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The Noof Samba Member
Joined: January 25, 2005 Posts: 4346
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Posted: Thu Mar 08, 2007 3:26 pm Post subject: |
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Thank you... |
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Stripped66 Samba Member
Joined: May 31, 2005 Posts: 3470 Location: Charleston, SC
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Posted: Thu Mar 08, 2007 3:50 pm Post subject: |
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To illustrate John's point,
[email protected] wrote: |
While it is true the longer stroke engine has "more leverage" due to the longer stroke, IT HAS A SMALLER PISTON PUSHING ON IT. So, it's a wash. |
Let's say you have 200 psi of cylinder pressure during a combustion event on 2 different engines, a 1904 (74 x 90.5) and a 1914 (69 x 94):
200 psi acting on a 90.5mm piston = 1994 lbs of force
200 psi acting on a 94mm piston = 2151 lbs of force
The moment-arm length changes as the crankshaft rotates, but it is never more than 1/2 the stroke; so, let's assume that these cylinder pressures occur at peak moment-arm length.
Maximum moment-arm length using a 69mm crank = 0.1132 feet
Maximum moment-arm length using a 74mm crank = 0.1214 feet
Torque = force x distance (the length of the moment-arm)
1904cc engine: 1994 lbs x 0.1214 ft = 242 ft.lbs
1914cc engine: 2151 lbs x 0.1132 ft = 243.5 ft.lbs
Anyway, hypothetical situation so that we can visualize how a given cylinder pressure produces torque under two similar displacements. Yes, it would be nice to have 240+ ft.lbs of torque, and yes, cylinder pressures are much higher than 200 psi. Before you go tearing down why the psi/torque numbers are off, remember that cylinder pressure is near it's highest *around* TDC, but this is where the moment-arm length is nearest to zero (at TDC, the moment arm length is zero). As the crank rotates and the piston moves down in the cylinder, pressures diminish quickly (remember, pressure is inversely proportional to volume). So, no...the pressure is not representative of anything in particular, but is merely a simple example to demonstrate the relationship between displacement and torque. _________________
66brm wrote: |
Bodacious wrote: |
Why not just make a custom set of wires with a Y splice in them. Then you could just run one distributor. |
I don't think electrickery works that way |
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veedubcrazy Samba Member
Joined: February 14, 2005 Posts: 2130 Location: La Porte, Tx.
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Posted: Thu Mar 08, 2007 4:01 pm Post subject: |
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I would like to see Jeff Denham type all this stuff... _________________ 1967 Deluxe Sedan |
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[email protected] Samba Member
Joined: August 03, 2002 Posts: 12785 Location: Salt Lake City, Utah
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Posted: Thu Mar 08, 2007 4:51 pm Post subject: |
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the difference is almost .75%! Oh snap.......
lets find some other <1% janx to worry about......
I will go on record and say a small bore stroker will not be hurt as much by a tightwad putting on some crappy heads as much as the big bore engine will, LMAO.
Build the small bore stroker if you want a tractor motor.
John
Aircooled.Net Inc. _________________ It's just advice, do whatever you want with it!
Please do NOT send me Private Messages through the Samba PM System (I will not see them). Send me an e-mail to john at aircooled dot net
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Stripped66 Samba Member
Joined: May 31, 2005 Posts: 3470 Location: Charleston, SC
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Posted: Thu Mar 08, 2007 5:09 pm Post subject: |
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The difference is about the same % as the difference in displacement...about 0.5% _________________
66brm wrote: |
Bodacious wrote: |
Why not just make a custom set of wires with a Y splice in them. Then you could just run one distributor. |
I don't think electrickery works that way |
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[email protected] Samba Member
Joined: August 03, 2002 Posts: 12785 Location: Salt Lake City, Utah
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Posted: Thu Mar 08, 2007 5:10 pm Post subject: |
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WTF do we know, everyone knows strokers make more torque
John
Aircooled.Net Inc. _________________ It's just advice, do whatever you want with it!
