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Lightspeed timing

ge9a

Well Known Member
I have a Lightspeed Plasma II (right side) with a Slick mag (impulse coupled, left side) on an IO-320. When timing with a strobe light, the manual shows two specs - one with the manifold pressure connected, the other with the manifold pressure disconnected. My question is do I need to plug (block) the connection at the engine side when the manifold pressure line is disconnected or will the engine run smoothly (at idle) with the line disconnected?

As always, thanks in advance for direction/explanation on this.
 
Just purchase a brass cap at the hardware store and an O ring that just fits inside it and install hand tight. The O ring will make up the difference between 37deg fitting and 45 deg cap, for this application only....

Or you can wait and order one from Spruce.
 
The engine will run smoothly, you’re only checking the electronic’s response to no manifold pressure for a change.
 
I am thinking the engine will pull in a lot of extra air and run very lean when the manifold pressure line is disconnected. Is this true, or not enough to be concerned about while checking the timing?
 
I am thinking the engine will pull in a lot of extra air and run very lean when the manifold pressure line is disconnected. Is this true, or not enough to be concerned about while checking the timing?

Typically we tap MP by screwing a restricted fitting into one of the unused cylinder primer ports. The restrictor (1) serves to minimize the intake leak if the MP line becomes disconnected, and (2) helps smooth the oscillating port pressure.

Will the engine run badly with the MP line disconnected? Depends on the size of the restrictor. A large one might make idle a bit lumpy. and would show up in the EGT display as a lean cylinder in cruise. In the context of checking a Lightspeed's timing, no problem. Even if it does run a little rough, it doesn't change the timing.
 
The need to cap the port off or not depends on the effect on idle speed. If it does not change enough to trigger a timing shift in the Lightspeed, then it does not matter if it runs rough, lean, or otherwise. You are simply looking for the same RPM based timing that you will see in normal ops.
 
So when I'm checking the Lightspeed timing, should both specifications (first one with manifold pressure line connected, second one with it disconnected) be checked at the same RPM, say idle ~800 RPM? I'm thinking I should check the timing with the manifold line connected at idle (adjust for ~800 rpm), then when the manifold pressure line is disconnected, I need to leave the throttle adjustment alone and the RPM is the RPM when the manifold pressure line is disconnected. That's why I'm asking if the manifold pressure connection on the engine needs to be plugged/blocked.

Am I over-thinking this?

Greg
 
Idle rpm is anything smooth and as low as possible. I have my idle set at about 450 at the stop for landing, but manually idle it at about 550-600.

If your idle is set at 800 rpm and you have a FP prop, you may have a hard time landing in a reasonable distance (float).

As you can see, the rpm really doesn't matter for checking the timing with and without the line connected. I would use 600... it may change 25 or so with the line disconnected but the lightspeed doesn't care during this test.

If you are worried about changes, just cap it off. If you don't want to buy a cap, tape a thumb tack over the fitting...... it's only there for 10minutes.

A snip from the manual......
ls.JPG
 
I have a constant speed prop, FWIW.

I checked my Lightspeed timing with a timing light and with the manifold pressure line connected, it appears to be around 34 to 35 deg. (clearly out of spec relative to what is stated in the manual of 38 to 42 deg). With the manifold pressure line disconnected, the timing is 19 deg, maybe 19.5 deg., so within the specified range 19 to 23 deg. with the manifold pressure line disconnected. Both timing checks were deliberately at ~800 rpm (and at 60’ MSL), which may have been a mistake on my part.

So with the timing needing to be adjusted, and having the (old style) direct crank sensor, how are people adjusting the timing without removing the prop to get to the sensor adjustment screws? Or do I just need to bite the bullet and remove the prop?
 
The bad news.... you need to remove the prop to adjust the timing!!..:eek:

The good news.... your timing W/O mp is fine. And the high numbers with mp is out of the range set by lightspeed...but, it's on the good side. I would be happy with that and just fly on.

Any adjustment to get back into spec will need the brain box sent in.
 
