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Rod and piston balancing - what is enough?  Rate Topic 
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 Posted: 05-10-2022 05:18 am
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Max_dvdt
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We are at the balancing stage.

I've seen it mentioned here "balance obsessively" but what does that mean?

reminder on our build
2.4l stroker billet crank with custom pistons and rods, outrageous road driver

0.1gram?

the guy I was thinking of taking things to get balanced is


https://www.google.com/search?q=paradise+motorsports&rlz=1C1CHBF_enUS1002US1002&oq=paradise+motor&aqs=chrome.0.0i355i512j46i175i199i512j69i57j46i175i199i512l6j0i512.3200j0j4&sourceid=chrome&ie=UTF-8#lrd=0x80dc756aac1cf813:0xb29237903b82200a,1,,,

I understand the process - just can't seem to find what precision we need to get to.

Thank you alll!!

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 Posted: 05-10-2022 10:18 pm
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Esprit2
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Since you're using custom crank, pistons & rods, contact the manufacturer of the parts you're using for their recommendations. Neither Jensen nor Lotus have any specs for those parts.

Good luck,
Tim Engel

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 Posted: 02-22-2023 11:35 pm
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Darth V8R
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Max_dvdt wrote: We are at the balancing stage.

I've seen it mentioned here "balance obsessively" but what does that mean?

reminder on our build
2.4l stroker billet crank with custom pistons and rods, outrageous road driver

0.1gram?

Honestly, balancing a 4 cylinder is a waste of time due to the inherent imbalance of an inline  four cylinder engine. Think about it, why are there no 3.0 liter I4 engines? Because the larger they are, the harder they shake.

Mitsubishi is the only company I know of that offered a solution, their so called "silent shaft" motors, which had a counter rotating balance shaft to cancel the vertical shaking inherent in the design. While that helps, it is only a partial solution since there is no overlap between power strokes in an I4 motor.

I4 engines shake, and you can't do much about it beyond what the manufacturer has already done. To get a smooth engine you need balanced and overlapping power strokes, and balanced mechanical components. Neither is possible in an I4 motor. There is no overlap of power strokes, and nothing that opposes the massive accelerative/decelerative forces.

Only inline six cylinder engines and horizontally opposed 4/8/12 cylinder engines with "fork and blade" connecting rods can be perfectly balanced.

Vance

Last edited on 02-22-2023 11:37 pm by Darth V8R

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