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Author Topic: Team Go Dog, Go! Modified Partial Streamliners  (Read 520867 times)
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wobblywalrus
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« Reply #2655 on: December 09, 2016, 02:33:45 AM »

This is the worksheet for the #208 cams.  The exhaust and intake systems are as good as I can get.  Power is optimized for 7,500 to 8,500 rpm.

The first ten runs under the circled "1" use the hybrid-sim method to select cam timing and duration.  It give ten combinations.  All lobe center angle combinations are modeled using the hybrid-sim method with #208 cam ten point descriptions.  Intake centerlines run from 90.5 to 94 degrees.  Exhaust centerlines are from 112.0 to 115.5 degrees.  Overlap at 0.006 varies from 105 to 110.5 degrees.  Good results come from some of these lobe timing combinations.

The three runs under the circled "2" use the filling-emptying method to select cam timing and duration.  It gave ten combinations.  Like with the first ten runs, the combinations are modeled using the hybrid-sim method with #208 cam descriptions.  Results were lousy so I modeled the first, sixth, and tenth combinations.  Intake centerlines vary from 102 to 104 degrees, exhaust centerlines are from 113.5 to 114.5 degrees, and overlap is 94.5 to 108 degrees.

The single run under the circle ed "3" is from the cam card timing.  It is modeled using the hybrid-sim procedure.  Power is lame.

The ten runs under the circled "4" used the wave-action method to figure out ten lobe center angle and duration combinations.  All were analyzed using the hybrid-sim method and ten point descriptions for the #208 cams.  Intake centerlines vary from 93.0 to 94.0 degrees.  Exhaust centerlines are from 103 to 109 degrees.  Overlap at 0.006 is 110 to 115.5 degrees.  Some combinations give good power.

Use as little overlap as possible, Dema advises in his paper.  The fifth combination under the circled "1" gives good HP with less overlap than many other combinations.  Intake centerline is 90.5, exhaust centerline is 112.5, and overlap is 110.0 degrees.  Idle quality and power below 3,000 rpm are awful according to the computer simulation.  That is a sacrifice made to the god of speed.


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« Reply #2656 on: December 09, 2016, 09:43:43 PM »

I assume the HP is at the crank..............which means something is not optimized for this 'sim' build. I see 94 to 95 HP which is about what I have in my 2v Honda motor at 750cc. Did I miss-read something? 
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2011 AMA Record - 250cc M-PG TRIUMPH Tiger Cub - 82.5 mph
2013 AMA Record - 250cc MPS-PG TRIUMPH Tiger Cub - 88.7 mph
2016 AMA Record - 750cc M-CG HONDA CB750 sohc - 130.7 mph
2016 AMA Record - 750cc MPS-CG HONDA CB750 sohc - 137.7 mph
Chasis Builder / Tuner: Dave Murre
wobblywalrus
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« Reply #2657 on: December 21, 2016, 03:20:32 PM »

Hi Dennis.  This is a late answer to your question.  Rose and I were in Hawaii for awhile.  Also, I did a lot of work with the program since the last post.  It is referred to as "recent modeling."  Some background info follows then an answer.  The program has a simulation method that uses general assumptions for intake and exhaust and it does not use wave action simulation.  It is the filling and emptying method.  It gives reasonable results assuming the intake and exhaust can be optimized.  Packaging considerations prevent this on this bike.  Tuned lengths and other wave making things are compromised 'cause everything needs to fit somewhere.  The F and E method generally is not applicable for this application and it was not used in recent modeling.

There is a wave action model that uses wave analysis to get output.  It is useful, however, a lot of the results are unrealistic.  It was not used for recent modeling.

The hybrid simulation uses features from both of the preceding methods.  It gives results as good the program can make.  It is used for recent modeling and most everything I will do in the future.  No canned "optimization" methods were used to figger out cam timing in recent modeling.

The ten point profiles for the cams I ordered with the optimized intake and exhaust systems were modeled.  The initial lobe centerline angles were 110 degrees each side.  Then I varied them and looked at power curve changes and wave forms.  The best power occurred when the intake cam centerline coincided with the crank degrees of peak demand.  This is a real tight centerline angle and the valves would be smashed into the tops of the pistons.  It looks like the method RansomT suggests for determining intake centerline angle, based on piston to valve clearance, will be best.  A 100 degree intake centerline is my best guess without doing the clearance measuring.

The exhaust centerline likes to be a bit wider than clearance, alone, would dictate.  A 115 degree centerline gives the best power and wave forms.  It gives a nice shaped power curve with 95 HP, peak.  This is flywheel HP at Bonneville conditions.  Tonight I will draw up the expected power curve at the rear wheel with SAE correction. 
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wobblywalrus
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« Reply #2658 on: December 21, 2016, 09:12:16 PM »

These are the latest power and torque estimates based on program input of 0 feet elevation. 68 degrees temp, and 0% humidity.  The flywheel numbers are reduced 90 percent to get the rear wheel estimates.  Peak HP of 110 occurs at 9,000 rpm.  It is my best estimate of dyno results converted to SAE.

The hybrid-sim models show that power and torque drop when density altitude rises, as expected.  Also, peak horsepower and torque rpms decrease.  Slightly different cam profiles, cam timing, valve sizes, etc are needed to optimize power at B'ville as compared to near sea level.


