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Starting a engine on electronic ignition.

loopfuzz

loopfuzz

Well Known Member
I have heard that starting on a electronic ignition is not a good idea. On my RV-4 I've been told to always start on the mag with the electronic ignition turned off and then switch it on after engine is running. (I'm running the ElectroAir system). But in the Emag/Pmag setup they recommend starting with the electronic ignition on. Why the difference? And also it sounds like some problems with the emag/pmag may have been during startups, so why not just start the engine on a normal mag and then switch over.

My last thread on questions on electronic ignitions got stopped short. Just looking to get some questions answered.

Chris.
 
It depends....

A good thing about electronic ignition is the good strong spark for starting. But timing is critical. An electronic ignition that does not retard the spark to TDC for starting is going to cause a kickback and break the starter.

So, conventional wisdom said its better to start on an impulse-coupled mag.

But some of the newer, better EI have a built-in spark retard for starting. The P-mags and the LiteSpeed ones do. Now you get the best of both worlds, a spark that is good and strong, and retarded to TDC for starting.

It is possible under very low voltage available to have the spark retard feature in the EI get disabled. This would be bad. You would have to have a fairly weak battery that the voltage would drop a bunch during cranking to cause that.
 
scsmith said:
It is possible under very low voltage available to have the spark retard feature in the EI get disabled. This would be bad. You would have to have a fairly weak battery that the voltage would drop a bunch during cranking to cause that.
Click to expand...

Which is almost certain to happen at some point in the life of the airplane -hence the advice to start on an impulse-coupled mag and switch the EI on after start. Batteries get old and die slowly; master switches get left on; winter days make for hard cranking. Look at the facts and play the odds.
 
loopfuzz said:
snipin the Emag/Pmag setup they recommend starting with the electronic ignition on. Why the difference? (snip)
Chris.
Click to expand...

The Emag/Pmag have a (programmable) "Run Mode Start Delay." This disables the coils until the engine has turned through a chosen number of blades, typically 4.

My understanding for the reason behind this is that the Emags, like most EI setups, are "wasted spark" which means they fire every time the timing magnet comes around, not just on the compression stroke. This means they will fire sometimes with the intake valves open, and may ignite any fuel vapors in the intake manifold/sump.

Turning the engine over a few times will clear any vapors out so you don't blow up your airbox.
 
It's a mixed bag. If you have dual EI's then obviously you have no choice. Given a choice, I'd setup to start on an impulsed mag every time, because I would always have one mag, and it makes sense that should the EI fail, you have the option of starting the engine. Non-impulsed mag, no option. Also I don't think i'd trust a EI in any kind of hand proping situation... which is something to think about.
 
The issue here is how do EIs know when to spark? Most count from a point before the furthest advance that will ever be required, based on engine rotational speed (rpm). Say the most spark advance that the EI will ever select is 40 deg, it might start counting at 50 deg, or even 60 deg.

When starting it is essential that the spark occurs at TDC or later to avoid kickback. So an EI that counts will have to count for 50 or 60 degrees of rotation to ensure the starting spark occurs at TDC. If the battery is weak, and compression is strong, and its not your day, it is possible for the engine to slow down enough as the compression rises for the counting process to get to TDC before the engine does. So the spark occurs too early and you risk a kick-back, and potentially a broken starter, etc. So the advice has been to start with the EI off. I'm sure that people like Electro air and Litespeed have improved their algorithms, but I understand that's how they work.

P/E-mags work on a different principle in that they measure the rotation position of the engine many times per revolution, so they don't have to count. They guarantee that no sparks will occur before TDC (and do a few other things to enhance starting). So they are recommended to be on for starting.

There's probably more to it than that, but it gives the general idea.

Pete
 
Dual P Mags Start Great

I can tell you that my dual p-mag IO-360 has been an easy starter since day one.

Hans
 
Some people add a very small isolated battery just for the EI (uses a diode so the small battery will charge when ship's power is available, but will not discharge otherwise). This ought to give you the best of both worlds.
 
loopfuzz said:
I have heard that starting on a electronic ignition is not a good idea.

Chris.
Click to expand...

I have one mag and a Lightspeed EI. I always start with both ignition sources. No problems to date. In fact, one thing i really like about the EI is the ability to put out a good hot spark, which helps starting, especially in cold weather or on a hot engine re-start, such as during a bunch of young eagle flights.

Steve Ciha
 
I have dual Lightspeeds and it starts just fine with the starter and it also starts fine hand propping it. No kick back at all.
 
nucleus said:
I can tell you that my dual p-mag IO-360 has been an easy starter since day one.

Hans
Click to expand...

Same here and I don't have the start delay turned on. It fires on the first compression stroke.

As for the reason for the delay, it was to keep from blowing out composite sumps. Either way, it is easy enough to set up.
 
It's a stupid EI that is not programmed and designed correctly that you get kickback with. It they can't get that part right, the rest of it would worry me too.

With ours, you hit the starter button and it starts... what a concept.
 
rv6ejguy said:
It's a stupid EI that is not programmed and designed correctly that you get kickback with. It they can't get that part right, the rest of it would worry me too.

With ours, you hit the starter button and it starts... what a concept.
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Exactly! It cracks me up when I have line guys comment on how easily my plane starts.
 
Ditto here. Superior IO-36- M1 with dual P-Mags. Easiest starting aircraft engine I ever flew, hot or cold.

Martin Sutter
building and flying RV's since 1988
 
With preheat?

