Lightspeed Fire Hazard???

Please look at the pictures below, I am running an Airflow Performance with a Lightspeed Ignition. The fuel lines to the injectors pass within about an inch of the coil. My concern is that if a plug wire comes off the coil, the spark from the coil will jump to the fuel line and cause a fire...

Is there reason to be concerned?
Has anyone else thought about this?

I imagine that even people with Silverhawk FI would have the same issue as the lines run nearly the same path...



and

Ask the pros

Matt,

I see you're at Superior's Build School. Why not ask Evan or one of the more than capable instructors about your concern? Those guys not only build and assist-build hundreds of engines in the very spot yours is standing, but they run every single one before it ships. I know - I stayed there and watched them run mine on their dyno rig. Plus, they constantly seek feedback from the field. As you well know, the instructors get phone calls daily from concerned builders, regarding things just like this; or at least that was my experience. I honestly think if this were a real concern, they would address it as they helped you bend those injector lines that close to the coil. Or the QA guy would have said something when he came around to check your work.

Clayton,

Evan was actually the one that suggested I ask others about it. He said that they have not done many (if any) of the combination I have. Most people dont use lightspeed (he said only about 10%) and those that do use the Silverhawk FI with it if using FI at all. With the Silverhawk it is a similar situation and he has not heard of any problems. He also said it is unlikely that the wires would come off the coil. The issue was originally brought up by Daryl who does the test runs at Superior.

So I am asking here based on that conversation. Plus, I am not to comfortable with making an assumption of safety based on the fact that he "has not heard any complaints thus far" and that it is "unlikely" to have the wires come off...

It was late in the day when I did those runs and we were running late on the class. When Daryl saw it and made the comment, Evan was quick to negate the issue and I know he needed to leave for an apt soon. I am not saying he was blowing it off because of time, however based on the circumstances and since he suggested it anyway, I think bringing up the issue on this forum was exactly the right thing to do.

P.S. Evan was great and the whole experience at the build school was awesome. It is worth the extra money and I would suggest it to anyone. I am definitly a satisfied customer and the reason I didnt explain this whole scenario leading up to my question in the original post is becaue I was afraid it would come off as a negative statement towards Superior and that is the last thing I want to do.

- Matt

THE SHORTEST DISTANCE!!!!!

idleup said:

My concern is that if a plug wire comes off the coil, the spark from the coil will jump to the fuel line and cause a fire...
/QUOTE]

If the wire does come off of the coil, it would jump the spark to the case of the engine. It is the shortest distance.
In order for the spark to burn through the injector line, you need AMPS!!!!!
The coils don't provide enough amps to do that. So this is not an issue....

Have fun.... go build.....

Warren

Click to expand...

it is questionable if the case is the closest if we are talking about the top plug.

so if it did arc to the fuel line but doesnt have the amps to burn through does that mean it wouldnt cause a problem anyway?

Yes, you would have one dead cyl, and a vibration that would get your attention!!!

Assuming an arcing wire did create heat, where is the source of oxygen for combustion if the tubing isn't breached?

What you mean is....

Grigson said:

Assuming an arcing wire did create heat, where is the source of oxygen for combustion if the tubing isn't breached?

Click to expand...

Oh, you have plenty of oxygen, it's trying to cool the motor. What you don't have is a source of fuel!

THERE IS NO PROBLEM HERE!

Here is a question for MEL. MEL, What do you think causes most enigne fires? Let's say we have a gas leak. OK, now where is the source of ignition? Could it be the exhaust? Or the brushes in the alternator?

Mel, or anyone..... what do you think??

Warren

Nice engine!!!!!

Nice looking engine.. You'll be fine.

Move the coils

Part of the problem is that you have the coils mounted in the wrong place.

How can I say this? Easy. I have my coils mounted in exactly the same place. A couple years ago at Oshkosh, I had my cowl off and plenum open. Who should walk up for a look but Klaus himself. He commented to me that my coils were in the wrong place, and should really be outside of the plenum chamber, for the sake of longevity. The high heat levels inside the plenum chamber degrade the life of the coils, according to Klaus.

I thanked him for the advice, and two years later still haven't bothered moving them. But, at the stage of the game you're at you might want to consider it.

Move the Coils

I have a dual Lightspeed set-up and my rear coil came on the engine in this very same spot. This is going to be a bigger issue than the fuel line as the coils are too far aft.

The wires that will connect to the aft side of the coils will come almost to the rear baffle leaving no room to connect up the wires. What I did was build a riser and extension to move the coils up and forward. The coils now reside directly over the fuel line and my question was the same a you as to the proximity to the fuel line and my intention was to somehow shield the fuel line. It seems a few people have already commented about this so we look good on that front.

