Coil input information

[ndutton]

I toned it down from "control freaks." Have you tried skipping that manual regulator across the inlet yet?

Remember the coil voltage is considerably less during starting due to starter load and no alternator contribution. Accordingly, resistance in the circuit can be overdone. Thatch's testing showed a minimum of 9 volts at the coil (if I recall) before performance degrades. Too much resistance could affect starting.

[sastanley]

Neil, good info..that type of stuff is yet to be determined..I can tell you that I agree with Tom T. that too little voltage can slow starting..& I might currently be right on the edge, since she doesn't "come alive" instantly with the current configuration. Maybe I need a switch to 'turn on' my resistor once the engine is running..

[Kelly]

she doesn't "come alive" instantly with the current configuration. Maybe I need a switch to 'turn on' my resistor once the engine is running..

and

I assume this would also mean running a wire from the starter+ to the coil+ to have full battery volts while cranking?

This was my question back in post #20. Our resistance is calculated taking into account contributions from the alternator. My thinking was to provide full battery volts to the coil during cranking by running a power wire from the starter. That way the direct connection to the battery is broken when you turn the ignition from "start" to "run".

Make sense?

[sastanley]

Kelly, yes it does...however, in my case, I also still have 30 year old wiring in the ignition circuit that I need to eliminate (the original C-30 engine wiring harness, which is notorious for having problems), so I get about a full 1 volt of voltage drop along the route.

So, I am really mucking up the works. The crank voltage was low enough the other evening that it made my LED cabin light flicker while cranking.

[ndutton]

Kelly,

That was not my experience. Prior to the addition of the resistor my engine always started within a second of cranking regardless of layoff time. After the resistor it did the same. I'm close to a full ohm less than Shawn hence my caution to him.

[edwardc]

...My thinking was to provide full battery volts to the coil during cranking by running a power wire from the starter. That way the direct connection to the battery is broken when you turn the ignition from "start" to "run".

Make sense?

Just make sure to use the right terminal on the starter!!! Not all starters have it!

If you simply wire it to the solenoid terminal, during normal running the coil's circuit will "back feed" through the resistor to the solenoid! It may even be enough to pull-in/hold-in the solenoid and cause the starter to keep cranking! Not good! You can destroy a starter that way, and the only to stop it once it happens is to disconnect the battery!

My starter has an extra terminal on it for just this purpose. While cranking, it is energized, but when not cranking it is completely isolated from BOTH the battery and the solenoid. In fact this usage is exactly what the terminal was designed for.

Some of us with electronic fuel pumps (myself included) have repurposed this terminal to bypass the Oil Pressure Safety Switch during cranking in order to get the fuel pump going right away while retaining the protection of the OPSS while running.

[Marian Claire]

I have noticed no change in start time, 1 to 2 seconds, after adding the resistor. Re: post 136 and 174 for my #s. Dan S/V Marian Claire

[sastanley]

Ok...so I fired up the boat this weekend and me and my lovely did a little shakedown/ harbor cruise. I am so OCD/AR/worried about this darn motor that I normally would have full sails rigged in the event the motor quit. I resisted that urge, and although I had sails aboard, I did not put the main on the boom, nor did I take the genoa out of its bag. I did check and make sure the anchor was ready to go in the event I had to keep from drifting into something!

The first part of this story is the engine harness re-wiring was a success. She fired right up and ran nicely at the dock. We took her down the creek to a friend's house and had some wine & cheese at their dock and then putzed around for 35-40 minutes.

So, here are the numbers I have...dirty bottom, prop last cleaned probably in late September if I recall...

5" vac at 1,900 RPM.

WOT right now is about 2,050...definitely a dirty bottom & some stuff on the prop, but after it sat all winter and to run this well in spring, I am tickled.

45 PSI oil

165°F average (raw) water temp

13.5 volts on the new meter.

