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Two stroke hop-up reading material - 3/5/2009 11:46 AM   
nitro joe


 

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Status: offline 		With all the pseudo hop-up analysis,"Mater of fact" statements going on in another thread,I felt the following link should be re-posted.Some of the lurkers among us, may be unsure with some of those claims presented as fact.These folks might like some alternate general high performance/tuning information to apply to there own engines.


Here is one book,while somewhat dated,is a pretty good "two stroke" treatise.The late author was mostly held in high regard as a tuner/author.

Take a look at the other pdf's on that page too.

You'll prolly need a basic Pdf reader to see it.This is the whole book...free of charge
http://www.edj.net/2stroke/jennings/


Google books also has a nice "free" on-line selection of reading material on this subject,to gain futher prospective.Some are just snippits,some are whole sections.

An example would be:
http://books.google.com/books?lr=&num=20&as_brr=3&as_pt=ALLTYPES&q=%22two+stroke%22+hop+up+date%3A1970-2009&btnG=Search+Books

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RE: Two stroke hop-up reading material - 3/5/2009 6:55 PM   
av8tor1977



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Status: offline 		That book by Jennings is a good one. I've read it several times over the years. He gets a bit technical for some people, but he sure knew what he was talking about.

AV8TOR

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RE: Two stroke hop-up reading material - 3/6/2009 12:21 AM   
richg99


 

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Status: offline 		Nitro...nice offer. Is his widow or family still around? Wouldn't it be proper to offer to send $5.00 ( the original cost of the book) to them if one downloads it? or, is everyone gone?? Do you have any addresses? thanks and regards Rich

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RE: Two stroke hop-up reading material - 3/6/2009 3:44 AM   
w8ye



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Status: offline 		Maybe some money to the site that posted it too?

< Message edited by w8ye -- 3/6/2009 6:13 AM >

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RE: Two stroke hop-up reading material - 3/6/2009 4:25 AM   
Ram Jet



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quote:

ORIGINAL: nitro joe

With all the pseudo hop-up analysis,"Mater of fact" statements going on in another thread,I felt the following link should be re-posted.Some of the lurkers among us, may be unsure with some of those claims presented as fact.These folks might like some alternate general high performance/tuning information to apply to there own engines.


Here is one book,while somewhat dated,is a pretty good "two stroke" treatise.The late author was mostly held in high regard as a tuner/author.

Take a look at the other pdf's on that page too.

You'll prolly need a basic Pdf reader to see it.This is the whole book...free of charge
http://www.edj.net/2stroke/jennings/

Google books also has a nice "free" on-line selection of reading material on this subject,to gain futher prospective.Some are just snippits,some are whole sections.

An example would be:
http://books.google.com/books?lr=&num=20&as_brr=3&as_pt=ALLTYPES&q=%22two+stroke%22+hop+up+date%3A1970-2009&btnG=Search+Books


Thanks Nitro, I have a PDF copy of this but it's missing a few pages. When I get some time I'll see if this copy is more complete. You seem to be pretty techy. Having read Mr. Jennings overview of the design and function of "tuned pipes" or, more properly, "expansion chambers", do you think these after market suppliers are really selling a well designed expansion chamber for model engines?

Bill
Moderator changed formatting of post

< Message edited by w8ye -- 3/6/2009 6:15 AM >

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RE: Two stroke hop-up reading material - 3/6/2009 7:13 AM   
buck1856



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Status: offline 		Theres a paypal addy to donate a few "bucks" as the person asks to help with the bandwith.Im going over there to download it right now and donate.

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RE: Two stroke hop-up reading material - 3/6/2009 7:24 AM   
Ram Jet



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quote:

ORIGINAL: w8ye

Maybe some money to the site that posted it too?



I think you are right.

Bill

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RE: Two stroke hop-up reading material - 3/6/2009 2:16 PM   
nitro joe


 

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Status: offline 		rich:
The site with the Jennings material is the result of a Google search.It was also
posted here last year in this forum.Contact the site owner.
I've owned my copy since the late '70's. It still finds it's way into the "library" from time to time...


Ram jet:
Jennings pipe formula is getting pretty old in the tooth now. 35+ years...
Tons of modern software out there now for manufactures to purchase.
All kinds of brand/design comparisons to be found on the boards,mags,etc.


Here is an interesting hot rod chainsaw forum... porting,carbs,muffler mod's,etc.

http://www.arboristsite.com/forumdisplay.php?f=9


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RE: Two stroke hop-up reading material - 3/7/2009 3:27 PM   
Ram Jet



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quote:

ORIGINAL: nitro joe

rich:
The site with the Jennings material is the result of a Google search.It was also
posted here last year in this forum.Contact the site owner.
I've owned my copy since the late '70's. It still finds it's way into the "library" from time to time...


