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The TTR250 FAQ web pages -> TTR250 -> Carb stuff -> Yamaha Energy Induction System (YEIS) - boost bottle, air chamber, resonator
Post Info TOPIC: Yamaha Energy Induction System (YEIS) - boost bottle, air chamber, resonator
TTRfan


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Yamaha Energy Induction System (YEIS) - boost bottle, air chamber, resonator
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Ever wondered what the little black bottle plumbed into the TTR's air intake was supposed to do?  I confess to having been ignorant until reading a review of the new Beta enduro bikes in the latest TBM magazine when the YEIS was mentioned. I did a search on t'internet and found some more information.

Apparently the YEIS is a very efficient invention. A small bottle, often called a "boost bottle", is installed between the carb and the intake port connected with a branch pipe. On the TTR fiche it is referred to as an “Air Chamber” - part 21 below but is situated the airbox side of the carb so I am guessing it has the same effect as the boost bottle but just stores air rather than a fuel and air mix.

airbox fiche.jpg

 

I confess to not fully understanding the theory bit it seems to be a "good thing" and so best not to remove it from your TTR!

This is what I found:

The purpose of YEIS is to get the engine to respond quickly from the bottom end without flat spots. 

It saves 10-15% in fuel consumption and makes the engine wake up at lower rpm.

Like many of Yamahas inventions, when it first came out there were many doubters. Just as they doubted the wisdom of a separate oil pump, the 7th port and torque induction (reed valves in 2-smokes). But, if done properly, YEIS does work.

Many people have since copied this modification.. The most common mistake people make is not placing the boost bottle above the cylinder, not getting the size right, using a common bottle for two cylinders and failing to make sure that the bottle drains back without collecting fuel.

Since carburettors can carburate both in and out, when the charge is out of phase with the engine it creates a double dipping intake charge (passing the jets twice). This kills the engines ability to make torque due to this RICH condition, thus creating the Torque\HP DIP just before the engine starts to take in the charge and use it all. This power dip can be seen in both 2 and 4 stroke engines. The boost bottle will help cure the problem by providing a storage tank, of the required volume and distance to resonate at this RPM. It stores the charge that once reversed back through the carb and returned as a DOUBLE RICH condition.

Brian



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brindabella


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Yamaha Energy Induction System (YEIS)
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I think these things are quite common (e.g. in automotive intake and exhaust systems, and in audio systems), and are known as Helmholtz resonators.

The airbox has a certain resonant frequency (presumably at low rpm), and at that specific frequency/rpm it induces pressure variations which upset the pressure at the jet, and therefore the fuel flow. Carburetor designers would hate this because they assume the pressure at the jet is determined simply by throttle opening and rpm (the venturi effect).

At higher speeds there may also be resonances (eg harmonics), but these may not be as important because they are smaller and the venturi pressure is higher in comparison, so less affected.

So to get proper jetting the airbox designers need to help the carburetor designers by trying to alter the airbox geometry to cancel out any weird stuff at low rpm, and adding a short necked Helmholtz resonator does the trick just nicely.

It also would reduce the audible intake noise at that rpm, which may even be the main design intent.

Can any Yamaha design engineers reading this thread please speak up now an enlighten us? [just joking].

Of course any airbox fiddling (like cutting the top off) would have unintended side effects on resonances.

PS it doesn't sound good if these little gizmos are poorly fitted and leak!




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barra8


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Thanks Brian, i knew that little black ''canister'' was good for something biggrin

They dont seem to be a bad fit to me? Mine takes quite a bit to get off but eventually manage (reminds me of taking the heads off barbie dolls when i was a kid :).When i put it back on i smear rubber grease around the seal & refit. No drama's or leaks yet & it is from a 1994 model so not sure why these would have a leaking problem???confuseconfuse

...............................

Jarrah.



-- Edited by barra8 on Sunday 14th of October 2012 04:30:29 AM

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BaronGreenback


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Thanks for that Brian. I haven't seen a boost bottle since building nitro RC cars. I thought they'd only be effective on 2 strokes. I saw the one on my bike and thought it may have been something to do with emissions. (I didn't follow the routing)
They aren't well fitted at all on the TTR. Quite a lot of play, and of course, leaks.

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BaronGreenback


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So that's how they work. Interesting stuff,  brindabella.



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petenz


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They have been around for years as yer know...
how/why they work....
pos / neg pressure...
when the inlet valves close the vacume though the carb stops
so dose the air flow.... at this point the boost bottle is in NEG
pressure so the air remains flowing into the bottle..when the inlet valves
open again the air is sucked out returning the bottle back to NEG
pressure.... basicly it reduces the pulse between open/closed valve cycle
helps maintain a continus air flow.... reduces the dead spot in the air flow
with no fuel till there is enough air flow/vacume to start picking up the fuel
again though the jets...

It was first seen on the YZ & IT in the early 80s they had the bottle
between the carb & reed valve "motor" they would fill with fuel if not
above the carb for it to drain back into the air stream....




...

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peteBLUEttr


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Alot of people put sealant round where they fit on, its not the most awesome of fixtures. Yeah it is just for smooth running isn't it like a pre fuelling thing like the accelerator pump is.

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BM Steve


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I cut mine off a while ago, it was wobbling around and so just cut it off, doesn't seem to make any difference at all and fuel economy seems the same

although a bit higher ATM only about 120-130kls before the reserve because I'm running 13/52 gearing

It may have caused a backfire/stall sometimes, if you have been powering along and then slow quickly or stop quickly a little backfire and then stall ?

anyone else get that ?  I may put it back on again, I'll see

 



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yamaha42


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My bike does as you described, but my bottle is still installed.

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BM Steve


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yamaha42 wrote:

My bike does as you described, but my bottle is still installed.

Ah I see, well a carby problem I guess, a bit of a clean and tune is probably the order of the day

ATM I just turned up the idle a little, it was idling at a point where it was almost stalling



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2004 TTR250 - Highway Dirtbike Hand Guards, 38mm Bar Risers, D606 Front & Rear, Opened up Airbox with Twin Air Filter, Re-jetted Carby, B+B Bash Plate & Frame Guards, DIY 3mm Alloy Tail Tidy, 14/47 Gearing.

 
sidecars48


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RE: Yamaha Energy Induction System (YEIS) - boost bottle, air chamber, resonator
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Hi,ive taken my YEIS bottle thing off and i cant get it back on, my bike has been apart for 8 months because of this and im to the point where im going to cut it off.

 any suggestions how to get it back on? 

very hard to get over bottom lip.



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TTRfan


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It's difficult to know what to suggest to help fit the bottle back other than the obvious of warming the rubber with a heat gun or hot water and using some sort of lubricant such as soapy water....  confuse

I recently fitted a couple of them and you really need three hands to make it easier no

Brian



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