I've dual P-mags and a Superior IO-360.

I've experienced a kickback during start once or twice so far (close to 50 hrs now)
It has been during the first start in the morning after the engine has been preheated to 75*F. (I always preheat during winter, it's coooold in Norway then)

Before start, I've been priming with the boostpump 4-5 sec's and mix full rich as I do on first starts in the summer. (I'm not using preheat in the summer ofcourse)

I was thinking that maybe I schould start the engine in winter (after using preheat) with the same procedure as I'm using for hot starts year around? That is to use boostpump only if fuelpress is below 15 PSI when turning power on? And then only for one second? (to get fuelpress indication)

What procedure do you people out there with dual P-mags use for startprocedure after using preheat?

Thanks.

PS: I don't mean to hijack this tread but I was thinking it was kind of related to the subject...
 
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Alf, the key to starting the IO engine with electronic ignition is the throttle position. The throttle should NEVER be open more than about 1/8 of an inch when cranking, hot or cold. Opening it more than that will result in occasional ignition of the vapors in the intake. Unlike many injected engines that start best with the throttle wide open when hot, our configuration always starts best with the throttle only minimally open. Mine and several others who have the same configuration always starts in that configuration without fuss. My basic rule is always crank with mixture full lean and throttle open 1/8", hot or cold. If the engine has not run in the last 4hrs prime with boost pump while mixture is full rich and throttle 1/8". Duration of priming is adjusted for how long the engine has not run starting with 2 seconds if it is around 4hrs, 3-4 sec if it has been a day or more and an other second or two more if it is colder than 40F. It is better to underprime than to flood the engine. Try it, you will be surprised. I learned that method from a highly experienced neighbor of mine and it has worked flawlessly for me over 400hrs in flying my 7A from anywhere from the Golf Coast to Alaska.

Martin Sutter
building and flying RV's since 1988
 
I have about 2400 hours starting with injected RV motors:
1. 1 mag and 1LSE
2. 2 LSE's

I have always started on both for reasons stated by others. Never junked a starter. ALL of mine have been with a c/s prop which has more to do with the kick back problems than the EI ignition. Light props stop fast, kick back easier. Heavy props carry through and are less suseptable. Weak batteries also contribute to the problem.

Im sure you can find cases of any config and any outcome.
My experience only.
 
The issue is voltage. If the starter load pulls bus voltage down to less that 8 volts, electronic ignition can lose its brain and may fire at any time causing the kick back and broken starter ring. This is especially true with the EI system. I believe Light Speed has modified their system to where it will be ok down to 6 volts. EI recommends using the B&C starter to lessen the voltage drop under load. Don't know how the p-e mag system reacts to a less than 8 volt start.

I broke one starter ring with EI and started on the impulse coupled mag after that event.
 
rv6ejguy said:
It's a stupid EI that is not programmed and designed correctly that you get kickback with. It they can't get that part right, the rest of it would worry me too.

With ours, you hit the starter button and it starts... what a concept.
Click to expand...

No doubt very true with your system, Ross. But some guys have had an issue with the Subby ECU on start, the cause a mystery. On first start with the H6, the engine would fire after one or two blades but then sputter, choke, fxrt and generally act like I don't want to run and then suddenly it was up and running just fine. I attributed it to the ECU finding its brain and getting things organized electronically. It only happened on the first cold start of the day but some days it would just pop off and be normal.

Never did figure out what was going on. Some guys thought it could be an induction leak.

I am still on a learning curve the the IO360 and 2 mags with the AFP system. But that's a different issue concerning pre start fuel management, not electronic ignition. That will be settled as soon as decent weather returns and our runway becomes flyable again.
 
David, that is true with some E.I's but not with P-Mags. They have built in safe guard that prevents them from firing under those conditions.

Martin Sutter
building and flying RV's since 1988
 
EI Starts

I have a Light speed ignition and an impulse mag, I start on both every time . As a Fuel injected lyc user , hot starts are a non event with the Lightspeed (my 3rd plane with FI) starts every time

Peter RV6

loopfuzz said:
I have heard that starting on a electronic ignition is not a good idea. On my RV-4 I've been told to always start on the mag with the electronic ignition turned off and then switch it on after engine is running. (I'm running the ElectroAir system). But in the Emag/Pmag setup they recommend starting with the electronic ignition on. Why the difference? And also it sounds like some problems with the emag/pmag may have been during startups, so why not just start the engine on a normal mag and then switch over.

My last thread on questions on electronic ignitions got stopped short. Just looking to get some questions answered.

Chris.
Click to expand...
 
I have duel Lightspeeds and have been told to crank for at least a couple of seconds before turning the ignition on
 
That would not be possible on mine because they are connected to the key switch. Well, I suppose I could pull the breakers. But it seems to me that if Klaus set it up so that they could be activated by the key switch, then it shouldn't cause a problem. At 50 hours, mine seems to start just fine.
 
G3i Ignition and Starting

Hello all,
With the Generation 3 Ignition (G3i), All your doubts of wasted spark, starter kick back, etc. are no issues. The Multiple Spark Discharge excites both mags when starting @ the proper timing event. If one still wants to start the engine on the magneto impulse coupler(s) only, leave terminal T2 off. However you loose the excellent benefits of G3i starting capabilities.
Generation 3 Ignition will be @ AirVenture booth #1148 this year with interactive displays and much information topics like this.
Sincerely,
Thomas S.
www.g3ignition.com
 
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