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 engine modifications

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webby
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Join date : 2011-11-08

PostSubject: engine modifications   Fri May 18, 2012 6:56 pm

i have a 33cc engine from a strimmer and i was wondering what mods i could do to make it faster?
ive seen that people have a straight through pipe? is this ok as its a 2stroke?
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Quarterscalelegends
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Join date : 2010-08-11

PostSubject: Re: engine modifications   Fri May 18, 2012 7:49 pm

Tuned pipes are MUCH better, but a straight pipe is OK. The only real purpose of the straight pipe is to keep the engine from sucking back in dirt and stuff. Also to redirect the smoke and oil. It will have torque but not much rpm.
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Darth
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Join date : 2012-04-26

PostSubject: Re: engine modifications   Fri May 18, 2012 10:11 pm

If you install a "restriction" in the straight pipe with a hole about 1/2 to 5/8 of the pipe diameter, it should develop more torque. I believe ... the further from the engine it is, the better. Of course, that is a relative statement.

One fellow I know installed a washer with a hole as mentioned above and reported a "very noticeable" increase in torque. He was running a completely open pipe before ... 2-strokes need some "back pressure" to run well.

Darth
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The Man
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Age : 51
Location : Long Island

PostSubject: Re: engine modifications   Sat May 19, 2012 12:27 am

i run straight pipes on all my drag motors.if 20 thousand rpm,s dino tested isnt alot of rpm,s,,,than i,m doing something wrong.also you can get more power out of the 2 strokes if the cylynder heads are ported and polished. it also helps if you polish the crank . you also get more power and compression if you change the deck hieght clearance from the piston to the cylynder head. another words,,if you have 20 thousandts clearance between the piston and the head on a full stroke,,, you can make it 12 thousandts by shaving 8 thousandts off the head bringing the deck claerance closer.you ask,how do i know this,,,,28 years experience, thats how,,,lol
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Darth
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PostSubject: Re: engine modifications   Sat May 19, 2012 1:13 am

No offense meant ... I was referring to us "basically stock weed eater" motor kinda people ...

Thanks for sharing the information ... Smile

Darth
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The Man
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PostSubject: Re: engine modifications   Sat May 19, 2012 12:10 pm

that can be done to any stock 2 stroke motor,weed eater, chainsaw,dirtbike,etc.
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Darth
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PostSubject: Re: engine modifications   Sat May 19, 2012 4:05 pm

A very lengthy read ... but a lot of good info ...

[You must be registered and logged in to see this link.]

An excerpt from the book:

Attended as it is by these many-fold inconveniences, one almost (but not quite) wonders why we bother with the expansion chamber. Unfortunately, damnable nuisance that it unquestionably is, there is nothing else in the engineer's bag of tricks that comes anywhere close to matching the boost a two-stroke engine gets from a properly designed expansion chamber exhaust system. For that reason, it has become the ubiquitous helpmate of the high output two-stroke engine, and for that reason it will be with us until we all change over to electric motors or gas turbines. And until that time, experimenters will be tossing away stock mufflers and trying different expansion chambers as a major part of their endless quest for ever-higher performance.

Darth
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webby
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PostSubject: Re: engine modifications   Sat May 19, 2012 6:52 pm

thanks for the replys. but if darth you are refering to me as being a nuub? Very Happy i do full scale dragracing with a small block chevy v8 injected slingshot dragster Twisted Evil
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Darth
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PostSubject: Re: engine modifications   Sat May 19, 2012 8:08 pm

Perhaps I’ve got off on the “wrong foot” here … I’m not trying to offend anyone, challenge anyone or make anyone angry. If I am “dead wrong” about an issue … I will admit it.

I only joined this forum because I felt this “hobby” would be fun.

And webby … I never said anything about anyone being a nuub … if I offended you … again, I apologize …

I’m simply trying to “share” some of the information I’ve learned over the years about 2-stroke engines “in general” and trying to keep an “open mind”.

Perhaps I should just keep quiet …

Darth
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The Man
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PostSubject: Re: engine modifications   Sat May 19, 2012 10:44 pm

everyone is entitled to put there 2 cents.i put that post just to basically to say,,,yeh tune pipes are what you need but there are many things you can do to a 2 stroke motor to get more compression and more horse power out of them.other peoples comments are always welcome,,,,thats what makes people try different set ups on there motors,,,,but i know from experience what i do makes more horse power.most of my motors are custom and there are no tune pipes for them so i do what i can to get the most out of the motor.
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Darth
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PostSubject: Re: engine modifications   Sun May 20, 2012 12:27 am

The Man wrote:
everyone is entitled to put there 2 cents.i put that post just to basically to say,,,yeh tune pipes are what you need but there are many things you can do to a 2 stroke motor to get more compression and more horse power out of them.other peoples comments are always welcome,,,,thats what makes people try different set ups on there motors,,,,but i know from experience what i do makes more horse power.most of my motors are custom and there are no tune pipes for them so i do what i can to get the most out of the motor.
I totally agree, there is “no doubt” in my mind, what you are doing will make more horsepower. Changing port timing, squish bands, ignition timing, port polishing, more compression etc.

Because of my “motorcycle” background, I tend to focus on exhaust first. But then again, you can buy chambers for those …

There are PC programs out there that can determine “tuned pipe” dimensions based on the engines “particulars” … I may have to check that out and build one for my little 41cc chainsaw engine … just to see …

And … thanks for “clearing this up” … I was starting to feel “attacked” …

Darth
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