Balance-Shafts Explained
Great thread guys. Good to see people looking into the operation of an engine component in a well thought out way, not just a magazine racer trying to justify a part just because someone claimed it worked. I personally would only remove the shafts if and only if it was a full racecar that will undergo scheduled teardowns. On the street it is simply idiotic to do it, but there is always those that want to go "full race" on the street. Its like considering counter weights on the crank not necessary.
Adrian, don't go away... be right with you.. probably this weekend. Real busy but definitely interested. Will continue.
Regarding the statement of privateer and knock being a big hurdle.. I meant precise detection and prevention across full engine speed and load range using cheap equipment. Pressure transducers and ion-gap technology are not cheap.
Regarding temperature.. yes I am fully aware. My phrasing was wrong and lazy. By gas properties I meant gas temps to be included. Interesting example of the effect of temperature is that in CART where variable intake tract lengths aren't allowed, they accomplished effective variable "length" by having standard injection along with a pre-compressor injector. By varying the amount of proportion of alcohol injected pre-compressor, air temperature could be changed and give perfect wave tuning even with varying RPM and fixed tract length.
Where you say it is NOT detonation and that it is auto-ignition, that is exactly Gordon Blair's point. What do you understand detonation to be? If it is the complete and instantaeneous ignition of the entire end gas mass and not a progressing flame front.. can't that be considered homogeneous auto-ignition as well, not just point auto-ignition that progresses into a second front?
I've scanned through the article and am having trouble reading it on screen. I need to zoom in to see anything in the pictures and then zoom back out to read the text. I will print it out and digest it at some point. At first glance there seems to be a few very unusual relationships and non-relationships that I've not seen elsewhere.
I need to get back to other things. If in the meantime you would be so kind as to define and differentiate between the following terms as you understand it from this paper and other advanced papers..
"Auto-ignition"
"Homogeneous auto-ignition"
"Pin point auto-ignition"
"Detonation"
"Knock"
You would think that modern researchers with modern equipment would pick up and continue where these guys left off. Perhaps it is a matter of just knowing roughly what happens and how to deal with it being good enough for them, rather than getting down into the extreme micro-dynamics of it which changes neither what happens, or the steps taken?
Best regards
Shaun
Back on the weekend!
Regarding the statement of privateer and knock being a big hurdle.. I meant precise detection and prevention across full engine speed and load range using cheap equipment. Pressure transducers and ion-gap technology are not cheap.
Regarding temperature.. yes I am fully aware. My phrasing was wrong and lazy. By gas properties I meant gas temps to be included. Interesting example of the effect of temperature is that in CART where variable intake tract lengths aren't allowed, they accomplished effective variable "length" by having standard injection along with a pre-compressor injector. By varying the amount of proportion of alcohol injected pre-compressor, air temperature could be changed and give perfect wave tuning even with varying RPM and fixed tract length.
Where you say it is NOT detonation and that it is auto-ignition, that is exactly Gordon Blair's point. What do you understand detonation to be? If it is the complete and instantaeneous ignition of the entire end gas mass and not a progressing flame front.. can't that be considered homogeneous auto-ignition as well, not just point auto-ignition that progresses into a second front?
I've scanned through the article and am having trouble reading it on screen. I need to zoom in to see anything in the pictures and then zoom back out to read the text. I will print it out and digest it at some point. At first glance there seems to be a few very unusual relationships and non-relationships that I've not seen elsewhere.
I need to get back to other things. If in the meantime you would be so kind as to define and differentiate between the following terms as you understand it from this paper and other advanced papers..
"Auto-ignition"
"Homogeneous auto-ignition"
"Pin point auto-ignition"
"Detonation"
"Knock"
You would think that modern researchers with modern equipment would pick up and continue where these guys left off. Perhaps it is a matter of just knowing roughly what happens and how to deal with it being good enough for them, rather than getting down into the extreme micro-dynamics of it which changes neither what happens, or the steps taken?