Alternator output 14.15 volts

Coil voltage with a 1.3 Ω resistor in place = 11.2V - I had no trouble starting her with this resistor..I didn't bring the infrared thermometer or anything, but the engine ran absolutely flawlessly today.

Now, if I can just get off my lazy butt and clean out the water jacket and get the FWC installed.

[ArtJ]

One item arises my curiosity. No one has mentioned the reactance, or AC
resistance of the coil, and what part this will play in the load and power
dissipation.
inductive reactance = xL =2 pi times f or frequeny times L Inductance of the coil . Or xL = 2 (3.14 ) f L

As RPM goes up, the AC resistance (reactance) goes up and dissipation
should therefore go down.

Just some thoughts

Regards

[joe_db]

I think I did mention that Ohm's law is an approximation at best for what is really an inductive AC circuit. That said, a lot of empirical evidence and testing went into these calculations and the resistors seem to do the trick. I also decided thanks to this thread the next EI system I get will be CD and not use the coil to store energy.

One item arises my curiosity. No one has mentioned the reactance, or AC
resistance of the coil, and what part this will play in the load and power
dissipation.
inductive reactance = xL =2 pi times f or frequeny times L Inductance of the coil . Or xL = 2 (3.14 ) f L

As RPM goes up, the AC resistance (reactance) goes up and dissipation
should therefore go down.

Just some thoughts

Regards

[ArtJ]

Not disrespecting the empirical findings at all, but since you guys are looking at
a relatively small change in voltage drop to effect a large power dissipation, I would
expect it to certainly play a significant role

Best Regards.

PS the easiest way to perhaps see what's going on ac wise would be to put a
isolated scope across the coil dc inputs. Just trying to be helpful

[ndutton]

If I may

you guys are looking at a relatively small change in voltage drop to effect a large power dissipation

The voltage reduction although small in absolute value is significant considering we're only talking about a 12 volt system. A 2 volt drop equates to a 15% difference. Looking at the same 15% in a 120V household system you'd drop to 102 volts, pretty significant.

More important is the system amperage and the fact that before this exercise some of us were operating beyond the specified maximum, some were right on the edge.

[Dave Neptune]

An FYI

Hey guys, I have been using an EI for years and have bragged of it's benifits. Although I'm not using the Pertroniz unit I have been following this thread. I bought my unit complete with coil and a new set of springs. It has woked flawllessly for many many years now. I decided to try a resistor in mine after reading about temp concerns to see if it made any changes at all. I did move the coil off the block too. Anyway I have about 10 hours running with the resistor and about 3 hours of that were at low RPM's and just over 7 hours at cruise. The engine has been started cold now about 6 times and I see no differance in the starting cycle at all. I do not and will not use a temp gun however I will report the coil does run somewhat cooler than before AND I am running the "EI box" on the reduced voltage side of the resistor as it is rated from 6 ~ 16 Vts and as stated no issues at all so far.

Dave Neptune

[ndutton]

That's great info Dave. I can report as well that my engine is running noticeably smoother and quieter than ever, starts easily with the resistor in the system. The only recent change has been a further voltage reduction due to lower alternator output, another 0.7 volts lower putting my ignition amperage at 3.3 amps.

[ArtJ]

The voltage reduction although small in absolute value is significant considering we're only talking about a 12 volt system. A 2 volt drop equates to a 15% difference. Looking at the same drop in a 120V household system you'd drop to 102 volts, pretty significant.

More important is the system amperage and the fact that before this exercise some of us were operating beyond the specified maximum, some were right on the edge.

So you guys should look at the ac impedance of the coil under load.
If you have the external resistor in the circuit you can determine
the ac current by hanging the scope across the ext. resistor, then knowing
the current, relocate the scope across the coil plus and minus .then measure
the ac voltage across the coil on the scope and determine the Z total =AC IMPEDANCE combined with the DC resistance.
(Do this by measuring the coil AC +DC voltage drop and divide by the AC +DC current measured across the external resistor).

Regards