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CorvAircraft> Dual Ignition toggle
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cookwithgas(at)hotmail.co
Guest

Posted: Mon May 01, 2006 4:38 am Post subject: CorvAircraft> Dual Ignition toggle

Guys and Gals:



Here's William's explanation of his dual ignition setup in the 601XL - I 

asked him for help on the subject and he asked me to forward the reply for 

the group's benefit.  I noticed there are a lot of 601XL builders using the 

Corvair, so I'm copying the Zenith-list with this post:



Enjoy,

Scott Laughlin

A lot of people get focused on hardware in the ignition system and loose 

sight of the

Two main points: It must work as a complete system and you must recognize 

that the pilot is the weakest link in the plane. Here is what we fly, and 

why we set it up this way:



On the 601XL's



Installation:

One DPDT switch high on the panel, centered in front of the pilot. Side 'A' 

has one ignition on it and the primary fuel pump on it. this pump is wired 

through the oil pressure cut off switch. Side 'B' has the same thing but the 

fuel pump is not run through an oil pressure switch.

Starter is a button on the panel hit with the index finger of the throttle 

hand without lifting it off the throttle. Key switch controls only the 

master.



Operation:

Engine is started on the 'B' side because the pump will run without the 

engine running. Both systems checked on run up. Take off and landing always 

done on 'A,' because in the event of an accident, the fuel pump will stop 

automatically.



Logic: Mark Langford inspired this design. The starter location is a Bob 

Lester tip. Pilot takes off and the power drops for any reason, Just move 

the switch to the other position. This eliminated the pilot having to 

diagnose anything. With an alert pilot, the time is much faster than 1 

second, and it always will beat any set up where the pilot has to look at a 

gauge to know what switch to hit. Even if the pilot is at 100 feet, and he 

waits 4 seconds, and restarts, he will loose only 50 feet or so. If you are 

frequently clearing anything at your airport by less than 50 feet, or it 

takes you more that for seconds to flip a switch and hit a button, you need 

a whole new game plan....



This system is simple, proven, takes into account the pilot and the 601's 

need for fuel pumps.

Do Not: wire the coils to 2 on off switches. Without fail, at some point you 

will have them both in the off position.



Do Not: use Pertronics ignition parts in place of the points. They are 

voltage sensitive, and quit working when the voltage drops. Points fly on 

long after these stop working. If you are worried about switching ignitions 

after one side quits suddenly, you want points because the almost always 

fade out slowly. When the pertronics part is starved for voltage it quits 

suddenly. and you cannot have a points back up because the pertronics part 

covers the points cam.



Do Not: Adjust the points in a WW distributor to the same gap. I set them in 

the machine to have the exact same timing. This sometimes causes the to have 

slightly different, but in spec., point gaps. If you spot this and "fix" it, 

you will have a bigger variation on rpm when switching from 'A' to 'B."



William

p.mulwitz(at)worldnet.att
Guest

Posted: Mon May 01, 2006 5:54 am Post subject: CorvAircraft> Dual Ignition toggle

This whole diatribe leaves me with two big questions:



1.  What is wrong with having both ignitions operating at once as is 

commonly done on certified aircraft engines?  This allows the pilot 

to spend his attention on flying the plane instead of managing the 

engine in the (apparently common for William's resurrected Corvair 

engines) event of an ignition failure.



2.  I find it ironic that a salesman who says the weakest part of his 

customer's system is the customer gets such a zealous following.



Paul

XL wings

do not archive



 	  Quote: 	
		  A lot of people get focused on hardware in the ignition system and loose

sight of the

Two main points: It must work as a complete system and you must recognize

that the pilot is the weakest link in the plane. Here is what we fly, and

why we set it up this way:


	


---------------------------------------------

Paul Mulwitz

32013 NE Dial Road

Camas, WA 98607

---------------------------------------------

frank.hinde(at)hp.com
Guest

Posted: Mon May 01, 2006 7:49 am Post subject: CorvAircraft> Dual Ignition toggle

Great...Right up until the switch fails!



