Topic: Prestolite vs Dyna S electrical load

[zabzob]

A recently put a Dyna S ignition in my 75 CB750. Runs great, but voltage seems a bit low and I had an issue with hard starting last year. I understand that Dyna S can put additional electrical load on the system. Previously I had a Prestolite, and I'm wondering if I'd save some juice if I went back to it?

The thing is I've also got this lovely heated vest, and the combination of it with the Dyna S might be too much...

[ekpent]

Don't have an answer to that comparison question but luckily the heated vest can hopefully go on the shelf. The vest and the Dyna might be pushing the limits. Other folks running Dyna's on the 750's also though it is said they do draw more juice then points.

[bustech51]

Juice is in a can and current flow is in a wire.  Sorry for the bad joke... that's what I tell other mechanics.

Sent from my LG-H812 using Tapatalk

[scottly]

There have been claims that the Dyna S draws more current that the stock points due to longer dwell time, but I've yet to see any scientific proof of this. I can tell you that with the stock coils and points, the average current is about 2.5A at lower RPMs, and decreases to about 1.5A at higher RPMs, due to the inductance of the coils. (inductors resist rapid changes in voltage, which causes the decrease in current as the RPM increases.) I have no idea of your Prestolite's draw?
How much power does the vest consume?   

[Deltarider]

[...] I can tell you that with the stock coils and points, the average current is about 2.5A at lower RPMs, and decreases to about 1.5A at higher RPMs [...]

I have the same results but...

, due to the inductance of the coils. (inductors resist rapid changes in voltage, which causes the decrease in current as the RPM increases.   

... I see this differently. When revved, voltages rise and as a consequence amps drop. But I'm an amateur, be it always open to learn something new.

[bryanj]

To loose 40% i n amps the voltage would have to be 17.6

[zabzob]

@scottly

It's a Black Jack heated vest, site says average draw 3.6 Amps / 49 Watts.

[Don R]

 If your ride isn't very long, could you just put a maintainer on it after every ride?

[zabzob]

@Don R

That is what I usually do... for most of the summer I won't be using the vest anyway. I do like to go on a big ride every couple of years, so I'm doing a little future planning. Probably I should make the switch to LED signal/brake lights. I have a flasher module that should work with them even with lower load. I already have an H4 setup for the headlight, so maybe an LED there too.

I generally favour reliability, and all the more so with electrical stuff. I might end up switching back to Prestolite to see if it charges better, or going with one of Hondaman's transistorized points, which I understand are the same load as stock.

[scottly]

[...] I can tell you that with the stock coils and points, the average current is about 2.5A at lower RPMs, and decreases to about 1.5A at higher RPMs [...]

I have the same results but...

, due to the inductance of the coils. (inductors resist rapid changes in voltage, which causes the decrease in current as the RPM increases.   

... I see this differently. When revved, voltages rise and as a consequence amps drop. But I'm an amateur, be it always open to learn something new.

No, if the voltage increases, the current also increases. If you have a 5 ohm coil with 12V applied, the current will be 2.4 amps, in a static, zero RPM condition. With 14.5V applied to the same 5 ohm coil, the static current will be 2.9 amps, but the inductance of the coils reduces the current as the RPM (frequency) increases.

[scottly]

@scottly

It's a Black Jack heated vest, site says average draw 3.6 Amps / 49 Watts.

Should be doable with a 750, as long as you don't spend a lot of time lugging the motor around town. I would keep the H4 headlight myself, and the turn signals and brake lights are only used intermittently, so not much power savings there, but the taillight and front running lights are 8 watts each, IIRC?
I'm still not convinced that the dyna consumes that much more power than stock points under running conditions, and if it's the newer version, they seem to be reliable so far. You could always carry the Prestolite with you on long rides as a spare.
What voltages are you seeing at the battery with the engine running? How old is the battery?   

[Deltarider]

[...] No, if the voltage increases, the current also increases. [...]

Not in my book. May I invite you to do a simple test? Connect an ammeter in the wiring to the headlight and read the current when revved and @ idle.

[TwoTired]

[...] No, if the voltage increases, the current also increases. [...]

Not in my book. May I invite you to do a simple test? Connect an ammeter in the wiring to the headlight and read the current when revved and @ idle.

I’m backing Scottly  on this one.

Your book is faulty if it does not include ohms law.  I = E x R.

A headlight filament has a fixed resistance. Raise the voltage and the current must increase, provided you are in the same physical universe the rest of us live in.

If your “ testing “ shows otherwise, your test method is faulty (or your equipment) and results should not be used by those of us in the real universe.  Adamant Reports of otherwise only confirm the report is unreliable and instantly categorized as sourced from a science denier.

A professional tech or engineer learns early to use calibrated test equipment and technique to trust and rely upon verifiable and repeatable information that can be trusted.  To do otherwise just wastes time and money.  Been there, done that, both my mistake and under influence from others.

