balance crank + piston a good idea?

[95GST]

In the process of building an engine, I have the options of balancing the crank, rods, and pistons for $175

if only balancing rods is like $50 or $70 something like that.. (can't remember)

Is this a good idea to balance everything? I talked to RRE they say it is totally optional.. usually they only recommend balancing the rods which is most important.

Yes, balance shafts will be removed. I do plan to maybe use stiff prothane mounts one day.. so maybe it's a good idea to have as much stuff balanced as possible?

[dsm4eva]

A system, or body of mass, has certain natural frequencies or 'the fundamental harmonic'. A frequency is harmonic if it is an integer multiple of the fundamental frequency. The fundamental is the first harmonic (although it's generally referred to as the fundamental). The second harmonic is two times the frequency of the fundamental, the third harmonics is three times the fundamental, and so on. So with a fundamental of 100 Hz, the second harmonic is 200 Hz, the third is 300 Hz, the fourth is 400 Hz, etc.

The balance/silent shafts are a cheap way to overcome the inherent vibration of an inline 4 cylinder engine. The 4G63 has a harmonic that occurs near 3250-3500 RPM which creates a 'lot' of vibrational energy in the passenger compartment. To market the car to the hardcore sports car enthusiasts and to the average sporty minded consumer the shafts need to be added. Why are they added? There are only a few ways to change the vibrational response of a system, and the balance/silent shafts are basically adding a bit of mass to the system which is by far the easiest. Removing these devices generates that extra vibration, but will have no discernable effect on the longevity of the lower end, or its rotating mass.

Balancing the lower end actually nets you very little in decreasing the vibration of the system. It will improve the lower end dynamic response, it will decrease the weight of the rotating mass, and it will also increase the longevity of the journal bearings. Is it worth it? Its a nice thing to do 'while you're in there' type of thing but is far from being necessary.

When reassembling the vehicle, buy a 250 mL bottle of Loctite 243 or 242 (blue removable grade, but I suggest 243 as it is more thixotropic and will last longer in your tool chest, e.g. won't seperate) from your local industrial distributor like Applied Industrial Tech. or Motion Ind., figure about $150. This will keep parts from vibrating loose, and you may be thinking "This guy is nuts, I'm not spending that much on glue!", but I've personally witnessed 3 engines grenade from doing this mod. Loosening rod caps, timing belt tensioner or other timing pulleys, oil system components, etc. etc., can really ruin a gorgeous engine and cost a lot more than $150-200 to fix. SO... when reinstalling, glue EVERYTHING you can that won't see more than 375 deg F continuously.

[dsm93talon]

WTF?

i'm lost, lol ;)

[galantvr41062]

"Welcome to the discussion boards. Hope you find the answers you need.

However.

This is absolutely, positively, completely and totally not an 'advanced technical discussion'. Please read the forum descriptions and review old threads before posting. Not doing so creates much unnecessary work for the moderators. Volunteers don't like unnecessary work.

--Tim"

Balance everything more hp and your engine last longer. get poly engine bushing they can only help on the transfer the rotating force of the motor to the ground to get a better launch, all in the 60' times. Just a thought

~John

[99gst]

A guy in my local club had a fully built engine. Crower rods, JE pistons, blah blah blah and had the balance shafts removed. A year later an oil squirter responsible for feeding oil to the #4 rod bearing popped out causing that bearing to seize. Time to rebuild the engine again. No one here ever heard of an oil squirter popping out. The only thing we could come up with was that the added vibration caused or helped cause that oil squirter to pop out. Hell they're pressed in. They should never just pop out on their own.

How much extra HP to the wheels do you get from removing the balance shaft anyway? I personally would not do this as I am not willing to take that risk.

[galantvr41062]

I heard that every 2.1-2.3lbs of rotating mass of the crank shaft is worth 1hp, now the balance shafts spin 2times faster than the crank, so I think you could doulbe the hp figure. The balance shafts weights likes 15-20lb? dont remeber, now just that is like 30-40hp to the flywheel, but I also read it could be off so only expect 15-20hp to the crank and 10 to the wheels and damit balance your entire engine for the sake of making it last longer, and more hp. less vibration less work to turn revolutions. just my 2cents again.

~John
LSE performance engineering and design

[95GST]

Originally posted by galantvr41062
"Welcome to the discussion boards. Hope you find the answers you need.

However.

This is absolutely, positively, completely and totally not an 'advanced technical discussion'. Please read the forum descriptions and review old threads before posting. Not doing so creates much unnecessary work for the moderators. Volunteers don't like unnecessary work.

--Tim"


I am confused, who wrote this!?

[galantvr41062]

well I did not see the quote button, that was said to my by some guy with a chevy cavity, my question was wether or not my computer was the problem but thats irelevent.

~John

[Jallen]

i had the crank, flywheel, pressure plate, rods & pistons done...about 2 weeks ago all for $125 ... $175 is too much...im pretty sure $125 is the goin rate...especially for a 4 cylinder engine...

ps. when you do get it done, make sure you include the flywheel bolts, front crank sprocket & bolt, and most importantly the little key wedge that fits in the front of the crank....ohh and the pressure plate bolts.... :)

hope this helps...

[Nick 92 TSi AWD]

Originally posted by dsm4eva
The balance/silent shafts are a cheap way to overcome the inherent vibration of an inline 4 cylinder engine. The 4G63 has a harmonic that occurs near 3250-3500 RPM which creates a 'lot' of vibrational energy in the passenger compartment.

Interesting note, that "technology" was inveted by porsche when they were experimenting with large four cylinders. Actually the macphersion strut type suspension that is used in the front of 1Gs was as well.
Another note, you'll notice when tuning that even well tuned sometimes you pick up knock in that rpm range, it's actually mechanical noise.

Yes I would do it.
Yes loctite EVERYTHING.

[dsm4eva]

Actually Porsche has licensed this technology from Mitsubishi, believe it or not.

Yes loctite EVERYTHING.

Thank you, you are making my 401K grow. :) But seriously, its good advice.

[90 Z24 5spd]

Originally posted by galantvr41062
well I did not see the quote button, that was said to my by some guy with a chevy cavity, my question was wether or not my computer was the problem but thats irelevent.

~John

Uh.. yeah. Why are you quoting me out of context, seemingly randomly? I'm confused.

--Tim

[Nick 92 TSi AWD]

Are you sure? Cause Porsche was making some pretty larger 4 cylinders in the 80s. I don't know about Mitsubishi, but I don't think they were making any large displacement four cylinders before that.....

[dsm4eva]

Yep, Mitsu holds the silent shaft patent, which is almost through so I expect to see more engine companies use this system to improve the NVH of their inline 4 engines over the next 5 years.

http://www.dsm.org/archives/1998/12/19981217.txt/17.html

[Nick 92 TSi AWD]

Just talked to my porsche (914 chalon 6) friend and yep I was wrong. Porsche paid mits to use the design on the 944...