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Author Topic: Team Go Dog, Go! Modified Partial Streamliners  (Read 1029689 times)

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Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #1365 on: September 21, 2013, 12:11:00 PM »
There are a bunch of dyno correction factors in use.  Some of the newer ones are more realistic.  They are more sophisticated about computing friction losses and they are based on standard atmospheric conditions we might experience.  Unfortunately, a lot of the info we have available, like on "airdensityonline," are based on the older standard atmosphere used for J607.

My feeling for a long time is that power losses due to increased altitude are more than those predicted by J607 or simply comparing air densities.  Air density comparison and similar methods like J607 assume the power loss is directly proportional to the amount of available oxygen.  Increasing altitude also lowers the compression ratio and this has a detrimental effect on performance.

Some recent looking around on the i-net dredged up this old study where folks looked at the effects of altitude and engine internal friction and pumping losses.  It is at www.naca.central.cranfield.ac.uk/reports/1929/naca-report-295.pdf  They used standard altitude.  I am assuming this corresponds to our modern concept of density altitude.

An old study where I know how they worked up the numbers beats a lot of the newer stuff where I do not, is this skeptical old bastid's opinion.  Based on a 5,800 foot average density altitude at B'ville durng BUB, the power correction factor is 0.81 using Curve E of the airplane study.

Educated second opinions on all of this are welcome.

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #1366 on: September 21, 2013, 12:15:58 PM »
I just tried the link.  It brings up the report index and not the report.  It is Report No. 295, "The Variation in Engine Power with Altitude Determined from Measurements in Flight with a Hub Dynamometer" by W.D. Gove. 

Offline fredvance

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #1367 on: September 21, 2013, 12:33:29 PM »
A friend of mine, who is way smarter than I am, says the you lose 1/2 point of compression for every 1000ft of altitude. That is why I start with about 16-1. :-D
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Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #1368 on: September 21, 2013, 12:44:46 PM »
Fred, are you running methanol?  Assuming 1500 feet DA in Belverde and 6,000 feet on the flats, that would be 4,500 feet difference.  16 - (4.5 x .5) = 13.7 to 1.

That link I gave you all is not very direct.  It brings you to a bunch of options.  Select "MAGiC NACA ARCHIVE."  Go to Citation #41 of year 1929.  There is a link to the paper there.     

Offline fredvance

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #1369 on: September 21, 2013, 01:09:36 PM »
I run ERC 110 in gas class and VP Q16 in Fuel class. The Busa does a lot of compensating for altitude, temp, etc. I am not sure what the etc is?? :roll: I have always run on my Dyno tune and it has worked well. My tuner says we are leaving some on the table. Next year we are going to try and put the 1660 bike on Scott Horners dyno in SLC.
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Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #1370 on: September 22, 2013, 01:37:48 AM »
The knock light I used this year worked great.  It flickered a bit and this showed me I was getting sporadic traces of out of control combustion.  This is with a 10.5 to 1 compression ratio and 110 octane leaded.  I am probably close to the limit on compression with this air-cooled twin.  Those Busa's are pretty amazing at what they do.  The triumph would be a rolling grenade with 16:1 compression.

Speeds on time slips, dyno horsepower, and drag coefficients based on air density all play a part in figuring out the aero drag coefficients.  The speeds are what they are.  I cannot adjust them for different altitudes.  The air density and horsepower can.  Everything is adjusted to Bonneville Salt Flats conditions on this table.  The STD dyno horsepower correction factor is 1.18.  The reciprocal is 1 / 1.18 = 0.85  The dyno horsepower is multiplied by 0.85 to estimate what it was on the salt flats.  The constant in the drag coefficient equation is based on the formula that includes air weight density.  The 0.0640 pounds per cubic foot Bonneville air density is used.

The drag coefficients using input data from the salt flats with other data corrected to Bonneville conditions are shown on the attached table.  The drag coefficients change a few percent from the earlier table where I did not used corrected values.   

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #1371 on: September 22, 2013, 01:05:11 PM »
Weather data are available from the Woomera Aerodrome and Nonning using links on the DLRA website.  There are some other nearby stations, too.  I can use this to figure out the Lake Gairdner climate.  Better would be some collected data from the location during the races for temperature, humidity, uncorrected baro pressure, and density altitude.  Does anyone have any?

As I recall, the race date might, or has changed.  What time of the year will the 2015 speed week be held?


