Hi Grumpyvette,
I'll bet you get a lot of emails concerning mechanical woes and tidbits?
Have read most of the links and found new info based on that info by using a google search. Found some really good info on valve shrouding, opening amts for best airflow, etc. However, found nothing on theoretical valve sizes, other than shrouding is important when considering the max size for cylinder bore--makes sense. I'm still trying to find info on what the exhaust valve size ratio to intake valve size should be. Generally, everyone talks about flow amts and the assume that the traditional valve size will be used.
The only solid bit of info about this was an article on valve shrouding, and that would tend to make me think that the builder of my heads thinks a 1.94 Manley Pro Flow is shrouded less than a typical 2.02. What are your thoughts on this subject?
I did come across an interesting topic on the Forum about ignition wires and resistance. Yup, everyone got it wrong--as an electronic engineer, I can tell you, what those people have posted is nothing but genuine snake oil. A typical GM high energy system is balanced for using 2,500Ohms/Ft wires. Anything less and not enough voltage is developed. Use low resistance wires and what is developed is current. Current is destructive to electronic components. Current is what eats sparkplugs and distributor contacts, and it overheats the coil. Current doesn't fire the plugs--voltage jumps the gap and fires the plugs. Too little resistance in the wires and the complete timing and build up of the magnetic field/voltage and current balance will be skewed the wrong way. The result will be an overheated coil, and quick erosion of the spark plugs and cap/rotor.
Regards,
Charles O'Toole
thats interesting, Ive always found resistor spark plugs and low resistance wire tended to get the best, most consistent ignition results on engines,keep in mind,wet, loose, or broken electrical connectors or corrosion on connectors, is also possibly a cause of intermittent problems
GRUMPYVETTE
Other than the coil overheating from drawing a high current to jump the gap (with voltage), and the various gap electrodes deteriorating at a high rate, there is no way you could tell the difference--the engine will fire with a high current, but it is voltage that jumps the gap and not current. The first rush of voltage across the spark gap can be as high as 20,000 volts in order to ionize the gap (generally, about 10,000 volts is what is needed), after that, the voltage goes down to as little as 2,000 volts and does this as the magnetic field collapses. Try to generate current vice voltage, and the coil will run hotter as more current flows thru. Remember Ohm's Law E=IR, where E is voltage, I is current measured in amps and R is resistance measured in Ohms. You can't have one without the other two. Lower resistance and either current or voltage must change, and since there is a required amt of voltage to jump the gap, then it is current that is increased. Since a low resistance wire is being used, then current must go up in order to generate the same voltage, and the amt of voltage required is determined by the total air gap at the plugs and at the distributor cap if the engine is equipped that way. Voltage is always measured thru a resistance.
Going with low resistance wire is not the way to go, in order to get the required voltage, Ohm's Law specifies that current must go up and it is current that erodes electrodes by transferring soft metals to hard ones, or just eating up both if they are the same metal. Lowering the resistance to as little as 200 ohms can double the current flow thru the system.
Remember those "special" distributor caps that have "premium" brass contacts??? Those are bunk. GM specifies aluminum in the caps becuz the rotors are brass--8 contacts made of aluminum will erode at the same rate as one contact made of brass. If all are brass, then the rotor erodes faster than the cap terminals.
Regards,
Charles O'Toole
your viewpoint may be very valid, but Ive got a question, like most things this might be a matter of ballancing ,compromise or degrees, ITs my understanding that
current or amps generate, HEAT and that the HEAT and THE durration of the SPARKS ARC has an effect on ignition efficiency? its not sufficient to simply jump the gap with a spark to ignite the compressed f/a mix, it needs to get a real kick-off on that ignition at high rpms to burn correctly as the time involved for effective ignition of the charge is fairly short at about .00012 seconds MAXIMUM
GRUMPYVETTE
That again is a misnomer that has been popularized by such companies as Taylor and Jacobs--it's called psuedo science. A 40,000 volt spark is "hotter" than a 2,000 volt spark, becuz it has more volts. Except that "hotter" does not relate to electricity. Any spark that can jump the gap and ionize the air is the same voltage. However, in order to jump the gap or generate the voltage in a coil based ignition system, there must be resistance. In fact, too much resistance will blow the so-called "secondary" side of the coil. Another misnomer that is popularized by Jacobs and others is that in a negative ground system, the secondary and primary are actually the secondary and primary. This is not true. In a negative ground system, the 2ndary is actually the primary and the primary is the 2ndary. This all makes sense when it is realized that voltage jumps the gap, and not current and the voltage jumps from the outside electrode to the center electrode of the spark plug.
