HomeLINKSEmail:
|
Subaru FAQ1.0 Is there
an archive of previous postings available ?
(This FAQ was prepared by someone else - it is a bit out of date - Kevin)
kevinh@interstice.com List Owner
We do have an archive of all old messages. Any new user with questions such as this can probably find answers by sending email to: majordomo@interstice.com The contents of this email should be: get airsoob archive.old get airsoob archive.0796 get airsoob archive.0896 This will send you three HUGE emails, but you will get plenty of soob reading. If you want an up-to-date web archive, follow this link.
Send an email to majordomo@interstice.com. The contents of this message should be "who airsoob".
The Subaru family goes like this. ea18, ea82, ej18, ej20, ej22, ej25, eg33(svx).
1.8 liter, weight dry with drive complete about 185 lbs, stock hp 72 at prop.
It will be 265 lbs for ej22. thats complete with drive starter alternator carbs etc. but no liquids.
The numbers are also easy but they need to put into context to be usefull. The prop on the Lyc was 58 x 72 and never optimized for the aircraft. It was diameter limited by ground clearance during TO and landing and had thick tips so thrust efficiency was not as good as it could have been. The subaru thrust line it up 3 inches which allowed a larger diameter higher aspect ratio prop with a bit less pitch to allow the engine to run fast near its peak HP. Also I modified the tips with carbon to thin them out. This prop is now matched to the airframe/power plant much better than with the Lyc. Also the first few flights with the subaru were pretty poor. It took quite a bit of experimenting to get the power up where it is now, so these numbers represent the present configuration. Also consider that the airframe is much cleaner aerodynamically than with the lyc so its hard to draw exact conclusions re power etc. Test conditions were not identical and no attempt was made to normalize. Lycomimg - ROC @ 850 flying wgt 1850 ft/min top speed at 1000 asl 173 KTAS EA-81 - ROC @ 850 flying wgt 2100 ft/min top speed at 1000 asl 176 KTAS Note that one cold day at -3C and with very little fuel , I saw 2500 ft/min at 100 Kts ias sustained for several thousand ft. Typical fuel flow on a xctry with the Lyc at 2550 rpm, leaned right out with ignition set at 29 deg BTC was 4.2 Imp gals/hr. The subaru burns 3.4 Imp gals/hr at the same speed 160 KTAS at a power setting of 22 in MAP giving typically 5200 RPM. I believe that the bottom line here is what really matters, and thats the performance of the aircraft as a complete system. It is clearly better with the subaru but I have no idea what HP I have because I cant measure it, and to be honest, dont care much. I would guess at 100 HP based on some rudimentary calculations but I can measure ROC, top speed and F/F.
The cost of conversion depends on who is doing the work. If you make all your own parts, you could come out farely low in $$$ cost, by extremely high in time cost. That is the option we took, but it took YEARS not weeks. I would probably do it again the same way, of course it would take much less time now :-) It is amazing how many parts we made two or three times! The hanger is full of previous iterations. I know a local guy that build a Pelican. He bought a Soob engine, built his own reduction from Reductions Inc plans, and flew. He used the engine straight from the car, with a total $ outlay of less than $1500. Anyway, you get the idea. It's the same old money/time balance. Good luck,
I highly recommend the following book if you are considering any experimentation with turbos: Turbochargers by Hugh MacInnes Publisher - HP Books It is sold at some autoparts stores (I bought it at Pep Boys)
By : Nigel Field The stock EA-81 is a nice solid little engine with great potential for an aircraft if modified. In stock configuration it will make about 75 HP at 4800 rpm and probably never wear out. At 3600 it is down the lower rpm is probably only making about 60 HP or less. By contrast, the iron block Honda Prelude also 1.8 litre, will make 125 HP at 5400 rpm. So, what do we do to get power up on the Subaru. There is no one answer. A number of things need to be done which all contribute their share of power. The first thing to do is to improve the mass airflow through the engine, which is after all just an air pump. This requires first that the cam shaft be reprofiled to allow the engine the "capability" to breath and scavenge better. I sent mine to formula power to be done but I think Stratus also will do this for about $120.00. This alone won't improve it much unless the rest of the induction system is modified. The intake manifold is replaced with a custom one with larger diameter runners