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High Accuracy Degree Wheel
- Thread starter posplayr
- Start date
Ray!
R
reddirtrider
Guest
That is exactly what I'm saying and it's something you didn't do.
For instance, what are the manufacturing tolerances associated with the camshafts? How close can you physically get the crank to the intended mark on the degree wheel given the stiction and friction associated with moving this part? I asked those questions early on, and what do I get in response?
Exactly, more bull****.
I mentioned 2, and yes TDC would be another.Nobody quantifies all error sources, so maybe you mean that there is a significant error source I have missed? Don't say TDC.
I'm sure you can, I just haven't seen it in it's entirety.
By saying my comments are uneducated? I thought you didn't need to denigrate me? That didn't last long.
More denigration.
I like technical discussions, particularly if you can address the points I made.
You got one right.
R
reddirtrider
Guest
Let me try to lay out my concerns.
Yes, you've improved the accuracy of the reading by an uncertain amount. That would be the accuracy of reading with a pointer vs. using your razor blade. That isn't in contention. What you haven't done is given any figure for this improvement taking all relevant tolerances into consideration.
Next, unless this is the only parameter in this system that has tolerances and whose deviation might affect the performance parameter of interest (the relationship between the crank and cams) then we must take into consideration these other factors to determine what role they play.
To sum it up, you can continue to improve the measurement accuracy, but there will come a time when no matter how much that parameter is improved it has no effect on the overall performace of the system. That is what I'm trying to find out. Have we reached that point? Where is that point?
Yes, you've improved the accuracy of the reading by an uncertain amount. That would be the accuracy of reading with a pointer vs. using your razor blade. That isn't in contention. What you haven't done is given any figure for this improvement taking all relevant tolerances into consideration.
Next, unless this is the only parameter in this system that has tolerances and whose deviation might affect the performance parameter of interest (the relationship between the crank and cams) then we must take into consideration these other factors to determine what role they play.
To sum it up, you can continue to improve the measurement accuracy, but there will come a time when no matter how much that parameter is improved it has no effect on the overall performace of the system. That is what I'm trying to find out. Have we reached that point? Where is that point?
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Let me clue you 2 sixth graders in on something, even being an entire DEGREE off on where you are trying to set the cams will have LITTLE affect on the engine's power!!! Hello?!!! do you 2 GET it?!!! LOL!!!!
Measure with a micrometer, mark it with a piece of chalk, and cut it with a chainsaw! Ray.
Measure with a micrometer, mark it with a piece of chalk, and cut it with a chainsaw! Ray.
R
reddirtrider
Guest
Which reminds me, we need a target for our performance parameter. This sixth grader and his pointer is capable of that.
B
Billy Ricks
Guest
1 degree out of 360 is just a little over .25%, not much and probably far less than tolerances from the factory. Probably wouldn't make but about 1 hp of difference if that.
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H
hp1000s
Guest
Measure with a micrometer, mark it with a piece of chalk, and cut it with a chainsaw! Ray.[/QUOTE]
Ha! Nice one...*That's all well-and-good, as long as the chalk has been sharpened to a suitably accurate point.* "I've told you a million times to not exaggerate"
Hugh
Ha! Nice one...*That's all well-and-good, as long as the chalk has been sharpened to a suitably accurate point.* "I've told you a million times to not exaggerate"
Hugh
Wheel of Fortune
Wheel of Fortune
However, you are also the main reason that I pursued this crusade to improve degree wheel read out accuracy.
There has been numerous times that you have posted here at GS resources to use an 18" degree wheel v.s. the smaller ones. You have told it to me personally at least three times and the last time you urged me was prior to buying those new 0.340 webcams (last week was it?). I had to debate about spending another $60 to get a larger degree wheel and having to pull my case savers off the engine in order to mount such a large wheel.
In addition, when I was at your house (last year) and you were degreeing my cams using the big 18" wheel , you asked me to read off an angle. I gave you my reading, and apparently not trusting me you came to my side of the engine to read it yourself. You said "no it's not you are 1 degree off". I did not argue as it is clear that depending upon where you stand you can get significant variation in readout.
So if I can be a degree off on an 18" wheel , all things being equal, I would be 2 degrees off with an 8" wheel.