Best regards
Shaun
Back on the weekend!
Thread Starter
Evolving Member
Joined: Jul 2005
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From: Davis, California
Gonna do the same bold-quotes thing as last time. (Because I'm basically lazy as I can't claim to be too busy right now.)
Look forward to catching your reply on the weekend!
Heh. Maybe someone should find a way to get the ion-sensing system to work on an Evo and give Shiv a small bit of competition for his "SMART" system.
-Adrian
Originally Posted by Shaun@SG
Adrian, don't go away... be right with you.. probably this weekend. Real busy but definitely interested. Will continue.
No worries. Not planning to leave any time soon.
Regarding the statement of privateer and knock being a big hurdle.. I meant precise detection and prevention across full engine speed and load range using cheap equipment. Pressure transducers and ion-gap technology are not cheap.
The ion-technology is just expensive to license from Saab as they hold the patent. GM brands might have access since GM now owns Saab 100%. But I've not seen it on any other engines myself, yet.
All it does is apply a 400V charge-bias across the spark plug gap during combustion and analyze the current "listening" for similar frequency spikes to a microphone knock sensor. The difference is that the spikes are caused by physical contact with the ionized gasses against the walls of the cyllinder; that's what generates the current and the two are directly related. It's remarkably simple and noise-free.
Were it not for the licensing, it wouldn't be very expensive at all as it hardly uses any parts not already found on most engines, coil-on-plug ignition with the addition of a solid state controller which can hold the 400v charge bias. Nothing too horribly fancy. Saab uses triac for it in the "black" newer DI racks, and in the older "Red" DI racks a thyristor was used. (Almost same thing. Triac just works in both current directions.)
Here's an article on triac: http://www.americanmicrosemi.com/tutorials/triac.htm
The Wikipedia on triac: http://en.wikipedia.org/wiki/Triac
And the Wikipedia page on thyristors: http://en.wikipedia.org/wiki/Thyristor
Regarding temperature.. yes I am fully aware. My phrasing was wrong and lazy. By gas properties I meant gas temps to be included. Interesting example of the effect of temperature is that in CART where variable intake tract lengths aren't allowed, they accomplished effective variable "length" by having standard injection along with a pre-compressor injector. By varying the amount of proportion of alcohol injected pre-compressor, air temperature could be changed and give perfect wave tuning even with varying RPM and fixed tract length.
That's awesome and a GREAT idea. Sorry for being pedantic. A lot of my friends don't understand this stuff and sometimes I make the mistake of forgetting that there are a LOT of people out there who do.
Where you say it is NOT detonation and that it is auto-ignition, that is exactly Gordon Blair's point. What do you understand detonation to be? If it is the complete and instantaeneous ignition of the entire end gas mass and not a progressing flame front.. can't that be considered homogeneous auto-ignition as well, not just point auto-ignition that progresses into a second front?
Spontaneous and homogenous auto-ignition of the end gas does not produce the "ring" associated with detonation. While the NACA article I linked you to wasn't able to induce knock without auto-ignition, they did mention an experiment which was conducted by another research group before the report I quoted was written.
The other research group was able to get homogenous auto-ignition without any detonation either visible in the schliren photos or audible to the pressure sensor or the ear.
They explain in the article I quoted why auto-ignition tends to happen with detonation. But that they cannot be the same thing if they can be induced seperately.
I've scanned through the article and am having trouble reading it on screen. I need to zoom in to see anything in the pictures and then zoom back out to read the text. I will print it out and digest it at some point. At first glance there seems to be a few very unusual relationships and non-relationships that I've not seen elsewhere.
