A3B6D vs A3B6

[201er]

What are the exact differences in terms of maintenance costs, operating costs, reliability, and performance? Has anyone had experience switching one to the other? Or flying both?

[fantom]

Love these objective, Ford or Chevy questions.....going to get the popcorn ;-)

[Becca]

Quote: 201er

What are the exact differences in terms of maintenance costs, operating costs, reliability, and performance? Has anyone had experience switching one to the other? Or flying both?

[201er]

Quote: Becca

- Limited to 20 degrees of mag timing, which is a slight loss of performance compared to the allowed 25 degrees of timing allowed by the A3B6D

[jetdriven]

Both engines have roller tappets.  The only difference is:

two separate slick 4300 series magnetos

different prop governor ratio

20 degrees ignition timing

oil cooler hose repositioned on rear accessory case.

 

Now, about the 20 degrees timing. The TCDS for the O-360 series engines (1E10) says that ignition timing is 25 degrees.  (optionally 20 degrees if SI1325A is complied with)  In 1976, Lycoming issued a service instruction,  SI1325A, which said that in extremely cold weather the engine can have detonation at high power settings.  They go on to say that the engine runs cooler CHT's at 20 degrees as well.  So their procedure was to change the lag angle of the impulse coupler in the magneto, set timing to 20 degrees, and either restamp the data plate or get a new one issued.   Seriously, I think it was all about the cooler CHT and warranty claims. If you recall, the Grumman AA5 series engines run real high CHT's due to a poor cowling design and they were looking for a bandaid fix. This was their lawyer-engineered fix. Since then, every engine to leave Lycoming is at 20 degrees.

 

The engine was certified to produce 200 HP +/- 5% IIRC for the cetification standards. Todays standards are +5% / -0.  Perhaps thats why the IO-390 IS rated 210 HP.   (Interestingly, it has a 5 minute takeoff limit of 210 HP then 27.4" MP continuous, 200 HP)  I would love to see Lycoming put an IO-360A3B6 on the dyno and show 200 HP on 20 degrees.  They never will.

 

Now about performance. I discovered the timing was 20 degrees on our A3B6D, which actually is NOT allowed. (probably because you cant change the lag angle on a Bendix dual mag, they were stuck).  Resetting it to 25 degrees was like a whole new airplane. It leapt from the runway, climbed better, and cruised between 3-7 knots faster. I logged quite  few flights and the IAS was a solid 5-7 MPH hogher in the same conditions.  That is not insignificant.  In fact, its about 500$ in operational cost in a 150-200 hour block of flying.  The only downside was a 20 degree hotter CHT. We used to run easily 350-360 and now it was more like 380 on #1. The rest were cooler. The LOP power did not fall off nearly as soon. 30 LOP was still producing the same speed as peak, but at  a half-gallon lower fuel flow.

 

There is a workaround.  Electroair has an STC'd electronic ignition approved to ONLY set at 25 degrees on 360 Lycomings. So you get your 25 degrees timing back.  Maybe I have to donate plasma or pick up a wagon load of aluminum cans for recycling, but I am gonna get me one of those.  Then you got your 25 degrees timing, eliminate one crappy Slick mag, and have the roller tappets.

 

 

 

[jetdriven]

Jim, we actually ordred an A3B6D.   But the factory called back and said we can get a B6 for no dissimilar core charge (5k) and it was 1800$ cheaper.  I then called Quality Aircraft Accessories, who has overhauled the mag, the fuel pump, the gear motor.   They said parts are available but if the housing or the cam breaker shaft is underviceable, they send it back and you are finished. The 500hr inspection is now 1100$, (up from 500$ a year ago), and i short, is a dead end engine. Which is a shame, beause I liked our 25-degree dual mag. Everyone says it, and I will repeat it. With a proper 500-hr inspection that dual mag is at least as reliable and perhaps more than two separate mags.  The mag gives you 25 degrees timing and they never disagree in timing. Slicks have all kinds of internal failures. All the accessories run through just one gear.

 

The B6 weights 3 LB more than the D.

I also have two mag hold-downs for sale for a B6D.  They are described in SI 1508C

[schule]

Electroair sets the timing to your engine placard timing.  This is one of the many questions required to order an STC'ed kit.  Once at altitude/below 24" manifold pressure the spark will start to advance.

-Mark

[jetdriven]

Quote: schule

Electroair sets the timing to your engine placard timing.  This is one of the many questions required to order an STC'ed kit.  Once at altitude/below 24" manifold pressure the spark will start to advance.

-Mark

[Kwixdraw]

My understanding of the B6 vs B6D is that there is a lot more that's different than just the roller tappets. I was looking into converting the accessory case on my A3B6D to the B6 configuration.  ECI sells the accessory case but tells me that there are differences in the gears because the case is bushed for the shaft to ride in as opposed to usual Lycoming practice of having the shaft bolted to the case and the gear bushed. The crankshaft is supposedly different in a number of dimensions. It would have required some fine and fancy machine work to get it all done and of course that is expensive. I looked into this because my engine has a rather checkered history of repairs due to sudden stoppages and cams making metal and then a long period of sitting unused. Lycoming would accept it as a core but at that time they were in no way inclined to make it a sensible thing price wise.

