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Author Topic: Team Go Dog, Go! Modified Partial Streamliners  (Read 518718 times)
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wobblywalrus
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« Reply #195 on: July 16, 2010, 12:43:03 AM »

Today I noticed that I am getting grey fast and wrinkly around the eyes.  I wear a hat often and smile with my mouth closed.  My hair quantity and tooth count are personal matters.  My attitude to racing has changed, too.  I am very careful and I scare easily, and sometimes I pursue my goals with grim determination, although I still have fun.  My goals have changed, too.  Simply racing in Australia, riding around the Isle'o'Man, and getting into the USFRA 130 club.  What made me think about this was a recent post by a newer member about setting a 300+ mph record in a Studebaker on his first visit to the salt.  I sure miss those days of youthful and boundless optimism, a time when everything is possible.

Today was dyno day.  The next two or three posts will show what happened.  Maybe this info will help a person who has not used this tuning instrument.

Preparation includes making sure that all systems are OK except for the one that needs to be analyzed.  Dyno work is expensive and it saves $ if it is focused on a specific problem.  In my session the goal is jetting the carbs.  This bike is built and raced in the old street rod tradition.  Normally it has air cleaners and exhaust baffles.  The filters are pulled and replaced with velocity stacks and the baffles are removed, and then it is race time.  The carbs are jetted for the stacks and open pipes.  One picture shows the table out in front of the shop with the baffles, filters, etc.  I make the change from street to racing configuration right after I arrive at the shop.   

It is nice to be able to compare a current dyno session result to a previous one.  I always use the same fuel type, as much as practical.  In my case it is unleaded ethanol-free premium.  I type "ethanol free gas oregon" into my search engine.  All sorts of websites that list places where I can get gas without corn likker are listed.  I fill up a 5-gallon jerry can with the gas, drain the old gas from my tank, and refill it with the good stuff.

The mechanic rolls Bonnie onto the dyno and clamps the front wheel into a vise and an exhaust gas sampler is put into the muffler.  A roller is centered under the rear wheel.  The torque that is transmitted to the roller is measured and this is called "rear wheel torque."  The amount of torque that is transmitted is affected by many things in the driveline, such as chain type and condition, tire pressure, and tyre type.  In order to compare session results to each other, I always use the same type of power transmission components, such as an x-ring chain in good condition and a radial tire inflated to 38 psi.  Some people have a tire that is used for dyno work, only.  My dyno tire is in the attic.  I am too lazy to put it on.

The dyno is a computerized system.  My run from three years ago is retrieved from the files and the mechanic discusses it with me.  The run data lists the work that was done to the motor at that time, the carb settings, the atmospheric conditions, and it gives output for fuel/air, torque, and horsepower.  The mechanic asks about my new engine build and he records the data.  I describe my problems with poor performance and say that it has something to do with the carbs.     



     


* Parts on Table.JPG (131.99 KB, 448x321 - viewed 188 times.)

* Exhaust Gas Sensor.JPG (72.01 KB, 448x299 - viewed 189 times.)

* Tire on Roller.JPG (85.05 KB, 448x299 - viewed 195 times.)

* Control Panel.JPG (82.59 KB, 448x299 - viewed 196 times.)
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wobblywalrus
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« Reply #196 on: July 16, 2010, 08:54:38 PM »

The mechanic asks me what jetting do I want.  I say "Jet it like a street bike.  This will be close enough for B'ville. I will fine tune the main jets when I am on the salt."  He can give me horsepower curves that are calculated by up to six different methods.  I ask for data figured by the Society of Automotive Engineers (SAE) procedure.  All of my old data is SAE and I can compare.  The dark blue horsepower curves on the printouts show the same dyno run.  The SAE method calculates 70.64 horses and the DIN, a European standard, calculates 72.34 horses.

The bike is shown in the dyno room.  It is a hot and noisy place.  I am sent to the showroom while the work is being done.  There is a new Bonneville there and it is painted in the 1960 color scheme.  The new tanks have a funny shape and I could learn to like it.  There is a fuel injection system in and under that tank.  No carbs.
 
The intial run on Bonnie yields 42 horsepower.  The mechanic discovers that the diaphragm for the vacuum operated slide on one carb was pinched during an improper installation.  The slide would not lift properly.  That was my big mistake.  He installed the diaphragm correctly.  The jetting is next.     