I thought the same thing. "Hotrod" over at nasioc pointed it out to me about a year ago. It blew my mind. Several people tried to debunk NACA's work in a discussion at nasioc. But in EVERY SAE paper anyone there (including several SAE engineers) could find the first lines read "Knock is generally assumed to be" ... and none of them ... not ONE actually asked if knock was before or after the flame-front. Only NACA did research on that to anyone's knowledge. I think it is very likely that this "general assumption" is self-defeating; no-one knows what knock is with absolute certainty yet and I think that assumption is why. Ironically the assumption by so many people may be the reason they are forced to make that assumption in the first place.
Interesting note: I actually met an engineer for NASA not long back. (His desk still said "NACA" on it.) And I talked with him briefly about this. He agrees that it's ironic so many people are making a living off trying to tace down information which was allready found 60 years ago through government programs with almost unlimited budgets. NACA was doing ultraviolet spectroscopy on the gasses, schliren films, and standard photos. (Detonation is a purple flame/flash, btw.) NACA used an engine which could be supplied with any pressure or temperature air they wanted at any air/fuel ratio and they used stellite mirrors on the pistons and loooads of other really cool stuff. And no one knows about it!!
I need to get back to other things. If in the meantime you would be so kind as to define and differentiate between the following terms as you understand it from this paper and other advanced papers..
"Auto-ignition" = Spontaneous, but otherwise "normal" combustion going through the "normal" combustion chemical processes.
"Homogeneous auto-ignition" = Spontaneous auto-ignition of an entire region of compressed un-burnt mixture.
"Pin point auto-ignition" = Spontaneous auto-ignition of small points in the compressed un-burnt air/fuel mixture ahead of the flame wave.
"Detonation" = An "abnormal" and spontaneous combustion which does not follow "normal" combustion chemistry or propogation speeds.
"Knock" = Same as detonation, except when it's just a loose main bearing making your rods knock on the cyllinder bores. heh.
The SAE is still publishing papers to this day "assuming" what knock is and stating that it is "pin point" autoignition, though using different words. NACA got those same pin-point auto-ignitions without knock, and knock without those same pin-point auto-ignitions many many times. But, so far, no one has ever cited that NACA document in an SAE paper and no-one has asked the questions asked int he NACA report. Consequently, no one has found the information NACA found and the people still writing papers today are very likely looking in completely the wrong place for knock.
You would think that modern researchers with modern equipment would pick up and continue where these guys left off. Perhaps it is a matter of just knowing roughly what happens and how to deal with it being good enough for them, rather than getting down into the extreme micro-dynamics of it which changes neither what happens, or the steps taken?
I think the problem is that they never asked the basic question of where knock comes from, in a literal sense. I've seen SAE papers showing spectroscopy of the pin-point auto-ignitions they think are knock and they are never conclusive. Every paper always seems to end with more questions. And every paper starts with "knock is generally agreed to be... ". If no one every asks the basic questions, and the assumptions are wrong, then what are we left with? NACA asked those basic questions back before people got carried away assuming.
Best regards
Shaun
Back on the weekend!
No worries. Not planning to leave any time soon.
Regarding the statement of privateer and knock being a big hurdle.. I meant precise detection and prevention across full engine speed and load range using cheap equipment. Pressure transducers and ion-gap technology are not cheap.
The ion-technology is just expensive to license from Saab as they hold the patent. GM brands might have access since GM now owns Saab 100%. But I've not seen it on any other engines myself, yet.
All it does is apply a 400V charge-bias across the spark plug gap during combustion and analyze the current "listening" for similar frequency spikes to a microphone knock sensor. The difference is that the spikes are caused by physical contact with the ionized gasses against the walls of the cyllinder; that's what generates the current and the two are directly related. It's remarkably simple and noise-free.
Were it not for the licensing, it wouldn't be very expensive at all as it hardly uses any parts not already found on most engines, coil-on-plug ignition with the addition of a solid state controller which can hold the 400v charge bias. Nothing too horribly fancy. Saab uses triac for it in the "black" newer DI racks, and in the older "Red" DI racks a thyristor was used. (Almost same thing. Triac just works in both current directions.)
