will kirkbride

Hi all. Happy to see this thread has started some interst. I agree with most of what has been said in the above posts. Too many "experts" give advice based on their experience in a limited field, not counting all the missinformation that gets thrown around in racing circles. In my case, I have spent many hours doing the reserch before deciding to go down this path. I would not recomend it to someone with limited knowledge of engines and their operating systems. Dave. to answer your questions. I am going to fuel inject the engine with a multipoint set up. Engine management system with closed loop O2 sensor and baro compensation. This is fairly easy to set up with the sysems available now. Sensors include ,crank and cam angle,MAP, intake temp ,coolant temp and knock sensor as well as tach. I am setting the compression ratio at 9.5 to 1. I am hoping to get around 100hp at WOT but anything between 80 and 100 will be ok for my aircraft. This is another consideration: what aircraft is the engine going to power. Mine is a STOL and fairly slow cruise so the torque of the engine is being set at around 4000RPM for cruise and the prop set to achieve this.

Sure Carl. The rods cost about $400 each including GST and weight the same as the standard ones believe it or not. They have series 2000 ARP bolts as I was worried about the integrity of the standard ones whilst operating at 4000 plus RPM constantly. The pistons cost about $850 with pins and clips. I am fitting Hastings rings. The pistons are forged and weigh 50 grams less than the standard ones. Have you made a pin puller yet? Easy to make out of an 8mm long bolt by grinding the head to the right shape. If you get stuck, I will send a photo of the one I made. Cheers

Hi. Carl The connecting rods and pistons for this engine are both custom items as getting off the shelf upgraded parts for this engine just doesn't happen. The rods are custom Argo to my spec. and the pistons I am using are JE forged with the narrow rings off the later model EA81. I want to set the compression ratio so I can run on MOGAS with the option of maybe Ethanol mix in the future as who knows how long AVGAS will be available and I believe its only a matter of time before ALL unleaded fuel contains some ethanol. This is one reason why I am going the auto engine route as i have control over how the engine is set up and have the option of tuning it for a different fuel in the future. I hear all the negativity on auto conversions for aircraft and I believe a lot of it to be justified, however, there isn't a whole lot of difference between a Rotax 912 with a reduction gearbox and what I am doing apart from material that the Rotax is constructed from and it being a newer design. They still have there own issues, as nothing mechanical is foolproof or maintenance free. I am not knocking these or any other engines for that matter, its just personal choice. Some of the problems I see from overseas owners of aircraft with these engines is the lack of proper procedures during the rebuild and general lack of knowledge about the importance of certain high stress parts. It is great doing these things on a budget, but you can't cut corners when depending on the engine to be reliable.

EA81 rebuild I will try again with some photos

EA81 rebuild Hi all. Moving my posts to this thread as it is more recent. Some people just like to do things themselves as they like the challange or whatever. I commend Carl for at least having a go. I will add some photos of my rebuild so far including the redrive I am making. Cheers

David. Have had a lot of experience with Subaru engines. Aftermarket parts are still available at reasonable prices. The only part hard to source is the oil pump if you should need a new one. My engine has custom pistons and con rods, however ,standard cast pistons in oversizes are still available. I will be posting new pics as I progress with the rebuild but feel free to ask any specific questions and I will do my best to help. cheers

Subaru EA81 update Just an update on the progress of the Subaru engine for anyone interested. After strip down and measuring, the block halves were machined and line bored, including the camshaft and oil pump housing. All threads were helicoiled to improve reliability. Custom steel con rods with larger bolts , ended up the same weight as the originals. Forged pistons with narrow rings for less friction. weight of these were approx. 50 grams lighter than the Subaru cast pistons. Block was machined for zero deck height for the pistons. Rebore and honing of cylinders to .5mm oversize. Crankshaft was polished and measured. As there was no wear, journals were linished. Next step is to balance the rotating assembly after the redrive is finished. [ATTACH]12141.vB[/ATTACH][ATTACH]12142.vB[/ATTACH][ATTACH]12143.vB[/ATTACH]

Have had a bit to do with the Subaru EJ20 and EJ25 engines in the likes of the WRX and Forrester autos. The problem as I see it is not so much the belt itself,rather the other items which are in the belt run such as the tensioner which is a bearing on a moving arm set up with a hydraulic finger to keep the tension. there is also the water pump and up to 4 other idler bearings in the mix. I have seen the hydraulic push rod assembly leak oil and therefor lose pressure causing the belt to skip a few teeth with disasterous results as in the later engines, the valves will hit the pistons if the belt skips more than 3 or so teeth. Also, this set up does not like to be wound in the reverse direction. this causes the tensioner to "back off" from the pressure put on it by the belt. Hope this helps.

Hi. Just wondering if anyone can tell me the out side diameter and wall thickness of the prop drive shafts used on most popular 100 HP engines with reduction drive eg. Rotax

Subaru EA81 Hi there. I to have decided to power my future kit aircraft with the Subaru EA81 engine after much research and indecision over the power plant. Like others on this forum,I looked at the Rotax 912uls 100hp. Great engine, but out of my price range. Jabaru 3300, same. I wanted around 80 to 100 reliable horse power. The Subaru has a proven record for reliability as well as the following . simple design .. one piece crankcase and cylinder assembly...no leaks from cylinder base gaskets push rod engine meaning less complicated......parts are still available at a reasonable cost.......the parts needed for reconditioning are in some ways superior than the original because of advances in production techniques and materials (gaskets,pistons and rings and bearings). This engine has less bolts holding it together than almost any other engine i have come across, meaning that it goes together really well and is easy to maintain. If anyone is interested,I can provide a step by step record of my engine from the strip down to the final completed item with accompanying photos on this thread