Does anyone know why the xB and xA engine does not have balancer shafts? Almost every 4 cyl. I have ever torn down has a set but not the scion. Why? I also noticed the motor has a lot of vibrations, I wonder if this is because it has no balancer shafts? Any imput would help.

 

hmmmm, im not sure about this either. maybe because the engine was designed a while ago... like '99 i think, when balance shafts were still in more expensive 4-cylinder models?? thats the only thing i could come up with. i think its still a smooth engine... and quiet, even without the shafts. but if it had the shafts then it probably wouldnt be as buzzy over 4,200 rpm, but its not that bad.

 

The old mitsubishi motors that came in eclipse's and stuff even had balancer shafts, and their engines go far back I think the 4g63 motors even had them. I just wish the motor had that smooth feeling, My SRT-4 has them and I love the way the motor runs above 3500rpm, and I wish the xB was the same.

 

i wish i had an srt-4, lol

no no i take that back... a PT cruiser GT

 

but those mentioned engines above are from sports cars, a category where the buyers are a little more picky. and those are performance engines. we have sub $15k sub-compacts where the driver is expected to just want reliable cheap transportation for the long haul. plus we have eco-minded engines, not performance. plus, when scion released, toyota already had thier "not to exceed" price range and maybe putting balancer shafts into the engine would have pushed them past that point? i know that is the reason that the scion xA does not have VSC and TCS like the xb because it would have put it past te "not to exceed" price point.

maybe our small engines arent compatible with them and building one that was would have put it past that "not to exceed" price point??? im sure theres a logical reason we just cant figure it out... please give me credit for tryin, lol

 

We don't have balance shafts. Quality toyota engineering doesn't need them

 

This is hilarious. People here WANT balance shafts for their engines. Go to 4G63 forums, and you can find kits to ELIMINATE balance shafts. A well designed, ECONOMY car engine shouldn't need balance shafts. Especially one of such small displacement. Same reason we don't have harmonic dampeners on the crank.

Mike

 

balancing shafts are normally in oversquare motors , and/or larger displacement 4 cylinders.


hell with a sentra if you remove them ( lessening service life but...) you gain like 13 or 14whp

 

ok so i was on the right track with trying to figure out why we dont have them... lol

 

Four cylinder engines have in inherent running (firing) imbalance that becomes more noticeable as displacement increases. On engines under 2 liters it is sufficient to use rubber mounts and harmonic dampers, both of which our 1.5 liter Scion engines do have. Over 2 liters, and especially over 2.5 liters, internal balance shafts are required to make the engine smooth.

 

We don't have balance shafts because they are complex, take space, and add cost, and small engines like ours can make do with rubber mounts and harmonic dampers.

 

they also decrease performance , mileage , and on such low hp . driveability.

 

yeah, no doubt... the first thing i did was eliminate mine, when i was building my mitsu starion

 

to tell you the truth most older engines had balancer shafts and alot of newer motors dont and i also own a srt-4 i also removed my balencer shaft and i have solid motor mounts and you cant tell a diffrence with or without them. the main reson thay install balencer shafts is because older engines where way out of balence and it was the cheap way to solve it now most cranks, conecting rods and pistons are so close to spec theres no need for a balencer shaft.

 

Old engines were balanced as well as current engines. The purpose of balance shafts is to counteract the vibrations of the 4 cylinder firing order -- they are only used in 4 cyl engines. The vibrations only become objectionable on 4-cyl engines beginning around 2.5 liters, which is where balance shafts begin to be designed into engines. Balance shafts add considerable expense, consisting of the two shafts, their bearings, and their gear or chain drives. The size of the engine also increases to make room inside for these items.

 

2.5 is a guestimate 2.4 is a commonly used size and more 2.4's are out there and almost all 2.4's come stock with em .

 

all i now is every 300+hp srt and 4g63 motor removes there balecer shaft(s) the srt only has one balencer shaft. and the only reson its in the motor is for the memovel of very small vibrations above 3000 rpm. this was all coming from a tech that designed the srt-4 motor thay get on the srtforums once in awhile he also said that it was talked about many times to leave it out of the srt but it would make more hassel and actualy cost more because the machine assembels the motor would have to be compleatly reprogramed just to leave it out and thay would have had to make a diffrent assembely book for the srt motro. so the balencer is only there for small vibration over 3000rpm and othere then that its just a 30lb 25hp robbing steel rod.

 

http://en.wikipedia.org/wiki/Balance_shaft