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Unread postAuthor: cdheller » Thu Oct 01, 2009 3:52 pm

[quote="rcman50166"]I'm sorry to kick up an old/off topic thread, quote]
+1 but anyways
a couple of things you may or may not have thought of.
adjusting your ignition timing offset keys between the crankshaft/flywheel or sloting the ignition coil holes used to work.

shaveing your cooling fins on the flywheel to cut down on how much energy is directed that way

old school way of tuning exhaust was to cut it off 1"past where the heat changed the pipes color
i think modern thought has insulating the pipes so you don't waste energy .


jeepkahn has it right in"Hence my statement earlier... DO THE MATH...."

edited to add
I'll probably get some major flames ,go to hell,or something for this

but
as far as I can tell from reading the rules they measure the fuel tank not the fuel system .
smokey"you didn't say I couldn't do that"yunick denied it but rumor has it after teck inspection failed on his cars fuel cell he took it out ,threw it at them and drove the car home.

2" fuel lines in case you'r wondering.
sooo turning off your tank might be something to watch out for.
just a thought
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Last edited by cdheller on Thu Oct 01, 2009 4:32 pm, edited 1 time in total.
"A lot of what is taken for engineering fact is nothing more than somebody`s opinion when you dig into it far enough."
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Unread postAuthor: Technician1002 » Thu Oct 01, 2009 4:24 pm

cdheller wrote:
rcman50166 wrote:I'm sorry to kick up an old/off topic thread, quote]
+1 but anyways
a couple of things you may or may not have thought of.
adjusting your ignition timing offset keys between the crankshaft/flywheel or sloting the ignition coil holes used to work.

shaveing your cooling fins on the flywheel to cut down on how much energy is directed that way

old school way of tuning exhaust was to cut it off 1"past where the heat changed the pipes color
i think modern thought has insulating the pipes so you don't waste energy .

jeepkahn has it right in"Hence my statement earlier... DO THE MATH...."



Many two stroke engines use an exhaust expansion chamber, mostly on boats with a long water cooled exhaust. Tuned exhaust is a science to scavange a 2 stroke cylinder to pull in extra fuel through and into the exhaust and then rebound back to compress it back some before the piston closed the port. It was mostly for performance and not efficiency. Sort of a turbo charge effect raising the fuel air charge in the cylinder.

On 4 stroke engines the tuned pipe does not cause this as the valve closes at the top of the stroke and not near the bottom like a 2 cycle. The intake and exhaust are not open at the same time like a 2 stroke. A tuned 4 stroke exhaust is less important than in a 2 stroke. Low back pressure is important so most of the spent gas is gone. Tuned ports help some, but only over a narrow RPM range. An expansion chamber near the engine may help relieve some back pressure during the exhaust stroke so less energy is used to expel the exhaust.

Insulating the pipe only carries the heat energy through the pipe to the end of the pipe without losing much heat along the way. How does this help efficiency? The hotter gas is expanded so the pipe is more restricting to the hot gas vs cooled gas. With no other changes I think insulating the exhaust may slightly lower efficiency.

Adjusting timing dependent on RPM is a well known fact. Any modern automobile uses variable ignition timing. I would go a step further and use a micro controller to sense engine RPM, crankshaft angle, throttle position, and use it to fire an electronic ignition module. This would be dynamic and exceed the performance of any set and forget timing. The controller can either do math or table lookup to provide the final engine control. This is a big step in improving efficiency and power. It is highly recommended.

A phase locked loop triggered by a TDC sensor on the flywheel magnet works fine if you can't come up with a crankshaft angle encoder any other way.

A Voltage Controlled Oscillator (VCO) divided down by a counter can be adusted by a phase detector to lock the VCO to a multiple of the crank pulse giving crank angle counts to base timing against. For example a VCO divided by 6, divided again by 6 then divided by 10 will provide a VCO running at 360 times the crank pulse rate, or 1 pulse per degree for the processor.

The processor would input the TDC sensor, the VCO angle counter, the throttle position and adjust the ignition angle based on a look up table.

Engine computers do this and more as they include some injection timing, input from intake air temperature, block temperature oxygen sensor, air mass sensor, transmission control, etc.
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Unread postAuthor: Solar » Thu Oct 01, 2009 11:50 pm

Teardrop is my vote. But why do you need to hug the ground? Seems like extra friction with ground effect. At those speeds you surely won't lift off either. I am just making assumptions.
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Unread postAuthor: rcman50166 » Sat Oct 03, 2009 9:00 pm

Wow, definitely information to keep.