All of this comes down to personal preference. On my Stratus I have the

primary ignition on the key switch and the second ignition, pump1 and

pump 2 all on separate on-off switches. The left and right systems are

wired from each independent battery.



For take off I run both fuel pumps and both electronic ignitions all the

time. I have a LOUD audible warning buzzer if I inadvertanty switch off

both pumps



I always have both pumps running for TO and landing. None of this is

wired through an oil pressure relay, not that I think this is a bad idea

necessarily, in fact it does give you a BIG warning your engine is about

to (or just has) seize. I personally couldn't imagine  the stress in

waiting for the second pump to partially fill the float bowls,

particularly if you are having to wait for the second pump to prime and

suck form the tank some feet away (hence my pumps are in the wing roots)

...But that's just me



Note I have run both ignitions continuously for 400 hours without ill

effect...I don't know what the Corvair setup is though..



Frank 



On the 601XL's



Installation:

One DPDT switch high on the panel, centered in front of the pilot. Side

'A' 

has one ignition on it and the primary fuel pump on it. this pump is

wired through the oil pressure cut off switch. Side 'B' has the same

thing but the fuel pump is not run through an oil pressure switch.

craig(at)craigandjean.com
Guest

Posted: Mon May 01, 2006 8:01 am Post subject: CorvAircraft> Dual Ignition toggle

Ignoring the prejudicial tone of your message I'll toss-out some answers. If

you are actually interested in more answers to your first question just

search the Corvair list archives.



1a. MSD (the maker of the coil mixer used in the design) recommends against

using both sides at the same time. There is another coil mixer (from

Mallory??) which is spec'ed for dual operation.



1b. Unlike a dual-plug engine with wide pistons in the dual-coil,

single-plug design there is no appreciable RPM drop when one side is lost.

So if you are cruising on "both" and any of the redundant parts fail you

will have no indication.



1c. "apparently common...ignition failure" - this has no basis in fact.

Every aircraft is design to handle failure modes.



2. The majority of accident investigations end in a conclusion of "pilot

error".



-- Craig

craig(at)craigandjean.com
Guest

Posted: Mon May 01, 2006 8:20 am Post subject: CorvAircraft> Dual Ignition toggle

 	  Quote: 	
		  > Great...Right up until the switch fails!


	


And magneto switches don't fail?



-- Craig

frank.hinde(at)hp.com
Guest

Posted: Mon May 01, 2006 8:32 am Post subject: CorvAircraft> Dual Ignition toggle

Yes they do...Thats why I have a separate switch feeding each EI system



Frank



Do not archive 



--

CLEONARD52(at)comcast.net
Guest

Posted: Mon May 01, 2006 8:48 am Post subject: CorvAircraft> Dual Ignition toggle

NOW, NOW, LETS BE NICE.

---

JAPhillipsGA(at)aol.com
Guest

Posted: Mon May 01, 2006 9:36 am Post subject: CorvAircraft> Dual Ignition toggle

Paul, I certainly have seen what your saying. Hard to understand. Course, Jim 

Jones got his followers to sip the grape kool-aid. Go figure. Best regards, 

Bill

do not archive

craig(at)craigandjean.com
Guest

Posted: Mon May 01, 2006 11:15 am Post subject: CorvAircraft> Dual Ignition toggle

The manufacture of the aircraft you are building respects the work William

has done with Corvair engines and routinely has a Corvair-powered 601XL in

their display at air shows, most recently Sun-N-Fun.



-- Craig

paulrod36(at)msn.com
Guest

Posted: Mon May 01, 2006 6:00 pm Post subject: CorvAircraft> Dual Ignition toggle