and no coolant passages to heat the charge. I made mine from carbon etc........... deleted...... (see my article on carbon manifold construction.................... The exhaust system is next. Use 1.75 inch pipe instead of the stock 1.25 inch, which is half the cross section. This is important and accounts for about 10 HP. Run each side back to the exit and couple them together with a cross-over as close as possible to the oil pan to form an ‘H' pattern. This gives two ways out for each pulse and also reduces exhaust noise by a big amount. The heads are next. Try to get some 1984 heads or later, as they have bigger intake valves than earlier models. Where the valve seats are pressed into the head there will be a lot of excess metal blocking the flow forming sort of an oval pattern. Use an end mill or whatever, and drill or dye grinder and remove this metal to give the port a more round smooth shape. Sand smooth as possible to prevent turbulence. Do the same to the exhaust ports, only these wont need as much cutting. Be careful not to cut through into a water jacket. When done, have the heads glass beaded, including the ports, it will make them velvet smooth inside. They don't have to be polished shiny, just smooth. Finally, have .040 milled off the gasket face. This does two things. It raises the compression ratio to 9.2 from 8.5 and restores the valve geometry that was disturbed by grinding off the bottom of the cam lobes when reprofiled by moving the heads closer to the cam by .040, otherwise you may need longer pushrods. Sounds like a big deal but can be done in one day and is necessary. Get a machine shop to do the beading and milling, about $30.00 per head. If you can't get the big valve heads, do it anyway to the existing heads. For carburation use your favorite model but not the stock Subaru, its far too small and complicated. I use a carter 2 barrel from a 318 V8 which is just right. Remember, it has to flow lots of air now that the engine has the capability to do it. For ignition I use the stock reluctor electronic. Take it apart and open up the slots in the centrifugal advance mechanism to allow more advance, up to 30 crank degrees (15 at the distributor), this is only to ease starting. Disable the vacuum advance and remove the diaphram. Lock the mechanism inside with a screw so it won't move. Set the timing for 37 degrees BTDC on the flywheel with the advance sprung over by hand to full advance. Should be about 7 degrees static. (No advance). This gets you to about 100 HP at 5200 rpm. The water pump and alternator will be running too fast and may cavitate, reducing cooling and wearing out your alternator. Make or buy a smaller drive pulley, about half the diameter of the stock one to cure this. I turned one from mild steel ant it works great. Obviously to do all this you have to disassemble the engine, again no big deal, but try to get a book so you know what is what. I got a generic one from the auto parts dealer for $15.00 which shows this engine. Once apart take the opportunity to clean, inspect and measure everything. Easy- off oven cleaner is great for removing baked on carbon, but it attacks aluminum, so don't leave it on for long and don't use it on the outside of the pistons. Get and install new bearings, rings and a gasket kit (about $200.00). Deglaze the cylinders do the rings will seat. I use 240 grit aluminum oxide paper and varsol making a spiral pattern. I don't like using a hone unless really nessary as it removes too much metal. If you like, go ahead and paint it with any good enamel from the hardware store, it won't burn as the engine never gets above about 230F. Break it in with 20 weight mineral oil for about 10 hrs or until the oil consumption stabilizes at almost nothing. Then use Aero Shell 15-50. Its an ashless dispersant high temperature, the best oil there is. To get 100 to 110 HP this engine has to run fast at 5200 rpm. This won't hurt it at all. I've had mine to 6800 and nothing let go. My normal cruise is 5200 rpm. If it won't turn this fast, you need less prop or a higher reduction ratio. It won't give you much at 3600 rpm even modified.
The EA81 stock coolant pump has two inlets one 1.25 inch which is the cold inlet from the rad(s) and one little one about 5/8 which is cold return from the heater core if you use one, most folks just block it off. The pressure side of the pump is integral to the block and pressurizes the engine coolant passages. You can pick off pressurized hot coolant for your heater anywhere after it leaves the engine and before it enters the hot side of the rad with a "T" fitting of some sort. If your using the big, ugly, hot, restrictive, stock manifold, then it already has a fitting for this.
