Why AMS recommends Race balance shafts
Jan 28, 2010, 07:48 AM
#31
bought this and love it, engine revs so easly. I did notice a little increase in vibration in certain rpm ranges, mostly low rpm around 2500-3500. However if you are doing this who really cares if it vibrates a little more.
Just a few questions for you AMS guys.
1. what is the weight of the stock (eliminated) shaft?
2. what is the wight diff. in the stock shaft vs. the milled one?
3. what if known is the rotational weight removed from the engine?
If you can answer thanks.
Just a few questions for you AMS guys.
1. what is the weight of the stock (eliminated) shaft?
2. what is the wight diff. in the stock shaft vs. the milled one?
3. what if known is the rotational weight removed from the engine?
If you can answer thanks.
Jan 28, 2010, 08:35 AM
#32
The weight of both of the factory balance shafts together is 5.2 pounds.
The weight of the rear ( oil pump shaft ) is 2.2 pounds.
The weight of our race shaft is 1.0
The weight of the front shaft which gets completely eliminated is 3 pounds.
You are eliminating 4.2 pounds from the motor all together and you are saving 1.2 pounds from the factory rear shaft to our race rear shaft.
I hope this helps
The weight of the rear ( oil pump shaft ) is 2.2 pounds.
The weight of our race shaft is 1.0
The weight of the front shaft which gets completely eliminated is 3 pounds.
You are eliminating 4.2 pounds from the motor all together and you are saving 1.2 pounds from the factory rear shaft to our race rear shaft.
I hope this helps
Jan 28, 2010, 11:36 AM
#33
yup thanks for the info. One more..lets say @ 6K rpm how much rotational force weight is lost. I'm not sure if that is the best way to explain it. Crank @ 6k bal. shaft @ 12k rpm. an object spinning that fast has rotational weight generated by spinning. any Idea how much is cut off using your kit?
Jan 29, 2010, 07:14 AM
#36
Quoted from the good old VFAQ for DSM's..
So why do it?
Simply put, reliability. The balance shafts are only there for your butt, not the engine. They are there to cancel out vibrations at idle and around 3-4K that would be annoying to the average driver that just owns a car for transportation, and wants the drive to be as smooth as possible. For the enthusiast, though, the slightly increased vibration from removing the shafts can easily be tolerated (right after doing this mod, you may think the vibration is much worse, but the vast majority of people barely notice it after a couple of days). The balance shaft system adds more complexity to the engine. Most importantly, if the front balance shaft belt breaks, it can tangle itself in the timing belt, leading to a trashed engine. Too many dealerships replace the timing belt and leave the old balance shaft belt in place if it looks OK. If you have a shop of any type replace your timing belt, MAKE THEM REPLACE THE BALANCE SHAFT BELT ALSO, no matter how new it is!. I know someone who had a balance shaft belt fail after roughly 30K miles, he got lucky and caught it before it tore up the timing belt and trashed his engine.
There is no reliability decrease from removing the shafts as long as the job is done properly. Reliability should actually increase, and the engine should rev slightly easier, as there is less reciprocating weight for the crank to accelerate/decelerate (roughly 5-7 lbs for both shafts). The only real drawback is that the engine will vibrate a bit more at idle and about 3-4K rpm (some people have reported it vibrating harder at 6K and up, but I haven't seen that on my 3 cars). You do NOT have to have your entire shortblock balanced to do this job. It will smooth out the engine a bit, but it isn't absolutely necessary. I balanced the engine on one of my cars, not the other 2, and they don't vibrate that much more than the balanced engine. However, if you are doing a complete rebuild on your engine, balancing it wouldn't hurt. 4G63s are usually very well balanced from the factory, so very little needs to be done to have them fully balanced.
Removing the balance shafts also makes future timing belt replacements a lot easier - I can replace a timing belt and all pulleys, etc, on my car in less than an hour (of course, I have removed the power steering and AC, that cuts down on the time a lot).
So why do it?
