4 stroke + H2o, can we get along???

Y

yamaslut

Guest
no fuel goes through the crankcase... it's injected directly on top of the piston after the piston closes of the exhaust port... why coundn't we do that???

think of crank life if no fuel was passing over it washing oil off...
and fuel economy w/ the direct injection
 
WFO Speedracer

WFO Speedracer

A lifetime ban is like a lifetime warranty !
Location
Alabama
Pretty much everything has been tried before including hybrid two strokes with belt driven camshafts and valves.Some things worked ,some didn't.The technology is there to do this ,what is not there is the technology to do it and make it affordable.
 
CRKarter99

CRKarter99

Location
Tampa, FL
Another alternative that would be interesting would be a rotary style engine similar to that of a RX-8. I am currently involved in the design of a rotary engine for a go-kart that weighs 33lbs and produces about 50hp with a wide powerband. A single rotar engine has 3 moving parts and can be pre-mixed, or oil injected.
 
tom21

tom21

havin fun
Location
clearwater FL
For me the real issue is if you suck enough water in and motor tries to compress that water, BAM! bent rod and or valves. We had a bunch of flood cars one time to fix and it was some of the coolest carnage I'd ever seen. Rods shaped like S's, half dozen valves bent. its great. not to mention the cost. anyone price a rebuilt 701 to a sd 3cyl or yami 4, hell its not even close doing a 1300r to a 4 stroke. it may be more powerful but it has some major issues and the cost alone is enough for me to say no thanks. maybe it it would be more fair to compare a X scream 1000cc to a yami 4. still easier and cheaper to rebuild the x scream. we did not even get into the sensors and ECM. way big costs there, makes msd or advent look cheap. plus how many peeps can diagnose and repair that stuff on the beach? again, NO THANKS!
 
WFO Speedracer

WFO Speedracer

A lifetime ban is like a lifetime warranty !
Location
Alabama
Tom I hate to tell you but four strokes are in the near future,they have taken over the sit down world and the standups are next,either that or there won't be any more standups,which do you prefer?Thing is what is probably gonna happen here is that they will find there way into standups,they won't really worry about the water ingestion problems,they will just hide behind some clause in the warranty and say hey it wasn't designed to be used that way sorry it won't be covered,that will leave guys like us to try and make it work for our intended applications.
 
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Kaveman

Kaveman

Born in USA(not Kenya)
Location
texas but soon tejas
wedoseadoo said:
Tom I hate to tell you but four strokes are in the near future,they have taken over the sit down world and the standups are next,either that or there won't be any more standups,which do you prefer?Thing is what is probably gonna happen here is that they will find there way into standups,they won't really worry about the water ingestion problems,they will just hide behind some clause in the warranty and say hey it wasn't designed to be used that way sorry it won't be covered,that will leave guys like us to try and make it work for our intended applications.
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Sad, but true
 
dbrutherford

dbrutherford

Parts Whore
Location
Fairmont, WV
yamasaki said:
... at the end of the day, what that really boils down to, is that a 4 stroke is just SAFER to ride...

am i crazy?
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Ask Doug Henry about when he was the only one running a four stroke and it died on take off at Budd's Creek. He front wheel cased the double and broke both his wrists. Not safer... well not safer back then.

Difference in frour stroke and two stroke MX is that the manufactures have been spending more R&D on the fours then the twos. Also they have had 10 years of developing/changing making the fours better. Four stroke water craft haven't been around for 10 years yet. Give it ten years and things maybe developed right for the water... maybe

Edwin of course you are crazy!
 
eel

eel

Our home is girt by sea
yamaslut said:
no fuel goes through the crankcase... it's injected directly on top of the piston after the piston closes of the exhaust port... why coundn't we do that???

think of crank life if no fuel was passing over it washing oil off...
and fuel economy w/ the direct injection
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Seadoo Di, (ORBITAL) Kawi/polaris (Ficht) (a typo, should have had a "U" instead of an "I") run a "dry" crank.

The fuel running over the crank has little issues as a dilutor as its just an extra, not a replacement for the oil. 2stroke oil is mostly designed to be mixed with petrol.

It has a couple of very big positives. First is that when the inevitable happens, the fuel has a dramatic positive effect of de-wetting the crank. The other is that the fuels latent heat has a cooling effect on the bottom end = hp. Most DI systems need case cooling and/or stator cooling.

A drowned DI 2stroke needs more attention AND way more post wet running than a carbed or wet crank injected engine to ensure that the crank will live. Let alone the extra measures you have to perform to make sure the DI specific components will survive the wet start!

As far as the performance difference?

Been proven. When the xp was the hot choice for stock class couch racing, the carbed boats kicked arse. We had access to the same stuff as ppg with their hyped DI stuff. We tried it, and found that carbs worked better than the DI in every instance except 300km enduro's. Then their exceptional fuel economy became an advantage.
PPG ended up altering comp. ratios and props to make the exhorbitant cost as justifiable as possible to the current DI owning customer.

EFI definately has advantages as far as AFR accuracy, but I think the dirty case or inlet injecting systems are better for making power and clearing water from a freestyle trick gone wrong wet engine.
 
eel

eel

Our home is girt by sea
Yamasaki, the MX teams accountants look fondly on the 2 stroke days.
 
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