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Author Topic: Team Go Dog, Go! Modified Partial Streamliners  (Read 813002 times)

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Offline Peter Jack

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3270 on: January 21, 2019, 01:14:02 PM »
Bo, I've sent you a PM.

Pete

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3271 on: January 22, 2019, 11:54:07 AM »
Pete, can you show a sketch or picture of the modification described in your PM?

Offline Peter Jack

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3272 on: January 22, 2019, 01:40:49 PM »
I'll try to figure out how to do that. I used to have fax which worked really well for that sort of thing but I'm not sure how to put a drawing on here. Computers tend to be a challenge for me and windows 10 has just completed the job.  :? :? :?

Pete

Offline Rex Schimmer

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3273 on: January 22, 2019, 01:58:46 PM »
Harold Bettes said: "You two stroke guys probably remember the "boost bottle" approaches from years ago. The same kind of application can be done for a 4 stroke." These were actual canisters that were connected to the inlet down stream from the carb and before the engine inlet port. Their function, as I understand it, was to help eliminate dips and flat spots in the torque curve. I have a 84 Yamaha YZ490 that has one. Their resonate frequency is dependent upon their volume, the diameter and length of the connecting hose or tube connecting to the inlet tract and is independent of the plenum or inlet tract frequencies. The " theory" is to have the Helmolz chamber have a resonate frequency close to the intake tract frequency at the rpm of the engine that you are interested in improving. The combining of the engine inlet pulsations along with the Helmolz chamber resonance causes a rise in intake pressure and therefore an increase in air flow to the engine i.e. more power. I have also seen these chambers used on exhaust systems, probably for the same reasons. It does work as all of the high performance I4 motorcycle engines use Helmolz chambers for power improvement.

We have all driven with one window open and at one speed had the air pressure in the car pulsate, that is Helmolz.

Rex

Rex
Rex

Not much matters and the rest doesn't matter at all.

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3274 on: January 22, 2019, 09:07:52 PM »
Pete, I scan them in as a picture and reduce its size using Paint.  Rex, you have more courage than me, for sure.  Tuning those things for Baja and the Mojive was one of my side jobs in the mid 80's.  Those bikes are animals.  They can go over 100 mph across the dez.  Half throttle was about all I could do.  Either lack of guts or brains was my throttle limiter.

Google "Intake plenum volume and its influence on the engine performance, cyclic variability and emissions" by M.C. Civiz.  That is what I am reading now.

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3275 on: January 23, 2019, 09:27:38 AM »
Publication titles, authors, and sources are listed rather than links to them.  Links often disappear but the other information can always be used to find the references.

Helmholtz effects at the intake runner ends were ignored during engine development until now.  The air filters were attached to the carb ends.  There was little plenum resonance effect from them.  The sides were pleated oiled fabric and metal screens.  This is very good at wave absorption rather than reflection and Helmholtz resonance was negligible.

Bell mouths are on the carb ends now.  Packaging considerations require some sort of enclosures around those bell mouths ends if air cleaners will be used.  The centerlines of the filters and bells are offset and the enclosures are the transitions between the two.  The transitions are plenums and Helmholtz resonance will occur in those cavities.  This could hurt, help, or do nothing for performance.  At the minimum, I need to learn enough about the process to verify that the resonance is not causing problems.  Better yet will be using it to improve performance.

The Helmholtz design process is described in American Society of Mechanical Engineers (ASME) Paper 73-WA/DEP-2, by H.W. Engleman, "Design of a Tuned Intake Manifold"  Manifold design using this method is described in International Journal of Scientific Technology Research , Issue 5, May 2014, by Shirinath Potul, Rohan Nachokar, Sagar Bheve "Analysis of Change in Intake Manifold Length and Development of Variable intake System."

That last publication describes software to figure out this stuff from Lotus Engineering in the UK.  This might be helpful.  The boost bottle concept is something I know about and have used.  It will be the subject of a future post.   

Offline RansomT

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3276 on: January 23, 2019, 10:14:40 AM »
And let me through something else at you...having the honor of tuning many hundreds of race motorcycle, I've come to realize as you change the intake path it also effects the exhaust tuning.  I've seen custom air boxes that picked up significant usable HP in the upper RPM range on one 1 motorcycle that did the opposite on a other motorcycle that was identical except for the exhaust. Both of those bikes made within 2 HP before installing the air boxes. Switching the exhaust system saw the HP improve to mirror the first bike.  I've seen it time and again, folks purchase aftermarket velocity stacks and loose HP.  It's not that the shorter radius stock don't work, it's the exhaust side doesn't match.  It's about the total package working together.

