The 140 hp gap

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addaon

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So in evolving my design, I'm realizing that the ideal engine would generate between 140 and 150 hp at around 2700 rpm, and it would be nice to maintain that power until at least 10k feet. Also, weight is absolutely critical; and I'm restricting myself to aircraft engines.

Currently I'm designing around an O-360-A1A (258 lbs dry, hoping to hit 320 lbs installed with a wooden prop). This is pretty overpowered (at sea level) for me. I'll probably drop to an O-320-A1A for a 14 lb savings on dry weight (and presumably not much more than that on install), but that's sure a small weight gain for a > 15% power drop; and the 150 hp 320s start looking marginal above 8000 feet or so.

Is there anything I'm missing in this power range? Frankly, I'm beginning to wonder whether an IO-233-LSA or ULPower UL350 could be comfortably turboboosted to the 140 hp range, and what reliability and weight would look like there. I know there's nothing wrong (heck, there's a whole lot of appeal) with "too much" power, but the combination of a heavy engine (even looking at the very lightest 360s out there), drastically more power than needed at low altitude, and mediocre altitude performance just doesn't feel like an optimum.
 

autoreply

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You might also include the Jabiru 3300. 120 hp stock, light and apparently a good engine.

There's a US company that "tunes up" the Rotax 914 a bit, for 135 HP and turbo-normalizing. I would get a bit nervous by some much "tuning up", let alone the hefty basic pricetag.
 

TFF

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If you dont want to loose the HP at altitude you either have to turbo or derate. Two examples, sorry both are helicopters. Robinson R44 use a bigger engine than needed at sea level because the power runs out at altitude. Actually that is what turbine helicopters do. The two helicopters I work on same brand but one is the old naturally aspirated one turbo. There is some minor differences for the engines but both are Lycoming Hio 360s made from mostly of the same parts. The naturally aspirated one tops out at 5000 ft; it will not make the power to do any more. The other helicopter has been to 12,500; 500 over the service ceiling. I know simplistic but real world.
 

Grelly

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I'll probably get shot down for suggesting it, but have you considered the Centurion 2.0L @ 135HP or the 2.0S @ 155HP?
 

autoreply

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I'll probably get shot down for suggesting it, but have you considered the Centurion 2.0L @ 135HP or the 2.0S @ 155HP?
They won't sell to non-OEM's, nor service you when it's installed in a non-certified aircraft.

Apart from that, it's over a 100K US$ and has the weight of a 300 HP engine.
 

addaon

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Yup, the problem with the Centurion (and the Austro Engine) is just its absurd weight; I'm only carrying about 5 hours fuel, so there's really no way to justify it.

Overrating is effectively what I'm doing now, with the O-360, except I'm not a helicopter so why not allow all the power when available? But 140 hp is what I need for both target cruise, and 1200 fpm climb at gross weight. Climbing at 2000+ fpm is cool, sure, but not necessary. And I'd rather be able to maintain target cruise (IAS) at 14k feet than top out at 10k feet.

I like the Jabiru 3300 a lot, but it's not fuel injected, which in my very limited understanding of engines (/not/ my area of expertise, even in potentia) makes turbocharging more difficult. So assuming 120 hp is not enough (and it's really not), this drops off the board, unfortunately. A Jabiru 5100 that had finished development and had good availability might have been the answer; a 4400 at 3000 rpm max would fill the gap perfectly at ~145 hp, but apparently there really just isn't much demand between 120 hp ("powerful lsa") and 160/180 hp ("wimpy/upscale so-called-four-seater").

I've seen the "super 914" Rotax designs. I guess what I really don't understand is what the compromises are on such a design. Obviously "reliability", but in what way? Large amounts more heat generated, which means a more complicated install in terms of managing cooling. But assume you run a standard Rotax 912 and a 45-psi MAP turbo'd 912 (140 hp at same rpm?) with the same CHTs for 1000 hours, cruising at 75% of available power. What actual failure modes would you expect to see with the boosted engine? Is the answer different for boosting an IO-233 (again, given cooling, which may be harder than in the Rotax case), with lower rpm, etc?
 

autoreply

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I like the Jabiru 3300 a lot, but it's not fuel injected, which in my very limited understanding of engines (/not/ my area of expertise, even in potentia) makes turbocharging more difficult. So assuming 120 hp is not enough (and it's really not), this drops off the board, unfortunately. A Jabiru 5100 that had finished development and had good availability might have been the answer; a 4400 at 3000 rpm max would fill the gap perfectly at ~145 hp, but apparently there really just isn't much demand between 120 hp ("powerful lsa") and 160/180 hp ("wimpy/upscale so-called-four-seater").
You could of course overboost the 3300, it's only a 17% or so extra power.