The WarnerIshi RHB52 turbocharger seems to work nicely as a muffler. It also seems to increase performance somewhat... :-) Stratus also sells an all stainless unit. weighs 4 pounds and actually gains about 3 to 4hp over straight pipes. It also quiets it significantly. The main thing is that both heads are connected. (crossover) thats what gaines you the power.
Reductions Inc, Box 16, Grp 15, RR#1,Dugald, Manitoba, Canada, R0E 0K0 (204-853-7998) Stratus Inc., 7750 Twelfth Avenue Northwest, Seattle, washington 98117 (206-783-3845) Ross Reductions ???
If you are planning to make one you will find that by the time you have bought the sprockets, bearings, steel, alum of various sizes, etc, etc, you will find it not reaaly worth it, especially if you have to farm out the substantial amount of machining. Just buy one ready to go, you will still come out way cheaper than a run out Lyc.
CONSTRUCTION OF A CARBON FIBRE MANIFOLD FOR THE EA-81 ENGINE By Nigel Field manifol3.rtf 4 Oct, 96 INTRODUCTION The stock manifold on the EA-81 has many drawbacks. It is restrictive to flow, and is heated by the coolant which reduces available normally aspirated power. It is heavy at 7 lbs, bulky, and has an awkward physical carburetor interface. A much improved manifold can be easily constructed from carbon fibre by the average builder. This article will attempt to describe how this may be accomplished. Carbon is used for its high modulus and low weight to give an acoustically solid structure. You will first make the head interface flanges from steel, and then design and construct the manifold itself. Although not complicated, construction is a multi step process completed as a series of small evening tasks. CYLINDER HEAD INTERFACE The first parts to make are the cylinder head manifold and cooling interface adapter flanges. No these are not carbon and they are the toughest parts, but still easy for a homebuilder. There are a number of design options available. The simplest method requires basic tools but some brazing or welding is required which unfortunately is unavoidable. The adapter plates will provide 1.5 in diameter stub tubes to couple with the carbon manifold. As the head ports are slightly smaller than this, the ports will require some slight enlargement. Using a 1 inch sanding drum on a drill gently open the head ports by grinding away aluminum on the inside face keeping the hole round. Try not to remove too much on the coolant passage side to leave as much clearance as possible for the coolant tubes to be added later. Check constantly with a piece of 1.5 inch stainless exhaust pipe until the ports are the correct size and match the pipe. Transition any ridges inside to make a smooth opening. There is a cast ridge running vertically into the port that will interfere with this process so grind it away at the opening area only and transition into the port. I'm not sure exactly what it does but all the experts say leave it in. Now using a cut up file jacket, make a template of the bell shaped interface at the head port to include the 3 mounting bolt holes and surrounding flat gasket face area. Using the template fabricate two plates from .125 minimum stainless or 4130 steel. Drill the three mounting holes to 1/4 inch to later take 1/4 X 28 cap screws. Cut out the induction hole using a series of closely spaced drill holes and then a 1/4 round file unless you have access to a lathe, then turn them. Fit snugly to 1.5 by .035 inch stainless exhaust pipe. Mark and cut out the curved coolant slot using a drill and file. Fabricate two 1 inch long induction stub tubes from the 1.5 in pipe and temporarily fit them into the induction holes in the flange. Next make coolant outflow tubes from 3/4 in 4130 or stainless about 4 inches long but whatever will best fit your installation. Cut these tubes at about a 30 degree angle up from the horizontal to fit over the coolant holes in the flange. Now trial fit everything on the head ensuring all holes and ports properly align and the coolant tubes clear the bolt holes. When satisfied mark the locations and then braze or weld the pieces together. If you don't have OA welding equipment try a friend, or farm it out. The welding will probably warp the plate slightly so using an inverted belt sander, hold the plate nice and square against the belt and grind it flat. Rotate it occasionally to avoid uneven grinding. To prevent hose blow off, make a raised end on the coolant tubes by wrapping 2 turns of solid copper wire about 22 gauge near the end and solder. Now etch and paint with your favourite epoxy paint or enamel. There is insufficient room to use standard bolts to attach these plates so the heads will need preparation to take allen head cap