 


* SAE Curve.jpg (36.57 KB, 336x444 - viewed 205 times.)

* DIN Curve.jpg (39.72 KB, 328x448 - viewed 207 times.)

* Dyno Room.JPG (108.16 KB, 299x448 - viewed 205 times.)

* EFI Bonnie.JPG (116.52 KB, 448x299 - viewed 207 times.)
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wobblywalrus
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« Reply #197 on: July 18, 2010, 12:21:26 AM »

The baffles are pulled out of the pipes and the velocity stacks are installed.  I ask the mechanic to jet it like a street bike and I say I will fine tune the main jets at B'ville.  I will never run the bike this way on the street, I use air filters and my quiet street pipes.  My jetting is just right, or very close, on the salt using the race gas.  This method works because of the difference in the oxygen contents of unleaded premium and race gas.

There are two subtle things about jetting this race engine that are not obvious, but they are very important.  First, it is assumed that the air/fuel mixture ratio shown on the printout is that of the exhaust gas, and it is not always the mixture in the cylinder and combustion chamber.  This cam has significant overlap and at some engine speeds the resonance in the intake and exhaust systems might blow fresh air/fuel mixture through the inlet valve and right out past the exhaust valve and down the exhaust.  At other engine speeds the reverse could happen, and the exhaust could be pulled back through the inlet valve and it can contaminate the fuel/air mixture.  For these reasons and others, the indicated fuel air mixture is not always the mixture that is being combusted.  This problem is overcome by different methods.  The mechanic doing this work prefers to determine optimal jetting by comparing the power curves that are produced by the different jets.  Years ago I watched a dyno operator that measured temperature to arrive at the optimal mixture settings.

Second, it is hard to find the best fuel/air ratio unless the ratios that are too rich and too lean are known.  Assuming the initial run indicates a lean condition, the mechanic will gradually decrease the fuel/air ratio until the mixture is obviously too rich.  Then, the jetting combination that produces the best mixture, between being too rich or lean, will be chosen.  Conversely, if the initial mixture is rich, the mixture will be made leaner until it is obviously too lean, then the intermediate size jets producing the best fuel/air ratio will be selected.  The attached printout shows the power difference, almost 1 horsepower, caused by simply moving the needle jet clip one notch.





* Needle Position Changes.jpg (37.52 KB, 336x437 - viewed 224 times.)
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wobblywalrus
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« Reply #198 on: July 18, 2010, 01:15:48 PM »

Heidi Rose, my oldest girl, is taking her motorcycle training course this weekend.  She is on the little red Suzuki.  This afternoon we will go to the Kawasaki shop and look at the 250 Ninja. 

The jetting is done and I have a torque curve for the new build.  This curve gives me a lot of useful information.  The torque peaks at 5,800 rpm and it drops off rapidly.  My target rpm, and this is the engine speed I try to run at through the measured mile, is 7,500 rpm.  The new build and the old one have the same torque at this rpm.

First, a look at sprocket sizes for this year's BUB meet.  Last year I ran 127.14 mph at 7,450 rpm using 19 and 43 tooth engine and wheel sprockets, respectively.  The new build has the same torque at that engine speed as the old motor.  It is likely that I will not go faster with the old 19/43 combo.  This year I will use 19/42 chainwheels.  The engine will be turning less rpm when I get to top speed.  The peak torque for the new build is at lower RPM, too, so this gearing change is a better match for the new build.

Will I go faster?  All of the gears, sprockets, wheels, etc. in the bike are levers, and the 19/42 gearing will give the pistons less leverage to move the bike across the salt.  This may offset the greater torque and result in speeds similar to last year's.  I hope for more speed, but the reality is, I probably will not get it.

The second thing I see in this dyno printout is the need to do more work.  Torque should fall off after 7,000 rpm, rather than 6,000 rpm.  More torque at higher rpm = increased horsepower = greater speed.  Less restrictive carbs and tuned intakes and exhausts will do this.  This will be next winter's project.