I'm with Warren. Leave it alone and be happy. If we base on Nigel Speedy's data using a parallel valve 360, the base timing retard will result in lower CHT with no practical performance difference in the common 6K~10K altitude range.
 

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The good news.... your timing W/O mp is fine. And the high numbers with mp is out of the range set by lightspeed...but, it's on the good side. I would be happy with that and just fly on.

Any adjustment to get back into spec will need the brain box sent in.

As Warren and Dan have posted. Your timing, as you have verified, is quite fine and you are on the safe side of perfection. All you need to do is fly it.
 
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This forum never disappoints. I always appreciate the input.

Based on what I've read here, I'll continue to fly it and continue to watch the engine temperatures closely (I do that anyway).

I'll keep the tools in mind in case I decide to venture down that path (thank you for the info, hgerhardt).

And thanks for including the data/graphs, Dan. Very interesting.

Thanks for everyone's input! That's why it's called Experimental. Always learning!
 
I have never checked the Lightspeed timing at other than a static, engine-off condition. It is pretty easy with a mag-hole trigger--turn the prop until the LED comes on. With the various crank sensors, the timing cannot be off if the trigger ring or mini-sensor is installed correctly and aligned with TDC. Yeah, the manual mentions using a timing light but I never bother (well maybe I did the first time I installed a system). You can tell if the zero-advance (starting) magnet is triggering at TDC just by pulling a plug and checking the spark. I suppose the advance timing could be off due to some internal defect in the electronic box but I've never heard of that. I've had several of these systems.
 
I seem to recall at least one case of a failed MAP sensor resulting in timing advance at high manifold pressure. Card, RV-9? It's here somewhere.

Anyway, with the manifold pressure sensor hose disconnected, the sensor is seeing high pressure, which should result in base timing. The timing light doesn't just check for proper Hall sensor position. It also tells if the MAP sensor is working.
 
I seem to recall at least one case of a failed MAP sensor resulting in timing advance at high manifold pressure. Card, RV-9? It's here somewhere. SNIP

Yep - on an RV-7. The MAP circuit failed so timing was 42+ degrees BTDC regardless of manifold pressure or RPM causing CHTs be dangerously high, and this was on both ignitions. Perhaps Klaus had a bad batch…..

I strongly recommend anyone still flying with Lightspeed do this check, along with annual coil and spark plug wire inspections.

Carl
 
As I recall, Lightspeed uses GM style MAP sensors (as does SDS), and after learning of this potentially catastrophic failure mode (hard over to full advance), I adjusted the base programming of my SDS products to ignore this anomalous condition. Since then I have seen one of these GM sensors fail on my system and due to my settings, it was a non-event.
 
As I recall, Lightspeed uses GM style MAP sensors (as does SDS), and after learning of this potentially catastrophic failure mode (hard over to full advance), I adjusted the base programming of my SDS products to ignore this anomalous condition.

Different system, same move. Timing advance schedule below is for an angle valve. I don't know what sort of MAP sensor is on the board of the Autosport Labs timing control device I use, but the software allows building the schedule from scratch. It's easy to assign 23 BTDC base timing to a very low MAP line.

Turned out, I hardly ever use this schedule anyway. I have two, inflight switchable, and most of the time it's running on 23 fixed.
.
 

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For what it is worth...there is at least one case of the internal timing being off.

My ignition timing display indicated that the Plasma II+ went to 45 or 46° of advance, but the engine sounded and felt fine. Increased CHT seemed to confirm that the timing was too far advanced, but I did check timing with a timing light and followed all of the other trouble-shooting steps Klaus put in his manual.

After performing all of those steps, I gave Lightspeed a call and they told me to send it in for repair. They replaced a capacitor to fix this problem and upgraded some other minor, unspecified components and had it back in the mail the day after they received it. I don't recall the cost, but didn't find it to be unreasonable.

Interestingly, a couple of A&Ps walking by as I tested the timing commented that they thought the engine would really sound and act horribly if the timing was advanced that far. I wasn't smart enough to know one way or the other, but thought I'd pass along the information.

Regards,
Rob
N706DR
 
Interestingly, a couple of A&Ps walking by as I tested the timing commented that they thought the engine would really sound and act horribly if the timing was advanced that far.