screws. The heads are metric so get some old bolts of the right thread and cut off ½ inch lengths of thread and screw these into the six mounting holes until flush or just slightly recessed with the head gasket face. First cut small slots in one end so you can turn then in with a screwdriver. Install these with JB Weld high temp epoxy available at any auto parts store. After cure drill and tap to 1/4 X 28. Purchase some 1/4 X 28 X 3/4 Allen head cap screws for mounting. Fabricate two gaskets from good quality gasket material to match your new adapter plates and bolt them on using Permatex gasket compound. The black rubber impregnated compressed paper stuff works best. Do not use cork or any other very soft material as it will squish out and leak when you torque the plates down. OK that was the worst part now on to the composite stuff. MANIFOLD You will make the inner core and fit it to the engine, then complete the various layups of carbon, then dissolve out the core, then fit attach tabs and the carb mountings, and finally finish the outside of your manifold. You first need to have the heads on with head gaskets and at least two bolts per side snugged up. This will a ensure proper fit of the manifold. Core The core is made from fine grained builders insulation Styrofoam SM in three pieces, the plenum and two runners. Do not use the expanded bead popcorn foam as it is too rough. The design and shape of the plenum depends on your particular application and carburetor installation but basically it is a cavity which feeds the two runners. It serves as a capacitor or storage tank if you like, to help even the flow through the carb caused by the vacuum pulses. Mine is a down draft 2 barrel mounted on top of a 7 X 4.5 X 2 in plenum. For low profile applications a side draft carb could be used so design your plenum accordingly. Try hard to keep it symmetrical and watch out for the steering effect of the throttle plate(s) which tend to direct raw fuel to one side at part throttle. This will cause uneven mixture and all the associated headaches of roughness, burnt valves ad nauseam. My throttle plates open fore and aft so it remains symmetrical. Throttle plate symmetry is very important. Cut your plenum core with a band saw or hack saw. Sit it on top of your engine in exactly the position you want it. Shim it up underneath to give at least 3/8 inch clearance from the block to allow for its eventual thickness and some running clearance. Now plan your runner shapes to provide a gentle curve from the plenum though a 90 degree down turn to mate with the top of the stub tubes on your head adapters. Make them by cutting foam out in two dimensions with a slightly tapered square cross section. In other words they are bigger at the plenum than at the heads. This keeps the velocity lower in the middle but provides more mass to help push the new charge in. Now trial fit the runners to the plenum and adjust as needed until you are happy. Use a sanding block to trim fit everything. Glue the runners to the plenum with a dob of 5 min epoxy or hot glue in the centre of the joint not the edges because its hard to sand. Then re-fit everything and push the runners gently onto the stub tubes to leave a slight impression sanding mark. Now start to shape the core by sanding the corners to a nice radius and working your way down the runners. Leave them basically square at the plenum and transition to perfectly round at the ends where they meet the stubs. They should be the same as the inner diameter of the stubs seen by the impression marks that you made earlier. Foam seems to sand easier in one direction only. Use light pressure, take your time, and trial fit regularly to check progress. The core will be a little rough due to the grain of the foam, this is OK. Any chunks that get torn out need to be filled with wax or something that wont stick to epoxy. It will not take long however to get a perfect Styrofoam core matched exactly to your application. STICKY STUFF The manifold is made of three plies of 282 2.7 oz bi-directional carbon re-inforced with extra plies at the plenum. The preferred laminating resin is PTMW Aeropoxy or Epolite 2184 and 2410 hardener as these have good high temperature properties and excellent peel strength. Any good laminating resin will probably do however. To avoid a mess and bumpy overlaps the layups pretty much have to be done in stages with a cure in between. Start with the plenum top or bottom and lay on 2 plies of carbon with the weave at 45 degrees to the long axis. Lap about 1 inch onto the base of the runners and fully up the sides of the plenum flush with the other side. Use gloves and conform it with your hands. Carbon is very stiff initially and