Here's an article on triac: http://www.americanmicrosemi.com/tutorials/triac.htm
The Wikipedia on triac: http://en.wikipedia.org/wiki/Triac
And the Wikipedia page on thyristors: http://en.wikipedia.org/wiki/Thyristor
Regarding temperature.. yes I am fully aware. My phrasing was wrong and lazy. By gas properties I meant gas temps to be included. Interesting example of the effect of temperature is that in CART where variable intake tract lengths aren't allowed, they accomplished effective variable "length" by having standard injection along with a pre-compressor injector. By varying the amount of proportion of alcohol injected pre-compressor, air temperature could be changed and give perfect wave tuning even with varying RPM and fixed tract length.
That's awesome and a GREAT idea. Sorry for being pedantic. A lot of my friends don't understand this stuff and sometimes I make the mistake of forgetting that there are a LOT of people out there who do.
Where you say it is NOT detonation and that it is auto-ignition, that is exactly Gordon Blair's point. What do you understand detonation to be? If it is the complete and instantaeneous ignition of the entire end gas mass and not a progressing flame front.. can't that be considered homogeneous auto-ignition as well, not just point auto-ignition that progresses into a second front?
Spontaneous and homogenous auto-ignition of the end gas does not produce the "ring" associated with detonation. While the NACA article I linked you to wasn't able to induce knock without auto-ignition, they did mention an experiment which was conducted by another research group before the report I quoted was written.
The other research group was able to get homogenous auto-ignition without any detonation either visible in the schliren photos or audible to the pressure sensor or the ear.
They explain in the article I quoted why auto-ignition tends to happen with detonation. But that they cannot be the same thing if they can be induced seperately.
I've scanned through the article and am having trouble reading it on screen. I need to zoom in to see anything in the pictures and then zoom back out to read the text. I will print it out and digest it at some point. At first glance there seems to be a few very unusual relationships and non-relationships that I've not seen elsewhere.
I thought the same thing. "Hotrod" over at nasioc pointed it out to me about a year ago. It blew my mind. Several people tried to debunk NACA's work in a discussion at nasioc. But in EVERY SAE paper anyone there (including several SAE engineers) could find the first lines read "Knock is generally assumed to be" ... and none of them ... not ONE actually asked if knock was before or after the flame-front. Only NACA did research on that to anyone's knowledge. I think it is very likely that this "general assumption" is self-defeating; no-one knows what knock is with absolute certainty yet and I think that assumption is why. Ironically the assumption by so many people may be the reason they are forced to make that assumption in the first place.
Interesting note: I actually met an engineer for NASA not long back. (His desk still said "NACA" on it.) And I talked with him briefly about this. He agrees that it's ironic so many people are making a living off trying to tace down information which was allready found 60 years ago through government programs with almost unlimited budgets. NACA was doing ultraviolet spectroscopy on the gasses, schliren films, and standard photos. (Detonation is a purple flame/flash, btw.) NACA used an engine which could be supplied with any pressure or temperature air they wanted at any air/fuel ratio and they used stellite mirrors on the pistons and loooads of other really cool stuff. And no one knows about it!!
I need to get back to other things. If in the meantime you would be so kind as to define and differentiate between the following terms as you understand it from this paper and other advanced papers..
"Auto-ignition" = Spontaneous, but otherwise "normal" combustion going through the "normal" combustion chemical processes.
"Homogeneous auto-ignition" = Spontaneous auto-ignition of an entire region of compressed un-burnt mixture.
"Pin point auto-ignition" = Spontaneous auto-ignition of small points in the compressed un-burnt air/fuel mixture ahead of the flame wave.
"Detonation" = An "abnormal" and spontaneous combustion which does not follow "normal" combustion chemistry or propogation speeds.
