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PostPosted: Sun Dec 31, 2006 9:00 pm 
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Not meant as an insult to you Murr, but you are wrong.


Happy New Year to all!

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PostPosted: Mon Jan 01, 2007 1:55 pm 
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Saying one is wrong doesn't do any good. How about explaination?

Ever knife edged a crank?

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PostPosted: Mon Jan 01, 2007 3:22 pm 
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I'm not an expert, but I've also heard and have read that I-4 engines balance themselves due to opposed reciprocating masses. My crankshaft, pistons and conrods were balanced separately, although the new vitara pistons are lighter than the standard GTi ones, so it seems to be that reciprocating masses have little to do with crankshaft balance.

The shop that did the job is the best in the region, they are the only shop certified by so many manufacturers, Mercedes Benz, Volvo, Caterpillar, Liebherr, to name a few. I was lucky they accepted my engine because I have some friends in there, otherwise they usually don't accept these 'small' jobs.

Basically, the reciprocating masses cancel themselves and there is no 1st order vibration. There are also 2nd order vibrations, at twice the RPM rate, that can be cancelled by a balancing shaft, or any other balancing mechanism, but it has nothing to do with crankshaft balance and there's nothing that can be done to the crankshaft to help this. Always talking about inline-4 engines.

Regarding rods, well, they add some rotating (not reciprocating) mass to the crankshaft, so, I think that the crank should be rebalanced whenever using different/beefier rods.

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Last edited by Caaarlo on Mon Jan 01, 2007 3:51 pm, edited 1 time in total.

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PostPosted: Sat Jan 06, 2007 5:06 am 
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4agze rods are the only way to go they will give you around 5% more power and make the motor last longer

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PostPosted: Thu Jan 11, 2007 11:16 am 
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so what are the necessary modifications?? as i am plannign to give my motor a complete overhaul sometime end of this year....


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PostPosted: Thu Jan 11, 2007 12:51 pm 
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Caaarlo wrote:
I'm not an expert, but I've also heard and have read that I-4 engines balance themselves due to opposed reciprocating masses. My crankshaft, pistons and conrods were balanced separately, although the new vitara pistons are lighter than the standard GTi ones, so it seems to be that reciprocating masses have little to do with crankshaft balance.

The shop that did the job is the best in the region, they are the only shop certified by so many manufacturers, Mercedes Benz, Volvo, Caterpillar, Liebherr, to name a few. I was lucky they accepted my engine because I have some friends in there, otherwise they usually don't accept these 'small' jobs.

Basically, the reciprocating masses cancel themselves and there is no 1st order vibration. There are also 2nd order vibrations, at twice the RPM rate, that can be cancelled by a balancing shaft, or any other balancing mechanism, but it has nothing to do with crankshaft balance and there's nothing that can be done to the crankshaft to help this. Always talking about inline-4 engines.

Regarding rods, well, they add some rotating (not reciprocating) mass to the crankshaft, so, I think that the crank should be rebalanced whenever using different/beefier rods.


Just to add a bit here, the pistons cancel each other out. 2 move up, 2 move down at the same time and all at the same speed, so -2+2=0. A crankshaft can be counterweighted to balance itself so that should be fine.
Conrods, are, however where the vibration comes from and why twin balancer shafts are sometimes used. They dont' move strictly in a circle, nor do they move up and down, nor do they counter balance another conrod. Basically, the center of mass of conrods move in an egg shape, so the instant vector of movement can never be directly opposite. Twin shaft balancers are close, but even they can't cancel all vibration out because they can't be in the place they need to be, but they can get close.
Also, the con rods are a fairly low weight compared to the rest so for a small motor such as ours, the shafts are less necessary.
Of course there are still vibrations because not everything works on exactly the same point, and things flex(if only an extremely small amount) which are, I believe 4th order vibrations and such...


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PostPosted: Thu Jan 11, 2007 5:03 pm 
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all you need to do is get a new set of pistons with the gudgeon pin move up 2mm from a g13b piston as the rods are 2mm longer you do need to get crankshaft ,rods, pistons,flywheel and the front pullys balanceds ALLTOGETHER not separately as the counterweights need to be the some as the rods if you dont do this you will brake your crankshaft i have done 2 b4 i got it right

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PostPosted: Fri Jan 12, 2007 12:22 am 
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Firstly 4agze rods are ONE way to go, NOT the only way, I have just measured up a set I picked up a few weeks ago, by my calculations the length is 122.5mm centre of big end to centre of small end, that is 2.5mm longer than a g13b rod and it has a 20mm small end so you will need to replace the bronze bushing with a 2mm one instead (if they make them???) which will give you 2mm more length and be able to use a 19mm pin. You will then need a different piston with a lower height, depends on whether it is a g13a/mk1 G10 (2valve diagonal) or sohc G13b/mk2 g10 (2valves side by side) or g13b twin cam (4 valve) as to what pistons are going to work in your engine.