Re your questions---------Certified engines , Lycoming, Continental, et =

al, have very big bores, which means the flame front won't go all the =

way across at higher rpm in time to do any good. Ergo, a plug on either =

side, so the flame front only has to go halfway. Yes, they are redundant =

systems, but come home on one mag, and you WILL know it.  WW's redundant =

ignition systems give you a pretty good safety factor, in that if one =

craps out, the other will give you equal quality ingition. Yes, there's =

only one spark plug, but really, when was the last time a spark plug =

axctually DIED on you? Even fouled plugs still have something left, and =

load up slowly. As far as the coil-and-points setup, the new electronic =

systems are way more efficient, pull less juice, and do all sorts of =

good things, better than the old systems. And they rarely fail. But when =

they do, they give no warning. Points frazzle, wear, and run poorly long =

before they die. Those of us old enough to remember when coil and points =

was all there was, still remember when a screwdriver was the operative =

tool, and a matchbook cover was the points gauge to get you running =

better.  It's not that ignition systems fail often---It's that you =

always want the deck stacked in your favor.   As to point two, name one =

thing that is absolutely consistent, that has a human element involved. =

We only think we're good, and aviation makes humbling us its secondary =

hobby.



Paul Rodriguez

601XL/Corvair --inventing a flap actuator

  ---

cgalley(at)qcbc.org
Guest

Posted: Mon May 01, 2006 6:47 pm Post subject: CorvAircraft> Dual Ignition toggle

2700 is NOT a high rpm.  Think of all the cars that run 5000 to 8000 rpm 

with only one plug. The speed of the flame front is very fast, especially at 

2700 rpm. Plug redundancy may help flame front speed but tell that to a 

Ferrari that is turning 12 grand on one plug per cylinder. I don't think it 

is a factor to even consider with our relatively slow speed aviation 

engines.

---

george(at)customcals.com
Guest

Posted: Mon May 01, 2006 7:04 pm Post subject: CorvAircraft> Dual Ignition toggle

That's pretty unkind.



---

btucke73(at)yahoo.com
Guest

Posted: Mon May 01, 2006 7:36 pm Post subject: CorvAircraft> Dual Ignition toggle

Paul,



     You are correct that if one spark plug fouls,

neither ignition would fire the plug, and the plug

must be cleaned.  To my knowledge, it has never

happened, but it is a possibility.  This is where the

extra 2 cylinders would be a good thing.



     The piston area of the lycos is so large that

running both spark plugs will produce a much more

complete fuel burn, as proven by the RPM drop on mag

checks.  The same results would likely not be realized

in the corvair with such a small diameter piston, even

with two spark plugs, so running both ignitions does

not help there.  Only in the case of seamless failure

is it beneficial to run both.  If there were not an

efficiency benefit of running both ignitions in

aviation engines, would we still always run both?  The

answer is yes, because it is convention and how

everyone was taught, but would it be convention?  I

learned in a turbo prop and am fairly new to piston

engine aircraft with only 300 hours in pistons, so I

feel unbiased here.  



     There are arguments that if you run both

ignitions all the time, you would have no indication

of a single ignition failure.  Sure, you do a mag

check on the ground, but what happens if it fails at

takeoff?  You continue on the other ignition unaware

that one failed, just for the second to fail after

climb out.  If you run one at a time, you simply

switch to the other ignition on failure, and if on

climb out, can turn downwind, and land immediately. 

This, in my opinion, is  valid argument.    



     Having separate switches for the ignition systems

is a good concept as well, but it can be argued that

one could accidently shut them both off.  Not likely,

but possible.



     With a single switch controlling both ignitions

(like my system), switch failure can cause a forced

landing.  It happened in an RV recently.



     What is the best way to go?  Who the hell knows. 

If we keep it civil, we will all make more informed

decisions.  Since the accident in the RV, I have

become aware that my automotive key switch could be a

weak link in my system, through civil textual

conversation on the corvair list.  I have a 3 position

switch that allows me to run ignition 1, 2 or none.  I

am considering a separate emergency ignition switch

run independently from the rest of my electrical

system feeding both ignitions, just in case the key

switch or ignition switch breaks.  I have a header

tank, so all I need in an emergency is an ignition.  



R/



Brandon Tucker

One wing painted, one to go



http://home.sandiego.edu/~btucker-03/



__________________________________________________

Do You Yahoo!?

Tired of spam?  Yahoo! Mail has the best spam protection around 

http://mail.yahoo.com

Bill(at)flyinmiata.com
Guest

Posted: Mon May 01, 2006 8:53 pm Post subject: CorvAircraft> Dual Ignition toggle

As others have pointed out, aircooled aircraft engines typically have

huge bores compared to any high revving car engines, some of which *are*

dual plugged. 911 Porsche for example, from IIRC, 1984 on. 



