OzVMX Forum
Clubroom => Tech Talk => Topic started by: mx250 on June 08, 2009, 05:31:26 pm
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Why do you think they have groved the crank flywheel? Increasing the 'windage' to have a supercharger effect?
(http://i323.photobucket.com/albums/nn458/mx250syd/crank.jpg)
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A mob in the US do this to lighten unsuspecting peoples wallets.Which it does with alarming regularity.
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A mob in the US do this to lighten unsuspecting peoples wallets.Which it does with alarming regularity.
So that's the claim is it? I was wondering. I know the opposite, polishing, is also done to reduce the windage, 'drag', and increase HP.
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I'd say some form of plot against 2 strokes as that would drop primary compression due to those chamfers on outside of crank :o
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windage and compressing air have 2 different meanings. If windage from oil drag then possibly as you are breaking up oil film, not sure what meaning that would have on a 2 stroke that runs dry crank. If you are talking about compressing air forget it and even if it did you need an exhaust valve to make it all work.
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Exactly Marc, these is pure snake oil. Show me the dyno print out. ;D
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The only benefit in this on a two stroke is lightening the crank.
But - I'm probably way off here - if it's a pressed four-stroke crank the grooves promote spray which cools the underside of the piston.
And, as mentioned before, lightens the wallet.
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if you really want to super charge a 2 stroke you need one of these
http://library.abb.com/global/scot/scot208.nsf/veritydisplay/7d71e16c42799eddc12575ca0049097c/$File/ABBTC_TPL_B.pdf
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Years ago I bought a siezed up Maico 250 engine and when I pulled it down I found something similar to the above. Some "genius" had used an angle grinder to grind similar grooves into the flywheels. There was no uniformity on depth or pitch and I often wondered why someone would do such bastardry to a perfectly innocent set of flywheels ???.
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I'm with Lozza - a dyno print out would be interesting and so would the shops profit margin !!! Nice engineering though .........
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MarcFX, unless you have a 2 stroke diesel which is totally different to a 2 stroke petrol engine the turbo can not work.
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Sorry to rain on your parade there monty but turbo's on 2T engines are all the rage in the sand drag and snowmobile drag(both summer and winter) worlds
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Something to wake up the Jawa ;)
(http://i39.tinypic.com/23ijbzm.jpg)
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I love thar jawa.
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I stand corrected Lozza :-[ although my post was not very clear I was referring to the link in MarkFX's post. Having said that I did not think that a 2 stroke spark ignition engines could be successfully turbocharged - Supercharged yes.
I wonder how they overcome the porting overlap issue and restriction in the exhaust? I would expect that the gains on a spark ignition 2 stroke would not be as easily found as in a 4 stroke.
Anyway that teaches me for opening my big trap ;D
Interesting links on this subject
http://www.physicsforums.com/archive/index.php/t-64413.html
http://www.youtube.com/watch?v=CjFOOG1WYws
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Stinger is the best place for a turbo, the only drama is the turbo over scavenging the cylinder. No easy gains eh, well........ should talk to sled tuners 350HP from a 1000cc triple is par for the course with a turbo sled. Try to tell THIS (http://www.youtube.com/watch?v=qpoEjY7KDdo&feature=related) bloke his turbo didn't gain anything !Sleds are now even coming turbo'd from the FACTORY (http://www.youtube.com/watch?v=IRfEvzLUGSs&feature=related) Beware of THIS (http://www.youtube.com/watch?v=O_P1l7kVeNc&feature=related) 50cc Vespa at the traffic light GP ;D
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This is approaching silly
http://www.youtube.com/watch?v=diCp4F7FU0k&feature=related
http://www.youtube.com/watch?v=H1KD_JFdYrA&feature=related
Or just bypass the piston engine altogether
http://www.youtube.com/watch?v=gbJvrC9Gejo&feature=related
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MarcFX, unless you have a 2 stroke diesel which is totally different to a 2 stroke petrol engine the turbo can not work.
ah unless you have a uniflow 2 stroke diesel with an exhaust valve and then it works..... how does 14 cylinders and 120 000 kw sound at 98 rpm. The all you need is 5 tonnes of fuel an hour. ;)
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Yes I realise how a uniflow diesel engine works. That is what I meant in my original post. The 2 stroke diesel is very different to the 2 stroke spark ignition engine used in our VMX motorcycles. The crankcase plays no part in the fuel flow through the uniflow diesel engine. The bottom end is basically like a 4 stroke.
The turbo 2 stroke spark ignition engine is an interesting and I think a relatively recent development, or at least a relatively recent succesful development, I am sure it has been tried numeous times over the last 100 years. Supercharging has been used very succesfully for many decades in many different forms.
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Yeah most of the turbochargers I deal with are about 14 tonnes so guess they would be unsuitable.
Anyways I think forced induction has the limitation of its complexity and cost..... you really have to have a good reason to adopt it, like a space constraint, technical reason or wanting more out of smaller capacity. The Japanese ran into that problem where a 750 turbo went like an 1100 non turbo and cost the same (actually more from the manufacturing side) so why bother.