Nope. On the ground it will sound and run just fine with advance in the 40's. At full throttle it may detonate, depending on conditions. However, even then it won't sound or run much different, only feel a little down on power.
 
Interestingly, a couple of A&Ps walking by as I tested the timing commented that they thought the engine would really sound and act horribly if the timing was advanced that far.

Another reason to be very careful about where you get your advice and guidance. I run 35* of advance at idle on my 320 to improve idle performance. At 1000 it is back to 23, but find that it helps to get the idle RPM lower, and still smooth, and that is important with FP props if you don't want to float.
 
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For what it is worth...there is at least one case of the internal timing being off.

My ignition timing display indicated that the Plasma II+ went to 45 or 46° of advance, but the engine sounded and felt fine. Increased CHT seemed to confirm that the timing was too far advanced, but I did check timing with a timing light and followed all of the other trouble-shooting steps Klaus put in his manual.

After performing all of those steps, I gave Lightspeed a call and they told me to send it in for repair. They replaced a capacitor to fix this problem and upgraded some other minor, unspecified components and had it back in the mail the day after they received it. I don't recall the cost, but didn't find it to be unreasonable.

Interestingly, a couple of A&Ps walking by as I tested the timing commented that they thought the engine would really sound and act horribly if the timing was advanced that far. I wasn't smart enough to know one way or the other, but thought I'd pass along the information.

Regards,
Rob
N706DR


Yup, its happened to me too. I discovered my timing on the LS to be stuck at 43 deg BTDC.

It was bit insidious in my case. I received my newly repaired engine with new cylinders in the spring some years back. I watched the temps come down during break-in. Just when I thought the break-in was complete, I began seeing the temps go back up. This was coinciding with warming summertime temps. Once I had trouble maintaining CHT's below 380, I knew something was amiss.

I bore-scoped, checked baffling, checked the Vernatherm, etc. Finally something on this site tipped me off to check the timing. The magneto on the right was right at 20 deg BTC, perfect for the angle valve. The LED on the LS also indicated perfect timing. Shot it with the strobe light and voilà, 43 deg BTDC. Not sure if it was in the MAP circuit or not, but there was a capacitor blown in the box. Klaus repaired it for a reasonable price.

That was my 3rd failure with my LS. I've had two of the Hall Effect sensors that go in the magneto hole go bad and the aforementioned capacitor. So I'm not exactly thrilled with it, but I do have 1800 hours on the system. When it works, it works exceedingly well. But when it doesn't, it's game over.
 
<SNIP>

Installed new cylinders on a 320 equipped with one Slick and one Lightspeed. Checked the Lightspeed with a timing light, manifold pressure line disconnected, intake port connection capped. Timing was observed to be fully advanced to max. Uh oh...

Quick review....at idle, with the MP line connected as normal, the system should advance to near max, as it is seeing low manifold pressure. When it sees high manifold pressure, it should deliver base timing or less. Disconnecting the MP line simulates high manifold pressure; with the line open, the sensor is exposed to ambient atmospheric pressure. Strobing the ring gear should show base timing. Advanced timing means the manifold pressure sensor or a supporting component has failed.

Reports suggest this is a common failure, enough so that I strongly recommend a strobe check of your Lightspeed at each annual. Along the same lines, strobe it any time you notice an elevated CHT in initial climb as compared to previous.
 
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Not sure if the LS has a direct timing or MAP display in the cockpit, but the SDS systems do and I have added the timing readout to my taxi/runup check to confirm it’s working properly. I have detected a failed MAP sensor prior to flight and the SDS direct readout saved the day. I was never a fan of “ECU displays”, but the ability to see timing MAP in real time is as valuable as any other engine instrument IMHO.
 
Not sure if the LS has a direct timing or MAP display in the cockpit
AFAIK it has... the question for me is how to wire it :unsure:
I installed a 3GX a couple of months ago, and when all done found about the feature in the 900+ pages manual... dooh.
I'll now have to find out which wire from my dual LSE II have to be wired to which pins on the GEA24... anyone with a clue?
 
