Aircraft dual ignition

Peter Gene · Post by **Peter Gene** » Wed Jun 06, 2012 2:14 am

Hi there
I'm currently fitting a dual ignition system to a Jodel D11 amateur built aircraft with a Franklin 4 engine.
One set of plugs is supplied from your standard Megajolt/EDIS/Coilpack using a very conservative ignition map.
The second set of plugs are supplied from an EDIS /coilpack with the sensor fixed at 32 deg BTDC (no MJ)
Both systems are independent and there is a small auxillery battery in case of failure.
I have a couple of questions in my quest to make the ignition fail safe

1. As part of the preflight I need to switch each system off in turn to ensure both are working. Is turning off the MJ likely to cause a problem while the engine is running or is it best to test by putting a switch in the power supply to the coilpack?
2. In the event of an alternator going over voltage what is the likelyhood of a failure to the EDIS or MJ. Should I incorporate some sort of overvoltage protection?

Cheers

Post by **brentp** » Mon Sep 03, 2012 6:09 pm

The EDIS will run independently of the Megajolt, just at at fixed "limp home" 10 degrees BTDC.

The Megajolt has a degree of over voltage protection, but I can't comment on the Ford EDIS module.

I would consider a high powered over voltage protection device for your whole aircraft, if you don't have one already

steve100 · Post by **steve100** » Mon Jun 10, 2013 12:44 pm

I have done the same in an a/c - except I kept one Slick mag ie self contained ignition. I use a relay in the power to coil pack wire. I have wired it such that the normally spring loaded closed contacts feed the coil pack in the default position. The relay coil has a permanant live taken from the coil pack power line. The other side of the relay coil in connected to the EDIS 'mag' kill switch to earth - ie when the switch is made the relay coil is earthed and operates the relay opening the normally closed contact and cutting the coil spark. ie earthing the switch kill the ignition just like a std mag switch. It also fails safe in case a wire to the kill switch breaks in flight
This has the advantage of not powering down the EDIS module or the Megajolt.
Regards
Steve

Peter Gene · Post by **Peter Gene** » Tue Jun 11, 2013 5:52 am

Thanks Steve

I'm all sorted now. Used two EDIS systems one controlled by an MJ the other fixed. Kept it simple. Switch of power to each system in turn to do the "mag" checks. The consensus from the electronic gurus is that it will cause no problems. I have a backup battery system a la Lightspeed design and am looking into fitting overvoltage protection.

To date have done 25 hours in the air with no problems.

Cheers

Peter

steve100 · Post by **steve100** » Tue Jun 11, 2013 6:31 am

Hi the B&C Overvolt system is really good. I use it.

http://www.bandc.biz/over-voltageprotectionmodule.aspx

Well done on getting the ignition up & running - I am currently getting installation approval via UK LAA (delegated regulator for Permit a/c from the main CAA). Did you similarly have to get approval or is it via experimental route?

Regards
Steve

Peter Gene · Post by **Peter Gene** » Tue Jun 11, 2013 6:55 am

The CAA were quite relaxed about it. After fitting I had to do 5 hours solo. Lets face it the system has to be more reliable than those Slicks!

Yes I'm using the same overvoltage gizmo but it will need a bit of thinking as I have a Lucas (Prince of Darkness) alternator with inbuilt regulator. Bob Nuckolls at Aeroelectric Connection seems to be the expert on this stuff but the solution seems to be a bit heavy handed.

Was it you that wrote the article that got me started on the MJ?

Cheers

Peter

steve100 · Post by **steve100** » Tue Jun 11, 2013 8:23 am

Possibly - my article Home Brew Ignition was in the LAA Light Aviation mag in Aug 2011. If it was, I'm really pleased

to hear that as I wanted to inspire others to try it out. I was mainly thinking of UK LAA guys but its fantastic if it has reached across the world.

I also did articles on Electric Carb Heat for the O-200 and higher compression (C85) pistons that has transformed the engine in terms of power and economy.

Regards
Steve

DanH · Post by **DanH** » Fri Nov 22, 2013 12:35 am

Brent, Steve, Peter,

Anyone know the average system (MJ/E + coil pack + EDIS module) power draw at some stated RPM?

