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 Post subject: Con-rods : GTI vs 4AGZE
PostPosted: Tue Dec 26, 2006 8:24 pm 
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Pics of GTI stock, polished and Toyota 4agze con-rods.

I've not made any measurements yet but looks very close match with much more "meat" in the 4agze rods.

http://www.teamswift.net/album_page.php?pic_id=10498

http://www.teamswift.net/album_page.php?pic_id=10499

Regards, Lee

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 Post subject:
PostPosted: Tue Dec 26, 2006 8:39 pm 
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Won't a heavier rod throw almost everything out of balance?

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 Post subject:
PostPosted: Tue Dec 26, 2006 9:29 pm 
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The mad quebecer
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You simply need to have the crank rebalanced.


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 Post subject:
PostPosted: Wed Dec 27, 2006 1:36 am 
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Jardamuth wrote:
You simply need to have the crank rebalanced.

...more than likely with a few expensive pieces of mallory metal (heavy metal used for balancing crankshafts) in each end of the crank.
It could easily double the cost of balancing when you use a really heavy rod, and/or piston.


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 Post subject:
PostPosted: Wed Dec 27, 2006 11:50 am 
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doesn't forged vs not forged come into play also?

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 Post subject:
PostPosted: Wed Dec 27, 2006 5:46 pm 
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What does connecting rod weight have anything to do with the dymanic /static balance of an inline 4 crank? or an inline 6 crank?

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 Post subject:
PostPosted: Wed Dec 27, 2006 5:55 pm 
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Casey wrote:
doesn't forged vs not forged come into play also?

Ever seen a rod that wasn't forged?

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 Post subject:
PostPosted: Wed Dec 27, 2006 7:35 pm 
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Cast rods are rare...only ones i recall are for the 350 pontiac V8.
...now powdered metal rods are becoming more common.
...every japanese engine i've ever seen has forged steel rods however.


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PostPosted: Wed Dec 27, 2006 7:51 pm 
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Some 305's had them, too, but I'll bet most of them are long gone.
I worked a bit on the LT-1(or was it LS-1?) powdwer metal rod program.

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 Post subject:
PostPosted: Wed Dec 27, 2006 9:28 pm 
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thanks for all the inputs. i'll post some weights of each rod once i weigh them.

as can be seen from the pics, the 4agze rod has been polished at the side. the lightened and polished GTI rod looks "skinny" beside the 4agze. quite a bit of metal has been taken off the lighten GTI rod.

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 Post subject:
PostPosted: Thu Dec 28, 2006 12:27 am 
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LT-1 mike, but the LS engine family does have PM rods too.

*drools over LS7...*

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 Post subject:
PostPosted: Fri Dec 29, 2006 1:39 am 
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Jardamuth wrote:
You simply need to have the crank rebalanced.

Well... no :)

Inline 4's during an engine stroke move 2 pistons up and 2 down, so only if weight of all pistons and rods is equal, you can assume that sum of forces are 0.

BTW about 4agze rods - why to install them? usually gti rods will handle 300HP and at hell lot of rpm. If someone is building more powerful engine, i think he can afford lighter forged rods.

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 Post subject:
PostPosted: Fri Dec 29, 2006 12:59 pm 
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Wow, You think engine dynamics are as simple as that? Think again.


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 Post subject:
PostPosted: Fri Dec 29, 2006 1:39 pm 
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With much respect to all, i'll explain engine balance a bit further.
Yes, you are correct that the weight of the piston and rod do not play a part in common inline 4 cylinder crank balancing. This is far from the end of the story. What is important is that the crankshaft is counterweighted to match to weight of the components that are attatched to the rod journal. If your idea that rod weight didn't matter because the opposite cylinders would cancel the forces out...why would we need counterweights on our crankshaft at all? We need them to counterbalance the parts attatched to the rod journal. If we make the rod and/or piston heavier, then the counterwieghts of the crankshaft should be corrected if you want the job done correctly. A weight change of less that 10-15 grams is probably OK for most applications.