Do not archive



TurboDog's Dad

Bill Cardell

www.flyinmiata.com 

1-800-FLY-MX5S

970-242-3800



--

Trainnut01(at)aol.com
Guest

Posted: Tue May 02, 2006 5:21 am Post subject: CorvAircraft> Dual Ignition toggle

You can add early 90s Ford Ranger 4 cyls to that list also.

Carroll Jernigan

 do not archive

gkrysztopik(at)satx.rr.co
Guest

Posted: Tue May 02, 2006 6:33 am Post subject: CorvAircraft> Dual Ignition toggle

1a. MSD (the maker of the coil mixer used in the design) recommends against

using both sides at the same time. There is another coil mixer (from

Mallory??) which is spec'ed for dual operation.



- is this first hand info?  Stratus recommended against running both at once

but others said it wasn't a problem.  I called MSD and they said it was ok.

Was the application described?  I run both for takeoff and landing.  It

would be nice to get some technical explanations from anyone who claims one

or the other but I didn't get any details and have never heard much either

way.



gary

frank.hinde(at)hp.com
Guest

Posted: Tue May 02, 2006 6:50 am Post subject: CorvAircraft> Dual Ignition toggle

I have never heared of a single failure of the coil joiner (I run mine

both at the same time for 400 hours), Does anyone else know of one that

has failed?



Note there is no warning against using both ignitions together in the

Stratus manual as far as I remember.

Frank 



--

Chris Lewis

Joined: 17 Mar 2006
Posts: 56
Location: Seattle

Posted: Tue May 02, 2006 8:16 am Post subject: Re: CorvAircraft> Dual Ignition toggle

Scott - I'm with you. Thanks for your efforts to document your build and share what you've learned with others. I'm just starting my Corvair teardown and your photos give me hope that my pile of parts will someday look bright and shiny new again.   



Chris in Seattle

_________________
750/ Zen-vair Semi-Scratch Builder
N750XT (reserved)

craig(at)craigandjean.com
Guest

Posted: Tue May 02, 2006 9:01 am Post subject: CorvAircraft> Dual Ignition toggle

This was Mark Langford's quote from the installation instruction sheet that

came with his 8210: "The MSD P/N 8210 Automatic Coil Selector may also be

used without a changeover switch. Running the two units simultaneously will

require more amperage and will shorten the time a battery will remain

charged.  Use this type of installation for short duration races". Nothing

like this appears on the sheet that came with my unit marked "Revised

08/01". In either case no dire warnings, no instant destruction. People have

spoken with MSD and received different answers. I suspect it is all a matter

of degree and a big factor would be the operating temperature of the unit

which in turn would be influenced by where and how it was mounted, etc.



The competing unit is Mallory's 29000. I can't find much on it. The

instructions may simple not address the point which leaves us free to assume

both legs can be used simultaneously. I believe that both the MSD and

Mallory units were dissected and found to contain differing numbers and type

of diodes. Way-too much information on the subject can be found in the

archives of the Corvair e-mail list at

http://www.maddyhome.com/corvairsrch/index.jsp



The "silent failure" issue is much more interesting to me.



-- Craig

daberti(at)sbcglobal.net
Guest

Posted: Tue May 02, 2006 2:09 pm Post subject: CorvAircraft> Dual Ignition toggle

The bore on my Rotax is 84mm (3.3").  I'm not sure what size the corvair has

but I'll bet it's larger.  The Rotax has a dual plug system with dual

ignitions that are checked just like the Lycomings and other similar

aircraft engines.  I get a rpm drop when switching one off just like they

do.  And just like the others my ignition switch grounds out the ignition

circuit so a switch failure is more apt to keep the engine running than kill

it...but that's for Murphy to figure out.  One check I do is when shutting

down the engine I let turn off one set 5 seconds before the other.  Shut

down is smoother and I get a "Mag" check on shutdown too.



Dave 601-HD 912ULS



--

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