fiberglass YICS replacement last night that just uses the same internal volume as the stocker, it's seemed to have held up relatively well, but I only got out 100 miles today before I crashed it, so I don't know if it will stand up.

One thing I noticed while fitting it to the bike is how profound an effect it had on the engine.  We all know that the RPM drop when you take it off, but as I was fideling around with it I managed to pinch just the rear tube and even just that had the same effect.  You really are getting "something" with it, with the same amount of airflow, and so same amount of gas you're getting enough extra energy to spin it up a couple hundred RPM extra.  That's not quite 100 technically correct but I'm sure you see what I mean with it.  Plus I find the bike much easier to start with it mounted, even my homemade one.

I wonder if it would some how be possible to tune the chamber size much like you would adjust the idle mixture screws.  Somehow get a type of syringe that could take the pressures of the YICS chamber and make it larger and smaller till you find the size where you get an RPM (or efficiency) peak.

[ozian]

Good idea but I tend to think the japs would have would have done all that mucking around on developement to make it good all round. Different vols might affect high rev or low rev performance but might be a pig elsewhere such as starting etc.Thats why most after market computers in cars are such pigs on cold start, they dont have enough cold motors to play with, where manufactuers do
Ian
Hope you didnt hurt yourself

[Glyn pickering]

Hi All

Getting some jets for my Weber at the carb shop today and they had a air turbulence product which claimed to improove fuel consumption, performance etc. Forget the name, but they make models for bikes. It's basically a fixed spiral vane which forces the air into a twist or spiral as it enters the carb,
hence producing a turbulence effect. Should have the same effect as a YICS, at all RPM's. Anyone seen these working?

Cheers

Glyn

[Extent]

Nope, but I did run acros some pictures of something that sounds similar in a tech paper I found while looking for a better formula for airbox resonance.  I think they were converting a bike to run on something other than gas.  They called them vortex generators or something like that.  The YICS should work at all RPMS tho.  The engine already has the fittings for it, I would personally just put the YICS on and go from there.

[Rob_OS23]

Hey Extent,
You say you made one out of fiberglass....
I have never used fiberglass, but I know of how it's done.  Don't you usually fiberglass over something, say for example, wood in the case of a boat?  Wouldn't it be very thin on it's own, and kind of brittle?  You may be onto something though, what about making one out of carbon fibre?  I hear that stuff is wicked strong.....some good ideas going around here!  Anyone know what kind of plastic the original yics is made of?

[Extent]

Well just the resin it's self is weak, but you use fiberglass cloth or matt and that's what actually gives it strength.  You can make it as thick as you want, fiberglass (or composites specifically) is used for car body panels, race car parts and missle fairings.  You could do one out of carbon, but that would be unnecissarily expensive.

[ozian]

What Glyn was refering to on the carb is sold in Aust as a Hyclone. After testing by Consumer Affairs Dept , most states have banned advertising of them , even sales of them in a few places because it's deemed as a con
Ian

[ps2/bikevision]

hey the sprial thing glyn was talking about is called a torando i belive. they sell them at auto zone here in the states and if i remember right they are $60 us. i dont know if they actually work but i have seen them in the past on tv. dont know any one who has bought them and im not going to spend the cash to test one out. would be a good thing if they do work i thought about buying one for my truck and opted for a k&n air filter instead. i have to go to auto zone tonight and buy oil i will check them out a little closer and let you know what i find out. i know the guys down there maybe they will let me test one out on my truck for awhile.

[ps2/bikevision]

i checked put the toronado last night. they are $65.99. they wouldnt let me test one out but said if i bought on and didnt like it i could return it within 30 days. they said a few people have bought them but havent heard wether they work or not. i might check it out if i got the money to blow. if i buy one ill let you all know.

[DancinOn1Wheel]

i checked put the toronado last night. they are $65.99. they wouldnt let me test one out but said if i bought on and didnt like it i could return it within 30 days. they said a few people have bought them but havent heard wether they work or not. i might check it out if i got the money to blow. if i buy one ill let you all know.

You know what works just as good as the vortec thing???




put a brik in your intake. Those things are garbage! I saw a big write up somewhere... where they put those and all the variations to the test and they actually decreased performance. Its kinda of one of those things that you hear and think this is great... then you try it and you still think it is great cuz you were told it is... when in fact it does nothing.

most combustions chambers are designed to promote swirling, usually by the shape of the head. things like YICS are designed when combustion chamber design or modification is not an option or is cheaper and still effective.

DONT WASTE YOUR MONEY! i will try and find a link.

look at it this way... you want themost flow from your intake, right? how is sticking something in there going to give you more flow... all it will be is a restriction, therefore lowering performance all around, however, by adding more restrictions, it will in fact increase bottom end performance marginally but significantly decrease top end performance.. its not worth it.

- Justin