Truth be told, the above was the deciding factor in my pursuit of better readout accuracy. To summaries:
a.) Rapid Rays insistence that 18" degree wheels are better than smaller ones "I don't mess around" to quote him. I'm not in anyway challenging his experience with respect to this benefits of the 18" wheel.
b.) The first hand experience at RapidRay's where he and I were reading the same wheel at the same setting and getting an answer that was a full 1 degree different.
What may not be obvious here and the reason I separated these two reasons, is that while b.) above is directly related to readout accuracy alone, a.) above relates to how the degreeing process improves due to improved accuracy. The first relates more to how the reduction in read out errors, improves measurement repeatability and insures that the final cam settings are within acceptable tolerances with fewer trials.
As I recall that day, we were within about 0.25 degrees on intake and about 0.75 degrees on the exhaust. As should be obvious there are measured quantities.
Pos
Wheel of Fortune
I know your are a funny guy.
However, you are also the main reason that I pursued this crusade to improve degree wheel read out accuracy.There has been numerous times that you have posted here at GS resources to use an 18" degree wheel v.s. the smaller ones. You have told it to me personally at least three times and the last time you urged me was prior to buying those new 0.340 webcams (last week was it?). I had to debate about spending another $60 to get a larger degree wheel and having to pull my case savers off the engine in order to mount such a large wheel.
In addition, when I was at your house (last year) and you were degreeing my cams using the big 18" wheel , you asked me to read off an angle. I gave you my reading, and apparently not trusting me you came to my side of the engine to read it yourself. You said "no it's not you are 1 degree off". I did not argue as it is clear that depending upon where you stand you can get significant variation in readout.
So if I can be a degree off on an 18" wheel , all things being equal, I would be 2 degrees off with an 8" wheel.
Truth be told, the above was the deciding factor in my pursuit of better readout accuracy. To summaries:
a.) Rapid Rays insistence that 18" degree wheels are better than smaller ones "I don't mess around" to quote him. I'm not in anyway challenging his experience with respect to this benefits of the 18" wheel.
b.) The first hand experience at RapidRay's where he and I were reading the same wheel at the same setting and getting an answer that was a full 1 degree different.
What may not be obvious here and the reason I separated these two reasons, is that while b.) above is directly related to readout accuracy alone, a.) above relates to how the degreeing process improves due to improved accuracy. The first relates more to how the reduction in read out errors, improves measurement repeatability and insures that the final cam settings are within acceptable tolerances with fewer trials.
As I recall that day, we were within about 0.25 degrees on intake and about 0.75 degrees on the exhaust. As should be obvious there are measured quantities.
Pos
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B
Billy Ricks
Guest
You can get different readings by using one eye versus the other. Most people have a dominant eye, it's what makes shooters and baseball hitters be a lefty or a righty.
Red
Red
I appreciate your improved tone, so I will try and answer in like kind.
From the above you have expressed a general concern for the diminishing return on "performance" improvement as a function of degree wheel accuracy. Well yes it should go without saying that my top speed of my GS will not keep increasing to the speed of light if I make my degree wheel ever more accurate. This is an absurd example to illustrate the point. This may sound sarcastic but should serve to reinforce your point and which should be pretty obvious.
So to if I might refine your question into something more specific, the main questions are :
1.) How accurately should your cams be set (physical accuracy relative to the pistons)
2.) How accurate (with respect to the dial indicator) does your dial indicator readout out need to be to achieve the accuracy in 1.).
3.) Are there any other relevant factors that effect the accuracy in 1.)?
The answer to 1.) is a "it depends" answer so there is no single answer. If you are happy with stock then live with stock tolerances which are probably +/-3 degrees of nominal (say 106/106 degrees for example). No other action requried.
If you are a drag racer, you probably want to get within 0.5 degrees (my guess). Hey Ray how accurate do you try and get on a built motor?
If you ride on the street and just spent $1500 for a top end rebuild on a $2000 bike then you probably want to at least follow the cam manufacturer's recommendations for degreeing the cams (somebody call my name?).
