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Yoshimura RS2 Dyno Testing Facts

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I hear people saying this and that about exhaust systems. Are you just buying a different sound? Are you "factually" getting better performance? Are you saving weight? over the next few days I'm going to post the Dyno test readings. I have a 2016 XR 650L and I purchased a Yoshimura RS2 Slip On. I'm being told that the HP could vary between 1 or 2 hp. One reason is the type of rear tire being used because the Dynotest is measured to the wheel. Nobbies and street tires test differently. The engine itself produces 41.5 hp and 37.6 ft/lb torque @ 6000 RPM. My bike with the stock exhaust and rear knobbie is producing 37.9 hp and 33.8 ft/lbs at 6000 RPM to the wheel. The Yoshi weighs about 1/2 pound less and the quality looks real good. Once I install the system, open the airbox, rejet the carb a couple times until I get it right, then I will post the actual scientific results. I'll check back with you guys on Tuesday. Wish me luck and pray that I don't grenade my engine on the Dynamometer!

 

 

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5 hours ago, Butkus said:

...The engine itself produces 41.5 hp and 37.6 ft/lb torque @ 6000 RPM....

How did you test that to get those numbers?  I've tested 3 over the past couple years, though none were as new as yours, and none of them came anywhere close to that horsepower number.  Torque numbers don't seem too far off.

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How did you test that to get those numbers?  I've tested 3 over the past couple years, though none were as new as yours, and none of them came anywhere close to that horsepower number.  Torque numbers don't seem too far off.

I just looked up the factory spec but not to the wheel.

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19 minutes ago, Butkus said:


I just looked up the factory spec but not to the wheel.

Is that listed in the owner's manual?  I've never had one.  Lol.  

 

Either way, as you probably already know, that number won't mean much to you and your dyno run but it's interesting to see they rate it that high.  I'd like to know if that's theoretical or actually tested at the output shaft.  But then, I'd like to know a whole lot of things about the bike that Honda won't tell the public.  I wrote them to ask what type of steel they use on the L's frame and they wouldn't (or couldn't) tell me.

Edited by Hollerhead

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59 minutes ago, Hollerhead said:

How did you test that to get those numbers?  I've tested 3 over the past couple years, though none were as new as yours, and none of them came anywhere close to that horsepower number.  Torque numbers don't seem too far off.

Here's the dyno chart for mine a year or two ago.  It has a 675cc piston and 10.5:1 compression, and the usual carburetor, airbox, and pipe mods.  41.6 at the rear wheel.  The top chart is a similar bike of the same year and everything, but with a stock piston.DynoCharts_zpsjumjy6px.jpg

Edited by ScottRNelson
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6 hours ago, Butkus said:

I hear people saying this and that about exhaust systems. Are you just buying a different sound? Are you "factually" getting better performance? Are you saving weight?

Most riders believe they are getting more HP because of the different sound and the 500g weight saved   :bonk:

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Wow ScottN, I wouldn't have thought that much difference.

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1 hour ago, ScottRNelson said:

... 41.6 at the rear wheel...

It is not shown that way if I'm reading what I think I am.  I can't zoom in and read it very will but it looks like it shows the SAE .85 correction is being applied. If that is listed in the details at the bottom it means that a mechanical efficiency correction was applied to actual measurements.  This means that the power numbers shown are the estimated crankshaft power.  Based on using the common 85% correction, the actual power measured at the wheel would have been 35.36 hp.  

Also, dyno pulls should be done with the transmission in its 1:1 ratio.  Based on top speed shown, yours looks like was pulled in 5th gear so, if it had been ran in 4th, yours would have more power than is shown.  That is unless you're running a higher final drive sprocket ratio and it'll go that fast in 4th.

I'll throw out that I've never operated a Dynojet dyno, setup their software, or printed out their charts so all that gibberish above may be all wrong.:lol:

Edited by Hollerhead
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20 minutes ago, Hollerhead said:

Also, dyno pulls should be done with the transmission in its 1:1 ratio.  Based on top speed shown, yours looks like was pulled in 5th gear so, if it had been ran in 4th, yours would have more power than is shown.  That is unless you're running a higher final drive sprocket ratio and it'll go that fast in 4th.

I'll throw out that I've never operated a Dynojet dyno, setup their software, or printed out their charts so all that gibberish above may be all wrong.:lol:

The guys making this particular set of dyno runs were doing it for free as a service to the local motorcycle community (plus some free advertising).  They ran every bike in 5th gear and they didn't keep track of engine speed on any of them.  I don't know how it works, but I'm pretty sure they didn't do the corrections you're postulating about.