takes about 1 to 2 minutes for the resin to soften it, then it conforms just fine. Now do the runners with 1 ply and overlap onto the plenum by ½ to 1 inch. Wrap the small ends around the core best you can and allow an overhang which will be trimmed later. While your all sticky, layup some mount tab construction material on saran or plastic sheet about 4 inches square, 3 or 4 plies of carbon or glass. After cure transition the edges with a hard block and 40 grit sanding belt cut up, or paper ensuring you don't damage the exposed core. Then do the same layup as above to the other side overlapping the first layup on the sides of the plenum and runners. Use wet resin rich layups, shiny bit not dripping as pin holes will leak air. When cured it will be much easier to handle so transition sand all the edges and do it all over again trying to move your overlaps slightly to avoid a big bump. When you are finished you should have 3 plies on the runners overlapped on their sides to 6 plies, and 6 plies on the top, bottom and sides of the plenum. If you are mounting your carb to the plenum add a 3 or 4 ply pad over the mount point for added strength and to allow for sanding flat. When cured have a last look and if you are satisfied then place in your oven pre heated to 150 deg F and let soak for 30 min then gently raise the oven to 170 F and soak for another 60 minutes. This will raise the creep temp of the epoxy to about 220F. Now trim the head ends of the runners flush with the foam core. Locate and cut out your carb inlet hole(s) with a dremel and dental burr or hole saw. Take a chisel and dig out as much foam as you can reach from all openings. Dissolve out the rest with MEK or lacquer thinner. Gasoline is not recommended as it turns the foam into a thick goo which won't completely dissolve and makes a real mess. Pour it full of boiling water with a little dish soap to remove any wax if you used it. Now slosh the inside with epoxy thinned out with a little MEK or alcohol, let drain and cure. This should make the inside nice and smooth. Repeat if necessary but a slightly rough plenum area helps vaporize and mix the fuel. The runner ends at the heads need to be very smooth as this is the point of highest velocity, so sand the inside curves best you can with small strips of paper on your finger. Mounting tabs(s) are next. Mount your nearly finished work of art on the engine and locate where you wish to secure it. Mine has one tab only on the rear which ties into the inner of two bolts on the cover plate on the former oil filler neck which is long gone. I fill my oil through a small fitting I made on a rocker cover breather pipe. Use the construction piece you laid up earlier and cut it into a tab about 1.5 inch wide at the junction of the plenum and tapered to about 3/4 inch at the bolt. Tack it in place with a dob of 5 min. When set make a flox fillet both sides at the junction and layup 2 plies carbon both sides overlapping onto the plenum. Cure, trim and drill out the bolt hole. Block sand the carb mount pad until flat then drill the holes to mount your carb. Install AN-3 bolts from the inside up through the holes to make studs. Rough up the inside of the bolt heads and coat them with JB Weld to hold them in. If your carb has big mount holes as mine does make some spacers from aluminum pipe or whatever to make a nice fit to the AN-3s. Add a vacuum port if you like made from small pipe. Drill a corresponding hole somewhere in the plenum and secure it with JB Weld epoxy. OK almost done. FINAL FINISHING To make your new manifold a true work of art it needs a nice finish. Final wet sand all bumps until presentable, then paint on a thinned coat of epoxy and let cure for a few hours until a firm tacky then bake at 170F until cured. This will fill most of the weave and look pretty good, but for a really nice look, wet sand it again and apply another epoxy coat as before. I took mine one step further and sanded it with 320 then sprayed on a clear coat of Dupont Chroma Clear. It looks like a mirror but this wont give you any more power. MOUNTING The transition to the stubs is made with a 2 inch length of 1.5 in ID silicon hose and worm clamps, just like Lycont do it. The carbon should just touch the top of the stubs so there is no heat transfer and the manifold will run much colder than ambient due to the latent heat of vaporization of the gasoline. The worst case is after a 5 minute shutdown and re-start where the manifold gets heat soaked from the engine, but it wont get soft or collapse and once running will rapidly cool. Oh, and be sure to provide for carb heat. This manifold will run cold and could easily ice up when conditions are right. Good luck and good flying..