I'd like to let you all know that we just got a $2000 grant for remote monitoring systems. This means digital recording of things like RPM, Estimated mileage, velocity, location, and communications. We are going to be feeding this information live to the internet for people to view. My question is are there such systems in existence and how much are we truly looking at as far as price. I'm high skeptical to the plausibility of this. Your thoughts?
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Unread postAuthor: rcman50166 » Tue Nov 10, 2009 9:58 pm

Hey guys. I've been looking for weeks now to find an electric start for this engine. I've looked everywhere and asked everyone, except you guys. Here is the info I have right now:

12v based system
designed for a Briggs and Stratton 5HP engine

Also I need ideas for what size electronic ignition I need. That would seem to be up Spudfiles' alley
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Unread postAuthor: jrrdw » Wed Nov 11, 2009 9:19 am

Look here it's where I been buying small engine parts for years.
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Unread postAuthor: rcman50166 » Wed Nov 11, 2009 9:37 am

I've already looked there. The part # based database makes it impossible to find starter motors, even more so to find starter motors that belong to certian engines.
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Unread postAuthor: psycix » Wed Nov 11, 2009 9:51 am

http://www.jackssmallengines.com/help.cfm
This page allows to search for a specific model.
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Unread postAuthor: jrrdw » Wed Nov 11, 2009 10:14 am

Being as how this is only 5HP you might not be able to find a eletric start set up/conversion for this. Maybe, maybe not. As for ignition it's all ready equiped with a Magnatron which is the best 'factory' ignition made for it.

If you want a hop up ignition from there, you will have to look for Jr Dragster parts. www.summitracing.com sells some Jr parts.

http://www.summitracing.com/search/?keyword=jr%20dragster&dds=1

Happy hunting and lets us know what happens.
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Unread postAuthor: rcman50166 » Wed Nov 11, 2009 10:16 am

Thank you both. I have found the starter (model #694504) after a few cross references with the engine.

Now onto the electronic ignition...
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Unread postAuthor: jrrdw » Wed Nov 11, 2009 10:51 am

Do you all ready have the ring gear mounted to your present flywheel? Some flywheels can't be converted and you might need a new one...
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Unread postAuthor: rcman50166 » Wed Nov 11, 2009 11:08 am

jrrdw wrote:Do you all ready have the ring gear mounted to your present flywheel? Some flywheels can't be converted and you might need a new one...


I'm getting a completely new flywheel. Most likely from the engine I linked above. This is so I know I have the right mesh and I also need a larger flywheel to smooth out the engine too.
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Unread postAuthor: Technician1002 » Wed Nov 11, 2009 12:39 pm

rcman50166 wrote:
I'm getting a completely new flywheel. Most likely from the engine I linked above. This is so I know I have the right mesh and I also need a larger flywheel to smooth out the engine too.


Be aware there are advantages to variable timing. The fixed magneto on lawn mower engines are timed for the power range and are inefficient at other loads and RPM. Plan on using an engine computer to set the spark and use a hall sensor on magnetic pickup to detect the flywheel magnet. A magneto coil can be used for power. Is anyone in your group well versed on electronic engine ignition?
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Unread postAuthor: rcman50166 » Wed Nov 11, 2009 2:46 pm

Unfortunately no. My partner and I have about the same knowledge as far as the workings of the engine. All the others are freshman or don't know as much as we do. I have a digital display readout dynamometer but as far as other technology we are extremely limited. We have a budget of $1500 for equipment an upgrades with both the engine and transmission so I think getting precise and complex testing equipment is out of the question. I'm thinking about just making a mechanical switch actuate on a lobe that will be made on the flywheel, I will be able to offset the cam to change ignition timing hopefully. Doing repetitive dyno testing and only changing the cam should give me a graph where I'll be able to find the peak power setting.
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Unread postAuthor: Technician1002 » Wed Nov 11, 2009 7:41 pm

rcman50166 wrote:Unfortunately no. My partner and I have about the same knowledge as far as the workings of the engine.


Bummer. That will put you at a disadvantage. I was going to recommend using a hall effect sensor to sense the flywheel magnet in the same way crank angle sensors work in cars and use a PLL to lock an angle counter to top dead center so you would have microcontroller programmable ignition timing. Without a crank angle counter, your microprocessor controlled ignition options are very limited. It may be worth investigating if an engine control computer is available for other small high performance engines such as snowmobiles. I don't know for sure if they exist. I haven't been in that side of the industry.

How it would have worked if you could have done it is the crank at TDC would provide a crank position pulse. A PLL would lock a timer to tick off 360, 512, 1024 (for degrees or simple binary counting) counts per crank pulse. For starting when you have no steady speed, it would fire at TDC. When the engine is up to speed and the PLL (Phase Locked Loop) is locked to the crank sensor, the PLL can count out degrees from top dead center to provide a timing advance under processor control. A look up table for engine load, throttle position, intake pressure, and temperature would provide the other inputs to the processor. The processor would calculate the time required, count the crank angle and fire the ignition at the best time.

The same processor can time and meter fuel injection.

Good luck. I hope you can find a mentor that can point you to an off the shelf engine control computer or help build and program one.

Anyone here know of any small engine computers?
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