Broken Balance Shaft Belt
Agree 100%.
This is to reduce engine movement from launches and shifts.
It will twist the engine/tranny/TC by preventing movement at the timing belt end. The drive shafts and center shaft should be able to pivot to deal with this, but I don't see the value of trading one motion for another.
I only can think of downpipe being happy since it won't pivot as much where it joins with O2 housing.
Seems a shock absorber like that would be used to quell exterior engine vibrations that balance shafts and vibration dampers attempt to quell on the engine’s interior. Don’t get me wrong, I understand the reason for installing it, but I wouldn’t call it an adequate replacement for a quality damper or balance shafts.[/QUOTE]
This is to reduce engine movement from launches and shifts.
It will twist the engine/tranny/TC by preventing movement at the timing belt end. The drive shafts and center shaft should be able to pivot to deal with this, but I don't see the value of trading one motion for another.
I only can think of downpipe being happy since it won't pivot as much where it joins with O2 housing.
Seems a shock absorber like that would be used to quell exterior engine vibrations that balance shafts and vibration dampers attempt to quell on the engine’s interior. Don’t get me wrong, I understand the reason for installing it, but I wouldn’t call it an adequate replacement for a quality damper or balance shafts.[/QUOTE]
Also , the Sentra SER Spec V using the QR25DE motor did not rev that high. If I remember correctly the redline/rev limiter was 6200 rpms . It was a 2.5L motor also used in the Altima .
I did notice improvement in MPG's . I went from best of 210-220 miles per 10 gallons to 240-260 miles depending on how I drove . Unfortunately , after removing the bs a few months later i had a argument with a tree and the tree won.
Originally Posted by barneyb
Since there's much speculation as to the cause of the secondary vibration that balance shafts were invented to correct, here's the explanation. Its a geometry problem.
When a crank moves 90 degrees from the top dead centre (TDC) in a single cylinder engine positioned upright, the bigend up-down position is exactly at the half-way point in the stroke, but the conrod is at the most tilted position at this time, and this tilt angle makes the small-end position to be lower than the half-way point in its stroke.
Because the small-end position is lower than the half-way point of the stroke at 90 degrees and at 270 degrees after TDC, the piston moves less distance when the crank rotates from 90 degrees to 270 degrees after TDC than during the crank rotation from 90 degrees before TDC to 90 degrees after TDC. In other words, a piston must travel a longer distance in its reciprocal movement on the top half of the crank rotation than on the bottom half.
Assuming the crank rotational speed to be constant, this means the reciprocating movement of a piston is faster on the top half than on the bottom half of the crank rotation. Consequently, the inertia force created by the mass of a piston (in its acceleration and deceleration) is stronger in the top half of crank rotation than on the bottom half.
So, an ordinary inline 4 cylinder engine with 180 degrees up-down-down-up crank throws may look like cancelling the upward inertia created by the #1-#4 piston pair with the downward inertia of the #2-#3 pair and vice versa, but in fact the upward inertia is always stronger, and the vibration caused by this imbalance is traditionally called the Secondary Vibration. - Wikipedia
When a crank moves 90 degrees from the top dead centre (TDC) in a single cylinder engine positioned upright, the bigend up-down position is exactly at the half-way point in the stroke, but the conrod is at the most tilted position at this time, and this tilt angle makes the small-end position to be lower than the half-way point in its stroke.
Because the small-end position is lower than the half-way point of the stroke at 90 degrees and at 270 degrees after TDC, the piston moves less distance when the crank rotates from 90 degrees to 270 degrees after TDC than during the crank rotation from 90 degrees before TDC to 90 degrees after TDC. In other words, a piston must travel a longer distance in its reciprocal movement on the top half of the crank rotation than on the bottom half.
Assuming the crank rotational speed to be constant, this means the reciprocating movement of a piston is faster on the top half than on the bottom half of the crank rotation. Consequently, the inertia force created by the mass of a piston (in its acceleration and deceleration) is stronger in the top half of crank rotation than on the bottom half.
So, an ordinary inline 4 cylinder engine with 180 degrees up-down-down-up crank throws may look like cancelling the upward inertia created by the #1-#4 piston pair with the downward inertia of the #2-#3 pair and vice versa, but in fact the upward inertia is always stronger, and the vibration caused by this imbalance is traditionally called the Secondary Vibration. - Wikipedia
Do you know the position of the weight when timing mark is set up? I think the front BS has weight down. Is it also down to cancel out the left and right motion so the only motion it induces it up from both BS at same time, which counters the power stroke pushing down for TDC to 90 degrees? This would make sense.