The dyno work took 7 hours at $80 per.  Big dollars, and is it worth it?  The bike I brought into the shop had a power band like a Kawasaki triple and made a trifling 42 horsepower.   It was thrilling to ride and it felt fast, but in reality, it was not.  It came out of the shop correctly jetted with 70 horsepower.  I have the info I need to set my gearing for next year, and I know what changes I need to do to the torque curve to go faster.  Money well spent.

This engine build has cost a lot of money and it required some very special parts and a lot of good advice.  We got a break on some part costs, a few things were given to us, and there was a donation of many hours of dyno time.  The team Go Dog, Go mutts would be sleeping under the porch all summer if it was not for this help.  Special thanks to Cascade Moto Classics of Beaverton, Oregon, South Bay Triumph of Lomita, California, and folks on this forum.  We are ready to go!   


* Learning.JPG (105.73 KB, 443x336 - viewed 217 times.)

* Torque Comparison.jpg (43.34 KB, 336x436 - viewed 190 times.)
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« Reply #199 on: July 18, 2010, 01:28:48 PM »

Tell her that the Ninja 250 can also work as a LSR bike, just as Slim and Nancy and Racer X on here. I'm planning on using the motor to power a Lakester myself. Nice little bikes!

Jeff
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Seldom Seen Slim
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« Reply #200 on: July 18, 2010, 03:03:56 PM »

Congratulations to heidi Rose for taking the MSF course.  I never did -- and still would take it if they'd let me in.  (I say that 'cause the course is only offered for a few months here and "newbies" get first dibs on the openings.  There are never opening for already-licensed bike riders.  Too dang bad. . .).

Anyway, WW, keep this in mind -- that you might have let the cat out of Pandora's box and now it's too late.  Nancy had never been on a motorcycle 'til she met me.  She took the MSF course about eight years ago -- and now she holds a record over 200 mph.  Best wishes to both of you!
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wobblywalrus
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« Reply #201 on: July 21, 2010, 12:37:36 AM »

The trip home was a lot of fun after the jetting.  There was a lot of power and noise.  The bike has a sharp exhaust note and it reminds me of the howls from cats making love.  It was entertaining for awhile and then it started to drive me nuttier.  About halfway home I pulled to the road side and I put in the baffles.  The bike ran OK at low rpm with the baffles and at higher er engine speeds it would sputter.  I could not go faster than 50 mph.  I pulled to the roadside again and I pulled the baffles out.  The baffles were covered with black soot and fresh gasoline was dripping from the filters.  This bike, with the baffles in, was obviously having reversion and standoff.  The bike must work well and be quiet at the same time.

Reversion is a reverse flow through the intake tracts from the intake valves out toward the bell mouths.  It can force clouds of unburned fuel out of the carburetor intakes.  The mixture can be suspended in the intake streams just outside of the bellmouths, hence the term standoff.  The standoff was saturating the air filters with gasoline.

Reversion starts in the exhaust system.  The exhaust gases travel travel down the headers and through the mufflers in waves.  There are pressure waves when the gas is pushed out of the exhaust ports and these waves are interspersed with vacuum waves.  The pressure waves suddenly expand when they exit the mufflers and this creates another set of pressure and vacuum waves that are reflected back into the exhaust system.  These pressure and vacuum waves interact with the opening and closing exhaust valves in different ways.

The exhaust and intake valves are open at the same time during the overlap part of the valve opening and closing cycles.  Valve overlap is hard to quantify.  I express overlap as inches lift x degree crank rotation.  Graphs of valve lift versus rotation during overlap have triangle shapes.  I call these overlap triangles.  See attached sketch.  The overlap period is a time when the exhaust gas that is pushed into the combustion chamber can travel past the inlet valve and into the inlet tract.  The #813 cam in 865 cc Build 1 has 0.53 inches lift x degree duration and the Triumph 790 cc cam has much less, at about 0.35 inches lift x degree rotation.  The new cam creates a much larger opening during the overlap period.

Note the torque curves on the torque comparison chart in the previous post.  Many factors contribute to the dips and bumps in these curves.  Reversion is the main cause of the the big dips at the lower-midrange engine speeds.  The 865 cc engine build has a much deeper dip.  Contributing factors are the larger overlap window to convey reversion waves and the more intense exhaust pressure waves created by the larger and higher compression engine.