These rods are also 80gms per rod heavier than standard g13b rods, yes they are much stronger but a bit of an overkill unless you are reving to 11000rpm, g13b gti rods with 19mm floating pin are pretty strong, I suspect the g13a rods with 17mm pressed pin would probably fail at the small end if they do fail.

As for the crank, minisprint is using the g13a crank which is very weak so balancing for the kind of revs he pulls is critical, I don't think the extra 80gms per rod will make much difference on a g13b or g10 crank so I'm not sure if the cost of balancing everything is worth it or neccessary.

Personally I think you would be better off getting the 4agze rods lightened so they are closer in weight to the stock items rather than rebalancing everything, there is so much meat on those rods it's crazy.

It all depends on the pistons, if you can find the right pistons then the improvement in rod to stroke ratio should get you a bit more torque and you might be able to increase the compression ratio without retarding the timing as normally happens when you shave the head or block.


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PostPosted: Fri Jan 12, 2007 1:35 am 
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i have used both the g13a and the g13b motors with this rods and all i have done is get new pistons thats all.
i only use the g13a motor cos i can get more torgue form it and when you are in my game that is a big thing and yes my motor will pull 11000rpm and if you can get a g13a motor to do this with going bang i must be doing it right. and yes the gudgeon pin is 20mm so you do need new bronze bushes want i got from the piston makers
and you will need to rebalance the crank with this rods even if you are only doing 5500rpm or you will wear the big end bearings out and blow the oil pump

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PostPosted: Fri Jan 12, 2007 9:26 am 
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Location: Melbourne
I like the idea of lightened 4agze rods to match the factory rods weight.


I really like the thought of using bike rods which are even lighter thanks to their Lightweight nutless design. However the lightened g13b rod in the pics gives me another avenue.

Is it possible you could show us the final lightened and polished 4agze rods?

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PostPosted: Fri Jan 12, 2007 10:29 am 
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Location: Kitchener, ON
Quote:
Conrods, are, however where the vibration comes from and why twin balancer shafts are sometimes used. They dont' move strictly in a circle, nor do they move up and down, nor do they counter balance another conrod. Basically, the center of mass of conrods move in an egg shape, so the instant vector of movement can never be directly opposite.


Just to try and straighten this out a bit, the imbalance of an inline 4-cylinder comes from unequal piston acceleration. The two approaching the top are decelerating faster than the two approaching the bottom of their stroke. It's inherent in the design of reciprocating engines.

Balance shafts do a good job of handling this and making YOU feel better. The vibrations can be minimized by using less reciprocating weight and higer rod/stroke ratios.

Balancing the rotating assembly is always a very good idea, as is the flywheel, clutch, crank-pulley, etc.


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PostPosted: Fri Jan 12, 2007 12:01 pm 
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martinq wrote:
Just to try and straighten this out a bit, the imbalance of an inline 4-cylinder comes from unequal piston acceleration. The two approaching the top are decelerating faster than the two approaching the bottom of their stroke. It's inherent in the design of reciprocating engines.


So, I'm certainly not saying you're wrong, because I'm not an expert, but how can that be true unless you are refering to the fact that even hardened metal isn't really 100% solid(it flexes and compresses and stretches under stress)? The crank moves in a circle and the pistons are 180 degrees apart.
The distance between the crank pin and piston is constant(mostly). the instant vectors of the opposite crank pins are equal and opposite, how can the piston move independent of that?
Probably something I'm missing...


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PostPosted: Fri Jan 12, 2007 1:22 pm 
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Thinking about it a little more... the egg shaped movement of the conrods does exactly what you've explained. It's not the crank that moves asymmetrically across the horizontal plane, it's the conrod. So we really were describing the same problem, I just picked the much lesser effect. D'oh.


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PostPosted: Fri Jan 12, 2007 3:11 pm 
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Location: Kitchener, ON
I think you've got it. One thing that helps is the realization that when the crank is at 90°, the piston is sitting less than halfway through it's travel. It travels more distance (and accelerates faster) through the upper half of its stroke than it does through its lower half.

I'll dig up some helpers.


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PostPosted: Fri Jan 12, 2007 3:46 pm 
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Location: Kitchener, ON
Not quite the page I was looking for, but these are pretty good.

http://www.epi-eng.com/ET-PstnMotion.htm
http://www.epi-eng.com/ET-PistnVelAccel.htm
http://en.wikipedia.org/wiki/Piston_motion_equations

... but oh my.... THIS is pretty slick.
http://www.wfu.edu/~rollins/piston/animation/graph_1/

If you select the Graph Mode: Acceleration, then you'll see the largest acceleration happens at the top of the stroke (-4.62) as compared to the bottom of the stroke (2.62).

This imbalance is the major cause of vibration in a balanced, inline, 4-cylinder engine.

Image
The crank is at 90°, but the piston is less than halfway through the stroke.

