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I know that the balance shafts are there to make the engine run smoother, and removing them will add power. Is there any other pros/cons with the balance shafts? How does the engine run after removing the balance shafts?

To be honest i have only JUST removed the balance shafts so i cannot comment on any gains/vibrations gained. Although its piece of mind knowing that you have these 2 massive lumps of metal out of the engine and it can only be better for economy (no matter how minimal the gain) and revs.

If i was to go fit extracts, exhaust, proper weber/turbo or whatever.. it would shit me to tears knowing i had teh balance shafts in there

removing the balance shafts is definitely a worth while modification to any astron. it reduces strain on the timing chain which is good for reliability and it reduces parasitic power loss as well.


I already had extractors with 2" exhaust , cam, higher compression and an impco 300A gas mixer on the car when i removed the balance shafts. when I did mine the difference was quite noticeable but only from about 5000 RPM through to redline. the engine and gearbox resonate and sounds like a swarm of pissed off bumble bees. the gearstick vibrates like a mofo...it's hard to describe but it seemed to make the car come alive. not sure if there was any measurable horsepower gain though.

but yeah until you hit 5000 RPM the difference isn't really noticeable.

remove the shafts! you won't regret it.

i know the chain rubs on the timing case sending alloy fragments into the sump

This is enough reason alone to piss them off

Frosty wrote:the engine and gearbox resonate and sounds like a swarm of pissed off bumble bees

lol, same effect here... damn it sounds good.

Can't really comment as i did mine with a few other things, but certainly makes it rev freely (less fly wheel effect if you want to draw a 'rough' comparison)

Nick.

81GL wrote:

Frosty wrote:the engine and gearbox resonate and sounds like a swarm of pissed off bumble bees

lol, same effect here... damn it sounds good.

yeah haha i actually decided to go for a drive after writing that post.

i got my engine without them then added them back in when i did my rebuild, This is because when u have LPG it's got a higher burning temp so the shafts help to keep the Block temp cooler because it's spinning alot slower then it would if it was to be in a fork lift or have a magna sump...

Frosty wrote:

81GL wrote:

Frosty wrote:the engine and gearbox resonate and sounds like a swarm of pissed off bumble bees

lol, same effect here... damn it sounds good.

yeah haha i actually decided to go for a drive after writing that post.

awww... i havn't enjoyed that in like 2 months now i think... hopefully make up for it next week end

I might consider doing the removal in the next couple weeks since I'll be taking the head off anyway. Higher compression head + PULP + Balance shafts removed, should see a bit more power.

Here is one on eBay at the moment, but without gaskets.
http://cgi.ebay.com.au/MITSUBISHI-MAGNA ... .m20.l1116

Found some more info here too : http://www.network54.com/Forum/75163/th ... ft+Removal

I used the endurotec kit same as the one on ebay.

COBWBS my engine is on LPG too, I haven't had any cooling issues and the engine's 'worked' enough so it's just on the far side of mild.

I'm sure everyone already knows, but balance shafts spin at TWICE engine speed. they weigh a couple of kilos each so you can imagine they put a fair bit of strain on the oil pump and timing chain.

thinking about it now, those suckas are HEAVY and the idea of them spinning at 13,000RPM defies common sense...but they did.

food for thought.

Cottees wrote:I know that the balance shafts are there to make the engine run smoother, and removing them will add power. Is there any other pros/cons with the balance shafts? How does the engine run after removing the balance shafts?

I don't have the shafts in mine, & runs/idles smooth as.

Don't know if it gave more power, but all the other mods done at the same time certainly did.

Just a couple of quick fact......

The balance shaft turns at twice the speed of the crank.
Porsche use the same system in there 944/968 4 cylinder engines (Under Licence from Mitsubishi)

E.g. 6000rpm crank speed = 12000rpm balance shaft speed

So if you run an Astron to 7500rpm like we do..... You do the maths

It removes a lot of weight from the rotating assembly, and therefore, due to less enertia, will be faster to spin to peak operating rpm.
Same as using a lightened flywheel on the back of the engine......

Hope this helps....

The balance shafts are there because of a 2nd harmonic which "bounces" the engine up and down at twice the RPM of the engine.
This harmonic is in ALL in-line 4 cylinder engines but only becomes apparent at higher RPM, in the larger capacity engines.

The reason they started to put them in engines greater than 1.8L is the weight of the pistons/rods in these engines, along with the higher RPM, cause this harmonic to become very noticeable.

Balancing the engine WILL NOT remove this harmonic, but it will reduce OTHER "vibrations".
Making the the rods and pistons lighter will help REDUCE this harmonic.

Hope this helps.


Cheers.

Excellent post, thanks Scott.