The UL 350 with some complex letters might suit you:
http://www.ulpower.com/engines/ul350iS/atmospheric-pressure-influence.html

125 HP @ FL180, 130 stock. Climbing from sealevel, you'll outperform an atmospheric engine after a minute. Fairly new and in my book relatively unproven, but what I've heard is reasonably positive.

I've seen the "super 914" Rotax designs. I guess what I really don't understand is what the compromises are on such a design. Obviously "reliability", but in what way? Large amounts more heat generated, which means a more complicated install in terms of managing cooling. But assume you run a standard Rotax 912 and a 45-psi MAP turbo'd 912 (140 hp at same rpm?) with the same CHTs for 1000 hours, cruising at 75% of available power. What actual failure modes would you expect to see with the boosted engine? Is the answer different for boosting an IO-233 (again, given cooling, which may be harder than in the Rotax case), with lower rpm, etc?
I guess it's the same if you compare the 912 (atmospheric) to the IO-233. You're putting much more stress on any single part of the engine. Thermal stress, loads on the crank and cilinders, exhaust thermal loads.

If I recall correctly, the 914 (turbo) is the 80 HP of the 912. The 912S (100 hp) already has a larger displacement.
 

autoreply

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I like the Jabiru 3300 a lot, but it's not fuel injected, which in my very limited understanding of engines (/not/ my area of expertise, even in potentia) makes turbocharging more difficult. So assuming 120 hp is not enough (and it's really not), this drops off the board, unfortunately. A Jabiru 5100 that had finished development and had good availability might have been the answer; a 4400 at 3000 rpm max would fill the gap perfectly at ~145 hp, but apparently there really just isn't much demand between 120 hp ("powerful lsa") and 160/180 hp ("wimpy/upscale so-called-four-seater").
You could of course overboost the 3300, it's only a 17% or so extra power.

The UL 350 with some complex letters might suit you:
http://www.ulpower.com/engines/ul350iS/atmospheric-pressure-influence.html

125 HP @ FL180, 130 stock. Climbing from sealevel, you'll outperform an atmospheric engine after a minute. Fairly new and in my book relatively unproven, but what I've heard is reasonably positive.

I've seen the "super 914" Rotax designs. I guess what I really don't understand is what the compromises are on such a design. Obviously "reliability", but in what way? Large amounts more heat generated, which means a more complicated install in terms of managing cooling. But assume you run a standard Rotax 912 and a 45-psi MAP turbo'd 912 (140 hp at same rpm?) with the same CHTs for 1000 hours, cruising at 75% of available power. What actual failure modes would you expect to see with the boosted engine? Is the answer different for boosting an IO-233 (again, given cooling, which may be harder than in the Rotax case), with lower rpm, etc?
I guess it's the same if you compare the 912 (atmospheric) to the IO-233. You're putting much more stress on any single part of the engine. Thermal stress, loads on the crank and cilinders, exhaust thermal loads.

If I recall correctly, the 914 (turbo) is the 80 HP of the 912. The 912S (100 hp) already has a larger displacement.
 

addaon

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The UL 350 with some complex letters might suit you:
http://www.ulpower.com/engines/ul350iS/atmospheric-pressure-influence.html

125 HP @ FL180, 130 stock. Climbing from sealevel, you'll outperform an atmospheric engine after a minute. Fairly new and in my book relatively unproven, but what I've heard is reasonably positive.
Where are you getting that FL180 number? I know that ULPower has done some work with turbocharged engines, but I was pretty sure that the 350iS was not it (nor are any of their available engines). My reading of their 0.5 bar numbers (FL180) is a power output of 45 hp or so... we must be looking at different engines?
 

autoreply

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I looked at the 0.5 bar numbers and the power on the power curve is clearly 125 HP if you look on the scale to the left. Very stupid that I didn't note that the scale on the left is torque not power. Sorry for that...

I did hear some people talk about this becoming turbocharged, but maybe that was just the typical forum-speak. They do continue with their 6-cilinder engine development though:
 

addaon

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Yeah. The 350iS is definitely one of the better candidates for turbo'ing to 140 hp in my mind, although the IO-233 (lower rpm, higher displacement, higher weight) is also in the running if I go this route.

I'd just really really love to save ~30 lbs firewall forward (since I'm currently nose-heavy enough to be doing silly things like putting batteries near the tail and running heavy cables, this is a significant gain) without compromising, or even with enhancing, performance.
 