A quick note about engine balance:
The parts attatched to the rod journal are put into two catagories. Those are Rotating parts, and reciprocating parts. The bottom of the rod, cap, rod bolts, nuts, and rod bearing shells are considered rotating components. The piston, top of rod, piston rings, piston pin, piston pin clips are considered reciprocating components.
The crankshaft should be counterweighted to compensate for 100% or the rotating component weights, as well as a percentage of the reciprocating component weights determined my the design and use of the engine (RPM), drive system, and mounting. It is common for banance shops to counterweight for 50% of the reciprocating weight for most applacations...and going up to maybe 62% when the engine is used in racing use around 10,000 RPM. This of course has a lot to do with how is is mounted, or restrained by it's mounting system.
To say that the rod weight is unimportant is not correct. If the crankshaft is not properly counterweighted, then the crankshaft itself is placed under extreme stress. In a four cylinder engine where the rod journals from #1 and #2 cylinders are opposite, one would think that the forced would simple be canceled out...not true. The force of the two opposing cylinders is indeed opposite (if we don't consider the cylinder firing) ...but the forces placed on the rod journal by the parts attatched to it should be counterweighted by opposing weight placed on both sides of the rod journal, not by an opposing cylinder. If the crankshaft is not properly counterweighted, and the forces placed on the rod journal are allowed to be opposed by the opposing cylinder on the other side of the main journal...the crankshaft will be forced to flex an extreme amount, and will eventually crack the crankshaft, and wipe out the main bearing.
The critical main bearings are the ones between the opposing cylinders, and these are of course the ones that show abnormal wear in an engine that we take apart, and find a cracked crankshaft. (#2, and #4 bearing show abnormal wear with a cracked, or improperly counterweighted crankshaft)
Balancing a crankshaft to be counterweighted to heavier componets is not a simple matter. I don't have the time to post everything about how to do it, but those interested in learning could search an Italian company called Soft-Engine, and download a demo copy of their program called
Vybro. Play around with it a bit, and enjoy an hour or so of learning.
I'd be happy to answer any further questions when i have time.

I hope i have not offended anyone, and for some of you...i realize that you already knew this stuff.
Have a great new years!
Darcy


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 Post subject:
PostPosted: Fri Dec 29, 2006 2:19 pm 
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Mr.Pipe wrote:
With much respect to all, i'll explain engine balance a bit further.
Yes, you are correct that the weight of the piston and rod do not play a part in common inline 4 cylinder crank balancing. This is far from the end of the story. What is important is that the crankshaft is counterweighted to match to weight of the components that are attatched to the rod journal. If your idea that rod weight didn't matter because the opposite cylinders would cancel the forces out...why would we need counterweights on our crankshaft at all? We need them to counterbalance the parts attatched to the rod journal. If we make the rod and/or piston heavier, then the counterwieghts of the crankshaft should be corrected if you want the job done correctly. A weight change of less that 10-15 grams is probably OK for most applications.

A quick note about engine balance:
The parts attatched to the rod journal are put into two catagories. Those are Rotating parts, and reciprocating parts. The bottom of the rod, cap, rod bolts, nuts, and rod bearing shells are considered rotating components. The piston, top of rod, piston rings, piston pin, piston pin clips are considered reciprocating components.
The crankshaft should be counterweighted to compensate for 100% or the rotating component weights, as well as a percentage of the reciprocating component weights determined my the design and use of the engine (RPM), drive system, and mounting. It is common for banance shops to counterweight for 50% of the reciprocating weight for most applacations...and going up to maybe 62% when the engine is used in racing use around 10,000 RPM. This of course has a lot to do with how is is mounted, or restrained by it's mounting system.
To say that the rod weight is unimportant is not correct. If the crankshaft is not properly counterweighted, then the crankshaft itself is placed under extreme stress. In a four cylinder engine where the rod journals from #1 and #2 cylinders are opposite, one would think that the forced would simple be canceled out...not true. The force of the two opposing cylinders is indeed opposite (if we don't consider the cylinder firing) ...but the forces placed on the rod journal by the parts attatched to it should be counterweighted by opposing weight placed on both sides of the rod journal, not by an opposing cylinder. If the crankshaft is not properly counterweighted, and the forces placed on the rod journal are allowed to be opposed by the opposing cylinder on the other side of the main journal...the crankshaft will be forced to flex an extreme amount, and will eventually crack the crankshaft, and wipe out the main bearing.
The critical main bearings are the ones between the opposing cylinders, and these are of course the ones that show abnormal wear in an engine that we take apart, and find a cracked crankshaft. (#2, and #4 bearing show abnormal wear with a cracked, or improperly counterweighted crankshaft)
Balancing a crankshaft to be counterweighted to heavier componets is not a simple matter. I don't have the time to post everything about how to do it, but those interested in learning could search an Italian company called Soft-Engine, and download a demo copy of their program called
Vybro. Play around with it a bit, and enjoy an hour or so of learning.
I'd be happy to answer any further questions when i have time.

I hope i have not offended anyone, and for some of you...i realize that you already knew this stuff.
Have a great new years!
Darcy


So why factory crank is balanced WITHOUT conrods?

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 Post subject:
PostPosted: Fri Dec 29, 2006 3:04 pm 
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The factory has designed the proper counterweights (counterweighted to compensate for the rod/piston weight they will use)into the crankshaft at the engineering level. The final balance is done just to fine tune the "couple" ...correcting for manufacturing tolerance.


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 Post subject:
PostPosted: Fri Dec 29, 2006 3:17 pm 
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Mr.Pipe wrote:
The factory has designed the proper counterweights (counterweighted to compensate for the rod/piston weight they will use)into the crankshaft at the engineering level. The final balance is done just to fine tune the "couple" ...correcting for manufacturing tolerance.


