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Dual Lightspeed interconnection?

P

Pilottonny

Well Known Member
Hello everybody,

I installed dual Lightspeed electronic ignitions. They are wired up to two separate electric systems (dual alternator and dual battery). The electric systems are completely separated (except for an “emergency cross-feed switch”) so that in case of an over voltage of one of the alternators, it will not affect both systems.

I am wondering what the benefit of the “optional” interconnection of the two ignition modules is, and if this will defeat the complete separation of my systems?

Kind regards, and as always, thanks in advance for your reply.

Tonny
 
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Lightspeed

I purchased the dual at Oshkosh this year ('08) from Klaus but have not installed it yet. My buddy, Casper has installed his dual and LOVES it!!
My suggestion is to call and talk to Klaus directly and post the answer?
Kenny Gene
 
The interconnect purpose is to advance the timing of the remaining ignition 5 degrees should one unit fail or be shut down.
 
Advance timing?

Alex, can you explain what the benefit of the 5 degrees advance is?

What effect will this have on the "ignition check" (L-both-R-both)?

Regards, Tonny.
 
MAP connection / cable

Larry, no I am using a single MAP-connection on the intake, that tees into both units. Why? (it also tees into the Dynon MAP-sensor).

I must admit that I am not to happy about this crappy wire, but since it is soldered and glued to the board with some sort of sealer, I am going to leave it as it is. I did cut off the soldered D-sub connectors though and replaced them with crimp-pin ones. This also makes running the cabe through the firewall a lot simpler. The cable also tends to kink if you run it in a sharpisch bend.

Regards, Tonny.
 
Pilottonny said:
Larry, no I am using a single MAP-connection on the intake, that tees into both units. Why? (it also tees into the Dynon MAP-sensor).
Click to expand...

I see this as a point of failure, but that is debatable. A vacuum leak in this line will send both units the same wrong readings and possible cause both units to fail at the same time. Weather this is an issue or not is debatable, but my LSE ignition failed with full advance timing due to (what I believe) was a vacuum leak. In any event, it might be a good idea to run a different MAP line to the other side of the engine for redundancy.

I'm certainly no expert on the subject, all I can tell you is my LSE failed full advance timing at any RPM and caused high engine temps and an emergency landing situation. Dual Slicks Mags for me, once bitten twice shy.
 
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From the manual:
Dual systems can be connected to each other such that each system knows if the other one is operating. If one of the two systems is turned off or has failed, the remaining system will automatically shift its timing curve to provide optimum engine performance with one system. This eliminates the common power loss when one magneto is turned off.
Click to expand...

On an operating dual-ignition setup, switching off a single ignition at run-up RPM, you should see no RPM drop. The single ignition compensates as well as it can, so I expect that the nearer to full power you operate the more likely you will see a RPM drop going to single ignition but I have not tried this. However, my setup is wired so that one CDI is on a different battery that gets alternator feed from them main buss but can be isolated if the alternator or either battery fails. The interconnect is signal only, so one CDI will not power the other in the event of a failure.
 
I have dual LSI and did not install the interconnect as I want to see the drop when I turn one system off so I know everything is working. Also used the same vaccum with a 'T', if you lose vaccum the system will not advance the timing (high vaccum reading = high power = no advance).
 
So, no interconnect it will be.

Thanks Walt, I am convinced, no interconnect for me neither. If one fails, all I want is getting to the next airport, no sporting performance. Indeed the RPM drop and back up when you switch both on, tells you everything is good.

So it will not cause a big problem if the vacuum line is cut, damaged or loose?

Regards, Tonny.
 
This statement here is a little bit erroneous:(high vaccum reading = high power = no advance). Vacuum is actually the opposite of manifold pressure. High manifold pressure usually means a high power setting, and there is very little vacuum at the sensor. Basically you will see atmospheric pressure less the drop across the intake manifold. The more efficient ones have very little drop, and the snout on Van's airplanes actaully allows for a ram air Increase in atmoshperic pressure at cruise speeds.
Low power settings, on the other hand, have a very high vacuum and a low manifold pressure reading.

Vic
 
Geico266 said:
I see this as a point of failure, but that is debatable. A vacuum leak in this line will send both units the same wrong readings and possible cause both units to fail at the same time.
Click to expand...

Hopefully someone will jump on me if I misunderstand this gizmo - I'd rather learn I was wrong than fly with bad systems understanding.

This depends on what you mean as "failure." At low RPM and / or high MAP, the units command a default of 25TDC timing. Only at high rpm AND reduced MAP do you see the unit advance the timing. As I understand this system only a failure of the MAP tube would affect both units (a leak), and that would only cause the timing to RETARD towards 25TDC (or 20TDC for high compression engines) up to the amount which would be commanded by Wide Open Throttle, and then only if you were high enough or running a low enough MAP that the unit would otherwise have been advancing the spark more than 25TDC.

Thus, as I understand things such a "failure" would only result in slightly less ignition advance. Worst case it would default to the same ignition timing as a Mag (fixed at 25/20 TDC).

Bill
 
Bill,
You are correct, if you lose the vaccum then the LSI goes to 25 deg with no advance.

And I stand corrected: "Vacuum is actually the opposite of manifold pressure" is correct, I have a tendancy to use these terms interchangeably because they are measuring the same thing differently.:confused:
 
Walt said:
Bill,
You are correct, if you lose the vaccum then the LSI goes to 25 deg with no advance.

And I stand corrected: "Vacuum is actually the opposite of manifold pressure" is correct, I have a tendancy to use these terms interchangeably because they are measuring the same thing differently.:confused:
Click to expand...