The max voltage that can be achieved within the coil is 12 volts at rated battery current or system current and 12 volts at rated system current is what is actually put out by the coil. The current and voltage at the Primary side (the one with all the turns and wires) is the max voltage that can be induced by the system's resistance. In order to create this voltage, the turns on the primary side must be far greater than the turns on the 2ndary side (remember, the names are reversed)...as voltage is increased then current goes down by Ohm's law. There is no way to violate this law or modify it and companies like Jacobs and Taylor like to use words such as "hotter" spark or more power to the plugs, etc., but the are ignoring and not stating voltage, becuz the induced voltage is virtually the same and is a measurement of the voltage necessary to jump the gap, increase the gap and more voltage is required to jump that gap and current goes down at the same time. All the while they are ignoring the fact that system voltage is determined by the total resistance as found in the spark plugs and the gaps. Too much resistance, as in a broken wire can cause the coil to internally short or blow thru an ingnition wire. Too little resistance and voltage goes down and more current is created and that means system degradation over time. GM specifies 2,500 Ohms/ft as the best balance between the system firing the spark plugs and system longevity. Current is destructive to a system and voltage is not. It is current that erodes spark plugs and the gaps between the rotor and cap terminals.
Max system voltage is always 12 volts at rated current. Battery current in a typical Corvette with a 700 amp battery is 700 amps. Now, try and shove that thru the coil--can't be done. In fact check out the differences in the main feed to the starter and the coil. The starter has at least 10 gauge wire and the coil generally has 16 gauge wire. This difference shows you that the ignition system is not set up to handle high current. However, coil saturation timing and total system voltage/current/resistance is set by GM. Any attempt to alter that means system failure, either right now or sometime later as it deteriorates from too much current. The reverse of this is that too much resistance will blow the coil (too much current can lead to hotter coil temps and coil insulation breakdown). Break a wire and induce high system resistance and the voltage generated by the coil not only goes up, but it must go somewhere to complete the circuit. Usually, the voltage will blow thru the spark plug wire insulation trying to jump the "gap" or it will blow thru the coil wires trying to find a gap of least resistance. Doesn't matter if it is the spark plug gap that has opened up, or if a wire has failed. The coil will generate the voltage that is necessary to complete the circuit, and the higher the voltage, the lower the current. IN this case, too much voltae and the system blows up.
Generally, the wires within the system can handle the current, but not the gaps, such as are found in the spark plug or the cap and rotor--it's current that erodes those.
I made a mistake...if resistance is reduced, current goes up, voltage goes down, but wattage is increased. Watts are usually referred to as "power" and watts can be used to measure everything from internal combustion engine power out to light bulbs.
I did some quick math and then verified this by measuring the filament resistance of a common three way light bulb. Here is what I found--notice that as resistance goes down, watts and current increases:
50 watt filament... 0.41 amp 30 ohms
100 watt filament.. 0.833 amp 20 ohms
150 watt filament.. 1.25 amp 10 ohms
Japanese light bulb claimed 75 watt is actually 68 watts....rated at 100 volts, and 11 ohms resistance with .688 amp of current. That was a strange one.
