A3B6D vs A3B6

[KSMooniac]

Quote: 201er

Can someone explain just how illegal it would be to slip on the mag timing and set to 25 BTDC by accident? Are we talking voiding warranty, insurance, FARs? How big of a deal is it? Seems so silly to have to invest so much money into changing to electroair for a paper problem.

PS Does the electroair maintain 20 BTDC in the climb? Does that mean takeoff/climb performance still suffers?

[jetdriven]

Id love to see proof of Kelly's statement!   FWIW, at below sea-level density altitudes, which is what Anchorage is at -40c, requires using less than maximum allowable manifold pressure to avoid exceeding maximum rated horsepower. Even turbocharged aircraft must follow this rule.  Dont exceed rated horsepower, dont damage your engine.

I live in south Texas anyways, when do we get "extreme cold weather."

I spoke with Lycoming today. Their rep agreed with me, that undoing SI-1325A and using the correct 25 degree lag-angle magneto, resettig timing to 25 degrees and making a log entry is legal, and airworthy. It is a service instruction, not an AD.  The Type Certificate allows 25 degrees. 20 degrees is an option, and one I do not want.

[N601RX]

A service bulletin was issued back in the 70's that gave owners the option to set the timing back to 20 deg, change the impulse coupling and remark the data plate to 20 deg.  It was not mandatory.  My motor never had this done to it even though it has just been through its second overhaul, so my timing is still at 25. I do make sure it stays on the low side of 25 and not the high side.

All the new motors shipped from Lycoming are marked at 20 deg with no factory option for increasing it.  I've also heard that the cam to crank timing has been retarded slightly to make sure the hp stays under 200. Does anyone know how high the electroair will advance the timing?  The install instructions says the base timing has to match the  nameplate, but I assume the controller would advance it from there?

[jetdriven]

Max advance is 40 degrees. Or you can unplug the MAP sensor and run straght 25 degrees.

Here is the advance curve, it starts at 24" MP.

[N601RX]

Suspose our planes were experimental for a minute.  It would be interesting to set one mag at 20 and one at 40.  Crank the engine on the 20 degree one and climb to altitude on it. When the MP is down to 17" switch over to the other mag and see how much speed is gained. A poor mans variable timing.

[201er]

Quote: jetdriven

I spoke with Lycoming today. Their rep agreed with me, that undoing SI-1325A and using the correct 25 degree lag-angle magneto, resettig timing to 25 degrees and making a log entry is legal, and airworthy. It is a service instruction, not an AD.  The Type Certificate allows 25 degrees. 20 degrees is an option, and one I do not want.

[jetdriven]

The CAFE foundation test reported a small but verifiable increase in performance with the Jeff Rose ignition (now Electroair) , especially when LOP by a large value and above 9,000' density altitude.   But remember they started with a highly modified M20E and 25 degrees ignition timing on Bendix 1200 series magnetos. I think going to Bendix mags which have more spark energy and 25 degrees might be enough.

[jetdriven]

I can share it with other A3B6 owners. Im not so sure Lycoming wants this broadcasted.

 

[KSMooniac]

That is great info, Byron.  If/when you do that, I'd make sure you get some warranty coverage in writing since you shelled out premium AMUs for that overhaul.  

I can't believe that the SI didn't trigger massive POH mods to cover the reduced performance.

[Skybrd]

Quote: JimR

This is very welcomed news!  I'm interested in a copy, Byron.  Hopefully it will be a while but I'm almost certain that a A3B6 conversion is in my future and I'd sure rather continuing on with 25 degree timing.  As you know I am already accumulating parts.  I will PM my email address to you.

Thanks!

Jim

[201er]

Quote: KSMooniac

I can't believe that the SI didn't trigger massive POH mods to cover the reduced performance.

[Sabremech]

Hi JimR,

I'm listening and any part that can't be acquired anymore is what I'm in business to manufacture and certify where necessary. 

[HopePilot]

If it turned out that 20 degrees wasn't manditory, maybe we could just buy 25 degree mags, restamp the plate, adjust the logs and fly?

How much would 25 degree mags run?  Quite a bit less than Electroair I think.

[smccray]

Quote: jetdriven

I can share it with other A3B6 owners. Im not so sure Lycoming wants this broadcasted.