Please do NOT send me Private Messages through the Samba PM System (I will not see them). Send me an e-mail to john at aircooled dot net
"Like" our Facebook page at
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and get a 5% off code for use on one order for VW Parts ON OUR PARTS STORE WEBSITE, vwparts.aircooled.net |
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[email protected] Samba Member
Joined: August 03, 2002 Posts: 12785 Location: Salt Lake City, Utah
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Posted: Thu Mar 08, 2007 5:15 pm Post subject: |
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you wussy, you should have at least an 86 crank in that thing Matt.......
John
Aircooled.Net Inc.
matt davis wrote: |
[email protected] wrote: |
People wake up!
Build the biggest BORE you can, and after you have done that if you have $ leftover, then stroke it. |
Which is why my street engine is 101x74 |
_________________ It's just advice, do whatever you want with it!
Please do NOT send me Private Messages through the Samba PM System (I will not see them). Send me an e-mail to john at aircooled dot net
"Like" our Facebook page at
http://www.facebook.com/vwpartsaircoolednet
and get a 5% off code for use on one order for VW Parts ON OUR PARTS STORE WEBSITE, vwparts.aircooled.net |
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redhot Samba Member
Joined: February 05, 2005 Posts: 447
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Posted: Thu Mar 08, 2007 5:16 pm Post subject: |
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Then what I believed is correct.... The simple laws of physics still apply, and that`s good to know
A follow up question: what would impact on how the torque/hp relates to RPM? Are there any variabels there that should be considered?
Thanks for the many replies! Guess it`s a topic that many have interest in |
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The Noof Samba Member
Joined: January 25, 2005 Posts: 4346
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Posted: Thu Mar 08, 2007 6:21 pm Post subject: |
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[email protected] wrote: |
WTF do we know, everyone knows strokers make more torque
John
Aircooled.Net Inc. |
ROTFLMAO...he finally said something I can agree with. |
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eng-man Samba Member
Joined: February 17, 2007 Posts: 16 Location: mendenhall ms
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Posted: Fri Mar 09, 2007 8:32 pm Post subject: |
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Ther is no match for cubie inches except more like big blocks rule |
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Eaallred Samba Member
Joined: May 18, 2003 Posts: 5756 Location: West Valley City, Utah
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Posted: Sat Mar 10, 2007 8:49 am Post subject: |
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eng-man wrote: |
Ther is no match for cubie inches except more like big blocks rule |
Not in the VW world. Heads reign supreme when looking for power. _________________ Eric Allred
You have to remember something: Everybody pities the weak; Jealousy you have to earn. |
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eng-man Samba Member
Joined: February 17, 2007 Posts: 16 Location: mendenhall ms
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Posted: Sat Mar 10, 2007 6:29 pm Post subject: |
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You can put the best heads in the world on and engine and help it . But realey all the wright parts must be put together to make things run. one part is good but when you get BIG bore Long stroke Good heads You syill have to have a good intake &carbs and good exhaust. and it all needs to work together . but the more CC the better |
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Eaallred Samba Member
Joined: May 18, 2003 Posts: 5756 Location: West Valley City, Utah
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Posted: Sun Mar 11, 2007 9:28 am Post subject: |
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eng-man wrote: |
You can put the best heads in the world on and engine and help it . But realey all the wright parts must be put together to make things run. one part is good but when you get BIG bore Long stroke Good heads You syill have to have a good intake &carbs and good exhaust. and it all needs to work together . but the more CC the better |
I'm just making it clear to anyone reading for info that the more displacement is not going to make the most power. That is what you are making it sound like.
It is very easy to build a 1776 that will spank a 2110. We see it all the time. Someone buys a big cc motor thinking they'll reign supreme while some guy with a "smaller" motor is spanking them all over the dunes.
Displacement is secondary. Leave that mentality to the V8 world. _________________ Eric Allred
You have to remember something: Everybody pities the weak; Jealousy you have to earn. |
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matt davis Banned
Joined: December 01, 2003 Posts: 53 Location: Livermore, CA
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Posted: Sun Mar 11, 2007 10:16 pm Post subject: |
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[email protected] wrote: |
you wussy, you should have at least an 86 crank in that thing Matt.......