Realizing that the three filament light bulb above is rated as such with amps, watts of power expended and resistance, which one gives off the most heat? Of course, you can feel the very hot 150 watt light bulb. In a car, that heat is absorbed by the coil, and that heat can be expressed in watts. Also, notice how much the current goes up...the 50 watt filament is 1/3 of the amps, and wattage of the 150 watt bulb and also, 1/3 of the resistance. This is by Ohm's law and is exactly the same for ignition systems, with the exception that current erodes the parts of the ignition systems. However, you might say the same thing about the 150 watt filament, which one will burn out first?
Here's a good primer on this..http://www.the12volt.com/ohm/ohmslaw.asp
Regards,
Charles O'Toole
WE ALL ocasionally make mistakes,
(I KNOW I DO FOR SURE!)
and we are ALL learning all the time,
as long as we get everything corrected,
its just all too frequent part of the learning process, and no big deal.
as your link points out...
Ohm's Law defines the relationships between (P) power, (E) voltage, (I) current, and (R) resistance. One ohm is the resistance value through which one volt will maintain a current of one ampere.
( I ) Current is what flows on a wire or conductor like water flowing down a river. Current flows from negative to positive on the surface of a conductor. Current is measured in (A) amperes or amps.
( E ) Voltage is the difference in electrical potential between two points in a circuit. It's the push or pressure behind current flow through a circuit, and is measured in (V) volts.
( R ) Resistance determines how much current will flow through a component. Resistors are used to control voltage and current levels. A very high resistance allows a small amount of current to flow. A very low resistance allows a large amount of current to flow. Resistance is measured in ohms.
( P ) Power is the amount of current times the voltage level at a given point measured in wattage or watts.
"
SO to get good ignition you need voltage sufficient to jump the spark plug gap easily and enought amps in the arc jumping the gap between the electrode and ground at the plug to generate sufficient heat to almost instantly and consistantly ignite the compressed fuel/air mix. obviously that spark must occure at the correct time in relation to piston location in its rotation and adjusted for its speed too allow the correct pressure curve to form above the piston, and at the precise time desired.
BTW heres some spark plug related info
/posting.php?mode=edit&f=70&t=202&p=237
a bit of ignition related info
viewtopic.php?f=70&t=232&p=1940&hilit=curve#p1940
I'll bet you get a lot of emails concerning mechanical woes and tidbits?
Have read most of the links and found new info based on that info by using a google search. Found some really good info on valve shrouding, opening amts for best airflow, etc. However, found nothing on theoretical valve sizes, other than shrouding is important when considering the max size for cylinder bore--makes sense. I'm still trying to find info on what the exhaust valve size ratio to intake valve size should be. Generally, everyone talks about flow amts and the assume that the traditional valve size will be used.
The only solid bit of info about this was an article on valve shrouding, and that would tend to make me think that the builder of my heads thinks a 1.94 Manley Pro Flow is shrouded less than a typical 2.02. What are your thoughts on this subject?
I did come across an interesting topic on the Forum about ignition wires and resistance. Yup, everyone got it wrong--as an electronic engineer, I can tell you, what those people have posted is nothing but genuine snake oil. A typical GM high energy system is balanced for using 2,500Ohms/Ft wires. Anything less and not enough voltage is developed. Use low resistance wires and what is developed is current. Current is destructive to electronic components. Current is what eats sparkplugs and distributor contacts, and it overheats the coil. Current doesn't fire the plugs--voltage jumps the gap and fires the plugs. Too little resistance in the wires and the complete timing and build up of the magnetic field/voltage and current balance will be skewed the wrong way. The result will be an overheated coil, and quick erosion of the spark plugs and cap/rotor.
