Turn it at a lower RPM and it won't be making 75 or 72HP any more. But that's what reduction drives are for.The 2180cc VWs can make 75HP without any problem, and they can maintain 72+ output for a long time >if< careful attention is paid to cooling. I don't mind that they have to turn at 3400 RPM to do that, it works fine for clean airplanes. If thrust at lower airspeeds is the main requirement, then a longer prop with resultant lower RPM, and lower HP (due to cooling requirements and off-peak HP RPMs) may be required. That's a choice and not a problem with the engine.
The added compression of the O-100 might make that possible. Cutting off 2 cylinders of a 4 cylinder won't give you half the power. You still have to drive the accessory case/oil pump gears. They take the same parasitic power regardless of the number of cylinders.Whatever the actual output of an O-200 is, the O-100 should be able to make half of that.
True, though I suppose it could be a lower volume pump using less power. I wonder how much HP they consume? For that matter, what about magnetos, alternator, etc? Detroit got in a big stink back in the day by quoting "gross" HP, with no accessories, not even the fuel or water pumps. But an aircraft engine may or may not have an alternator or fuel pump, may have different magnetos, etc... I don't know what the industry standard is as to what to include in the HP ratings.You still have to drive the accessory case/oil pump gears. They take the same parasitic power regardless of the number of cylinders.
That is determined by the marketing department...... I don't know what the industry standard is as to what to include in the HP ratings.
There are valid reasons for seeking lighter conrods, but they won't, in themselves, result in any measurable increase in HP at the crank. Once the rods are accelerated to speed, the only difference in power between a heavy set and light set is any >infinitesimal< difference in bearing friction. Unmeasurable.As i recall pete made the con rods and pistons quite a bit lighter than o200 bits.. less hp spent making that mass make U-turns will account for some HP per cylinder gains
Not directed at this project specifically, but there are >so< many questionable dyno runs published that I suspect knowledgeable buyers of >any> engine would be more convinced by torque/HP measurements resulting from some engine runs with calibrated test clubs and an optical tachometer. That's lots cheaper to do, too, and an accompanying video can show the test, show the engine configuration (air cleaner? Exhaust setup? Generator?), etc.I too am curious to know what the real dyno results are on the final config
58hp would be akin to 116 on an O-200. Let's say an O-200 really puts out 100 hp at 2750 and the O-100 runs at 2900, that would be 52.5HP, add 5% for the CR increase, That would be 55hp absolute best scenario. The lightweight parts won't add any measurable power. Now let's assume an O-200 puts out 80hp. The numbers for the O-100 become 44 hp. Realistically, the O-100 is a 45-50hp engine at 2900 rpm unless it has more magic going on than we know about.As i recall pete made the con rods and pistons quite a bit lighter than o200 bits.. less hp spent making that mass make U-turns will account for some HP per cylinder gains as well as the increased CR over an o200.. I too am curious to know what the real dyno results are on the final config, but I dont think his published predictions are crazy or worth getting worked up about.
I don't know how much I should say, but I can probably say this without saying "too much": The DP-1 is not just half of a stock O-200. At this point, it's essentially an all-new airplane engine that happens to use some O-200 parts. Direct comparison to the O-200 would be misleading.In case anyone isn't clear here, we're talking about a dead stock O-200 turning 2800 rpm. Yes, we all know F1 O-200s can make something close to 150hp turning 4000+ rpm...
The point being, taking half of a stock O-200 and turning it to 2900rpm isn't going to make 60hp. If you up the CR or VE with a better cam grind, yes, possible.
I can second that. The little "CrackerJack" really gets up and moves with the DP-1 up front, and Pete in the cockpit. Climbs really strongly. I've seen this myself, in person, standing alongside the runway. Pete's about 6' and you can see his build in the video I posted earlier, so I think the performance, at least in this airplane, is fairly representative. It certainly wasn't "struggling" by any stretch of the imagination, either on the ground nor in the air. The CrackerJack isn't exactly a motorglider, so it's not like a surfeit of span was creating the climb performance....Based on my personal eyewitness experience and the experience of those who have flown and operated the engine, it produces more than enough thrust to power an LSA class single seat sportplane. ...
I don't know how much I should say, but I can probably say this without saying "too much": The DP-1 is not just half of a stock O-200. At this point, it's essentially an all-new airplane engine that happens to use some O-200 parts. Direct comparison to the O-200 would be misleading.
I won't argue with you since, to the best of my knowledge, the final production design has not been on a dyno yet. Pete's the kind of guy that, when the time comes for him to do a dyno run, he'll probably shell out the cash to send it to an outside testing firm, rather than do it himself, just so there's no doubt about validity. The man is ... well, I'll use "obsessed" without intending the negative connotation ... with "doing this right" and being on the up-and-up. He doesn't have dyno values because a dyno run hasn't been done yet. Whenever I've met with him, he's been absolutely open about everything he's doing, knowing that I'm going to keep his confidence until he's ready to fully pull the wraps off the final engine, and so won't talk about details of what I've seen. I've absolutely never gotten any impression that he's inflating numbers, relying on unobtainium, or otherwise "selling" me on his project and, given my career path, I'm pretty good at catching "sales jobs." I wasn't getting one here.But let's also keep in mind that the power is directly related to the cylinders, and those ARE O200 parts. A cam , compression and induction will help, but you are still hamstrung by the Continental jugs. No way around that.