If this is the case, I (personally) will always keep both my BS because the timing is set to counter the power stroke on every cylinder. There isn't anything else that is timed this closely. If I plan to brace the engine directly to car frame and prevent any engine movement, then I will get rid of BS since the braces will do the same thing. But car vibrations will be nuts
I have a good amount of experience developing balance shaft systems for OEMs. I've literally reviewed hundreds of hours of run data on engines, talked about this same stuff with other engineers who design these systems for a living, seen results first hand. Removing balance shafts will cause no damage to an engine. They are only for NVH purposes.
There are TONS of 4 cylinder engines that don't use balance shaft systems and you don't hear of them chewing through bearings because they vibrate so badly. And if you think that a 4 cylinder engine without balance shafts has a lot of vibrations, you should see the kind of vibrations an odd firing V10 has. I've talked to engineers who've had viper engines rip motor mounts out of the walls they were mounted to because they were vibrating so badly.
There are TONS of 4 cylinder engines that don't use balance shaft systems and you don't hear of them chewing through bearings because they vibrate so badly. And if you think that a 4 cylinder engine without balance shafts has a lot of vibrations, you should see the kind of vibrations an odd firing V10 has. I've talked to engineers who've had viper engines rip motor mounts out of the walls they were mounted to because they were vibrating so badly.
Check out this video I found if a DSM dynoing before and after BS removal . Also lightened flywheel.
Thanks for chiming in!
So the only stress from removing BS goes to the engine and tranny mounts?
So the only stress from removing BS goes to the engine and tranny mounts?
I have a good amount of experience developing balance shaft systems for OEMs. I've literally reviewed hundreds of hours of run data on engines, talked about this same stuff with other engineers who design these systems for a living, seen results first hand. Removing balance shafts will cause no damage to an engine. They are only for NVH purposes.
There are TONS of 4 cylinder engines that don't use balance shaft systems and you don't hear of them chewing through bearings because they vibrate so badly. And if you think that a 4 cylinder engine without balance shafts has a lot of vibrations, you should see the kind of vibrations an odd firing V10 has. I've talked to engineers who've had viper engines rip motor mounts out of the walls they were mounted to because they were vibrating so badly.
There are TONS of 4 cylinder engines that don't use balance shaft systems and you don't hear of them chewing through bearings because they vibrate so badly. And if you think that a 4 cylinder engine without balance shafts has a lot of vibrations, you should see the kind of vibrations an odd firing V10 has. I've talked to engineers who've had viper engines rip motor mounts out of the walls they were mounted to because they were vibrating so badly.
This was exactly what I was imagining. Thanks for the link.
Here is a good video explaining balance shafts in general for inline 4 motors.
https://m.youtube.com/watch?v=hwigSbyQ7AI
https://m.youtube.com/watch?v=hwigSbyQ7AI
I have a good amount of experience developing balance shaft systems for OEMs. I've literally reviewed hundreds of hours of run data on engines, talked about this same stuff with other engineers who design these systems for a living, seen results first hand. Removing balance shafts will cause no damage to an engine. They are only for NVH purposes.
There are TONS of 4 cylinder engines that don't use balance shaft systems and you don't hear of them chewing through bearings because they vibrate so badly. And if you think that a 4 cylinder engine without balance shafts has a lot of vibrations, you should see the kind of vibrations an odd firing V10 has. I've talked to engineers who've had viper engines rip motor mounts out of the walls they were mounted to because they were vibrating so badly.
There are TONS of 4 cylinder engines that don't use balance shaft systems and you don't hear of them chewing through bearings because they vibrate so badly. And if you think that a 4 cylinder engine without balance shafts has a lot of vibrations, you should see the kind of vibrations an odd firing V10 has. I've talked to engineers who've had viper engines rip motor mounts out of the walls they were mounted to because they were vibrating so badly.
So I’ve heard, the larger the displacement of the I4 engine (longer stroke) the worse the second order vibration, as the pistons have to achieve higher speeds at any given rpm. So the balance shafts may be something worth keeping when expanding stroke.
Here is a good video explaining balance shafts in general for inline 4 motors.
https://m.youtube.com/watch?v=hwigSbyQ7AI
https://m.youtube.com/watch?v=hwigSbyQ7AI