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wobblywalrus
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« Reply #2659 on: December 23, 2016, 12:40:38 AM »

This graph compares SAE conditions of 0 feet equivalent altitude, 68 degrees fahrenheit, and 0 percent humidity to B'ville conditions of 6025 feet equivalent altitude, 72.1 degrees Fahrenheit, and 34percent humidity.  B'ville power is 77 percent of SAE.  Usually I figure it should be 84 to 86 percent less.  Density altitudes from a bunch of timeslips is averaged to get the 6025 value.  Perhaps the equivalent altitude is less than density altitude and more like the physical altitude?  I might be making a mistake and need some help with this.  The user's manual does not address it in any detail.

Note that peak power occurs at 8,500 rpm with both cases.  I made a math error and it looked like the power peaked at lower rpm at higher altitude.  What I said about this in the last post was wrong.


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« Reply #2660 on: December 23, 2016, 08:56:02 AM »

Wobbly,
In your text it is not entirely clear whether you applied the 6025 density altitude in addition to the temperature and humidity factors.  The density altitude already takes the temperature and humidity into account so, if so, you may have doubly reduced the expected Bonneville power.
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« Reply #2661 on: December 23, 2016, 11:11:02 AM »

Wobbly,
In your text it is not entirely clear whether you applied the 6025 density altitude in addition to the temperature and humidity factors.  The density altitude already takes the temperature and humidity into account so, if so, you may have doubly reduced the expected Bonneville power.


Good Catch!  With the weather conditions, altitude should be 4220 ft.
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« Reply #2662 on: December 24, 2016, 11:18:01 AM »

Thanx for the advice.  Yes, I entered the DA as the equivalent elevation.  This morning it will be changed to 4220 feet and I will rep lot the data.
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« Reply #2663 on: December 25, 2016, 07:50:18 PM »

The corrected virtual dyno curve is shown.  It looks like 92 HP at the rear wheel on the salt.  There are two methods I use to calculate the power required for different speeds.  To get 165 mph needs 109 or 111 rear wheel HP depending on the calculation method.  It looks like the engine will be the focus this year and aero the year after with a visit to the wind tunnel.   


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wobblywalrus
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« Reply #2664 on: December 27, 2016, 09:08:48 PM »

The virtual power curve shows 110 rear wheel horsepower under SAE corrected conditions.  This is realistic and about all I can hope for based on what I have seen others do with this engine.  So... speed has to come from somewhere else.

The Aussies remove the balancer shafts and knife edge the crank.  That is something I can do next year.  It will give a few more HP.  This is my best tuck from one of Scooter's photos.  If I get lower the top of the helmet eye port blocks the track and I cannot see where I am going.  In my younger days I could arch my back in reverse like a sway back horse and get real low on the tank and see where I was going.  That was 40 to 45 years ago.  The plan is to figure out some sort of helmet that lets me see better.  Then I can tuck down more and this will give me the speed I need.www.scootershoots.com/BUBMotorcycleSpeedTrials/2014-Bonneville-Motorcycle-Spe/i-xPgLVn9   
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« Reply #2665 on: December 27, 2016, 11:40:35 PM »

The helmet may just be your key. Some are much better than others when it comes to aero while in the wind, look for that.
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« Reply #2666 on: December 28, 2016, 12:10:36 PM »

Bo,
The only way I can see ahead is to rest the chin of my helmet on a cushioned chin rest. It pushes the helmet up as well as taking a lot of weight off your neck.  Not easy to do on your bike, but I'm betting if you can, you'll be able to comfortably get down another 4 or 5".  You can see it here.

Tom
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We get too soon oldt, and too late schmart!
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wobblywalrus
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« Reply #2667 on: January 01, 2017, 12:23:54 AM »

This is the first winter I tried to do outdoor construction since I was in my 20's.  It is a lean-to attachment so things can be stored away and give more room to work on things in the shed.  Tomorrow the last roof sheathing will be nailed on if it does not snow.   


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« Reply #2668 on: January 02, 2017, 06:20:02 PM »

I've been traveling for the past few weeks...........110 RWHP may be a bit optimistic, but anything over 100 should get that record smiley smiley

Tom certainly gets his head down smiley smiley smiley and so do other riders on well known Triumphs...........including Tom Mellor smiley smiley  I'm told that the angle of your back has more to do with poor aero than the shape of your helmet. I adjust my helmet before each run to get proper visibility...........but it gets more difficult to bend my neck with each year..........hmmmmmmmmmm
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2011 AMA Record - 250cc M-PG TRIUMPH Tiger Cub - 82.5 mph
2013 AMA Record - 250cc MPS-PG TRIUMPH Tiger Cub - 88.7 mph
2016 AMA Record - 750cc M-CG HONDA CB750 sohc - 130.7 mph
2016 AMA Record - 750cc MPS-CG HONDA CB750 sohc - 137.7 mph
Chasis Builder / Tuner: Dave Murre
wobblywalrus
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« Reply #2669 on: January 03, 2017, 01:07:22 AM »

The back should be as level as possible I was told years ago.  Some peeking around on the i-net tells me that a company in Portugal makes a helmet with a tall eye port.  That is the easiest solution and I am investigating it.     
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