You may want to address this issue of coil placement before you leave the engine shop. You will have to deal with this later if not now.

Sorry I do not have pictures of my set-up but I can post them next week. Dan Checkoway also ran into this issue and built a new bracket, different from my fix, and solved his same problem. Check out his website.

Not an issue here but on the coils mounted on the front of the engine, the situation with the proximity to the baffles was the same. The front fix was easier as I just turned the coils around so the spark plug wires conntected on the front not aft.

sprucemoose said:

Part of the problem is that you have the coils mounted in the wrong place.

How can I say this? Easy. I have my coils mounted in exactly the same place. A couple years ago at Oshkosh, I had my cowl off and plenum open. Who should walk up for a look but Klaus himself. He commented to me that my coils were in the wrong place, and should really be outside of the plenum chamber, for the sake of longevity. The high heat levels inside the plenum chamber degrade the life of the coils, according to Klaus.

I thanked him for the advice, and two years later still haven't bothered moving them. But, at the stage of the game you're at you might want to consider it.

Click to expand...

This is interesting for several reasons:
1. Engine assemblers (Aerosport for example) mount them right on the case
2. Klaus ships em with wire lengths that will ONLY work if the coil are mounted there.

Ive got 2000 hours on LSE's in RV's mounted on the case with no issues. YET!
My experience only

Best,

I asked the Superior people about the placement of the coils and they said that where they are now is where they put all of them and that is where Klaus says to put them in the instructions...

I have often wondered about this setup. Even if the plug wire never comes off it is absolutely, positively, without any doubt, possible for a minor fault in the insulation to allow a spark to intermitently go to the fuel line, and it will burn a hole in it....how do I know?

In the late 70's VW vans (fuel injected) and fuel injected beetles had a spate of engine fires. The cause was mechanics not following the factory routing of spark plug wires. The wires, when routed close to the steel tube "fuel rail" would over time burn a hole right in the fuel line, and ignite the fire.

The fix was, of course, to route and secure the wires so that they could not come that close. In addition, some areas of the fuel rail were replaced with plastic and rubber.

The spark energy in those VW point-style ignitions was much much lower than it is in Klaus' system. Of course out of hundreds of thousands of cars only a few dozen had this happen, so we may never see it due to the increased vigilance of aircraft mechanics, and the small number of planes.

But, if it were me, I would either change the mounting so that the wires are not near the lines, or I would inspect for carbo arcs, very closely, at each oil change.

Just FYI I have my coils on the next case bolt forward (I don't have FI to deal with), they must be making the wires longer these days cause mine wouldn't reach if they were mounted where yours are. You are going to have some issues with the rear baffle coil wiring the way it is.

As far as a fire hazard there is none, if the wire came off the plug the injector line "might" act as the closest path to ground but even if it did would cause no ill effects to the SS line (it may may a mark on it but definately would not penetrate it). Good chance the coil would begin to short internally as the resistance there is less than penetrating the plug wire and air gap between the wire and the injector line. I'm sure you would notice the problem quickly with a rough engine and next time you did a mag check it would be very obvious. I would also replace any coil that ran with a disconnected high tension lead due to internal damge that likely occured between the primary and secondary insulation of the coil.

I don't think it is an issue either, but.......you could make an "insulator" by splitting a piece of automotive fuel line (or similiar hose) and wrapping it around the fuel line tubing in the coil area.

Kahuna said:

This is interesting for several reasons:

Click to expand...

After having this conversation with Klaus, I was thinking the same things. I could always buy some longer plug wires and move the coils, but I decided to leave them as-is, partly as a scientific experiement, and partly our of pure laziness and "don't-fix-it-if-it-ain't-broke" thinking.

I'd double tie-wrap them together to prevent chaffing. No worries on the electical versus fuel tubing, IMO.

Low Pass,

Never, never, never tie wrap to steel or aluminum with the nylon tie wraps! The nylon can actually wear thru the metal. Doesn't seem likey, but it can happen. If you want to gang them together, put some cusioning such as fuel hose fuel hose over the steel line.

Tighter installation maybe?

I have my coils mounted in exactly the same place. A couple years ago at Oshkosh, I had my cowl off and plenum open.

Click to expand...

Could Klaus have possibly made this comment because in normal operation these coils were inside the plenum, a tighter installation than just being inside a cowl?

Don't try to insolate the fuel line, instead...

As part of the bracket that holds to coils, build a small extension of aluminum that would come close to the end of the coil. If the wire comes off the closes path would be through the bracket. Problem solved.

I also had to move my coils forward one hole on the case. I didn't worry about the wire coming off, maybe I should.