The general build method was spawned by Nigel Field. Basically the builder forms a male plug using Styrofoam. Forming Styrofoam entails cutting the foam using a hot wire saw followed by trimming with a sharp knife followed by sanding with regular sand paper. (Use good quality Styrofoam ). Once a satisfactory shape is achieved cover the surface with paraffin wax by rubbing the wax against the foam whilst being heated with a hair dryer. The wax acts as a release agent. In parallel to this exercise, make two boards of glass fibre approximately 1/4" thick and larger than the tops of the injector runners. After cure and using the injector runners as a pattern, cut the boards to match the top of the injector runners. Drill and locate all attachment holes. Next cut six pieces of 3/4"(long) x 1.75" (dia) 0.035" (thick)stainless exhaust tubing (Aircraft Spruce) and line this up as best as possible over each induction orifice of the injector runner and scribe a line around the tube. using a drill press (Max Speed) and a 1/2" tungsten carbide cutter, set the depth to 1/4" below the top of the runner. Wear adequate eye protection and a pair of stout gloves. Switch on the drill and with the injector manifold pressed firmly against the surface of the drill base platform, tease the cutter against the aluminium. The Aluminium is quite soft at it is a simple job to open the hole out to match the scribed line discussed previously (you have made a poor mans mill). Check periodically to get a good snug but not tight fit for the stainless tube into the manifold. Repeat for all six openings. Once the six openings have been milled out, there should be a bad discontinuity between the stainless tube and the aluminium. Using a wood cutting bit in an electric drill, and whilst holding the stainless tube in location, remove the excess aluminium. The stainless tube protects the manifold in the region needing protection but allows you to make a good blend between the two without a lip. Now go back to the glass fibre flanges that you just made and stick masking tape over the interfacing face. Remove the six stainless tubes and put a thin coat of black grease on the manifold face. Insert the attaching bolts and press the two parts together so that the grease marks the masking tape thereby aligning the 1.75" holes. Now remove the masking tape and cut out these holes so the stainless tubes are a loose fit. Grease the surface of the injector manifold again this time going into the milled region. Insert the six stainless tubes and flox them in place. (Flox is a mixture of Safe-T-Poxy and a cotton flox. Suppliers AS and Wicks) The flox bonds the two together. After cure break the newly made flange away from the injector manifold, the grease should have worked as a release agent. Replace the two flanges into their respective injector manifolds and bolt down lightly. Now with your male Styrofoam plug you should be able to insert the ends of the foam into these flanges with a good fit. Use wax to fill any voids. Next remove the structure from the aluminium manifolds and cover the whole structure with BID cloth and laminating epoxy such as Safe-T-Poxy. This first coat should use an excess of epoxy to seal the pores. After a partial cure reinstall the structure on the engine to ensure the structure fits exactly and let it cure in that position. After cure sand the rough spots. You have now created a shell of glass fibre. I added a couple of extra layers in the region of the plenum. Once the structure has cured release the assembly and cut the unit into two pieces, left/right. Now dig out the foam as best you can removing the last pieces by dissolving with gasoline. Next wash them thoroughly using a hot wash in a dish washer this removed the excess wax. Now sand the inside of the plenum and lay up three plies of carbon fibre on the top and bottom surfaces lapping up the sides a much as possible. Peel ply the lay up and let cure. Remove the peel ply after cure. Now make a 1/8" thick board of glass fibre that will more than blank the left from right sides of the plenum. Drill three large holed in this board approx. 1.75" diameter along the length. This piece is going to provide support to the centre of the plenum yet allow the left plenum to talk to the right plenum which is good for high RPM performance. Now assemble the two halves with the centre support plate in place on the engine and flox the components together. After cure clean the excess flox away and add more as appropriate. Let it cure. Sand the surface best as possible then lay up two layers of carbon fibre over the whole structure and four layers over the plenum. Let it cure in place on the engine. After cure clean up the structure. Now drill out the attachment holes oversize and add either steel or aluminium inserts with a top hat arrangement to prevent pull through. These top hat arrangements should be pre drilled to accommodate the attachment bolts. Bond these top hats in place with an adhesive such as JB Weld. CAUTION: This method works for the SVX because there is a separate injector manifold that is not present on the EA81 & EG22. It is not possible to make the flanges in the same way for these alternative engines.
I think Stratus are now offering this option again for approximately
$120.00 (Cam and lifters exchange.)
Smothers Parts International. This place sells Soob parts mail order: 800-752-8078. You will need to know the exact part you want before calling for a quote. Don't mention airplanes, because they don't want to deal with the liability.