Simply put, reliability. The balance shafts are only there for your butt, not the engine. They are there to cancel out vibrations at idle and around 3-4K that would be annoying to the average driver that just owns a car for transportation, and wants the drive to be as smooth as possible. For the enthusiast, though, the slightly increased vibration from removing the shafts can easily be tolerated (right after doing this mod, you may think the vibration is much worse, but the vast majority of people barely notice it after a couple of days). The balance shaft system adds more complexity to the engine. Most importantly, if the front balance shaft belt breaks, it can tangle itself in the timing belt, leading to a trashed engine. Too many dealerships replace the timing belt and leave the old balance shaft belt in place if it looks OK. If you have a shop of any type replace your timing belt, MAKE THEM REPLACE THE BALANCE SHAFT BELT ALSO, no matter how new it is!. I know someone who had a balance shaft belt fail after roughly 30K miles, he got lucky and caught it before it tore up the timing belt and trashed his engine.
There is no reliability decrease from removing the shafts as long as the job is done properly. Reliability should actually increase, and the engine should rev slightly easier, as there is less reciprocating weight for the crank to accelerate/decelerate (roughly 5-7 lbs for both shafts). The only real drawback is that the engine will vibrate a bit more at idle and about 3-4K rpm (some people have reported it vibrating harder at 6K and up, but I haven't seen that on my 3 cars). You do NOT have to have your entire shortblock balanced to do this job. It will smooth out the engine a bit, but it isn't absolutely necessary. I balanced the engine on one of my cars, not the other 2, and they don't vibrate that much more than the balanced engine. However, if you are doing a complete rebuild on your engine, balancing it wouldn't hurt. 4G63s are usually very well balanced from the factory, so very little needs to be done to have them fully balanced.
Removing the balance shafts also makes future timing belt replacements a lot easier - I can replace a timing belt and all pulleys, etc, on my car in less than an hour (of course, I have removed the power steering and AC, that cuts down on the time a lot).
Jan 29, 2010, 10:29 AM
#37
Evolved Member
iTrader: (17)
Join Date: Apr 2004
Location: 41° 59' N, 87° 54' W
Posts: 6,224
Likes: 0
Received 0 Likes
on
0 Posts
l8r)
Feb 6, 2010, 12:55 PM
#39
This is certainly one informative thread and I've learned a lot. I'm presently getting a 2.4L build by SBR. The engine block is going to be sent to JMS Racing @ San Antonio where it will be matched to my JMS Racing built head and installed into my EVO VIII. My question is whether or not I need to send the race balance shaft to SBR in Florida or to JMS Racing in San Antonio?
I don't know how you can adamantly disagree with the shafts not providing a benefit. Yes, I understand the knock concern when dealing with the stock ECU but I'm sure that issue can be remedied, right? 
This is very nice to know.
This is very nice to know.
Awesome!
It is generally recommended that you remove the balance shafts if you're trying for very high RPMs - i.e. in excess of 8500. Since the shafts spin at twice the RPM, they may become a liability as you rev the engine higher. IMO, the AMS kit is especially nice if you're road racing or Autocrossing, since it provides some support during high cornering loads. If you plan on tuning with the stock ECU, however, I would strongly recommend sticking to a lower RPM limit and keeping the shafts in there.
With the AMS race balance shaft kit the belt is eliminated along with the shaft that was driven by it. We have the counterweight machined off of the shaft that is driven by the oil pump. Once that is done it can be re-installed so that you have all of the support of the full balance shaft without all of the weight.
Awesome!
Feb 6, 2010, 07:58 PM
#41
Evolved Member
iTrader: (17)
Join Date: Apr 2004
Location: 41° 59' N, 87° 54' W
Posts: 6,224
Likes: 0
Received 0 Likes
on
0 Posts
l8r)
Mar 9, 2010, 11:36 AM
#45
The bearings for the shaft that is completely eliminated need to be rotated so the oiling holes don't line up anymore, this will prevent oil pressure loss when the shaft is removed. The bearing for the race shaft can be put in however because the shaft feeds the oil itself rather than the block feeding it through the bearing, I believe that this bearing doesn't have a hole in it.