Ok. But that kind of crankshaft won't be balanced if conrods won't be installed. And all 4 and 6 cyl cranks I've seen were balanced. Also if counterweights removed with stock rods engine should fall apart at high rpm's - I've seen one opel with such mod (no counterweights) made by some german tuner (lot's of $$$ for that) at 8500rpm (CIH engine) and it was fine - just idle was very bad due to lack of rotating mass (also flywhell was very light). Nothing happened to it...

Next example - try to add weight on car's rim (eg. 50gram on same place in inner and outter side) and drive it. Add second 50gram on oposite side of rim (exacly 180deg) and drive it. In first case You will have hell a lot of vibration, in second there will be nothing like that. Leave weights and install lighter rim - it will also be balanced and there won't be any vibrations.

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 Post subject:
PostPosted: Fri Dec 29, 2006 3:20 pm 
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For those interested in reading a bit about the engineering involved in engine balance, go to:

http://www.soft-engine.com/pagine.web/i ... saggio.htm

then click simulation software,
then click price list, then go to Vybro from there...I couldn't get the direct link to work...sorry.

and download the Vybro demo...i think the help file (with lots of good explainations) works on the demo version.

Darcy


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 Post subject:
PostPosted: Fri Dec 29, 2006 3:30 pm 
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Mr.Pipe wrote:
For those interested in reading a bit about the engineering involved in engine balance, go to:

http://www.soft-engine.com/pagine.web/i ... saggio.htm

then click simulation software,
then click price list, then go to Vybro from there...I couldn't get the direct link to work...sorry.

and download the Vybro demo...i think the help file (with lots of good explainations) works on the demo version.

Darcy


Well when I started setup like swift has there was something written during cycles at the bottom of window:
Quote:
The sum of 1st and 2nd cylinders pair torque is always zero


It's enough for me...[/quote]

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 Post subject:
PostPosted: Fri Dec 29, 2006 3:40 pm 
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Colin The Barbarian wrote:
Ok. But that kind of crankshaft won't be balanced if conrods won't be installed. And all 4 and 6 cyl cranks I've seen were balanced. Also if counterweights removed with stock rods engine should fall apart at high rpm's - I've seen one opel with such mod (no counterweights) made by some german tuner (lot's of $$$ for that) at 8500rpm (CIH engine) and it was fine - just idle was very bad due to lack of rotating mass (also flywhell was very light). Nothing happened to it...

Next example - try to add weight on car's rim (eg. 50gram on same place in inner and outter side) and drive it. Add second 50gram on oposite side of rim (exacly 180deg) and drive it. In first case You will have hell a lot of vibration, in second there will be nothing like that. Leave weights and install lighter rim - it will also be balanced and there won't be any vibrations.


I'm not sure what you mean by:Ok. But that kind of crankshaft won't be balanced if conrods won't be installed. And all 4 and 6 cyl cranks I've seen were balanced.

Regarding the Opel...I suspect there is a good reason why you've only seen one of these...and while Germany has some of the best engineers in the world, not everyone is Germany is an engineer! I suspect he has lost a lot, to gain a little in the way of rotating weight reduction.

The wheel example is apples to oranges, as the wheel is rotating only, and is supported much different than a crankshaft...but, the wheel with opposing 50 gram weights on opposite sides of the wheel will have a roll couple imbalance.
On the rear of the car, it would run smooth, on the front it will shake the steering wheel of the car. There is a reason the old bubble balancers are gone these days!

Darcy


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 Post subject:
PostPosted: Fri Dec 29, 2006 3:46 pm 
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Sometimes the last page of a book has as much good information as the first...
I won't force you Colin, you don't have to balance your crankshaft if you choose!

...but still, have a great new year!

Darcy


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 Post subject:
PostPosted: Fri Dec 29, 2006 4:05 pm 
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Mr.Pipe wrote:
Sometimes the last page of a book has as much good information as the first...
I won't force you Colin, you don't have to balance your crankshaft if you choose!

...but still, have a great new year!

Darcy


I always balance my crank :P

Happy new year :)

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 Post subject:
PostPosted: Sun Dec 31, 2006 7:19 pm 
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Question, ever had watched the balancing of a g13b crankshaft? In no way is there EVER bobweights attached to the crank like that of a v-8.

So I guess, no one is this world is allowed to run different pistons? over sized pistons for that matter? or different connecting rods?

The balance of an engine is ALOT different then engineering a crank shaft.
You engineer a crank shaft to work with a set of rods, and a set of pistons etc... If you change the piston or rod weight, you are going to upset the lifespan of the engine. Not make it outta balance.

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 Post subject:
PostPosted: Sun Dec 31, 2006 8:22 pm 
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 Post subject:
PostPosted: Sun Dec 31, 2006 8:50 pm 
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Murr wrote:
If you change the piston or rod weight, you are going to upset the lifespan of the engine. Not make it outta balance.


And what do you think will shorten the lifespan of the engine?

You know Liam, energy is required to create an action. The 'upseting of an engine' as you call it, is an action, right? So, energy is required to perform the task. It's up to you to decide if you want to waste that energy into upseting the engine, or use it to something more profitable such as propelling the car even faster.


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