Regards,
Charles O'Toole
thats interesting, Ive always found resistor spark plugs and low resistance wire tended to get the best, most consistent ignition results on engines,keep in mind,wet, loose, or broken electrical connectors or corrosion on connectors, is also possibly a cause of intermittent problems
GRUMPYVETTE
Other than the coil overheating from drawing a high current to jump the gap (with voltage), and the various gap electrodes deteriorating at a high rate, there is no way you could tell the difference--the engine will fire with a high current, but it is voltage that jumps the gap and not current. The first rush of voltage across the spark gap can be as high as 20,000 volts in order to ionize the gap (generally, about 10,000 volts is what is needed), after that, the voltage goes down to as little as 2,000 volts and does this as the magnetic field collapses. Try to generate current vice voltage, and the coil will run hotter as more current flows thru. Remember Ohm's Law E=IR, where E is voltage, I is current measured in amps and R is resistance measured in Ohms. You can't have one without the other two. Lower resistance and either current or voltage must change, and since there is a required amt of voltage to jump the gap, then it is current that is increased. Since a low resistance wire is being used, then current must go up in order to generate the same voltage, and the amt of voltage required is determined by the total air gap at the plugs and at the distributor cap if the engine is equipped that way. Voltage is always measured thru a resistance.
Going with low resistance wire is not the way to go, in order to get the required voltage, Ohm's Law specifies that current must go up and it is current that erodes electrodes by transferring soft metals to hard ones, or just eating up both if they are the same metal. Lowering the resistance to as little as 200 ohms can double the current flow thru the system.
Remember those "special" distributor caps that have "premium" brass contacts??? Those are bunk. GM specifies aluminum in the caps becuz the rotors are brass--8 contacts made of aluminum will erode at the same rate as one contact made of brass. If all are brass, then the rotor erodes faster than the cap terminals.
Regards,
Charles O'Toole
your viewpoint may be very valid, but Ive got a question, like most things this might be a matter of ballancing ,compromise or degrees, ITs my understanding that
current or amps generate, HEAT and that the HEAT and THE durration of the SPARKS ARC has an effect on ignition efficiency? its not sufficient to simply jump the gap with a spark to ignite the compressed f/a mix, it needs to get a real kick-off on that ignition at high rpms to burn correctly as the time involved for effective ignition of the charge is fairly short at about .00012 seconds MAXIMUM
GRUMPYVETTE
That again is a misnomer that has been popularized by such companies as Taylor and Jacobs--it's called psuedo science. A 40,000 volt spark is "hotter" than a 2,000 volt spark, becuz it has more volts. Except that "hotter" does not relate to electricity. Any spark that can jump the gap and ionize the air is the same voltage. However, in order to jump the gap or generate the voltage in a coil based ignition system, there must be resistance. In fact, too much resistance will blow the so-called "secondary" side of the coil. Another misnomer that is popularized by Jacobs and others is that in a negative ground system, the secondary and primary are actually the secondary and primary. This is not true. In a negative ground system, the 2ndary is actually the primary and the primary is the 2ndary. This all makes sense when it is realized that voltage jumps the gap, and not current and the voltage jumps from the outside electrode to the center electrode of the spark plug.
The max voltage that can be achieved within the coil is 12 volts at rated battery current or system current and 12 volts at rated system current is what is actually put out by the coil. The current and voltage at the Primary side (the one with all the turns and wires) is the max voltage that can be induced by the system's resistance. In order to create this voltage, the turns on the primary side must be far greater than the turns on the 2ndary side (remember, the names are reversed)...as voltage is increased then current goes down by Ohm's law. There is no way to violate this law or modify it and companies like Jacobs and Taylor like to use words such as "hotter" spark or more power to the plugs, etc., but the are ignoring and not stating voltage, becuz the induced voltage is virtually the same and is a measurement of the voltage necessary to jump the gap, increase the gap and more voltage is required to jump that gap and current goes down at the same time. All the while they are ignoring the fact that system voltage is determined by the total resistance as found in the spark plugs and the gaps. Too much resistance, as in a broken wire can cause the coil to internally short or blow thru an ingnition wire. Too little resistance and voltage goes down and more current is created and that means system degradation over time. GM specifies 2,500 Ohms/ft as the best balance between the system firing the spark plugs and system longevity. Current is destructive to a system and voltage is not. It is current that erodes spark plugs and the gaps between the rotor and cap terminals.
