Simulated FJR vs C14 race

[MCRIDER007]

Did some more searching on the effects of RAM air and found this: https://www.sportrider.com/tech/146_9912_ram/index.html

Looks like the effects are not very predictable based on speed, but it also looks like the gains are only in the 6% range. I could work something into my simulation to at least attempt a vague guestimate of how the RAM air will help. I would have to make some assumption like 6% gain at 150mph to determine the gain at any speed. I'm not sure if it should be proportional to speed, or to the square of speed.

The best test that Sport Rider did on the Kawasaki ram air systems can be read at: https://www.sportrider.com/tech/146_9508_ram/index.html and it seems to be very predictable based on speed, especially above 90 mph...and a 6-8 percent gain can have quite an effect. That article summarized ram air with this statement:

"Having said that, the effects of even small amounts of boost on throttle response haven't really been investigated and may help to explain some of the surging acceleration typical of big Kawasakis.

It does, however, clarify the impressive figures that Kawasakis deliver at the strip and explain why a ZX-7 putting out the same power as a GSX-R on a static dyno will romp away under speed testing."

I can't say that I notice the ram air effect on the C14, but it is very noticeable on the ZX-14.

 

[FJR Bill]

I like the fact that Mr. Sour Pickles predicts a perfect run in the upper 10's on the FJR. Anything less than perfect but done well likely will be in the lower 11's. After buying my FJR I compared it's "feel" to my modded B12 Bandit and I estimated that the two would be damn close in the 1/4. My Best on the Bandit was 11.2 at 125 MPH. I'm convinced the FJR is very close to those numbers although I haven't put her on the drag strip. I'm really enjoying these computer models...they can only get better with time and tweeking.

Thanks, Bill

 

[carlson_mn]

I like the fact that Mr. Sour Pickles predicts a perfect run in the upper 10's on the FJR. Anything less than perfect but done well likely will be in the lower 11's. After buying my FJR I compared it's "feel" to my modded B12 Bandit and I estimated that the two would be damn close in the 1/4. My Best on the Bandit was 11.2 at 125 MPH. I'm convinced the FJR is very close to those numbers although I haven't put her on the drag strip. I'm really enjoying these computer models...they can only get better with time and tweeking.

Thanks, Bill

I also had a slightly modded B12. pod filters and pipe, really opened that thing up. I just sold it this fall actually.

On my last ride of the year this November I was with a friend who has a stock 03 B12. We lined them up at 40mph in 2nd gear and hit it at the same time. The bandit held close to about 60mph or so and then I just walked away pretty good from him. They're a quick bike though for old technology, probably faster than the EFI 1250.

You can tell it's December in the north with these discussions

 

[UselessPickles]

The best test that Sport Rider did on the Kawasaki ram air systems can be read at: https://www.sportrider.com/tech/146_9508_ram/index.html

Thanks for that link. The link I provided either didn't have a very good test procedure, or I just didn't read it carefully enough.

The link you provided shows that air box pressure approximately increases with the square of speed (which is what I expected since aerodynamic drag does the same), and the HP gain approximately increases linearly with air box pressure. That means the HP gain from RAM air approximately increases with the square of speed. All I need to know is the gain in HP (as a percentage) at any given speed from RAM air on a particular bike, and I can approximate the effects of RAM air at all speeds on that bike.

Now I just need to get that one data point for a C14.

BTW - I've also found another contributor to my simulations placing the C14 and FJR closer together than you expect. I had gotten my top speeds from 2 different sources for the 2 bikes, but then found a single source that reported a larger difference between the measured top speeds. Therefore, my aerodynamics were relatively wrong between the two bikes. After fixing this, there's an extra 0.1s and 15 feet of gap between the 2 bikes at the end of the 1/4 mile, so it's moving closer to your experiences (and closer to the 1/4 mile results from that same source of the top speeds). This also makes me wonder if the torque data I found for the C14 is just more pessimistically inaccurate than my FJR data. It might also have something to do with the fact that I only have C14 data points at every 1000rpm, but I have data for the FJR at every 100rpm.

Just a sobering reminder that no matter how correct a calculation is, the result is only as good as the data you put into it. What I really need is data for all bikes from a single source too keep the data as comparable as possible. Maybe I need to partner up with a motorcycle magazine to give them simulated results based on their data that they collect while testing the bikes

 

[UselessPickles]

Looks like RAM air doesn't have a huge effect in the 1/4 mile...

From that SportRider article about RAM air on the ZX9R, I calculated that they saw a 5.78% gain at 150mph. I simulated that same amount of gain on the C14 (scaled based on the square of speed). With an average weight rider, launching at peak torque, 0.32s shifts, etc., etc...

