Subaru EA81

Hello all,

I've been kicking around a few engine options for my 601 HDS project (about 60% finished) - I've disassembled two Corvair engines and prepared to rebuild to WW specs, considered Jab 3300s, Rotax, Viking, even an Aeromomentum (suzuki geo). I figured it was important to make a decision relatively soon so I can plan out things like the fuel system, EMS, panel layout, W&B...Anyway, one engine I had sort of forgotten about was the Subaru EA81. On the Zenith website, there are dozens of photos of 601's flying behind the engine, and they even reference having factory support for Stratus Engines (now out of business). I've rebuilt several high HP Subaru engines for auto use, so I feel comfortable with the design and layout of the engine. 

All that said, I just picked up a running Subaru EA81 flight engine with a "reductions" (by Dave Johnson) belt redrive and 72" 3 blade Powerfin prop for an absolute song. The engine is in great shape and has 120 flight hours in a Rans S7. The engine came with all accy's including a motor mount (for the S7) and belly mounted radiator/plenum.

I've got a few questions about the engine:

-Does Zenith still support the EA81?

-Does the EA81 fit under the Rotax 912 cowl? What sort of spinner should I use?

-Is anyone flying behind an EA81 with a "reductions" redrive?

-What diameter prop would you recommend for my HDS - 72" 3 blade seems a bit long

-Dave Johnson (Winnipeg, CA), the designer of "reductions" belt driven PSRU's has passed away - are there any manuals floating around for his systems? 

-Is this redrive still serviceable or has his design become obsolete? Is it worth investing in a new unit? (Air Trikes seems to have a good following - no belts to adjust, lightweight, good price...) 

-I'll need an engine mount - is there anyone out there selling one, or could you send me measurements? (I'd rather not reinvent the wheel)

I've attached a photo of my engine still attached to the crate and the prop just resting on the hub.

Thanks for your input! Any other advice is always welcome!

Chad 

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Permalink Reply by John Edwards on April 14, 2016 at 2:34pm

Support for the EA81 is limited, but Jan Eggenfeller of Viking Aircraft engines used to be the go to guru and supplier of all things Subaru.

Contact him and see what support is still out there.

Permalink Reply by Normand Lambert on April 14, 2016 at 9:54pm

Hi Chad,

Check my plane out (CH701). Flying with a Subaru EA-81 converted for aircraft. I use a gearbox (no strap) which is oil by the engine oil system. I use an oil radiator, glycol rad and no thermostat. The EA-81 swings a WarpDrive 3 blade 70 inch propellor. Has lots of power and works very well. I also have twin ignition.

The static thrust is nose to nose with the Rotax 912uls (100HP).

This website has a lot of infos  : http://www.ramengines.com

This is not my engine but it looks interesting.

Regards,

NormTheStorm

CH701SP C-GFEU

Permalink Reply by Chad Drzewiecki on April 18, 2016 at 10:46am

Thanks Norm! Your 701 looks awesome - thanks for that info! 

From what I can tell, my belt redrive isn't a bad system, but it needs to be understood. I like gears more than belts, but I'm not sure if I want to spring for a whole new PSRU system...

I asked the guys at powerfin about the 72" 3 blade prop and they said it would be a pretty good match - my plane isn't on it's gear yet (hopefully it will be soon) so I was worried about ground clearance - 72" seemed kinda big! 

I sent an email to the guys at ram engines this morning and asked about the possibility of converting the engine to fuel injection and dual ignition - what carb do you run? There's a holley on my engine now.

Permalink Reply by Normand Lambert on April 18, 2016 at 9:43pm

Hi Chad,

The Holley is not a bad carburator. I got an AeroInjector from http://www.aeroconversions.com/products/aerocarb/

It is very good. I installed it and it worked right out of the box. Only modification I made was to add an insulation plate between the AeroInjector and the intake manifold. Otherwise the fuel would vaporize before entering the intake manifold because of the heat generated.

My engine turns a Warpdrive 70 inch large 3 blades. I could of used a 72 inch 3 blade but felt the propeller would be too close to the ground if a flat tire on the nosegear happened or the bungee collapsed.

Let me know what you come up with. Question ? Dont hesitate.

Regards,

NormTheStorm

Permalink Reply by Kerry Yacucha on September 7, 2016 at 6:33pm

Hey Chad,

Have you had any luck finding info on the Reductions PSRU by Dave Johnson? I have a 601HD that has one in it and I am also looking for info, not having much luck either. It seems like they are out there but not much else other than pictures.

Kerry

Permalink Reply by Chad Drzewiecki on September 8, 2016 at 9:14am

Kerry,

I haven't had any luck in finding info on the Dave Johnson PSRU. I ended up buying a flying HDS with a Stratus 2000 enigne/PSRU so the project I was working on is now for sale. I still have it all in my garage though, so I might be able to help you with some things. What sort of info are you looking for?

Permalink Reply by Kerry Yacucha on September 8, 2016 at 5:55pm

Hey Chad,

Thanks for the response. I was basically trying to find a manual of one of Dave's PSRUs. I was wondering what vintage I have as some of the info I found suggests that his later units were much improved over his earlier ones. Also wondering about belt truing and what he thought was acceptable for belt drift and what RPM's to check it at. Also how to check and or set belt tension and what it should be set to. I have zero experience with belt drive PSRUs so any info or insight you can pass on would be double the knowledge than I presently have.

thanks in advance Chad,
Kerry

Permalink Reply by Chad Drzewiecki on September 9, 2016 at 11:01am

Kerry,

I don't have a manual for Dave's PSRU, but the plane that I have now has a belt redrive system on it, and after looking at both of them, I can tell you that they are both well engineered systems...if anything Dave's PSRU is over engineered.

With belt systems, its always a good idea to set the tension first, then set the tracking. The best way to measure the tension is by using a tension gauge (like this). Setting the belt tension on a synchronous belt is a pretty common thing in industrial applications, so there seems to be quite a few articles (like this) that describe the procedure. 

For my Stratus 2000, the best way to set the belt tracking is to measure the distance between the upper and lower cogs (at the front and rear) with a telescoping gauge and check for the difference between the two. If you had a difference of .003 (you'll need a micrometer) or less, your belt should be tracking perfectly. On your PSRU, you should be able to loosen the bolts on the plate that carries the bearings on the front and rear and adjust the set screw which will cause the cog to 'tip' to the front or rear - that will adjust your tracking. 

Another thing to consider is that belts usually have a shelf life of about 3 years, so it might be a good idea to replace your belt if it hasn't been done in a while. 

Permalink Reply by Kerry Yacucha on September 10, 2016 at 9:14am

Thanks Chad, gaining knowledge from those with experience is a very good thing and much appreciated.

Permalink Reply by Chad Drzewiecki on September 12, 2016 at 8:46am

Not a problem! 

Permalink Reply by charlie rosenzweig on November 4, 2016 at 12:41pm

I too hope to hear more about PSRU - gearbox options - engine choices.     

If anyone is using the Aeromomentum?

I join Chad in encouraging folks to post on this thread.

Charlie 

Permalink Reply by Chad Drzewiecki on November 4, 2016 at 12:48pm

Charlie,

Personally, the more I'm around auto engines with a well made gearbox/PSRU, the more comfortable I get. I sent a bunch of emails back and forth with the guys at Aeromomentum and I can tell that they know their stuff and have done their homework. They were in my top 3 for sure.

As far as I know, they are looking for some beta testers to develop a fwf package for zeniths, but have a few engines flying!

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