Steve Makish (in Boca Reton, FL) says he'll supply them. He's been flying his KR2 w/EA81 for several hundred hours and apparently plans to act as a supplier for BIngs, mufflers, mounts, etc... You can Email him at smakish@aol.com.
Stratus Inc., 7750 Twelfth Avenue Northwest, Seattle, washington 98117 (206-783-3845) Formula Power ???
The first location would be your local automobile salvage yard. (Don't let them know it is for aircraft, they may charge you more. You could also check the classified ads in the local paper. Since the bodies don't last on the Subaru, you can get a pretty good deal on a relatively low milage engine. OR, you can monitor this list. Sometimes guys sell engines here.
They can be run direct or with a reduction. It depends on your particular situation. Remember, for a particular engine, the power produced at 3600 rpm will be less than that produced at 5000 rpm using a reduction. Also, when using the engine direct drive, the prop size is limited to keep the tips from going supersonic. Alot to consider.
Fortunately the computer is sufficiently smart to detect a connected or disconnected O2 sensor, but not a lead fouled sensor. According to Subaru, the O2 sensor is not present to meet the pollution requirements, it is there to meet the fuel efficiency requirements. Apparently if the sensor is disconnected, the ECU reverts to an open loop mode which is slightly richer than the closed loop condition but by law it has to meet the pollution criteria in this condition. Subaru told me that I might even detect a power increase due to the richer mixture but I shouldn't bank on it. This all sounds too good to be true so what is on the down side: Well it appears that the O2 sensor is also used to provide a back up system should other sensors fail i.e. the famous limp mode. If you remove the O2 sensor this mode may be limited. I have known about this for some time but my source did not sound too convincing basically he was saying this should happen, not that it actually happened. At Oshkosh this year I met with, I can't remember his name but he advertises Subaru harnesses in Sport Aviation, and he was flying an EG22 with the stock ECU and no O2 sensor. I asked him about this and he said that he could not tell the difference with or without the sensor, but he had only a few hours on the plane. It seems that my contact at Subaru was correct.
First, advancing or retarding a camshaft is no substitute for having the correct camshaft. Advancing or retarding will only result in fine tuning. One of the things that you are changing when you move the camshaft in relation to the crankshaft is the compression of the engine. Let's say you measured your cranking compression of a given engine and you came up with 140 lbs. When you advance 4 to 6 degrees the compression test will show and increase to 155 to 160 lbs. (approx.). This increased compression will increase your low torque. There are many excellent books on the market on this topic area. If any one is interested I could list those books on the airsoob list.
I would consider the following instrumentation as mandatory for any auto conversion: 1.) Tachometer (obviously) 2.) Water temperature 3.) Water pressure - idiot light and gauge 4.) Oil pressure - idiot light and gauge 5.) Oil temperature - gauge 6.) Manifold pressure (mandatory with turbo only) 7.) Exhaust Gas Temperature Unless you are exactly duplicating another installation, I would monitor everything you possibly can. There is a company called Rocky Mountain Instrument (they're on the web- http://www. rkymtn.com/). They make a COOL engine info kit that will tell you anything and everything you wanted to know about your engine. It is not necesarily cheap (around $1000 - maybe a little less), but it is not too bad when you consider how much buying all of the guages and senders would cost you separately. It also saves you a TON of panel space. There is another one available that I have ordered from Grand Rapids Technologies, Inc. 616-531-4893. It should be here in a few days. It has Tach, Dual CHT, Dual EGT, Oil temp & pressure, Coolant Temp. Hourmeter, Voltmeter, Timer, Adjustable alarms, out of range warning light, plus fuel. This unit with all senders is about $650.00 US. Depending on what inputs you want to switch, anything with thermocouple inputs can get a little unreliable.
The problem with what you want is because the Soob is not an FAA certified engine they won't let you do it. Even if certified some would have to get that engine approved for your bird, you could then get it done. Certification takes lots of bucks (make that lots and lots). This is why you only see 'saurs in certified birds and new design engines in homebuilts. It may not seem fair, but that is the current state of things. There may be a way to do this is the aircraft is reregistered in another catagory. The particulars would have to be found out from the appropriate athorities. |