Without RAM gains: 10.869s @ 121.97mph

With RAM gains: 10.825s @ 123.19mph

It increases the trap speed more than it decreases the elapsed time, because all the extra acceleration from RAM air is near the end of the race. Here's some acceleration boost percentages for various speeds:

60mph: 0.92%

70mph: 1.26%

80mph: 1.64%

90mph: 2.08%

100mph: 2.57%

110mph: 3.11%

120mph: 3.70%

Only about the last half of the race (in terms of time) is at/above 90mph.

So the RAM air is unfortunately not the culprit for the discrepancy between my simulation and MCRIDER's and SportRider's observations, but it did make a difference, and I'm glad to be move closer and closer to an accurate simulation. Then again, even though SportRider shows a 0.4s difference between the two bikes, we have know idea how each bike was tested. Same, or different riders? How much did they weigh? What RPMs did they launch at on each bike? When did they shift? I could easily tweak these variables between the two bikes to replicate their results, but that's not the point.

I have discovered a flaw with my shift-point calculations: it assumes that the next gear is selected immediately with no change in speed. In real life (and my simulation), the shift takes time, and the bike decelerates during that time due to drag, so you end up at a lower speed/RPM in the next gear than my calculations assume. That's going to be quite a complex problem to solve. Like the RAM air, I expect it will make a slight difference, but it won't make up for the discrepancy in the FJR vs C14 comparison (especially since it will slightly improve the time for both bikes). For example, the shift from 3rd to 4th on the FJR is only dropping about 100 RPMs and 1mph lower than if it was an instant shift. The correct optimal shift point would probably be about 50 RPMs later, which won't make much of a difference.

I think I really need to obtain some better dyno data for the C14 with higher resolution and that is known to have SAE correction applied.

 

[MCRIDER007]

BTW - I've also found another contributor to my simulations placing the C14 and FJR closer together than you expect. I had gotten my top speeds from 2 different sources for the 2 bikes, but then found a single source that reported a larger difference between the measured top speeds. Therefore, my aerodynamics were relatively wrong between the two bikes.

One other item to confuse the issue. It appears that you have used each bike's respective top speed to calculate aerodynamic drag...but...the FJR is not geared to obtain maximum top speed. From what I have read, it has a top speed around 155 which would mean that it is pulling redline in top gear which is too low of gearing. To obtain maximum top speed, it should be geared to reach its maximum HP point in top gear, which I think is around 8,000 rpms. It will take longer to get to top speed (which I would guess would be between 160-163) with higher gearing but that is a better indicator of aerodynamic drag...and I think that the FJR does have much better aerodynamics than the C14 and would probably beat the C14 in top speed with the correct gearing.

 

[carlson_mn]

I suspect the Gen2 is capable of more than 155 based on its gearing, if it has the power to do it. I saw 158mph on my 04 on GPS. (~165 indicated). It was past redline but not sure exactly where, was not looking very closely. I have not done any high speed runs with my 08.

Rumor has it Wicked Webby saw over 170mph on his Gen2 speedo.

 

[HotRodZilla]

Pickles, why are you assuming that Sport Rider ran actual fair, equal tests? Lighter rider, less fuel, tons of factors could screw with their observations...I donno that I'd care much what a magazine reports.

Just a thought anyway.

 

[UselessPickles]

I calculated the aerodynamic drag coefficient (drag area) based on the amount of linear force produced by the rear wheel (engine torque multiplied by overall gearing reduction, divided by radius of tire) at the reported top speed. At the top speed, that force must be equal to the force caused by drag. I do this in every gear that can reach the reported top speed and use the largest result to deal with bikes like the C14, where top speed cannot be reached in top gear.

I rearrange the aerodynamic drag formula for the drag so that I can calculate the "drag area" from that force. Now I have the "drag area" coefficient for the bike and can calculate the force caused by drag at any speed.

Now it's also possible to calculate the max possible speed that a bike COULD go if it was geared optimally. Power is simply force multiplied by speed (one of its many definitions), so you can multiply the force of drag formula by speed and get a formula for power of drag (which involves the cube of speed now; force of drag is based on the square of speed). Rearrange the formula to calculate speed from power, then plug in the bike's peak power number. Now you know that IF the bike was geared to be at that speed while it's producing peak power, then that would be the max speed it ever be geared to attain.

One thing I'm not accounting for is the density of the air at the time that the reported top speed was measured. I'm assuming a "standard" air density. I could get more precise results if I knew the air temperature, pressure and humidity (or dew point) at the time the top speed was measured, but magazines don't provide this info. I could also use the same info to apply SAE correction to the torque/hp numbers used in calculations.

If anyone wants more details about these calculations, I can show all formulas used

 

[UselessPickles]

Interesting observation: temperature and humidity don't seem to have much of an effect on top speed.