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I hear people saying this and that about exhaust systems. Are you just buying a different sound? Are you "factually" getting better performance? Are you saving weight? over the next few days I'm going to post the Dyno test readings. I have a 2016 XR 650L and I purchased a Yoshimura RS2 Slip On. I'm being told that the HP could vary between 1 or 2 hp. One reason is the type of rear tire being used because the Dynotest is measured to the wheel. Nobbies and street tires test differently. The engine itself produces 41.5 hp and 37.6 ft/lb torque @ 6000 RPM. My bike with the stock exhaust and rear knobbie is producing 37.9 hp and 33.8 ft/lbs at 6000 RPM to the wheel. The Yoshi weighs about 1/2 pound less and the quality looks real good. Once I install the system, open the airbox, rejet the carb a couple times until I get it right, then I will post the actual scientific results. I'll check back with you guys on Tuesday. Wish me luck and pray that I don't grenade my engine on the Dynamometer!
 

 

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Unless you use the same dyno, the same day, run by the same guy, at the same temp, and about 6 other factors,  the measurments are not comparable.

That, and, dyno results are for wide open throttle only.  Does not tell you anything about partial throttle, which is where you are riding 99% of the time.

A dyno is just a tuning tool, and does not create absolute measurments of anything.

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Unless you use the same dyno, the same day, run by the same guy, at the same temp, and about 6 other factors,  the measurments are not comparable.
That, and, dyno results are for wide open throttle only.  Does not tell you anything about partial throttle, which is where you are riding 99% of the time.
A dyno is just a tuning tool, and does not create absolute measurments of anything.

Buzz Kill.

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9 hours ago, Krannie McKranface said:

Unless you use the same dyno, the same day, run by the same guy, at the same temp, and about 6 other factors,  the measurments are not comparable.

That, and, dyno results are for wide open throttle only.  Does not tell you anything about partial throttle, which is where you are riding 99% of the time.

A dyno is just a tuning tool, and does not create absolute measurments of anything.

Dyno data can vary greatly and, I also believe, they really are designed to be a tuning tool but they do measure absolutes in a very accurate manner.  They get a bad rap because of lack of understanding.  They absolutely measure how fast the bike can accelerate the dyno's drum.  They can also accurately measure the bike's RPM.  Lots of things can be calculated, with very good accuracy, from this information.  There are certainly operators in the industry that intentionally manipulate settings to get extra money out of customers.  I've known a few and I've seen it happen.  

All that stuff you mention certainly can be true, and is commonly an issue, but doesn't have to be.  We don't have the information we need to know how accurate the numbers shown on those charts really are.  Knowing the software setup and calibration is the only way for us to really know.  But then, we'd have to understand how to interpret those software setups.  If setup is done accurately and correctly the operator, other than rolling the throttle and hitting the go and stop button to record data, doesn't matter much after that and the output is very accurate and comparable.  

Using the software's SAE correction shown at the top of his chart, the software normalizes for changes in temperature, humidity, and pressure on different days and locations.  If two sets of numbers both use SAE corrections then the data is comparable.  The high level of smoothing chosen on his run just makes the chart prettier but doesn't actually affect minimums, maximums, and the overall shape of the curve, or the data file from the run.  Though the power of his was definitely determined at the rear wheel I can't tell whether the curve shown represents that measurement or if it is estimated brake horsepower so, when compared to someone else's data, it'd be hard to tell whether it is a fair comparison.  This is where the dyno bragging right game gets shaky.  Power at either location can be displayed on the chart.  The brake horsepower is always an estimate with a wheel dyno and is easily swayed by the efficiency correction used.  Most common is to choose 85%, or .85 which is what I think I see listed in the run data at the bottom of his chart, but that's just a guess.   

Also, dynos are not for wide open throttle only.  It may be true that they don't all have the ability to control the bike's RPM but, if properly setup, all dyno's data is going to be accurate from the start of the pull to wide open throttle.  Inertia only dynos just won't have the ability to tune at a requested RPM.  Again, the details of their dyno aren't shown but Dynojet makes several load control dynos that can add any load desired and can hold the bike at an certain RPM to determine power exactly there.  They may have one of those models.  Load control dynos can give accurate data and any throttle position on demand.  These guys didn't monitor RPM and it is the reason they don't list, any torque numbers.  Accurately knowing engine RPM is the only way torque can be calculated on a dyno.  The fact that the charts above show no RPM information or torque leads me to believe that the dyno is probably not properly setup.

I'll be interested to Butkus' before and after numbers but probably won't be comparing them to anyone else's and I won't be comparing his numbers to the published specs.  

