cumminsbayou4x4
New member
but if a engine doesn't need back pressure shouldn't you be able to run one with out any muffler or exhaust
Engine backfires!!
- Thread starter peterbilt
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devino246
Official DIYGK Chem Nerd
You can, but then there's no scavenging effect. Scavenging and backpressure are two totally different things.
Doc Sprocket
*********
Forget it, my friend. I'm 39, married to a woman whom I not only love very much, but continues to remain an enigma...
It certainly is, isn't it!
peterbilt
New member
I know 2 strokes need back pressure which helps the engine put out a tad more power but didn't know 4 strokes needed back pressure. To bad there's not a muffler out there that makes our karts sound like old muscle cars.
devino246
Official DIYGK Chem Nerd
Forget it, my friend. I'm 39, married to a woman whom I not only love very much, but continues to remain an enigma...
It certainly is, isn't it!
Yeah, I'm very well aware that neither sex will ever understand the opposite.
That may be a future work-related rant!
peterbilt
New member
How's the pipe coming along?
a tuned expansion pipe on a two stroke pushes back in waves at the right time to push the fuel air mix it spit out back into the cylinder. they dont need backpressure. scavenging is the mass and speed of the exhaust gasses continuing out of the pipe creating a low pressure area(when the exhaust valve closes) and pulling more out of the cylinder when the exhaust valve opens again. too large or too short a pipe and it doesnt help.
peterbilt
New member
I've got a massive 2 stroke pipe on my scooter, excellent back pressure which results in great power throughout all power bands. Back pressure doesn't do anything for 4+ strokes and up. Bigger wider exhaust let's pressure escape easier without any restrictions. Blow through a coffee straw and your cheeks will puff out and hurt, blow through a garden hose an you won't blow your cheeks out. Kinda the same principle with engine gases.
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Doc Sprocket
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Not to rag on you, but we've got to keep this stuff clear. Back pressure is BAD. A tuned pipe on a two-stroke essentially bolsters scavenging, and reduces unburnt losses.
There is ONE "power band" not multiples. The power band is the specific RPM range wherein an engine makes the most power.
And up? Ever heard of a 6-stroke? Neither have I...
And once again, Back pressure is bad. All the way around. However, ALL engines can benefit from exhaust systems that produce a scavenging effect. And bigger is not necessarily better.
Again- not picking on you, just trying to dispel some common misconceptions.
devino246
Official DIYGK Chem Nerd
Well there goes any potential validity in that post...
jman231994
New member
Well actually....they do exist. I know nothing about them, just that they exist. The rest of it I completely agree with you....but there are 6 stroke engines
EDIT: Heres the wiki page http://en.wikipedia.org/wiki/Six-stroke_engine
peterbilt
New member
The meaning behind what I was sayin about 4 strokes and up is that you have 2 stroke engine, and then from there it goes 4 cylinders, 6 cylinders, 8 cylinders, 12 cylinders, and finally 16 cylinders. And yes back pressure plays a huge roll in 2 strokes and there is more than 1 power band. Don't believe me? Then I suggest you read this thread:
http://www.gopednation.com/forum/showthread.php?t=327205&highlight=back+pressure
http://www.gopednation.com/forum/showthread.php?t=327205&highlight=back+pressure
Doc Sprocket
*********
I can see this creating a spitload of confusion. The above is not a true statement, no matter how you slice it. Strokes (properly called cycles) have absolutely nothing to do with how many cylinder an engine has. There are many, MANY multi-cylinder 2-stroke engines out there! Like my buddy's 3-cylinder Yamaha 700 triple snowmobile, or my Mercury 6-cyl outboard- even automotive engines like the awesome Detroit Diesels, (2-stroke) having as many as 24 cylinders! And if you want to talk about 4-strokes, you've forgotten 1,2,3 and 5 cylinder engines. Don't forget about radial engines, which can have some pretty large, uneven-numbered cylinder counts.
Do not confuse these terms, you will only confuse others.
Nobody is arguing the purpose or benefit of a tuned pipe on a 2-stroke. But again, the terms can lead to confusion. "Back Pressure" (as it were) is derived (properly) from "static pressure" which is a technical term- and is used in measuring and calculating flow restriction in a pipe or duct. Back pressure is bad. Period. What your linked article refers to as "back pressure" really isn't, per se. It is manipulating and timing sonic waves or pulses, essentially to assist in the shortcoming of a 2-stroke- the lack of a valvetrain. Without re-writing the whole article, let it suffice to say that if you introduce a real restriction to that tuned pipe, the engine will fall flat on it's face.
Now- using the very same article with a different highlight term, show me where it alludes to multiple power bands? http://www.gopednation.com/forum/showthread.php?t=327205&highlight=powerband+power+band
GregMartin
I like fast cars
Well this has been entertaining.
When I mentioned the dreaded " back pressure ". I kind of new I'd get someone pop up and talk about the scavenging effect. I believe it's important to explain concepts thoroughly in quality forums like this one and as I simply wanted to post some quick dimensions of a pipe that would work, and because I'm lazy I just used the term back pressure. Of course the savaging effect relies on a pressure differential so I think the result has been fairly well explained now.
Not being able to fathom the female of the species is something I'm quite comfortable with I'm 44 and have been married to my beautiful wife for twenty years. I am happy in the knowledge that I will never understand. Anyone who isn't probably won't stay married for long.
Final what I like about this forum is there are plenty of people willing to provide helpful advice and explain consents. When forums become full of people trying to bamboozle others with un-described principals it's not such a cool place.
Finally finally I used the web site ( not the forums ) to get ideals to build my go kart and learnt a lot along the way. It was only after I had finish that I checked out the forums. This is because way to often forums are full of tools. In this case however the moderators have done a good job in reducing tool-like behavior. I contribute because I have learnt a bit over the years and am happy to share that knowledge.
When I mentioned the dreaded " back pressure ". I kind of new I'd get someone pop up and talk about the scavenging effect. I believe it's important to explain concepts thoroughly in quality forums like this one and as I simply wanted to post some quick dimensions of a pipe that would work, and because I'm lazy I just used the term back pressure. Of course the savaging effect relies on a pressure differential so I think the result has been fairly well explained now.
Not being able to fathom the female of the species is something I'm quite comfortable with I'm 44 and have been married to my beautiful wife for twenty years. I am happy in the knowledge that I will never understand. Anyone who isn't probably won't stay married for long.
Final what I like about this forum is there are plenty of people willing to provide helpful advice and explain consents. When forums become full of people trying to bamboozle others with un-described principals it's not such a cool place.
Finally finally I used the web site ( not the forums ) to get ideals to build my go kart and learnt a lot along the way. It was only after I had finish that I checked out the forums. This is because way to often forums are full of tools. In this case however the moderators have done a good job in reducing tool-like behavior. I contribute because I have learnt a bit over the years and am happy to share that knowledge.
Doc Sprocket
*********
Greg- Good on ya, all the way around! Thanks for the props, congratulations on 20 years, and here's to the rest of your lives!
cumminsbayou4x4
New member
im gonna start it this week does 30 dollars plus shipping sound fair
peterbilt
New member
That works for me. Send pics when your done please.
peterbilt
New member
Any word on the pipe?
cumminsbayou4x4
New member
oh man i completely for got you probilly think im a dick sorry. Ill get the stuff to build it this week end. Did you want a muffler on it
peterbilt
New member
Na, I actually need a new carb. I figure I'm just gonna sell the Tec when I get it running and upgrade to the Hf 212
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