I added air density calculations (affects drag) and SAE horsepower correction factor calculations based on air temp, pressure and humidity. Just from experimenting with a few combinations ranging from 60°F to 90°F and various humidity levels, the top speed reached in the simulation only varied by about 1mph. Looks like the extra power from the denser air cancels out the increased drag from denser air.

So if atmospheric conditions are not the cause for wildly varying top speed reports on bikes, then it must be other factors like indicated vs actual speed, wind, saddlebags on vs off, and slight uphill/downhill roads. For example, I've found reports of the C14's top speed ranging from 152mph to 168mph.

 

[HYCLE]

Looks like RAM air doesn't have a huge effect in the 1/4 mile...

From that SportRider article about RAM air on the ZX9R, I calculated that they saw a 5.78% gain at 150mph. I simulated that same amount of gain on the C14 (scaled based on the square of speed). With an average weight rider, launching at peak torque, 0.32s shifts, etc., etc...

Without RAM gains: 10.869s @ 121.97mph

With RAM gains: 10.825s @ 123.19mph

It increases the trap speed more than it decreases the elapsed time, because all the extra acceleration from RAM air is near the end of the race. Here's some acceleration boost percentages for various speeds:

60mph: 0.92%

70mph: 1.26%

80mph: 1.64%

90mph: 2.08%

100mph: 2.57%

110mph: 3.11%

120mph: 3.70%

Only about the last half of the race (in terms of time) is at/above 90mph.

My personal 1/4 mile run at Sacramento Raceway was showing 99.8 mph at the 1/8 mile mark and 116.4 at the 1/4 mile.

This is with a Gen 1 and 250 lb rider. I also have a +4 +2 windshield that causes more drag at high speed.

 

[FJR Bill]

In the aviation world performance is based on a standard atmosphere ie 15 degrees centigrade, baro pressure at 29.92 inches of mercury, and at sea level. I thought current dyno results are corrected to standard atmosphere yielding a valid comparison of tests. The same engine tested in Denver for example will differ greatly from one tested in Miami. But the differences can be caclulated to place both tests on an even playing field.

Bill

 

[UselessPickles]

Yup; that's what the SAE correction factor is intended for (as well as the several other engine power correction standards). The simple version of the formula for coming up with the correction factor (which is used by the typical dynos) makes many assumptions about the engine and its efficiency, so it's not perfect, but it's a fairly accurate estimate within certain temperature and pressure ranges.

There's two key pieces of info I need for an accurate simulation:

1) SAE corrected torque curve from a properly-calibrated dyno. Many dyno charts you find online from bike websites do not specify whether it is corrected, or what standard was used to correct it. Many of the images I find are too small for me to get precise measurements. Getting a hold of the original dyno run file is the best option, because I can open the file in a dyno run viewer program and export the raw data, rather than trying to take measurements from a graph.

2) The bike's "drag area" coefficient. This can be calculated from an observed top speed, as long as the top speed is limited by drag (rather than electronically limited), and the top speed run was made on a level road, adjusted for wind, and is an actual (not indicated) speed. Knowing the air temp/pressure/humidity could make the calculation more accurate, but it appears that these might not have a very significant impact on top speed anyway. Top speed reports found online vary too much to be trustworthy, and no one specifies weather conditions or whether they confirmed that the road was actually level.

For bikes with RAM air, there's a 3rd piece of info I need: the percentage increase in HP at some high speed as compared to the reading on a dyno at the same speed. This is probably the most complicated of the three.

 

[UselessPickles]

How's this for accuracy...?

I created a representation of the Yamaha FZ6R for my simulation (wife's bike). I forget where I got the torque data from, but it was an SAE-corrected torque chart. I got the top speed from Cycle World.

To compare to the rest of the Cycle World specs (0-60mph, 1/4 mile), I figured it would be more reasonable to assume the test rider weighed more along the lines of 170lbs, rather than the 204lbs I came up with based on the average weight of American men (I suspect the average weight of American men who ride motorcycles is lower than the overall average).

Cycle World's results:

0-60mph: 3.8s

1/4 mile: 12.26s @ 106.93mph

My simulation results:

0-60mph: 3.76s (rounds up to 3.8s)

1/4 mile: 12.26s @ 106.00mph

I'd say that's a good indication that I'm doing something right. I suspect that my simulation results will more closely match real results on less powerful bikes, because they are easier to launch near their full potential.

 

[UselessPickles]

To obtain maximum top speed, it should be geared to reach its maximum HP point in top gear, which I think is around 8,000 rpms. It will take longer to get to top speed (which I would guess would be between 160-163) with higher gearing

To obtain max speed, you calculate at what speed the power of drag is equal to the peak HP (at the wheel) of the bike. Then you gear the bike such that it will be at that speed in top gear when the RPMs are at the peak HP.

