Yamaha 2 stroke basics (Builder) - Post By BoatTest.Com

[vzlan999]

@woopass250 good point, the so known "scavenge loss"

[partyguy9]

so what stops the mixture from escaping out the exhaust port when the piston begins to compress?

[warius100]

its okei, i didnt want to see the rest of te video anyway

[justinroxxxohyeah]

why is there two horses fucking in the related videos?

[Ieatpeople2]

@justinroxxxohyeah well, the videos that come up are based off of your viewing history, so you tell us why???

[WaterFall1973]

Also love how it looks like it's compressing the mixture with an open exhaust port. Fail.

[133shinchan]

@WaterFall1973 it's like that on a 2 stroke engine.....

[WaterFall1973]

@133shinchan The only compression you can get while the exhaust port is open is caused by the pressure wave that can come back from the exhaust. This is limited however to specific rpm's

[sacadito]

este es el video mas explicativo que vi hasta ahora, muchisimas gracias

[bmxty82]

2 stroke is faster

[kddcc]

e-tecs top two strokes and mercury makes the top 4 strokes...yahama is a joke.

[soldierholland]

how can the compressed fuel mixture don't escape true the exhaust?

[SecondPIayer]

@soldierholland I think a bit of it does.... i am guessing though...

[1850KAMZ9]

@soldierholland some does

[christosGTAIV]

@soldierholland it does

[btownmxer]

@soldierholland

It does. A two stoke engine actually requires a lot of backpressure from the exhaust to run at peak performance. If the pressure in the exhaust is low then the fresh Air fuel mixture excapes into the exhaust quite easily. When it has backpressure it holds back the fresh air fuel mixture compressing it adding more volume of mix per stroke

[lands3r]

but when the burned gas escape into the exhaust port there comes new air in the intake bud than you have a mixture out of burned air and new air so not 100% new

when its posseble to create somthing that allows real 100% new feul air mix into the chamer does it provide more power than? or is it not so important i hope my q is understandble xD

[legox50]

I always wondered why there isn't a sliding valve where the exaust port is to prevent fuel/oil/air mixture from excaping... I mean, the sliding valve can be powered directly by the crankshaft...

[TheOfficialKC]

@legox50 Honda tried it with the EXP-2 Dakar bike. I think it worked great. DI works even better, injecting the fuel after the exhaust port is closed. But a combination of the two? Could work best and eliminate the need for an expansion chamber.

[MKUltraProject]

AHA! So reed valves are 'sucked' open! And air compressed closed! I always wondered how they worked on their own! Thanks uploader. Great video!

[woopass250]

this video doesnt show the air fuel mix lost out the exhaust port when the pistons coming up

[JETZcorp]

@woopass250

Direct-injected two-strokes don't have that particular disadvantage. However, the model they showed in their little diagram wasn't injected. The most common cure to the problem to an expansion chamber, which sends a resonance wave back toward the engine to cram that lost air-fuel mixture back into the engine if the engine is at the proper RPM for the chamber.

Direct-injection, as well as some new valve Boyesen has developed, are working to fix the problem, though.

[XELA2T]

@JETZcorp

very good explanation you made (I was also laughing on the scavening wave faithfully stopping at the exhaust port), but as you said there are certain ways...

In reality the high performance 2 stroke engines turns this "disadvantage" in combination with the expans.chamber into an advantage, the reso.exhaust works like a charger but without moving parts.- What is this Boyesen valve, a kind of ex. port timing valve?, - never heard of it.

[JETZcorp]

@XELA2T For more information on the Boyesen thing, type "Boyesen Exhaust Valve" into Google and click the first link.

[GeneraleRamon]

@woopass250 for this reason a good 2T engine have an expansion exhaust

[burmkilla]

@GeneraleRamon its called a power valve

[WaterFall1973]

@GeneraleRamon The expansion exhaust will only bounce back gasses @ the correct time when the rpm is right. So it doesn't solve the blowback.

[galactophore]

@woopass250 That's because if they are still making them they are now direct injection. Only air with no fuel mixed in passes out the exhaust port. With direct injection they are now cleaner(especially in Nox emissions) than four strokes with the same power.

[nacho1741]

what do u mean ur bike goes backwards