Edited by Hollerhead
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Dyno data can vary greatly and, I also believe, they really are designed to be a tuning tool but they do measure absolutes in a very accurate manner.  They get a bad rap because of lack of understanding.  They absolutely measure how fast the bike can accelerate the dyno's drum.  They can also accurately measure the bike's RPM.  Lots of things can be calculated, with very good accuracy, from this information.  There are certainly operators in the industry that intentionally manipulate settings to get extra money out of customers.  I've known a few and I've seen it happen.  
All that stuff you mention certainly can be true, and is commonly an issue, but doesn't have to be.  We don't have the information we need to know how accurate the numbers shown on those charts really are.  Knowing the software setup and calibration is the only way for us to really know.  But then, we'd have to understand how to interpret those software setups.  If setup is done accurately and correctly the operator, other than rolling the throttle and hitting the go and stop button to record data, doesn't matter much after that and the output is very accurate and comparable.  
Using the software's SAE correction shown at the top of his chart, the software normalizes for changes in temperature, humidity, and pressure on different days and locations.  If two sets of numbers both use SAE corrections then the data is comparable.  The high level of smoothing chosen on his run just makes the chart prettier but doesn't actually affect minimums, maximums, and the overall shape of the curve, or the data file from the run.  Though the power of his was definitely determined at the rear wheel I can't tell whether the curve shown represents that measurement or if it is estimated brake horsepower so, when compared to someone else's data, it'd be hard to tell whether it is a fair comparison.  This is where the dyno bragging right game gets shaky.  Power at either location can be displayed on the chart.  The brake horsepower is always an estimate with a wheel dyno and is easily swayed by the efficiency correction used.  Most common is to choose 85%, or .85 which is what I think I see listed in the run data at the bottom of his chart, but that's just a guess.   
Also, dynos are not for wide open throttle only.  It may be true that they don't all have the ability to control the bike's RPM but, if properly setup, all dyno's data is going to be accurate from the start of the pull to wide open throttle.  Inertia only dynos just won't have the ability to tune at a requested RPM.  Again, the details of their dyno aren't shown but Dynojet makes several load control dynos that can add any load desired and can hold the bike at an certain RPM to determine power exactly there.  They may have one of those models.  Load control dynos can give accurate data and any throttle position on demand.  These guys didn't monitor RPM and it is the reason they don't list, any torque numbers.  Accurately knowing engine RPM is the only way torque can be calculated on a dyno.  The fact that the charts above show no RPM information or torque leads me to believe that the dyno is probably not properly setup.
I'll be interested to Butkus' before and after numbers but probably won't be comparing them to anyone else's and I won't be comparing his numbers to the published specs.  

You will have all this information by Tuesday. I also can't wait to see it.
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It has already been mentioned.  But dyno numbers are 100% relative.  One dyno to the next even the same brand of dyno you are going to get a different number.  Folks are so concerned about dyno numbers and how theirs stacked up against joe blows off the forums,  When in reality it means nothing.    What means something is one run to the next on the same machine and bike after changes are made.  No doubt it will make better power once you open it up.   No doubt at all,  It can't do anything but run better unrestricting your exhaust from a exhaust outlet of 1/2" to straight through pipe.  Looking forward to seeing real results.

Edited by Pat4wd
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I hear people saying this and that about exhaust systems. Are you just buying a different sound? Are you "factually" getting better performance? Are you saving weight? over the next few days I'm going to post the Dyno test readings. I have a 2016 XR 650L and I purchased a Yoshimura RS2 Slip On. I'm being told that the HP could vary between 1 or 2 hp. One reason is the type of rear tire being used because the Dynotest is measured to the wheel. Nobbies and street tires test differently. The engine itself produces 41.5 hp and 37.6 ft/lb torque @ 6000 RPM. My bike with the stock exhaust and rear knobbie is producing 35.9 hp to the wheel. The Yoshi weighs about 1/2 pound less and the quality looks real good. Once I install the system, open the airbox, rejet the carb a couple times until I get it right, then I will post the actual Dyno results. I'll check back with you guys on Tuesday. Wish me luck and pray that I don't grenade my engine on the Dynamometer!
 

 

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I hear people saying this and that about exhaust systems. Are you just buying a different sound? Are you "factually" getting better performance? Are you saving weight? over the next few days I'm going to post the Dyno test readings. I have a 2016 XR 650L and I purchased a Yoshimura RS2 Slip On. I'm being told that the HP could vary between 1 or 2 hp. One reason is the type of rear tire being used because the Dynotest is measured to the wheel. Nobbies and street tires test differently. The engine itself produces 41.5 hp and 37.6 ft/lb torque @ 6000 RPM. My bike with the stock exhaust and rear knobbie is producing 36.72 hp to the wheel. The Yoshi weighs about 1/2 pound less and the quality looks real good. Once I install the system, open the airbox, rejet the carb a couple times until I get it right, then I will post the actual scientific results. I'll check back with you guys on Tuesday. Wish me luck and pray that I don't grenade my engine on the Dynamometer!
 

 



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IMG_3588.thumb.JPG.195ff6ff540726a81ad7cdd13c2ac39b.JPGIMG_3590.thumb.JPG.e51a67b5602065d5aee3b46b4bff0589.JPG

I picked up 3 hp, a beautiful throttle response, and an awesome sound! Removed air snorkel, stock air filter, and 165/58 jetting. So, those are the facts and I'm very pleased.
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