Luckily, the Gen II FJR is limited by drag (can't reach redline in 5th gear on a level road with no tail wind), so its drag area can be calculated, then the calculations I just described can be done.

I suspect the Gen2 is capable of more than 155 based on its gearing, if it has the power to do it. I saw 158mph on my 04 on GPS. (~165 indicated). It was past redline but not sure exactly where, was not looking very closely. I have not done any high speed runs with my 08.

Rumor has it Wicked Webby saw over 170mph on his Gen2 speedo.

Assuming the FJR has a top speed of 155mph (seems to be a common number)...

155mph occurs at 8300 RPMs in 5th gear. The bike develops 118.94* HP at that RPM. Peak HP is 121.20* @ 7700* RPM. If geared properly, that peak HP would make the bike capable of 155.97 mph. That would require the gearing to be about 8% taller, which would either reduce acceleration across the board, or require the gear ratios in the transmission to be spread across a wider range to retain acceleration in the lower gears (but still lose top-gear passing power). Not worth it for an extra 0.97mph.

The gearing of a Gen II FJR would get the bike up to 168mph at redline (9000 RPM) in 5th gear, but it would require 151.45 HP and 88.38 ft-lbs of torque at 9000 RPM!. Peak TQ is currently 86.62* ft-lbs at 6800* RPM.

*Note: all HP/TQ/RPM values are based on an SAE corrected dyno pull that I witnessed. The RPMs at which peak TQ and peak HP are slightly off from what Yamaha reports, but this this the data we got, so that's what I'm using.

 

[Bustanut joker]

Damned smart guys......My head just exploded. :blink:

 

[MCRIDER007]

Assuming the FJR has a top speed of 155mph (seems to be a common number)...

155mph occurs at 8300 RPMs in 5th gear. The bike develops 118.94* HP at that RPM. Peak HP is 121.20* @ 7700* RPM. If geared properly, that peak HP would make the bike capable of 155.97 mph. That would require the gearing to be about 8% taller, which would either reduce acceleration across the board, or require the gear ratios in the transmission to be spread across a wider range to retain acceleration in the lower gears (but still lose top-gear passing power). Not worth it for an extra 0.97mph.

The gearing of a Gen II FJR would get the bike up to 168mph at redline (9000 RPM) in 5th gear, but it would require 151.45 HP and 88.38 ft-lbs of torque at 9000 RPM!. Peak TQ is currently 86.62* ft-lbs at 6800* RPM.

I think your speeds vs. rpms are a bit high...my GEN II shows an actual (GPS) speed of 72-73 mph at 4,000 rpms. However, I don't know any way to verify if the tachometer is accurate at 4,000 rpms.

 

[UselessPickles]

RPM:speed ratio is correct as far as I can tell. This is all based on the gear ratios and the circumference of the rear tire. It will be a bit different with a new tire vs a worn tire, and probably even between different brands of tire.

I have a data logger on my bike, and I have confirmed that the data log's speed matches GPS speed at 75mph. It also logs RPM exactly as measured from the timing of the camshaft position sensor signal (no analog display to be inaccurate). I found a point in my data log at 75mph and 4004 RPM (5th gear).

[75mph] * [9000 RPM]/[4004 RPM] = 168.58mph

[75mph] * [8300 RPM]/[4004 RPM] = 155.47mph

 

[UselessPickles]

BTW... I would only need to wear down 2.7 millimeters of tread on my tire to cause a speed of 73mph at 4000 RPM as compared to my 75mph at 4000 RPM. 4.1 millimeters of wear would get me to 72mph.

 

[carlson_mn]

Assuming the FJR has a top speed of 155mph (seems to be a common number)...

155mph occurs at 8300 RPMs in 5th gear. The bike develops 118.94* HP at that RPM. Peak HP is 121.20* @ 7700* RPM. If geared properly, that peak HP would make the bike capable of 155.97 mph. That would require the gearing to be about 8% taller, which would either reduce acceleration across the board, or require the gear ratios in the transmission to be spread across a wider range to retain acceleration in the lower gears (but still lose top-gear passing power). Not worth it for an extra 0.97mph.

The gearing of a Gen II FJR would get the bike up to 168mph at redline (9000 RPM) in 5th gear, but it would require 151.45 HP and 88.38 ft-lbs of torque at 9000 RPM!. Peak TQ is currently 86.62* ft-lbs at 6800* RPM.

I think your speeds vs. rpms are a bit high...my GEN II shows an actual (GPS) speed of 72-73 mph at 4,000 rpms. However, I don't know any way to verify if the tachometer is accurate at 4,000 rpms.

Not sure on Gen2 but when I brought my netbook for a cruise with me the RPMs displayed on the power commander software were 3850rpms compared to an even 4k on the bike's tach.