Since for my Web cams that is 105/107 degrees as opposed to Bill's bike which is 110/110 I'm figuring close to 0.5 degrees off is good enough for me, 0.75 will not kill anything. If it comes up 108 and the spec is 107 I will try harder and get closer.
As to the answer for question #2, if you want to be able to determine where your cam is set with respect to your TDC reference in one pass to within +/- 0.25 degrees then you are going to have to measure to within +/-0.18 = (0.25/1.41) . That is because you need two measurements to measure a lobe center and have two errors associated with each.
Determining Physical accuracy (with respect to measured TDC) of +/- 0.5 degrees requires:
an estimate (average of two points) with uncertainty of about +/-0.25
which requires individual measurement accuracy of approximately +/-0.18 degrees.
If your TDC is also in error it will only serve to increase the absolute error of the cam lobe timing with respect to the physical TDC. Of course this is only the TDC of cylinder #1 only and if you have a twisted crank then cam timing of the other cylinder will be off even further.
A crank from a 3" stroke motor will be out by about 0.026" from nominal with a 1 degree twist.
I don't know how tightly cams are ground but a 0.002" error at 1.5" radius is .15 degrees on the crank.
One might be well advised when degreeing your cam to check for crank twist by degreeing #1 cylinder and insuring that #4 is the same. As per the calculation above, if it is not you can likely attribute that to crank twist.
Finally the question #3, what else effects the overall accuracy of cam timing with respect to TDC.
First let me dismiss two of the sources you referred to namely stiction and friction. Stiction is a type of friction so I'll assume you mean dynamic friction; friction involving forces that oppose dynamic or actual movement. Since all measurements are performed statically, no dynamic friction is even present during the measurements. If you are talking about differential friction on main bearings causing differential loads which twist the crank when in operation than let me refer you to the section on "the price of cheese in Denmark"
.
Realistically the best that can be done is to statically degree the cams. For that purpose dynamic friction has no bearing because the measurement is performed statically. As far as stiction is concerned, if anything this actually might help the measurement process. As the crank is set to a position it would tend to cause the engine to "set" and not move once the force from the wrench turning the engine was released. In a recent session I noticed that a movement of 0.5 degree (Bill at the wrench) ,would retrace to about 0.25 degrees. With the raser blade accuracy this was easy to see and what helped insure repeatability of what was going on.
Getting back to relevant topics, the only primary factor effecting the ability to degree the cam relative to TDC is in fact the determination of TDC itself. The angular accuracy of the TDC determination is based on two primary factors alone.
3.) How accurately the TDC can be measured by the degree wheel, and
4.) How accurately the piston height translates into a fixed TDC rotation.
For the answer to #3 see the answer to #2.
The answer to #4 is the subject of the "High Accuracy Piston Stop" how to.
Red,
I will not be the least bit surprised if you will be unsatisfied with the above explanation. I don't know if it will be simply to reinforce an argument that cam timing accuracy is irrelevant or if your objections will derive from an inability to limit the sope of the discussion to questions that can be answered v.s. those that can't. Regardless of which, I've done about all of the foundational work I care to to justify the pursuit of increasing degree wheel accuracy.
Pos
Red
I appreciate your improved tone, so I will try and answer in like kind.
From the above you have expressed a general concern for the diminishing return on "performance" improvement as a function of degree wheel accuracy. Well yes it should go without saying that my top speed of my GS will not keep increasing to the speed of light if I make my degree wheel ever more accurate. This is an absurd example to illustrate the point. This may sound sarcastic but should serve to reinforce your point and which should be pretty obvious.
So to if I might refine your question into something more specific, the main questions are :
1.) How accurately should your cams be set (physical accuracy relative to the pistons)
2.) How accurate (with respect to the dial indicator) does your dial indicator readout out need to be to achieve the accuracy in 1.).
3.) Are there any other relevant factors that effect the accuracy in 1.)?
The answer to 1.) is a "it depends" answer so there is no single answer. If you are happy with stock then live with stock tolerances which are probably +/-3 degrees of nominal (say 106/106 degrees for example). No other action requried.
If you are a drag racer, you probably want to get within 0.5 degrees (my guess). Hey Ray how accurate do you try and get on a built motor?