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3277 on: January 24, 2019, 12:45:18 AM »
The stack length is what it was before and it works OK.  It matches what computer programs say it should be.  The engine is insensitive to intake length based on past experience.  The performance is very, very, sensitive to the configuration of the intake inlet edge.  It makes a big difference if I get this right.  That is what I am monkeying around with now rather than tuned length.

These engines flow well at low valve lifts during the overlap.  The valves are in rows next to each other.  There is no piston dome separating the combustion chamber intake side from the exhaust side.  It is very easy to design an exhaust that over or under scavenges.  Either makes a big power loss.

The exhaust has tapers and transitions that are deliberately designed to kick back softer waves that are less likely to over or under scavenge and that are useful over a wider rpm range.  The elliptical bell is designed to do the same thing.  It is intended to reflect softer waves that will have less tendency to over or under scavenge.  This, combined with the increased flow capacity of the elliptical bell will hopefully increase the spread in rpm between the peak torque and power curves. 

The intake helmholtz resonance will be an unavoidable factor in performance.  Hopefully the Lotus program will provide the tools to make this resonance do beneficial work.   

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3278 on: January 25, 2019, 04:29:29 PM »
The Lotus Engineering software website is www.lesoft.co/  They have a freeware version to make a simplified model of a single cylinder engine.  The engine will be a 500cc single cylinder for the freeware model.  The more complex program will be ordered if I can figure out the simple version.  Then there will be models in EnginePro, Dynomations 5 and 6, and Lotus.  This will be a big help.

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3279 on: January 27, 2019, 11:09:08 AM »
Lots of research and conversations with experts say that a plenum volume between 100 and 120 percent of the cylinder swept area is a good starting point.  The volume can then be refined based on dyno work or more detailed calculations.

The narrower part of the bell mouth that acts like the inlet runner for harmonics is filled with rubber.  The amount filled is a best guess on my part.  The plenum is filled with ATF up to the plate.  Volume is 104 percent of cylinder swept area.  That is plenty good for now. 

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3280 on: January 29, 2019, 07:29:25 PM »
Some expert help and fancy computer programs will be the key to making this bike go faster.  Castings are needed for the ports and combustion chamber.  The old ones are obsolete.

Urethane with Shore Hardness 20 is used for the ports and combustion chamber.  There is better filling and less chance of bubbles if the cylinder head and rubber are around 75 degrees for the pouring.  In this house during the morning the only warm place is near the stove.

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3281 on: January 29, 2019, 07:34:42 PM »
A release agent is always sprayed in the port before casting.  It is never enough.  Submerging the part in soapy water while pushing out the rubber helps a lot.  This darker rubber is Shore Hardness  30 urethane.  It works OK on manifolds but is to hard for ports.  It cannot be pushed out. 

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3282 on: January 29, 2019, 11:44:06 PM »
Note the black dot in the bell mouth.  The tuned length and runner entrance width are based on the assumption that everything downstream from it is a runner for harmonic design.  The back of the air filters are shown.  They are resting on the backs of the plenums now.  Tomorrow I will weld them on.

The Lotus engine design package is intended for the auto industry and it costs big, big money.  They offer a month of its use for free.  November is pretty quiet around here.  The plan is to use the program for that month and to see if it shows where improvements can be made.  In the meantime the single cylinder freeware program will be what I use in addition to engine pro and dynomation.

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3283 on: January 29, 2019, 11:53:34 PM »
This is the combustion chamber area.  The common practice is to use valves 5 and 6 mm oversize.  The intake is 2 mm oversize and the exhaust 1mm bigger than standard.  The inlet mach level is between 5 and 5.5 at 10,000 rpm based the formula used to calculate it.  That is plenty good and there appears to be no need to use bigger valves.  The milling required to install those big valve seats in will drop the compression ratio a lot so it seems to be a good idea to avoid them.

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3284 on: January 29, 2019, 11:58:12 PM »
The rubber for the manifold plug is dark brown.  The lighter rubber is for combustion chamber and ports.