John
Aircooled.Net Inc.
matt davis wrote: |
[email protected] wrote: |
People wake up!
Build the biggest BORE you can, and after you have done that if you have $ leftover, then stroke it. |
Which is why my street engine is 101x74 |
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_________________ www.mattdavisracing.com
1967 Sedan Vert
1967 Hardtop Sedan
1967 Ghia'tine Drag Car
1966 Hardtop Sedan
Livermore, CA |
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krusher Samba Member
Joined: September 24, 2002 Posts: 7652 Location: europe
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Posted: Mon Mar 12, 2007 10:12 am Post subject: |
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So what makes good low end TQ?
high air speeds at low rpm= good chamber charge fill
And if so does a longer stroke crank to bore ratio promote this is any way?
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[email protected] Samba Member
Joined: August 03, 2002 Posts: 12785 Location: Salt Lake City, Utah
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Posted: Mon Mar 12, 2007 10:44 am Post subject: |
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http://aircooled.net/gnrlsite/resource/articles/t1hpeng.htm
John
Aircooled.Net Inc. _________________ It's just advice, do whatever you want with it!
Please do NOT send me Private Messages through the Samba PM System (I will not see them). Send me an e-mail to john at aircooled dot net
"Like" our Facebook page at
http://www.facebook.com/vwpartsaircoolednet
and get a 5% off code for use on one order for VW Parts ON OUR PARTS STORE WEBSITE, vwparts.aircooled.net |
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runslikeapenguin Samba Member
Joined: August 07, 2005 Posts: 4674 Location: Federal way WA
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Posted: Mon Mar 12, 2007 2:07 pm Post subject: |
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i learn so much from topics like this one. its good to be able to read stuff like this. _________________ never forget 1-31-07 |
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[email protected] Samba Member
Joined: August 03, 2002 Posts: 12785 Location: Salt Lake City, Utah
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Posted: Mon Mar 12, 2007 2:17 pm Post subject: |
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the biggest hurdle is trying to overcome the "I read it on the Internet so it must be true" rubbish that is flying around all over the place.
John
Aircooled.Net Inc. _________________ It's just advice, do whatever you want with it!
Please do NOT send me Private Messages through the Samba PM System (I will not see them). Send me an e-mail to john at aircooled dot net
"Like" our Facebook page at
http://www.facebook.com/vwpartsaircoolednet
and get a 5% off code for use on one order for VW Parts ON OUR PARTS STORE WEBSITE, vwparts.aircooled.net |
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60freak Samba Member
Joined: October 08, 2002 Posts: 861 Location: Indiana
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Posted: Wed Mar 21, 2007 1:07 am Post subject: |
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[email protected] wrote: |
the biggest hurdle is trying to overcome the "I read it on the Internet so it must be true" rubbish that is flying around all over the place.
John
Aircooled.Net Inc. |
How about some "real world" experience with these two engines? From what I know a 1915 is a BUG engine, and a 1904 is more of a BUS engine. And here is a good example I have witnesses myself, keep in mind both buses are splits and both have same size tires and RGB's and carbueration: one buddy has a 1915 in his splitty Bus, it goes along pretty good, but the second he hits a hill, it's game over and falls on it's face and chugging along in third gear.... the bus with the 1904 following the 1915 bus on the hill can easily pass and even accelerate up the hill past the 1915 bus like he's standing still. Keep in mind the 1915 bus is a bare empty panel and weighs hardly anything....the 1904 bus is a pop-top westy fully loaded, now how do you explain that? The 1915 bus runs perfect and is in tune too, and is actually damn near brand new. Both the 1915 and 1904 are damn near identical, Kadrons, 110 cam, standard header, etc. Now explain that one to me. From what I read, Aircooled John seems to think the 1915 is more powerfull or at least the same as the 1904, no way! |
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dereke Samba Member
Joined: April 06, 2006 Posts: 154
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Posted: Wed Mar 21, 2007 8:53 am Post subject: |
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