The baffles are reflective surfaces and they increased the intensity of the waves traveling back through the exhaust system.  The torque curve shows that the reversion dip was present when the baffles were out and baffles simply made the problem worse.  The next posts will show how I fixed the problem.             

 


* Overlap Triangles.jpg (56.97 KB, 441x336 - viewed 217 times.)
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« Reply #202 on: July 21, 2010, 06:53:19 AM »

Wobbly !...just to let you know that I enjoy intensely reading your posts here ( and elsewhere, for that matter )!

(Some of it goes right over my head, but that's my problem.)


Thanks !
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« Reply #203 on: July 21, 2010, 09:48:17 AM »

Wobbly, would you please make the last image of your notes larger if you can, 58 kb is too small  it only shows up as pixels when I try to enlarge. 75 to 80 kb is better as previous pics. Your notes especially is highly regarded and much appreciated.
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wobblywalrus
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« Reply #204 on: July 21, 2010, 11:45:35 PM »

The overlap triangles are included in a bigger format.  Hopefully this works.  The old Triumph twins had independent exhaust and intake cams and there was a feature that allowed them to be adjusted.  Cam timing during overlap was an important part of performance tuning.  I put a dial indicator on the valve keeper and a degree wheel on the crank to determine the cam timing.  This time, I made some educated guesses based on the timing card data and estimated the cam timing curves.  This will illustrate the idea I am talking about.  The actual measured overlap triangles may be a bit different.

Years ago, about 45 to be exact, my buddies and I were thrashing and crashing Triumph and BSA twins.  One day I crumpled up my header pipe and I scrounged a replacement from my friend.  His header pipe was from a later model A-65 and it had a cross-over pipe between the headers and in front of the cylinder head.  I had to replace both headers because my older pipes did not have the cross-over.

My bike had a cammy Spitfire engine and it was hard to ride.  It had dips and peaks on the torque curve.  The torque curve was much smoother after I installed my friend's header pipes and it was the cross-over pipe that made the difference.  The later model Triumph twins had cross-over pipes, too, and we put them on a few bikes in order to make them more manageable.

These old memories were remembered when I got home last weekend.  I took off the sexy titanium Italian Arrow pipes and put them away.  I hunted around and found the frumpy steel Triumph header pipes out in the bone yard.  They have a cross-over pipe, and I polished them up and put them on.  A short romp around the neighborhood, sans mufflers, proved that the cross-over pipe trick worked again.  No reversion.

The principles are easy to understand.  Let's look at the right hand header.  Exhaust gas pressure and vacuum pulses travel down the right header and they pass over the cross-over pipe opening.  Pressure and vacuum pulses from the left header are coming in through the cross-over pipe.  These pulses are timed so the pulses coming in through the cross-over from the left header occur when pulses of the opposite type are passing by in the right header.  The pressure pulses partially neutralize the vacuum pulses, and vise versa.  The pressure and vacuum pulses in the headers downstream from the cross-over are less intense than they are upstream.

These less intense pulses travel down through the muffler and out of the exhaust.  They expand when they are no longer confined, and pressure and vacuum waves are created that travel back up the pipe.  The important thing is, the weaker pulses going out create weaker pulses going back in, and there is some further weakening of these pulses when they pass by the cross-over pipe openings on their return trips.  The weakened return pulses do not have enough energy to push the inlet charges back into the inlet tracts. Reduced or no reversion are the results.

 

     


* Triangles of Overlap.jpg (195.23 KB, 1006x768 - viewed 206 times.)

* Crossover Pipe.JPG (75.62 KB, 448x299 - viewed 194 times.)
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wobblywalrus
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« Reply #205 on: July 22, 2010, 09:10:53 PM »

It was 1973 when I crashed my BSA and put on the new pipes.  This is 37 years ago.  My math was off and I like to keep things accurate.

Fortunately, there are all sorts of mufflers out in the bone pile.  I tried a few and one pair worked very well.  The bike is quiet and there is no reversion problem.  They are Triumph off-road mufflers.  They are straight through glass packs with a 1-inch inner diameter.