 

[wishboneash]

Quote: jetdriven

I can share it with other A3B6 owners. Im not so sure Lycoming wants this broadcasted.

 

[bd32322]

Restarting a very old thread .. But wondering if you guys with A3B6 were able to get performance back?

Also whats wrong with getting an A3B6-D with roller tappets and plopping in an electroair ignition instead of the bendix dual mag?

I am guessing its not possible to get an A3B6-D with roller tappets from lycon?

In which case I would rather let go of roller tappets instead of losing performance!

[201er]

Bendix Mag with 25 degree timing did the trick. Basically on par and not particularly faster or slower. Byron thinks his is faster now but I think he's full of it. The timing plays more of a role than anyone is willing to admit. The best solution is to have separate mags, 25 degree timing, AND roller tappets. However, it's also the most expensive. But with the way things are going, it would be a bad investment to go back to a b6d because serviceability of those dual mags isn't going to last forever.

[bd32322]

Bendix Mag with 25 degree timing did the trick. Basically on par and not particularly faster or slower. Byron thinks his is faster now but I think he's full of it. The timing plays more of a role than anyone is willing to admit. The best solution is to have separate mags, 25 degree timing, AND roller tappets. However, it's also the most expensive. But with the way things are going, it would be a bad investment to go back to a b6d because serviceability of those dual mags isn't going to last forever.

Good news indeed! I was reading up on electroair and it didnt look particularly appealing with high CHTs and reduced performance, unless flying very lean and very high. Coming up on TBO early 2014

[jetdriven]

We have 120 hours on the new A3B6 engine and it runs really well. I got most of the speed back after  65 hour break in. It literally took that long. And for some reason, 23 degrees timing is the best all-around performance of the engine. 20 degrees is slower and cooler (about 4 knots and 20-30 degrees), but 25 degrees can push 380 when just LOP on even a moderately warm day.  You have to watch it more.   23 degrees gives the fastest overall WOT sea level speed, and the LOP performance of 25 degrees is 2 knots better than 23 degrees timing. Legally you can only run 20 degrees or 25, take your pick.

 

We dumped the Slick mags and went Bendix 1200s as well.

[bd32322]

We have 120 hours on the new A3B6 engine and it runs really well. I got most of the speed back after 65 hour break in. It literally took that long. And for some reason, 23 degrees timing is the best all-around performance of the engine. 20 degrees is slower and cooler (about 4 knots and 20-30 degrees), but 25 degrees can push 380 when just LOP on even a moderately warm day. You have to watch it more. 23 degrees gives the fastest overall WOT sea level speed, and the LOP performance of 25 degrees is 2 knots better than 23 degrees timing. Legally you can only run 20 degrees or 25, take your pick.

We dumped the Slick mags and went Bendix 1200s as well.

Thanks for sharing the data! When you said it is 4 knots slower at 20 degrees, is that number compared to the a3b6d or is it compared to 23 degree on the a3b6?

What delta are you seeing with the a3b6 at 25 when compared to the a3b6d ?

[jetdriven]

20 degrees on the A3B6 is slower by 4 knots than 23 degrees in cruise.  A 23 degree A3B6 and a 25 degree A3B6D are about the same.  This is my particular installation. All the airplanes are hand-built and so are the engines.  But this is what I found out about mine.

[201er]

What delta are you seeing with the a3b6 at 25 when compared to the a3b6d ?

I'd say it's within the margin of error. Since the engine is new, gami spread is outstanding, so LOP performance is very good. I still think I saw higher speeds on the ROP side than now, but LOP cruise is as good as before if not a few knots better. Climb performance is great too. I don't have hard numbers but I can tell you that at 20 degree timing, I knew it wasn't the same plane anymore. At 25, I really can't tell the difference.

[jetdriven]

Our GAMI spread is .8 GPH, which sucks. I am having Lycoming send me two new injectors under warranty.

[201er]

Our GAMI spread is .8 GPH, which sucks. I am having Lycoming send me two new injectors under warranty.

What prompted this? The mag change?

[jetdriven]

Nope. It was .6 when it was delivered and I moved the #3 injector to #2.  Now #2 is flowing 10% more fuel, that cylinder peaks 90 degrees ahead of the others. I finally gave u after cleaning them 3 times.