Max system voltage is always 12 volts at rated current. Battery current in a typical Corvette with a 700 amp battery is 700 amps. Now, try and shove that thru the coil--can't be done. In fact check out the differences in the main feed to the starter and the coil. The starter has at least 10 gauge wire and the coil generally has 16 gauge wire. This difference shows you that the ignition system is not set up to handle high current. However, coil saturation timing and total system voltage/current/resistance is set by GM. Any attempt to alter that means system failure, either right now or sometime later as it deteriorates from too much current. The reverse of this is that too much resistance will blow the coil (too much current can lead to hotter coil temps and coil insulation breakdown). Break a wire and induce high system resistance and the voltage generated by the coil not only goes up, but it must go somewhere to complete the circuit. Usually, the voltage will blow thru the spark plug wire insulation trying to jump the "gap" or it will blow thru the coil wires trying to find a gap of least resistance. Doesn't matter if it is the spark plug gap that has opened up, or if a wire has failed. The coil will generate the voltage that is necessary to complete the circuit, and the higher the voltage, the lower the current. IN this case, too much voltae and the system blows up.
Generally, the wires within the system can handle the current, but not the gaps, such as are found in the spark plug or the cap and rotor--it's current that erodes those.
I made a mistake...if resistance is reduced, current goes up, voltage goes down, but wattage is increased. Watts are usually referred to as "power" and watts can be used to measure everything from internal combustion engine power out to light bulbs.
I did some quick math and then verified this by measuring the filament resistance of a common three way light bulb. Here is what I found--notice that as resistance goes down, watts and current increases:
50 watt filament... 0.41 amp 30 ohms
100 watt filament.. 0.833 amp 20 ohms
150 watt filament.. 1.25 amp 10 ohms
Japanese light bulb claimed 75 watt is actually 68 watts....rated at 100 volts, and 11 ohms resistance with .688 amp of current. That was a strange one.
Realizing that the three filament light bulb above is rated as such with amps, watts of power expended and resistance, which one gives off the most heat? Of course, you can feel the very hot 150 watt light bulb. In a car, that heat is absorbed by the coil, and that heat can be expressed in watts. Also, notice how much the current goes up...the 50 watt filament is 1/3 of the amps, and wattage of the 150 watt bulb and also, 1/3 of the resistance. This is by Ohm's law and is exactly the same for ignition systems, with the exception that current erodes the parts of the ignition systems. However, you might say the same thing about the 150 watt filament, which one will burn out first?
Here's a good primer on this..http://www.the12volt.com/ohm/ohmslaw.asp
Regards,
Charles O'Toole
WE ALL ocasionally make mistakes,
(I KNOW I DO FOR SURE!)
and we are ALL learning all the time,
as long as we get everything corrected,
its just all too frequent part of the learning process, and no big deal.
as your link points out...
Ohm's Law defines the relationships between (P) power, (E) voltage, (I) current, and (R) resistance. One ohm is the resistance value through which one volt will maintain a current of one ampere.
( I ) Current is what flows on a wire or conductor like water flowing down a river. Current flows from negative to positive on the surface of a conductor. Current is measured in (A) amperes or amps.
( E ) Voltage is the difference in electrical potential between two points in a circuit. It's the push or pressure behind current flow through a circuit, and is measured in (V) volts.
( R ) Resistance determines how much current will flow through a component. Resistors are used to control voltage and current levels. A very high resistance allows a small amount of current to flow. A very low resistance allows a large amount of current to flow. Resistance is measured in ohms.
( P ) Power is the amount of current times the voltage level at a given point measured in wattage or watts.
"
SO to get good ignition you need voltage sufficient to jump the spark plug gap easily and enought amps in the arc jumping the gap between the electrode and ground at the plug to generate sufficient heat to almost instantly and consistantly ignite the compressed fuel/air mix. obviously that spark must occure at the correct time in relation to piston location in its rotation and adjusted for its speed too allow the correct pressure curve to form above the piston, and at the precise time desired.
BTW heres some spark plug related info
/posting.php?mode=edit&f=70&t=202&p=237
a bit of ignition related info
viewtopic.php?f=70&t=232&p=1940&hilit=curve#p1940