TFF

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You defiantly are going to need O2 for times up that high.
You are limited to how much fuel the engine can consume with O2; when you are at high altitudes you lean the engine to maintain this ratio. Less fuel and O2 less power. I have seen calculations but dont know them. A 200 hp sea level engine makes under 150 hp at 10K ft; think closer to 125. ALso to extend range most fly at 75% power. A friends Mooney I0-360 is going to consume close to 20 gal an hour full power at sea level full rich; at 5000ft at 75% power its about 12 gal an hour giving up about 5 kts in speed at 75%, but you gain about 1.5 hours endurance at that pace. Thats 5 kts faster per hour or have enough fuel for more 200 miles. Fix pitch prop is going to hurt you more in all around performance. To add to milage, there is lean of peak operations where you can get another gal an hour savings at the risk of melting your engine if you dont do it right.
 

addaon

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TFF, no oxygen needed for 14k. I'm in northern California, so having a service ceiling of at least 14k is pretty essential.

The reason I'm leaning towards turbocharging is exactly to get more oxygen to the engine at higher altitudes. In the absence of this, power basically goes linearly with atmospheric pressure; so 75% around 10k, 50% around 18k, etc.
 

TFF

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You dont have to have O2 if the flight is less then 30 min at that level; at 15k passengers are required to have it.
 

autoreply

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The reason I'm leaning towards turbocharging is exactly to get more oxygen to the engine at higher altitudes. In the absence of this, power basically goes linearly with atmospheric pressure; so 75% around 10k, 50% around 18k, etc.
If turbocharging is mandatory anyway, I'd go with the Rotax 914, even if it involves a considerable change in your design or lower performance. I'm by no means an engine expert, but turbonormalizing an engine is by no means a trivial task. Putting out some 15% more power is even more involved and you might have to do a lot of redesigning, but I'll leave that up to those who have considerably more experience with turbocharging.

I've long doubted on this very point for my own design (high altitude performance mandatory too). I compared the IO-390 with the 914 with fairly surprising results. The extra weight of the Lycoming (plus the extra fuel and extra aircraft structure) for a 3-hour cruise came down to such a high number (400+ pounds!) that my initial climb rate at sealevel was almost the same, the 200 HP Lycoming climbed only 200 fpm faster than the Rotax. By the time you were at 5000 ft density altitude the Rotax easily outperformed the Lycoming.
 

Grelly

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I hadn't noticed how few engines there are in the 130 - 160 HP range.

My little home made database suggests that Continental (used to) have O-280 that made 140HP. Lycoming had an O-290, also 140HP.

ULPower are rumoured to be working on a 6 cylinder engine that might well be in that range.

The only other engine I know in that power range is the rotec 9-cylinder R3600 rotary. 275Lbs dry according to the website. But I don't suppose you were thinking of a Rotary.
 

fadec

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This company is working on a bolt on supercharger for the IO-360 which is probably more than you need but they may be able to derate the system for an IO-320

http://www.forcedaeromotive.com/homebuilt.htm

Jaribu engines have issues with cylinder head overheating. Forced induction will only make this worse on a stock engine. Rotec water cooled heads would be a good idea (you might even get full TBO)

http://www.rotecaerosport.com/products/lch/
 

orion

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One quick point - the 9-cylinder R3600 is a radial engine, not a rotary. Historically the term rotary applies to engines where the entire case and cylinders rotate (WWI era: example is the Gnome rotary http://www.youtube.com/watch?v=CYc-H8Wg-MQ), with the prop being attached to the case. Radial engines have the case and cylinders static while the crank rotates.
 

TFF

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I dont think anyone could design a plane that would use either a IO390 or a 914; it would not be optimized for either. At some point the 914 will out perform in HP but it will never out perform in torque, not in practical flying. The 390 will turn a bigger prop with more pitch. The only 914 I know at my airport is in a wrecked 3/4 Storch, It is a good sized airplane and light. There is a IO-390 in the hangar next to it in a RV8A. No way the 914 would ever fly that RV unless you had 10,000 ft runway. In the summer, the density altitude at my airport can be 5000ft; still no way with the 390 handicapped. The 390 has made it the fastest RV at the field; he went from the slowest with an RV4 and 0-320. The 390s are now STCed for Mooney injected replacements. A Mooney 20E is almost 2600 gross takeoff stock. There is a Pulsar with a 912 an airport over, cool little plane; way smaller than the RV; about the same speed.
 

SVSUSteve

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You dont have to have O2 if the flight is less then 30 min at that level; at 15k passengers are required to have it.
You beat me to pointing that out. I will add that just because you don't have to use it is not the same thing as it being a good idea not to use it.
 
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