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Yamaha Energy Induction System

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Posted by: MX175

Can someone give me a thorough explanation of this Y.E.I.S., Yamaha Energy Induction System? I understand that it is supposed to improve the transition from low rpm to high rpm. It appears to have something to do with the pressure and resonance in the intake system. It is essentially a "boost" bottle that holds a volume of intake fuel/air. I understand that the volume of the bottle is close to the engine displacement. It is located on the intake manifold, between the carburetor and the reed valve. The bottle is attached to the manifold with a relatively small (<3/8") hose. This hose is the only way in or out of the bottle. So what does it really do? I probably need to better understand what is occuring in that manifold. I guess it is not just a constant flow of fuel/air mixture. (my cousin has an '86? IT200 with one)

Mark
'80 KDX175
'85 KDX200
'81 XS850 Special


Posted by: MONKEYMOUSE

I was woundering what that is also. Ive had my '82 YZ100 for about 2-3 years now and still have no idea what it does lol. Does It need to be cleaned? If so how? What does it do? why are they not on new bikes? Was this used in place of the PV on smaller CC bikes (because my bike dosent havea PV, just woundering)?


Posted by: techman

I once accidentally found the paper the engine guys at Yamaha published about that. AT the time it really struck me as neat because we had a (82?) YZ250 with said bottle. They had graphs describing the poor resonance conditions at mid rpm, or at a certain transition rpm and figured out the little boost bottle as a way to change the pneumatic resonance of the intake tract to boost torque via better charge flow at this "torque trough that is characteristic of two stroke engines" as they put it. It might have been a resonant node near the carb jets, thus messing up the continuous flow needed to get better air fuel mixing (?). Foggy memory! You ought to find that pulling your boost bottle and plugging the hole reduces a bunch of the lower-mid torque of your engine. It's possible other tuning and design methods have provided alternate methods of removing the so-called "typical torque trough" as there aren't any resonant chambers on any modern two strokes that I've seen.

I think it was an SAE paper - but it's been more than 10 years since I stumbled across it, so don't quote me on that.


Posted by: Rich Rohrich

Quote:
Originally posted by techman
I think it was an SAE paper - but it's been more than 10 years since I stumbled across it, so don't quote me on that.


YEP, it's an SAE paper. I have it at home somewhere. I'l dig it up and post the number an abstract info.


Posted by: David Trustrum

To breeze over the subject in far less detail, they are useful as a means of filling in a power-dip in the curve presumably caused by too steep a baffle cone or another mismatch.

I have had some success with an adjustable one I made up, but truth be known I should have remade the pipe. The long & the short of it is you don’t see them anymore, but they were the hot aftermarket bolt on 20 years back.

TSR have a program for predicting the volume depending on the rpm the dip in the power curve is, tube length, , carb etc.



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