Image
Pistion motion for three rod/stroke ratios. Stroke radius of 1.8, 2.0, 2.2.


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PostPosted: Sat Jan 13, 2007 8:53 pm 
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minisprint91r wrote:
all you need to do is get a new set of pistons with the gudgeon pin move up 2mm from a g13b piston as the rods are 2mm longer you do need to get crankshaft ,rods, pistons,flywheel and the front pullys balanceds ALLTOGETHER not separately as the counterweights need to be the some as the rods if you dont do this you will brake your crankshaft i have done 2 b4 i got it right

how do u move the gudgeon pin 2mm up fromt he piston? :? isnt it fixed??


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PostPosted: Sun Jan 14, 2007 12:58 am 
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you get someone to make new pistons with the pin moved up 2mm from a copy of the g13b piston to take the 4agze rods :thwack:

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PostPosted: Sun Jan 14, 2007 3:29 am 
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Which means custom forged pistons which means $$$$$$$$$$$$
Which is why many of us are spending a lot of time researching pistons from other cars and motorbikes so we can use an off the shelf piston at a fraction of the cost...


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PostPosted: Sun Jan 14, 2007 4:15 am 
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a set is only around $750nz whats not that much

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PostPosted: Sun Jan 14, 2007 8:16 am 
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$750nz where and who?

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PostPosted: Fri Jan 19, 2007 4:40 pm 
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This is very interesting reading... :shock:

Since we´re comparing, where do the 1.6 rods stand in the middle of this??
I mean are they shorter, lighter or weaker then the gti ones?

I´m thinking of turbocharging a 1.6 engine with the gti head, and i´m a bit worried the rods may be the weak link... But on the other end, is not for high RPM, boost will be low like 0,8bar, maybe 1 bar ocasionally on a already low comp ratio...

Should i even be considering alternative rods?

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PostPosted: Fri Jan 19, 2007 6:25 pm 
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The 1.6 rods are longer, it's not the rods you need to be worried about with the 1.6 it's the hollow crank!

This thread is really in the wrong forum, it needs to be in the 1.6 and conversions forum.

Still waiting to hear where I can get 4 custom made pistons for NZ$750 (US$450) :razz:


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PostPosted: Sat Jan 20, 2007 12:05 am 
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Dattman wrote:
The 1.6 rods are longer, it's not the rods you need to be worried about with the 1.6 it's the hollow crank!

This thread is really in the wrong forum, it needs to be in the 1.6 and conversions forum.

Still waiting to hear where I can get 4 custom made pistons for NZ$750 (US$450) :razz:


The g16 hollow crank is stronger than previously thought. :D

To date no one has bent one with the right tune. Even the daihatsu hd sohc 1.6 with a weaker crank with bigger bigger and more hollow sections and spun to 9ooorpm has never let down the 3 time under 2ltr winning rally cars raced by MRT. Rods have let go but thats all.
Ive had many rods to analyse from the g16 to look at and Ive come to the conclusion that after looking at the honda d16 ones which are thinner again (hard to believe but true and handle 200hp) they are weak but with the right tune and 1 bar should still survive. Anything over 180-200 plus you should look at better rods to be safe. The hollow crank will handle alot more abuse than most people think but I prefer the Honda d16 forged one anyway for serious boost or torque.

Dattman as you said "Im still waiting for the 750nz custom forgies info" :razz:

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PostPosted: Sat Jan 20, 2007 12:18 pm 
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By any chance the height difference between the 1.3 and 1.6 rods are the same as the 4agze rods?

And the big end and small end of the rod? Is it equal in the 1.3 and 1.6?

I´ve read that the piston crown should be about 7 - 10% of the piston diameter for it to be thick enough to withstand boost.
So 4agze with 1.6 skimed pistons could work on a 1.3?

Does anyone have the piston diameter, piston height from top of crown to bottom of skirt and piston height inside measurement to bottom of skirt of the 1.6?

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PostPosted: Sat Jan 20, 2007 10:44 pm 
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I think the rod lengths are the same between the g13b and g16b only the g13b are the rods of choice being forged and decently sized.
Pretty much all other suzuki engine rods of the 4cyl are cast except in some of the small turbo engines.

As for the figures they dont mean anything when you consider whether the rods are cast or forged, how they are shaped and the same goes for the pistons and pin, materials used, design etc. There are alot of variables.

The vitara pistons are cast and the honda tuners and everyone has been proven wrong in regards to their strength. Some vitara pistons handle 24psi without a problem and over 400hp in masses of turbo d16 hondas.
All depends what figures you are looking for first.
under 180-200hp you will prob get away with stock low comp internals using low boost, good tuning and a good 2mm copper head gasket.
Anything over: better rods, head gasket and lower comp. The longer the rods eg. 4agze youll need a custom piston with at least 27mm pin height maximum. Im not sure youd want to risk skimmed pistons at these low pin heights. Its would be a different story if the block was taller.

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