"Knock" = Same as detonation, except when it's just a loose main bearing making your rods knock on the cyllinder bores.
heh.The SAE is still publishing papers to this day "assuming" what knock is and stating that it is "pin point" autoignition, though using different words. NACA got those same pin-point auto-ignitions without knock, and knock without those same pin-point auto-ignitions many many times. But, so far, no one has ever cited that NACA document in an SAE paper and no-one has asked the questions asked int he NACA report. Consequently, no one has found the information NACA found and the people still writing papers today are very likely looking in completely the wrong place for knock.
You would think that modern researchers with modern equipment would pick up and continue where these guys left off. Perhaps it is a matter of just knowing roughly what happens and how to deal with it being good enough for them, rather than getting down into the extreme micro-dynamics of it which changes neither what happens, or the steps taken?
I think the problem is that they never asked the basic question of where knock comes from, in a literal sense. I've seen SAE papers showing spectroscopy of the pin-point auto-ignitions they think are knock and they are never conclusive. Every paper always seems to end with more questions. And every paper starts with "knock is generally agreed to be... ". If no one every asks the basic questions, and the assumptions are wrong, then what are we left with? NACA asked those basic questions back before people got carried away assuming.
Best regards
Shaun
Back on the weekend!
Heh. Maybe someone should find a way to get the ion-sensing system to work on an Evo and give Shiv a small bit of competition for his "SMART" system.
-Adrian
Last edited by SaabTuner; Jul 19, 2005 at 12:38 PM.
Originally Posted by SaabTuner
However, I just thought of what could possibly be a more important issue; the knock sensors are just vibration microphones on the block. Large second-order vibrations would show up as noise with a frequency of twice the RPM of the engine. Knock sensors generally "look" for noise at about 6,300-6,800 Hz. Which means that when the engine is at 3,150-3,400 RPM these second order vibrations will show up as "noise" dampening the detection of knock.
Originally Posted by Shaun@SG
...I wonder if amplitude of the two sources is similar though. If they are, and frequency and amplitude are similar, then it is really bad because depending on setup, the 3000-3500 RPM window is right in the high torque zone which is exactly where knock is most likely to occur. If differentiation is no longer possible, then increased safety buffer in tune is necessary...
l8r)
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Evolving Member
Joined: Jul 2005
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From: Davis, California
Originally Posted by Ludikraut
Wouldn't the stock ECU potentially pick up the additional noise as knock activity and therefore pull timing? This would mean that in the 3000-3500 rpm window I would only risk losing power, which in turn I would only see on the street, where I personally don't really care that much about it. On the other hand, when I'm running on a road course, revving up to 9000 rpms (and never really below 4000), then it should be a non-issue, right?
l8r)
l8r)
Most people who remove their balance shafts are probably running turbos so large that they are not fully spooled by 3400 RPM anyway, so it's probably not going to show up as a huge issue.
I just thought it was worth noting that your engine would be, to some degree, "noisier" to the knock sensor if the balance shafts are removed.
Now we just have to figure out how much noisier and if it'll ever be "masking" bad knock you have or "faking" knock you don't have.
-Adrian
Adrian,
Would building a stroker motor require changing the balance shafts in any way? The mass of the pistons/conrods would change as well as the dynamic velocity and acceleration of the moving parts, whereas the rotational speeds of the balance shafts would remain the same as they were in the stock setup.
Maybe I'm not understanding the true purpose of the balance shafts. Their rotation at twice the speed of the crankshaft produces a harmonic noise that cancels out the harmonic noise generated by the rotating assembly? If that's the case, and digging into my horrible memories of my vibrations class, the mass does have a direct effect on the frequency and changing the mass of the rotating assembly (via different components in a stronger 2.0L buildup or different weight and geometry components in a 2.3L stroker buildup) would have an effect on it's natural resonant frequency. Couldn't this result in the frequency of the balance shafts and the rotating assembley occuring at different RPM ranges and no longer cancell each other out?
I hope that made sense, I know what I'm thinking but I have a hard time putting it into words coherently.