[scottly]

[...] No, if the voltage increases, the current also increases. [...]

Not in my book. May I invite you to do a simple test? Connect an ammeter in the wiring to the headlight and read the current when revved and @ idle.

I did a discharge test of an LiFe battery under controlled conditions, using a "60 watt" quartz halogen headlight as a load, while monitoring current, voltage, and time elapsed. Here's the short version:
13.42V 5.08A
12.75V 4.79A
12.45V 4.72A
12.00V 4.64A   

[Deltarider]

Thanks for performing the test. I already felt forced to do it myself, but am glad I don't have to: it's too cold today. I'll repeat the test ofcourse in the near future and intend to use the fuse clips for measuring, after removal of the 7A headlight fuse.
Let me confess that I can't tell a Volt from an Amp let alone an Ohm, when I'd meet one in real life but – and this may come as a shock - none of us can. It's because they do not exist. We, humans have invented them. They are phantasies..., but – and this is the good news - we can work with them. So does the at the time much criticised Ohm's law, show us the real physical world? Mwah, we don't know. Ohm's law is but a trivial closed loop where the outcome is always correct.
I remember that not that long ago, I've shared what I've learned from Marco in the German forum. For those interested, here it is: http://forums.sohc4.net/index.php/topic,188940.msg2195751.html#msg2195751
What we agree on is, that in general, the power consumption of other than stock ignitions is grossly exaggerated in this forum, and I can't help concluding that most must just parrot the other. I repeatly have urged others to do tests themselves, since I, even by applying 3Ω coils, had only found a minor difference. For my homebuilt transistor ignition I had chosen to maintain the same dwell as in the stock set up. I can't see why I would need a longer dwell and possibly endanger the coils. If I was forced to have a breakerpointless EI, I'd give the Tytronics a try. They advertise Duty Cycle is limited to 50% and IMO that's wise. If it is a product from China, I'd refrain from it however, but that's crazy freedom loving me ofcourse.

[newday777]

Get one of Anders alternator upgrade. From stock 17 amp to 32 amp and you can run the dyna and heated gear all day at idle.

http://forums.sohc4.net/index.php/topic,117735.0.html

[scottly]

Let me confess that I can't tell a Volt from an Amp let alone an Ohm, when I'd meet one in real life

Obviously. Try pissing on an electric fence and you will experience a high voltage, low amperage "thrill" that you will not soon forget.

[Deltarider]

You know, Scottly... over at you, one could wonder what exactly kills a convict after courteously been invited  by the law to take a seat: volts, amps, joules?

[Tracksnblades1]

You know, Scottly... over at you, one could wonder what exactly kills a convict after courteously been invited  by the law to take a seat: volts, amps, joules?

Delta,
 
  NIOSH states "Under dry conditions, the resistance offered by the human body may be as high as 100,000 ohms. Wet or broken skin may drop the body's resistance to 1,000 ohms," adding that "high-voltage electrical energy quickly breaks down human skin, reducing the human body's resistance to 500 ohms".

We learned it as 1000ohms because you would be working and moist from sweat. Depending on your heart’s condition, just .1 - .2 amps to stop it. Resuscitation after shocks above .2 may not be as successful due to damage.
This is old info like me… Your Ohm’s law will let you know you have a chance with 120volt. But one 240volt leg of three phase 480 will kill instantly if your resistance is to low..

[Deltarider]

Wow!! Makes a great subject for a presentation by say a 12-year old at school.

[dave500]

here in Australia our normal household power is 240 volts,our three phase is 415,better not lick a wire to see if its live?

[bryanj]

Same as UK , 3 phase is 415 which is phase to phase, domestic is 240 which is phase to ground point

[Deltarider]

Yeah... why go to an execution site, when you can do it home?

[dave500]

do it yourself kits now available!plug n play,err,i mean die.

[Tracksnblades1]

Same as UK , 3 phase is 415 which is phase to phase, domestic is 240 which is phase to ground point

On this side of the pond, Ameren and other are up to 120volts 60 hertz.  Measured from L1 or L2  to the arbitrary neutral of a (single phase primary) center tapped secondary. Usually measuring 125volts  leg to neutral and 250volt across the split phase L1 and L2. Up from the 110volt to supply the minimum 100 volt specified by Edison for his light bulb. Our household 240v circuit only requires the two hot legs L1 and L2 that are 180*split  +120vac and -120vac for a 240vac potential. Older 240 volt appliances didn’t even have a neutral terminal. Some may have had a ground terminal but it was seldom used. Now required. Most reduced neutrals are connected to the house hold earth ground rods through the household service panels.

It’s interesting your commercial 3 phase is 415vac. It’s 480 here up from 460 up from 440. All 60 hertz 120* phase angles.
Usually Delta to Delta or Delta to Wye…for some lighting circuits...Some plants still have some dark phase but it’s not as common as it was..