All I know is the LSE I had on my IO-540 advanced the timing tp the point where the engine was over heating and running very rol I got smart enough to turn it off and fly it home.

What else would advance the timing so far as to cause potential damage to the engine?
 
Geico266 said:
All I know is the LSE I had on my IO-540 advanced the timing tp the point where the engine was over heating and running very rol I got smart enough to turn it off and fly it home.

What else would advance the timing so far as to cause potential damage to the engine?
Click to expand...

Unless the timing was not set correctly initially or something happened in flight to change the setting (virtually impossible with the crank sensor, but the Hall Effect sensor could turn if not tight), the only things which should advance the timing are higher RPM and lower MP. If you were at high altitude and lowered your power setting and THEN your MP tube got blocked, it could be "stuck" thinking you were at a low power setting/high rpm when you increase power.

Also, I suppose if your Lightspeed were accidentally hooked up to the vacuum system you could be in big trouble!

Anything else I imagine would have to be a problem with the actual controller - maybe a bad MP transducer.
 
Just FYI, for those with dual LSEs there is a simple diagram posted on their website that shows how to wire in LEDs to indicate an ignition failure since there isn't an RPM drop with the interconnect in place.

Larry and I have talked a few times about LSE (and other things) and while I understand his decision to remove the ignition from his plane, I have a dual setup in the same model of plane (RV-10) and love them. Larry purchased his plane flying and it's important to note that it suffered from some installation issues. Whether this contributed to his problem I don't know.

Bob
 
Geico266 said:
All I know is the LSE I had on my IO-540 advanced the timing tp the point where the engine was over heating and running very rol I got smart enough to turn it off and fly it home.

What else would advance the timing so far as to cause potential damage to the engine?
Click to expand...

I am not sure if Larry had the LSI display, but I recommend it as it will show the actual advance and also the MP that the EI is seeing. In addition it will also show RPM. I rarely look at mine but it is reassuring to know what the EI is up to and if the timing has changed for some reason. It would also a useful backup instrument for RPM and MP. :cool:

Fin
9A
 
breister said:
Anything else I imagine would have to be a problem with the actual controller - maybe a bad MP transducer.
Click to expand...

That could have been, but like I said; "Once bitten twice shy." No problems at all since I replaced the LSE with a Slick. ;)
 
bcondrey said:
Just FYI, for those with dual LSEs there is a simple diagram posted on their website that shows how to wire in LEDs to indicate an ignition failure since there isn't an RPM drop with the interconnect in place.
Click to expand...

Taking this a bit further, I have dual LSE Plasma II+ units and two AF3500s (AF3500EF/AF3500EM). The AF3500s have 3 switched inputs each (either open or grounded). If I connect the 5V output from each LSE unit to a switch input, I could then have the AF3500s alert me when an EI unit has failed, and which one without having to drill another hole in my panel.

Will this work? What am I missing? Surely it can't be that easy?????
 
Toe easy!: Does the 5 V realy act as an indicater of failure?

Good idea, but maybe the 5 Volt output will just stay on while the unit is stil not pushing out any "sparkies" through your fat red wires?

Actually I believe the 5 volt will be on, to power a display or something, as soon as you put power to it, even if the engine is not even running. Right?

If you find out it does indicate failure, I want to connect it to two of my contacts of the Dynon EMS. Please let us know if that realy works.

Tonny
 
Will do

Dunno if you've seen it, but the LSE schematic (http://www.lightspeedengineering.com/Images/dualindicator-LSEr3.pdf) implies there is no current if/when the unit fails, hence the current differential powering the LED.

I'm still a few weeks away from powering it up, but will definitely let you know what happens, but would still appreciate anyones thoughts on the viability of this (esp. if I'm likely to do damage)

As I said, surely it can't be that easy! :)
 
Steve

Hey Steve. did you ever hook your LSE up to your AFS to display a failed ignition? How did it work out?
 
Dual LSE interconnect

When you do a run-up with a dual LSE and have the interconnect in place, because of a slight delay in the circuitry, there will be a momentary drop in rpm, and then the rpm will return to almost, but not quite, the rpm before switching. As far as losing the MAP input to an LSE, if you are at any altitude above sea-level where the static pressure is lower than sea-level pressure, the timing will revert to where it should be at that static pressure. So if you are at WOT, the MAP the LSE would normally see is the static pressure plus stagnation pressure, minus the pressure drop in the inlet duct, filter, and carburetor, if present. So if your MAP tubing came off at WOT, the LSE would sense the pressure where the tubing is open. In this situation there would be only a small change, up or down, so the timing may only change a degree or so depending on the induction pressure loss or gain. If you were running at part throttle, lower MAP and more advanced timing, and the tubing opened, the MAP would would probably be at a higher pressure which would cause the timing to retard to the higher pressure value. Other than a circuit failure that would give maximum advance, I think the proposition put forth of the tubing becoming clogged at a low MAP with advanced timing and then the plane descending to a lower altitude and given more throttle is a good explanation. Another scenario would be if a circuit failure caused the timing to revert to the TDC timing it uses at engine start, this would definitely cause the engine to run hot, but that would only occur with a single LSE, since dual failures of the same type is highly improbable.
 
Noah said:
Hey Steve. did you ever hook your LSE up to your AFS to display a failed ignition? How did it work out?
Click to expand...

Gidday Noah, yes I did and while it does work it does quite come out as the alarm I was expecting in that the two screens do not share inputs. Ssssooooo what I've ended up with is a "Left Ignition" (or "Right Ignition") message on my AF3500EM which is in front of the right seat so I need to ensure that's in my scan...

I'll try to remember to take a photo over the weekend.
 
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