- Steve
Would building a stroker motor require changing the balance shafts in any way? The mass of the pistons/conrods would change as well as the dynamic velocity and acceleration of the moving parts, whereas the rotational speeds of the balance shafts would remain the same as they were in the stock setup.
Maybe I'm not understanding the true purpose of the balance shafts. Their rotation at twice the speed of the crankshaft produces a harmonic noise that cancels out the harmonic noise generated by the rotating assembly? If that's the case, and digging into my horrible memories of my vibrations class, the mass does have a direct effect on the frequency and changing the mass of the rotating assembly (via different components in a stronger 2.0L buildup or different weight and geometry components in a 2.3L stroker buildup) would have an effect on it's natural resonant frequency. Couldn't this result in the frequency of the balance shafts and the rotating assembley occuring at different RPM ranges and no longer cancell each other out?
I hope that made sense, I know what I'm thinking but I have a hard time putting it into words coherently.
- Steve
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Joined: Jul 2005
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From: Davis, California
Originally Posted by SuperHatch
Adrian,
Would building a stroker motor require changing the balance shafts in any way? The mass of the pistons/conrods would change as well as the dynamic velocity and acceleration of the moving parts, whereas the rotational speeds of the balance shafts would remain the same as they were in the stock setup.
Maybe I'm not understanding the true purpose of the balance shafts. Their rotation at twice the speed of the crankshaft produces a harmonic noise that cancels out the harmonic noise generated by the rotating assembly? If that's the case, and digging into my horrible memories of my vibrations class, the mass does have a direct effect on the frequency and changing the mass of the rotating assembly (via different components in a stronger 2.0L buildup or different weight and geometry components in a 2.3L stroker buildup) would have an effect on it's natural resonant frequency. Couldn't this result in the frequency of the balance shafts and the rotating assembley occuring at different RPM ranges and no longer cancell each other out?
I hope that made sense, I know what I'm thinking but I have a hard time putting it into words coherently.
- Steve
Would building a stroker motor require changing the balance shafts in any way? The mass of the pistons/conrods would change as well as the dynamic velocity and acceleration of the moving parts, whereas the rotational speeds of the balance shafts would remain the same as they were in the stock setup.
Maybe I'm not understanding the true purpose of the balance shafts. Their rotation at twice the speed of the crankshaft produces a harmonic noise that cancels out the harmonic noise generated by the rotating assembly? If that's the case, and digging into my horrible memories of my vibrations class, the mass does have a direct effect on the frequency and changing the mass of the rotating assembly (via different components in a stronger 2.0L buildup or different weight and geometry components in a 2.3L stroker buildup) would have an effect on it's natural resonant frequency. Couldn't this result in the frequency of the balance shafts and the rotating assembley occuring at different RPM ranges and no longer cancell each other out?
I hope that made sense, I know what I'm thinking but I have a hard time putting it into words coherently.
- Steve
As for the harmonics, I can't claim to be an expert here, but the engine is continuously generating these forces twice every revolution, so they must occur at least at that interval. However, the metal in the engine itself DOES disperse some of this vibration into the upper harmonics such as 4th, 5th, 6th ... and, of course, into general noise at all frequencies. Though, as you can see from the spectrum graph already posted, the second order vibrations are worst for inline engines, and likely always will be without the balance shafts.
A stroker motor usually has a shorter rod-ratio because it usually requires shorter rods. There are some downsides to that: shorter rods generate far more second order vibrations because the un-balance in the engine which occurs when the pistons/rods each reverse their motion is amplified. In fact, if you could build an engine with infinitely long rods, there would be no large second order vibrations at all because the ascending and descending pistons would reverse motion simultaneously.