I have detected a failed MAP sensor prior to flight and the SDS direct readout saved the day.

Yes, you and I have inserted setup values which return timing to base when the system thinks it is seeing very low manifold pressure...as it would if the MAP sensor failure mode is full low. Example, top line in the grid, post 19. I don't think it's possible with a Lightspeed. I don't know if it can be done with a P-mag, nor if the dead sensor default is to high or low.

Have to wonder about the MAP sensor failure rate across the fleet. Also have to wonder how much we contribute as builders. For example, this most recent subject did not have any sort of restrictor installed in the #3 primer port from which the pressure signal was taken. Despite instructions from folks like Ross, I don't think folks realize intake port pressures are radically rough. Without a restrictor or accumulator, it has to beat the crap out of the sensor.

Here's a snip of raw data capture taken with a Honeywell differential sensor, illustrating how port pressure is nothing like a smooth line. Upper plot is port pressure, lower plot is a spark signal used as a reference to crank position. The tall spark spikes are #1. Between the tall spikes is 720 degrees of crank rotation at about 2440 RPM.

Anyway, returning to topic....if you have a Lightspeed, do a timing light check on a regular basis. Think about the effect of MAP sensor failure with other brands too.

ScreenHunter_2123 Feb. 18 10.22.jpg
 
AFAIK it has... the question for me is how to wire it :unsure:
I installed a 3GX a couple of months ago, and when all done found about the feature in the 900+ pages manual... dooh.
I'll now have to find out which wire from my dual LSE II have to be wired to which pins on the GEA24... anyone with a clue?
Can’t help with the G3X but pin 3 on the Lightspeed output connector is for timing display (.01V/degree).

I have the pre wired display from Lightspeed which shows MAP, RPM and timing.
Fin
9A
 
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Have to wonder about the MAP sensor failure rate across the fleet. Also have to wonder how much we contribute as builders. For example, this most recent subject did not have any sort of restrictor installed in the #3 primer port from which the pressure signal was taken. Despite instructions from folks like Ross, I don't think folks realize intake port pressures are radically rough. Without a restrictor or accumulator, it has to beat the crap out of the sensor.
I ran across this as well with my SDS install, the MAP was all over the place compared to my HDX display - but the HDX does some internal logic smoothing and the SDS does not. I used a small Briggs-and Stratton fuel filter inline on my MAP line going to the SDS to act as an accumulator, settled it down quite nicely. I put the filter very close to the MAP sensor to let the line absorb as much of the pulsing as it could before the accumulator.

https://www.industrialspec.com/shop...L0fFmBULDffjQj-fi-9tXRW1448sNSvhoCW84QAvD_BwE
 
Not sure if the LS has a direct timing or MAP display in the cockpit, but the SDS systems do and I have added the timing readout to my taxi/runup check to confirm it’s working properly. I have detected a failed MAP sensor prior to flight and the SDS direct readout saved the day. I was never a fan of “ECU displays”, but the ability to see timing MAP in real time is as valuable as any other engine instrument IMHO.
There is a LS to EFIS adapter available from LS or ACS. I installed one and have the timing displayed on my GRT EFIS.
 
AFAIK it has... the question for me is how to wire it :unsure:
I installed a 3GX a couple of months ago, and when all done found about the feature in the 900+ pages manual... dooh.
I'll now have to find out which wire from my dual LSE II have to be wired to which pins on the GEA24... anyone with a clue?
Well, you could have done a search.... but I'll save you the trouble. See this post on how to implement an op-amp to display LS timing on a G3X: https://vansairforce.net/threads/display-lightspeed-ignition-advance-on-g3x.119508/ And if wiring an op-amp is too hard, LS sells the L2E amplifier now: http://lightspeed-aero.com/Products/Accessories.htm

See section 22.4.12 GP (General Purpose) Inputs of the G3X Installation Manual for how to connect to the GEA 24.
 
Well, you could have done a search
What I did... and it led me to this thread ;)
But not the other reference (though I had the one from the install manual which finally led me to the possibility).
In any case, thanks for chiming in, your time and help.
 
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