There are two things about these mufflers that make them work well with the long duration cams.  There are no obstructions that project into the exhaust openings.  A broom handle will pass through the entire length.  Also, the transition from the 1-1/2 inch diameter header to the 1-inch diameter muffler is gradual.  The lack of projections or abrupt transitions help to minimize reversion.  There are no surfaces or sharp transitions inside the exhaust to create pressure and vacuum waves.  Now the bike is quiet and it runs good.

Right now there are pod filters on the intakes and there is no runner length upstream from the carburetors.  Experts on these bikes recommend that I reinstall the air box for street use.  They say the bell mouths in the air box are another countermeasure against reversion.

The moral to the story.  Never toss anything.  There are advantages to having a small personal junkyard.  Who knows what parts will be handy in the future.       


* Quiet Pipe Outlet.JPG (54.49 KB, 448x299 - viewed 186 times.)

* Triumph Off Road Pipes.JPG (103.06 KB, 448x299 - viewed 198 times.)
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« Reply #206 on: July 26, 2010, 12:33:46 AM »

It is getting close to salt time and the last minute thrash.  Will this bike withstand the rigors of LSR?  Is the engine put together OK?  Are the rods and pistons strong enough?  Yesterday my oldest daughter and me devised the Flower Picture Test.  We pottered around near the east side of town and photographed the flower fields.  This is what we saw. 


* A Bee 1.JPG (102.73 KB, 448x316 - viewed 182 times.)

* Daisies and Poppies 1.JPG (141.49 KB, 448x299 - viewed 190 times.)

* Lots of Flowers 4.JPG (109.21 KB, 448x299 - viewed 204 times.)

* Pink and Purple.JPG (125.91 KB, 448x299 - viewed 190 times.)
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« Reply #207 on: July 26, 2010, 12:37:14 AM »

The bike survived the test.  A few more pix.


* Flowers and Me 3.JPG (149.2 KB, 438x336 - viewed 227 times.)

* Pink and Purple 4.JPG (137.01 KB, 448x295 - viewed 190 times.)

* Wheat and Poppies 1.JPG (133.4 KB, 448x299 - viewed 185 times.)
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« Reply #208 on: July 26, 2010, 05:16:06 PM »

"Remove the pod filters and put the air box back on.  This will improve your gas mileage and smooth out the power curve at low to mid range."  Two people with a lot of knowledge about these bikes tell me this.  I go out to the junk pile and find the air box.  A quick spray of Raid takes care of the resident arachnids and I put the air box back on.  Now the question is "Is my Unifilter oiled foam filter OK for a 70 horsepower engine, or do I need another type?"

I do not have a clue as to the answer, so I do my usual routine.  I go to Borders Books, buy a latte, and browse through the Transportation section.  I do this a lot so I know what books are there.  There is a new book that has been put on the shelf last week, I look in it, and it has the information I need.  The book is ISBN 978-1-934709-17-7 David Vizard's "How to Build Horsepower:  Proven Methods for Increasing Horsepower in Any Engine."  Mr. Vizard lives in America and he is originally from England.  Things I learned from his articles in Hot Rod and other magazines have been used previously in this build.

Air filter flow capacities are discussed in Chapter 2:  Primary Induction.  The oiled foam filter is not the optimum setup.  It can filter air for engines up to 3.5 horsepower per square inch filter area without measurable power loss based on Vizard's experience.  Now I measure the air filter area.  The area width is the circumference as shown in the photo.  The Triumph filter has a 6" x 10.125 " = 60 square inches area.  This filter is adequate for 60 x 3.5 = 210 horsepower engines.  My 70 horsepower motor is well below this and the oiled foam filter is OK.

The air box does make the engine run better.  There is no noticeable dip in the torque curve at the low to mid range transition.  Gas mileage is slightly better at 39 mpg on the highway.  I had my crab trap, crab pot, portable stove, and beer cooler on the bike when I recorded this mileage.  It was not very aerodynamic.  Mileage should be in the 40's for normal highway use.  It was always in the mid 30's with the pod filters.

 


* Vizard's Build Hp Book.JPG (126.67 KB, 391x336 - viewed 218 times.)

* Filter Circumference.JPG (83.53 KB, 448x327 - viewed 210 times.)
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« Reply #209 on: July 26, 2010, 05:23:02 PM »

So, WW....how was the crabbing?   rolleyes

Lynda
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