If you ride on the street and just spent $1500 for a top end rebuild on a $2000 bike then you probably want to at least follow the cam manufacturer's recommendations for degreeing the cams (somebody call my name?).
Since for my Web cams that is 105/107 degrees as opposed to Bill's bike which is 110/110 I'm figuring close to 0.5 degrees off is good enough for me, 0.75 will not kill anything. If it comes up 108 and the spec is 107 I will try harder and get closer.
As to the answer for question #2, if you want to be able to determine where your cam is set with respect to your TDC reference in one pass to within +/- 0.25 degrees then you are going to have to measure to within +/-0.18 = (0.25/1.41) . That is because you need two measurements to measure a lobe center and have two errors associated with each.
Determining Physical accuracy (with respect to measured TDC) of +/- 0.5 degrees requires:
an estimate (average of two points) with uncertainty of about +/-0.25
which requires individual measurement accuracy of approximately +/-0.18 degrees.
If your TDC is also in error it will only serve to increase the absolute error of the cam lobe timing with respect to the physical TDC. Of course this is only the TDC of cylinder #1 only and if you have a twisted crank then cam timing of the other cylinder will be off even further.
A crank from a 3" stroke motor will be out by about 0.026" from nominal with a 1 degree twist.
I don't know how tightly cams are ground but a 0.002" error at 1.5" radius is .15 degrees on the crank.
One might be well advised when degreeing your cam to check for crank twist by degreeing #1 cylinder and insuring that #4 is the same. As per the calculation above, if it is not you can likely attribute that to crank twist.
Finally the question #3, what else effects the overall accuracy of cam timing with respect to TDC.
First let me dismiss two of the sources you referred to namely stiction and friction. Stiction is a type of friction so I'll assume you mean dynamic friction; friction involving forces that oppose dynamic or actual movement. Since all measurements are performed statically, no dynamic friction is even present during the measurements. If you are talking about differential friction on main bearings causing differential loads which twist the crank when in operation than let me refer you to the section on "the price of cheese in Denmark"
.Realistically the best that can be done is to statically degree the cams. For that purpose dynamic friction has no bearing because the measurement is performed statically. As far as stiction is concerned, if anything this actually might help the measurement process. As the crank is set to a position it would tend to cause the engine to "set" and not move once the force from the wrench turning the engine was released. In a recent session I noticed that a movement of 0.5 degree (Bill at the wrench) ,would retrace to about 0.25 degrees. With the raser blade accuracy this was easy to see and what helped insure repeatability of what was going on.
Getting back to relevant topics, the only primary factor effecting the ability to degree the cam relative to TDC is in fact the determination of TDC itself. The angular accuracy of the TDC determination is based on two primary factors alone.
3.) How accurately the TDC can be measured by the degree wheel, and
4.) How accurately the piston height translates into a fixed TDC rotation.
For the answer to #3 see the answer to #2.
The answer to #4 is the subject of the "High Accuracy Piston Stop" how to.
Red,
I will not be the least bit surprised if you will be unsatisfied with the above explanation. I don't know if it will be simply to reinforce an argument that cam timing accuracy is irrelevant or if your objections will derive from an inability to limit the sope of the discussion to questions that can be answered v.s. those that can't. Regardless of which, I've done about all of the foundational work I care to to justify the pursuit of increasing degree wheel accuracy.
Pos
This is easily rectified by placing one eye ball or the another onto a tripod ^o
D
doctorgonzo
Guest
God will you guys stop tempting me to degree my cams. I have to reinstall the whole top end of my motor anyway so I could get a degree wheel... NO!!!!!
G
Guest
Guest
You really should degree in your cams.
S
Suzuki_Don
Guest
You really should degree in your cams.
Yeah! But who's going to show me how to do it?
G
Guest
Guest
Fly me over.
S
Suzuki_Don
Guest
Fly me over.
I would if I wasn't on the breadline.
S
Suzuki_Don
Guest
Any better offers than an 18" degree wheel and a piece of bent wire.
P
paco13
Guest
I think you guy's are all crazy. I decided to see what all the fuss is about and hooked up 2 temperature senders, one on each cam end, and there is no way they run close to 107/109 degrees. My bike still runs fine.
J