Offline Old Scrambler

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #1372 on: September 23, 2013, 09:26:49 AM »
Bo......................10.5 Compression is a LONG way from a relatively mild 12 or 13 to 1 for a competitive landspeed effort.  If you have the valve to piston clearance.........maybe a thinner head-gasket will help. Maybe TRIUMPH has some limitations I am not aware of? 
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Offline tauruck

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #1373 on: September 23, 2013, 11:08:54 AM »
Bo, Your attention to detail is unbelievable and I hope you get what you're aiming for. If I was a man of means (MEGA $$$$) you'd be doing my motor for sure. You're a good example to us all. I mean that. Thanks.

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #1374 on: September 23, 2013, 10:43:55 PM »
Us west coast tuners pay a lot of attention to this stuff.  A bike might race at Sears Point at elevation less than 100 feet and at Toelle which is as high up as Bonneville.

Check this out.  Maybe, if I show up early on Sunday morning...with a box of chocolates for the lady at the front desk...www.test-trak.com/woomera.htm

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #1375 on: September 24, 2013, 12:39:51 AM »
The south end of Lake Gairdner is 360 feet above sea level.  There are no weather stations there.  The DLRA list two nearby stations.  One is at Woomera Aerodrome to the northeast and the other is at the mine at Nonning to the southeast.  Both are at slightly higher elevation.  Salt flats are visible in the background in pictures of Woomera.

The Australian government gives us some data www.bom.gov.au/climate/averages/tables/cw_016032.shtml.   The race is held at the end of February and the beginning of March and I figure on running down the salt around midday.  Data from the morning and the afternoon of both months is averaged to get a temp of 79 degrees Fahrenheit.

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #1376 on: September 24, 2013, 12:47:58 AM »
The relative humidity is also averaged the same way.  It is estimated to be 40% on the average.  This is high for places out in the dez.  Water evaporating from the lakes must contribute to this airborne moisture.

No air pressure data is provided in the summaries.  The airport near Red Bluff is at a similar altitude and there is a lot of accessible climate data for it.  It is at altitude 352 feet.  Data is available from the National Weather Service website.

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #1377 on: September 24, 2013, 01:21:28 AM »
Make sure to use the uncorrected "Station Pressure" when you do this.  Data from the weather service for the last seven days is looked over and the pressure is recorded for all readings with the temps from 78 to 80 degrees.  All fourteen readings are averaged to get a station pressure of 29.45 inches mercury.  Note how the station pressures vary a lot.  Pressure is the most important input variable in these equations.  This is a weakness in all of this figuring.

Next, the pressure, temp, and humidity is entered into Wallace Racing's "Dyno HP Correction Calculator" at www.wallaceracing.com/dyno-cor-calc.php  The SAE J607 dyno correction factor is 1.04

Now the pressure and temp are entered into Wallace Racing's "Air Density Calculator" at www.wallaceracing.com/air-density-calc.php   The estimated air density at Lake G is 0.0724 pounds per cubic foot.

The statistically correct way to do this is to calculate the dyno correction factor and the air density for each day and to average those.  I do not have enough information to do this.  This procedure makes the best use of what I have.
     
     

Offline thefrenchowl

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #1378 on: September 24, 2013, 08:01:06 AM »
Quote
A rule of thumb for methanol consumption is one gallon per horsepower per mile

Wobbly, it seems a bit excessive for an estimate... This year, my KHK 900cc bike went 121.775 at about 5300rpm (loads of wheel slip) using about 1 litre of methanol per mile.

We kept increasing the main jet, it is still a touch lean probably, that's a 4mm diameter main jet for a 47mm carb, plus an adjustable main jet for fine tuning, 3mm diameter with a Mikuni adj. needle in it, at the moment 1 turn 1/2 out.

Still, way more increase than the often stated 2.2 bigger surface than on gas... As it stands, for my bike, that is nearer 5 times more jet surface than gas jet for that carb...

Patrick
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...What exactly are we trying to do here?...

Offline joea

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #1379 on: September 24, 2013, 02:48:37 PM »
wobbly...I hope you really are not using the "knock sensor" as gospel with respect to tuning....

as evidenced by your thinking you have "unstable combustion" by the "flickering knock sensor light"...
with 10.5 -1 static CR....running at a DA of over 5000 ft....with very stable ERC 110 fuel....