Kent

Is it possible to use a 45 dgree elbow exiting from that injector to redirect the line???

Kahuna said:

This is interesting for several reasons:
1. Engine assemblers (Aerosport for example) mount them right on the case
2. Klaus ships em with wire lengths that will ONLY work if the coil are mounted there.

Ive got 2000 hours on LSE's in RV's mounted on the case with no issues. YET!
My experience only

Best,

Click to expand...

Here are the actual pictures off his website on mounting the ignition coils. Are you sure you were not talking about the control box? He does recommend that be inside.
http://www.lsecorp.com/Products/IgnitionInstall.htm

RScott said:

Low Pass,

Never, never, never tie wrap to steel or aluminum with the nylon tie wraps! The nylon can actually wear thru the metal. Doesn't seem likey, but it can happen. If you want to gang them together, put some cusioning such as fuel hose fuel hose over the steel line.

Click to expand...

aluminum - I could see. Steel??? You sure bout that??

Good eye

You have a good inspector eye. Probably not an issue but you point out it COULD............. make sure the COULD.....can't, ie make it harder. Add some more security or insulation, separation. Can't be too careful with fuel. I doubt the ignition can burn thru the stainless steel line but.............who knows unless you test it.

There was an airliner that had a electrical fault burn a hole in a hydraulic line in the wheel wheel. The pressurized hydraulic fluid was sprayed out and ignited like a torch.

idleup said:

Evan was actually the one that suggested I ask others about it. He said that they have not done many (if any) of the combination I have. Most people dont use lightspeed (he said only about 10%) and those that do use the Silverhawk FI with it if using FI at all. With the Silverhawk it is a similar situation and he has not heard of any problems. He also said it is unlikely that the wires would come off the coil. The issue was originally brought up by Daryl who does the test runs at Superior.

So I am asking here based on that conversation. Plus, I am not to comfortable with making an assumption of safety based on the fact that he "has not heard any complaints thus far" and that it is "unlikely" to have the wires come off...

It was late in the day when I did those runs and we were running late on the class. When Daryl saw it and made the comment, Evan was quick to negate the issue and I know he needed to leave for an apt soon. I am not saying he was blowing it off because of time, however based on the circumstances and since he suggested it anyway, I think bringing up the issue on this forum was exactly the right thing to do.

Click to expand...

Matt,

I'm not questioning if it was right to bring it up on this forum. Look at all the great dialogue it created - I agree it was good to bring it up. And I didn't intend my comment to be taken as critical - but rather to be taken as a bit of practicality in a world that can spin out of control with theories. In the end, most decisions that are made about experimental aircraft are "assumptions" made by very educated individuals in the pertaining field. By pointing to Evan and Daryl, my intention was to express their vast knowledge on engine / ignition construction - and take what they say as valuable. IMHO if it were an issue:
1) It would be known within the industry, and addressed at Superior
2) Evan / Daryl would have made a bigger deal out of correcting it.

TerryWighs said:

Is it possible to use a 45 dgree elbow exiting from that injector to redirect the line???

Click to expand...

Yes - there are straight's, 45's, and 90's available. I use them daily with this same line.

rvpilot said:

Could Klaus have possibly made this comment because in normal operation these coils were inside the plenum, a tighter installation than just being inside a cowl?

Click to expand...

Possibly. It was a couple years ago, but my memory is that he was concerned that the coils would get hot during the time right after engine shutdown, when temps in the area above the engine reach their peak. I wonder if temps would get higher in a tight plenum installation vs. a normal baffle setup? My gut tells me that it would, but I have nothing scientific to back that up.

airguy said:

Yes - there are straight's, 45's, and 90's available. I use them daily with this same line.

Click to expand...

That is a great idea. What is the part number for the 45's and 90's that would work there?

plastic and steel...heat in plenum

Steel??? You sure bout that??

Click to expand...

Yes, plastic wire ties will wear holes in steel. Seen it myself on engine mounts. I have an IA friend who loves to cut off wire ties and make the owner redo the standoffs with Adel clamps. As pointed out above, it's probably best to avoid wire ties as standoffs in this type of situation. Better safe than sorry!

I wonder if temps would get higher in a tight plenum installation vs. a normal baffle setup? My gut tells me that it would, but I have nothing scientific to back that up.

Click to expand...

Agree, don't have anything to back it up, but once the engine is shut down, you'd have a lot of concentrated heat in this area, more so I would think than in a standard cowl and baffle arrangement. Will it seriously effect the life of the coils, maybe someone else can comment on that. Klaus must have thought so to even mention it.
Could be that the coil life lost is of no consequence. After this discusion, I think I'll keep my coils out of the plenum though!