Ram jet:
Jennings pipe formula is getting pretty old in the tooth now. 35+ years...
Tons of modern software out there now for manufactures to purchase.
All kinds of brand/design comparisons to be found on the boards,mags,etc.


Here is an interesting hot rod chainsaw forum... porting,carbs,muffler mod's,etc.

http://www.arboristsite.com/forumdisplay.php?f=9




Thanks Nitro. Not trying to challange any aftermarket suppliers technical skills but it's more than just "cutting or lengthening the header pipe" as I have read here on various posts. It's even a far more involved undertaking than intake and exhaust timing. It's beyond my little brain. As far as Jenning's concepts being dated. Yes maybe, but most of "Two Stroke Tuner's Handbook" is as fundamental as gravity and a sunrise. You can't change basic physics.

Ring-ding-ding-ding.
Bill

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RE: Two stroke hop-up reading material - 3/7/2009 4:24 PM   
combatpilot



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Status: offline 		I will agree with that RamJet. I really dont consider any material dated. I dont know how many times I found a concept idea or practice that I though was new only to find it had been done many years ago and somhow lost or forgoten only to be brought back and utilized again. Besides if it wasent for jennings laying a foundation what would the rest of us have to build off of?

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RE: Two stroke hop-up reading material - 3/7/2009 4:35 PM   
Ram Jet



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quote:

ORIGINAL: combatpilot

I will agree with that RamJet. I really dont consider any material dated. I dont know how many times I found a concept idea or practice that I though was new only to find it had been done many years ago and somhow lost or forgoten only to be brought back and utilized again. Besides if it wasent for jennings laying a foundation what would the rest of us have to build off of?


Combat, I have a neighbor who races a two cycle motocross motorcycle professionally. His bike has what I think is a remarkable design feature. It has an exhaust port valve that opens and closes with the engine RPM. Wow, the Achillle's heal of two stroke engines. Blowing fresh fuel air charge out the exhaust pipe at low RPMs. Ingenious I thought. Until I remembered Enyas with the exhaust flap that opened and closed the exhaust port in synch with the carb butterfly/barrel. What goes around comes around. "And the seasons go round and round,And the painted ponies go up and down".

Bill

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RE: Two stroke hop-up reading material - 3/7/2009 5:04 PM   
combatpilot



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Status: offline 		see there ya go theres the perfect example. whats old is new again.

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RE: Two stroke hop-up reading material - 3/7/2009 5:14 PM   
Nosedragger


 

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Status: offline 		Snowmobiles have put exhaust valves to good use for years, when it comes to engine "innovation" everything has already been done or tried before. The only difference is now technology advance in materials, manufacturing,analysis and electronic control capability have made these ideas possible to implement.
Although possible to develope performance enhancing features, applications such model aircraft given weight and size constraints, make it impractical to utilize.If you are looking for state of the art two strokes, look at outboard motors and snowmobiles.
Jennings and other authors have noted that their concepts would be easier to apply if computers were available at the time.The time area principles laid out by Jennings are valid today.Using a computer program makes time area calculations easy, several companies market software that perform these functions.

If you are looking for more in depth and "modern" material on the subject look up Gordon Blairs book "The Design and Simulation of Two Stroke Engines"

There hasn't been much published on the subject of two stroke engines in recent years except about emission reduction strategies.

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RE: Two stroke hop-up reading material - 3/7/2009 5:36 PM   
av8tor1977



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Status: offline 		The exhaust valve(s) you speak of.... On the Enya, (and others), it was done to keep the glow plug warm at low speeds and idle. It didn't change the exhaust port timing; just provided some back pressure to keep things warm at low throttle settings.

On the newer two stroke engines with an exhaust valve, the valve actually changes the exhaust port timing, allowing you to have a more radical timing at high rpms, and a lower, more tractable timing at low rpms. Rotax also uses this technology, among others.

AV8TOR

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RE: Two stroke hop-up reading material - 3/7/2009 5:39 PM   
Ram Jet



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quote:

ORIGINAL: av8tor1977

The exhaust valve(s) you speak of.... On the Enya, (and others), it was done to keep the glow plug warm at low speeds and idle. It didn't change the exhaust port timing; just provided some back pressure to keep things warm at low throttle settings.

On the newer two stroke engines with an exhaust valve, the valve actually changes the exhaust port timing, allowing you to have a more radical timing at high rpms, and a lower, more tractable timing at low rpms. Rotax also uses this technology, among others.

AV8TOR



av8 you are scareing me. You are right! Honda too!

Bill

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RE: Two stroke hop-up reading material - 3/7/2009 10:47 PM   
blw



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Status: offline 		I just had to clean up a lot of argumentative posts and I'm not going to PM each poster as to which of your messages got the ax.

This is too interesting to let slide into petty fighting. The moderators will keep it cleaned up from arguing so the rest of us can enjoy the collection of good knowledge. BTW, thanks already to the contributors!!!

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