To make the point more clear, here is a graph showing piston position in the bore of an engine. Do you see how the piston spends more time at the bottom than at the top? The descending piston starts to move downward before the ascending piston begins moving upward:
----
Now observe the truly telling accelleration graph. The assymetry in the accelleration is, quite literally, what produces the second-order vibrations in the engine. The ascending and descending pistons are not accellerated at the same rate so, therefore, there is an un-balance during the turnaround twice every revolution:
And now, another truly telling graph, the longer the rod ratio, the lower the assymetry in the motion. A 1.7:1 rod ratio is often said to be the "perfect" rod ratio because it is the shortest rod ratio which gets rid of the "hump" in the accelleration graph.
Hope this has been enlightening at least!
Cheers,
-Adrian
Last edited by SaabTuner; Jul 20, 2005 at 10:37 AM.
I always head about the 1.7 rod ratio being the best, but never truely understood why, now I do! That's awesome....
So in your opinion, even on a built motor/stroker motor, having the factory balance shafts there and not tuned to the geometry of the stroker motor is still better than not having them there at all?
- Steve
So in your opinion, even on a built motor/stroker motor, having the factory balance shafts there and not tuned to the geometry of the stroker motor is still better than not having them there at all?
- Steve
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From: Davis, California
Originally Posted by SuperHatch
I always head about the 1.7 rod ratio being the best, but never truely understood why, now I do! That's awesome....
So in your opinion, even on a built motor/stroker motor, having the factory balance shafts there and not tuned to the geometry of the stroker motor is still better than not having them there at all?
- Steve
So in your opinion, even on a built motor/stroker motor, having the factory balance shafts there and not tuned to the geometry of the stroker motor is still better than not having them there at all?
- Steve
But, I think the car will be much nicer to drive day to day with them in, especially with a stroker which will vibrate even worse. But, that's totally subjective. If you like a smooth-running engine, I reccomend keeping them, especially with a stroker. That's just my two cents.
-Adrian
p.s. It's definitely cool to know why the 1.7:1 is considered "ideal"! However, longer rod ratios are still slightly smoother the longer they are. It's just that you have a lot to gain by going from 1.5:1 up to 1.7 or so (1.64:1 isn't too bad). But when you go beyond 1.7:1, the gain in smoothness is much smaller compared to the additional weight in the rods.
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I removed my balance shafts on my Eclipse with an Evo III 16G. The turbo spools to 15psi by 3000RPMs. Absolutely no problems with extra knock showing up. Even if there was, I could turn it off at that RPM. There is a little more vibration.
But the liability of leaving the balance shafts in the engine makes removing them a very attractive option. If your engine is running at 7500RPM, the balance shafts are spinning at 15,000RPM! Screw that! It isn't at all rare to hear about high milage DSMs shreading their balance shaft belts, sending rubber bits into the timing belt. It also isn't rare to hear of the balance shafts wearing out their bearings and sending powdered bearing material to the rest of the block. Bad stuff. Remove them and you get a more reliable car.
There is a little more vibration. But the liability of leaving the balance shafts in the engine makes removing them a very attractive option. If your engine is running at 7500RPM, the balance shafts are spinning at 15,000RPM! Screw that! It isn't at all rare to hear about high milage DSMs shreading their balance shaft belts, sending rubber bits into the timing belt. It also isn't rare to hear of the balance shafts wearing out their bearings and sending powdered bearing material to the rest of the block. Bad stuff. Remove them and you get a more reliable car.
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From: Davis, California
Originally Posted by ShapeGSX
I removed my balance shafts on my Eclipse with an Evo III 16G. The turbo spools to 15psi by 3000RPMs. Absolutely no problems with extra knock showing up. Even if there was, I could turn it off at that RPM. There is a little more vibration. .
There is a little more vibration. .If the stock system leaves a large enough margin, there would be no appreciable difference in removing the shafts. But I wonder how the "SMART" system would react to second-order vibrations and if there would be noticably more "noise" in the signal.
Hey, Shiv, if you ever tune someone's car without balance shafts using the new "SMART" system, I'm sure lots of people would be very interested to know the impact of second-order vibrations on knock sensing.
-Adrian