Any real temperature data?

Coils mounted on the top side of the engine will run almost all their life in ambient temperatures, only seeing heat for a while after shutdown. Coils elsewhere under the cowl will see warmer operation all the time, and still may see hotter temperatures after shutdown than they would above the engine.

Anyone have actual data showing temperature profiles? This discussion would benefit from competently obtained data.

LSE Coil Life

Any idea of preemptive (before failure) replacement schedule on the coils?

I sort-of have some data.

I have just installed two temp probes to explore temps under the cowl. I am using the CHT probes for #5 and #6 on my AFS 2500 engine monitor sense they are not needed for my 320 engine.

My first test case was to place one probe behind the oil cooler (mounted on the baffle) and behind the oil vent. I thought that I would watch the temp of the air as it exits the oil cooler and the general under cowl air temp.

At about 55f OAT and oil temp of 185f degrees, the oil exit air was running at about 105f degrees, the cowl air was 118f degrees. I was in a low speed cruse setting doing other testing and only doing about 130 kts with cht running about 330f degrees.

After shutting down both temp under the cowl increased to about the 155f degree mark after a couple of minutes.

I will be moving to probes to other positions in the future to check various things. One data point that I want to explore is what is the temp on the two sides of the engine driven fuel pump. The one that has a blast tube compared to the other side. IE do I need a shroud around the fuel pump?

Anyone of other point of interest that I should put on my test list?

Kent

Kent,

Excellent idea. How about mounting one of them high on the engine case, where the coils are mounted in the original post. This would seem to be the hottest part of the engine, shortly after shut-down.

kentb said:

I have just installed two temp probes to explore temps under the cowl. I am using the CHT probes for #5 and #6 on my AFS 2500 engine monitor sense they are not needed for my 320 engine.
(snip)

Anyone of other point of interest that I should put on my test list?

Kent

Click to expand...

I have stuck a bunch of these temperature monitors on all my accessories. The right side of my accessory case runs hotter than the left, and I was surprised by the temps of the diode pack on my alternator (I beefed up the blast cooling)

IMHO they are relatively cheap and easy.

Jeff, I'll at that to my test plan....

Each time that I pull the cowl off I will be move the probes.

Kent

Here's something to consider in waste-spark systems. The coil/transformer secondary winding is isolated from ground; it is just a winding with the two ends brought out to posts. But, capacitance of the leads to grounded metal, such as the engine or fuel lines, can form a capacitive voltage divider. What this means is if one lead runs very close to the crankase and cylinder and the the other doesn't, that will cause an unbalanced capacitive voltage divider that will put more of the transient voltage on the lead with less capacitance, and less transient voltage on the lead with the greater capacitance. The (-) spark current comes out of one terminal, goes to the center electrode of its plug, jumps the gap to the case electrode, goes through the engine to the other plug case electrode, jumps the gap to the center electrode, then returns to the other (+) coil post. The two plugs are in series. When the spark occurs, a 0.03" plug gap on the exhaust cylinder will have an initial voltage drop of about 1500 V so that the majority of the voltage appears across the plug on compression. That is, if the capacitance of the two leads is balanced. So what I'm trying to say is try to keep your plug wires at least 1/2" from any metal and the same from other leads to prevent cross-firing. 'Remember the Cadillac engine that used to crossfire the 5 & 7 plugs, which were adjacent in firing order, if the wires were close and parallel? You were supposed to put them in the wire holders with 3 & 5 reversed, to give 1-5-3-7 order. Those wires had at least a 1" center-to-center separation. The hot plug center electrode generates a thermionic emission that's worth several hundred volts. With a points/coil/capacitor system that didn't put out the voltage or current of the EI systems, it was imperative that the coil primary be wired correctly to give a negative spark that the thermionic emission aided. If the +/- on the coil primary wasn't observed, a positive spark would result, from which the thermionic emisssion was subtracted. The EI systems have so much voltage available that the situation is similar to the effect of a 20 mph headwind on an RV vs a Cub. The Plasma III actually puts out both (+) and (-) in succession, so that spark polarity is a non-issue.

Ok, I found it.

sprucemoose said:

Kent,

Excellent idea. How about mounting one of them high on the engine case, where the coils are mounted in the original post. This would seem to be the hottest part of the engine, shortly after shut-down.

Click to expand...

I move one of the probes inside the baffle. I used electrical tape to attach it to one of my lightspeed coils.

In flight temp:
OAT 54F
coil 67F
behind oil cooler 121F
after shutdown coil 156F

Temp peeked after 3 minutes and then started down.

Kent