Likewise, power draw for the MJ/E alone, and for the Ford side of the system?

steve100 · Post by **steve100** » Fri Nov 22, 2013 5:05 pm

Yes thats almost correct, except I don't power down the EDIS module - only the power to the coil pack is interrupted during a/c power/'mag' checks. - correct otherwise.

I did a current draw vs RPM tabulation/graph for the LAA as part of my Mod application - I recall it was about 1.05Amps at 14.4 supply voltage at 2750 rpm and about 0.45 amps at around 1000rpm

Thats everything - majority of load would be the Ford bits - I'd guess the MJ alone is less than 0.2 Amps

I also use a DP DT mag swich on the elec ign to switch over the tach pulse to the EDIS tach pulse line when the mag is disabled during power/mag checks.

Default position with both mag and EDIS operating is for the tach to read the mag pulse.

Regards
Steve

DanH · Post by **DanH** » Fri Nov 22, 2013 7:25 pm

Thank you Steve.

Those amp numbers are excellent. I figured you had them, given the regulatory requirements in your part of the world. Did you get an approval? Anything I can do for you on this side of the pond?

The GRT EIS has two tach inputs. When it detects no signal on #1, it will display #2. Makes life easy.

I'll continue to run one Slick for a while, but the next step will be the installation of a B&C SD-8 (http://www.bandc.biz/alternator8ampshomebuilt.aspx) and small battery to drive the second EI.

Any operating issues I should know?

Here's the subject; RV-8SS, IO-390 Lycoming, Hartzell BA, GRT and Garmin:

steve100 · Post by **steve100** » Fri Nov 22, 2013 8:21 pm

Yes - got full LAA Mod approval after 5hrs test flying and then a general update report after 25hrs but all good and no problems.
Regretfully my Grand Rapids EIS 4000 (what a great bit of kit that is!!) is an earlier board version without the 2 tacho inputs.

Recently fitted a B&C 30A 433H gear driven alternator.

I like your drawing skills! What package do you use?
Regards
Steve

DanH · Post by **DanH** » Fri Nov 22, 2013 9:03 pm

Yes, I'm very pleased with GRT. The EIS is mounted front and center as a dedicated fuel totalizer. All its other data is displayed on the EFIS via serial line.

The drawing tool is just an old version of AutoCad.

Did you notice any operational improvement with EI on the O-200?

steve100 · Post by **steve100** » Fri Nov 22, 2013 10:42 pm

Slightly higher CHT's - 2-4 deg C

I have Map 2 at 24 deg fixed and the other Map 1 as variable with rpm & manifold pressure

Leaned out at 12L/hr at about 2150 rpm at about 2-3000ft - on the fly switching from Map 2 fixed timing to Map 1 variable gives an approx 1 L/hr drop in fuel flow for the same rpm/speed

It idles much better too (smoother and about 40 rpm higher ie from 740 rpm on map 2 up to 780/800 rpm on map 1 as well)

Havent done much evaluation at higher altitudes but there is definitely a benefit.
Not enough benefit though to spend over $2,500 on a Lightspeed or Electroaire one!!

My 20 yr old son at uni (Mech Eng) is just learning and seeing the benefits of Autocad - I'll get some lessons off him!
Regards
Steve

DanH · Post by **DanH** » Sat Nov 23, 2013 12:19 am

Great minds and all that rot...one map fixed, one map dynamic is what I was thinking.

Very pleased to hear of the fuel flow reduction. I love the 390, but this is typical fast cruise and fuel flow:

Mixture is near peak power (EGT ~100 ROP), 10.4 GPH, 185 knots true. I'd give up some speed for fuel savings, but LOP isn't smooth at altitude. I suspect mapped EI will allow me to set 25-50 LOP, maybe bump RPM up a little, and get pretty close to the same speed. Anyway, that's the plan.

steve100 · Post by **steve100** » Sat Nov 23, 2013 10:59 am

What EFIS version is yours - are you pleased with it - any regrets, wish I had.....
Regards
Steve