[Becca]

Quote: Kwixdraw

My understanding of the B6 vs B6D is that there is a lot more that's different than just the roller tappets. I was looking into converting the accessory case on my A3B6D to the B6 configuration.  ECI sells the accessory case but tells me that there are differences in the gears because the case is bushed for the shaft to ride in as opposed to usual Lycoming practice of having the shaft bolted to the case and the gear bushed. The crankshaft is supposedly different in a number of dimensions. It would have required some fine and fancy machine work to get it all done and of course that is expensive. I looked into this because my engine has a rather checkered history of repairs due to sudden stoppages and cams making metal and then a long period of sitting unused. Lycoming would accept it as a core but at that time they were in no way inclined to make it a sensible thing price wise.

[bnicolette]

Jim,

What is the price for the kit?

[Becca]

Quote: JimR

I just talked to Vanette at Dugosh about ordering the parts necessary to make this conversion.  She was very familiar  and said that both a MAC prop governor bracket and a MAC prop governor plate are required as are a bunch of clamps that are used to reroute either the throttle, propellor, or mixture cable.  She couldn't remember which.  Pictures of the MAC prop governor parts, as installed, are available here on MooneySpace courtesy of a member who went through this process a few years ago.  Search for the thread "The Saga Continues".

Dugosh has either the bracket or the plate in stock and have placed an order with MAC for the other.  She says that there are several of us 201 owners preparing for this conversion.  I have added my name to her list and as soon as she can acquire all of the parts she is going to send me a A3B6D to A3B6 conversion kit.  Might be worth having on hand if you have a long ownership horizon as I do.

Jim     

[KSMooniac]

Any chance Stacey/Mooney would cut the drawings loose for a vendor to make the perpetually out-of-stock parts?  Surely they're not difficult to fabricate... alternatively if someone has a spare, we could likely reverse-engineer it and try to get a PMA.  I'm thinking about doing something like this as a side business in the near future, but I want to start with composite parts first...

[jetdriven]

Brian at Willmar said only order the 660235-001 bracket.  Everything else is fine.

[Becca]

Deleted.

[schule]

Byron - the Electroair timing set up details are in the installation instructions.  You are correct it is not easy to find on the main website.  As I am learning with an install of this STC there are also a couple other issues each particular install has to work through.

 

Jim - good luck with you upgrade.  The A3B6 upgrade to my Mooney was STC #SA250GL and Installation Instructions MW2030 arroding to the 337.  It was completed by Midwest M20.  The new owner running the shop in IL may be able to give a couple of pointers.  He has been very helpful to me in the past when I was broken in NM.

 

-Mark

[sellis]

Quote: KSMooniac

Any chance Stacey/Mooney would cut the drawings loose for a vendor to make the perpetually out-of-stock parts?  Surely they're not difficult to fabricate... alternatively if someone has a spare, we could likely reverse-engineer it and try to get a PMA.  I'm thinking about doing something like this as a side business in the near future, but I want to start with composite parts first...

[Antoni Deighton]

I don't wish to hijack the thread but to further Stacey's comment, the drawings are Mooney's most valuable asset. Sure the tooling has some limited value, but if we're hoping that Mooney will restart the production line, then we need to recognize that no investor is likely to invest in the company without the drawings. Everything else is old equipment and buildings. If you want drawings in order to make new parts, the consider buying the company!

[jetdriven]

Interestingly the cable mounting bolts are out past the end of the bracket.   I had to fabricate a 4" extension to this bracket to mount the cable to it.   Then I had to fabricate the governor arm bracket as well.   Sems like a lot of fabrication for a drop in engine. 

[jetdriven]

For us, for now the A3B6 is about 5-7 knots slower and the climb rate is down by perhaps a third, to about 500 FPM at sea level at 120 KIAS. Or, in other words, does 145 ktas on 9.5 GPH and won't go leaner that peak without falling on its ass.  This is very close to what our A3B6D was like with 20 degrees timing.  I have sheets and sheets of logged data withs 151-153 KTAS and ff in the 7.5-9 gph range, 15-50 lop.   This delivered a consistent 17-18 NMPG.   Right now it's about 15.    There's a difference between 5-7 knots slower (such as a piper arrow) and 5-7 knots slower on a gallon higher fuel flow.  That's significant.  

[201er]

Byron, how soon are you putting the electroair in? What is holding you back?

[Skybrd]

Quote: 201er

Byron, how soon are you putting the electroair in? What is holding you back?

[Skybrd]

I just thought of another concern with changing from the single coupling dual mag (for the A3B6D) to the two independant magnetos (for the A3B6). If the new slick mags are like most setups one will be with a impulse coupling and the other non impulse. If that's the case, the starter switch will need to ground the right mag "P" lead during start or a kickback could occur. My former "E" model ignition switch had that setup so the right mag would be disabled during crank. The single coupling magnetos that we started with had only one impulse coupling for both mags and didn't need to disable the right mag. Maybe the new slicks will have impulse on both mags and won't need the ignition switch cutoff. any comments about this?

[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?

[Becca]

Quote: JimR

Not very encouraging.  I was hoping for an easier installation than that.  Thanks for the info, Byron.

Jim