IO VS O

FORANE

FORANE

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FORANE
+ & -...
IO VS O
Which is better and why?
We all know io eliminates carb ice.
IO also requires higher pressure fuel pumps.
I hear IO can be hard to start hot and suffer from vaporization in the lines.
Any reason one is better than the other?
 
I like the fuel injection much better than carb as a renter. No carb ice to worry about. They run great. In the sr 22, with io-550 hot starts are no issue, crack the throttle, mixture full rich, fuel pump to boost, turn the key, fires up within a second or two, every time.
 
I should add that I have the opportunity to convert my o-340 Titan to io.
 
I like my io, but I have my hot start procedure down pretty solid
 
My understanding is that the issue of vapor lock is most determined by such things as fuel line routing, cowling design, baffle designs. In other words it is very airplane specific. Perhaps you can find a type club for specific information.
 
There's a lot of benefits to IO, but when I reviewed all the SB's and AD's for my 360 overhaul, there are probably 100 more for the IO than the O. Take that for what it's worth.
 
At least on the 360, a little more horsepower, although that my be due to the angle valve heads as well.

O-360: 180hp
IO-360: 200hp

Fuel injection is more amenable to running lean of peak, especially with Gami injectors. Like @eman1200 , I have a pretty decent hot start procedure that works 100% of the time.
 
I run my IO lean of peak, which I understand is difficult in some carb engines. *Edit* Bill beat me to it, so what he ^ said.
 
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Bill Jennings said:
At least on the 360, a little more horsepower, although that my be due to the angle valve heads as well.

O-360: 180hp
IO-360: 200hp
Click to expand...

Bill, the HP difference has nothing to do with the O vs. IO - it has everything to do with the angle valve heads.

There are 180 HP IO-360s - they have parallel valve heads.

Personally, after 3,000ish hours flying almost exclusively IO engines (and so figure that comes out to more like 5,500 hours of IO engine time since most of that is in twins), I have found the advantages to out weigh the disadvantages. Yes, easy LOP operation. Hot starts - no big deal once you get the hang of it (which really comes down to the Ted procedures I've outlined elsewhere on here). No carb ice to worry about. Better operation at higher altitudes. In all that time, the only times I've had to do any work on the fuel injection system... let's see... bought one fuel pump, rebuilt the systems on the 310 when I overhauled the engines and on the 414 for good measure because they were old (would've done the same with a carbureted engine). But that's been it, otherwise trouble-free.

However, Bill Harrelson had an O-320 in his Lancair and flew it just fine at 17,500 ft (and probably higher) on some of his record runs.

So, do what you want. If you're happy with the carburetor then you probably won't see any life-changing differences going to IO.
 
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Bill, the HP difference has nothing to do with the O vs. IO - it has everything to do with the angle valve heads.

There are 180 HP IO-360s - they have angle valve heads.
Click to expand...
Huh? Seems contradictory.
 
FORANE said:
I should add that I have the opportunity to convert my o-340 Titan to io.
Click to expand...

There are some really good fuel injection systems available for exp Lycomings. Precision's Silver Hawk is the exp equivalent of the Bendix system. Not bad but not my fav. I prefer the Airflow Performance zero leakdown 200A injection system. Both are mechanical. Again, my preference. I have friends with electronic injection and they can control their fuel flow better than I can and since they prefer to fly lean of peak they can do so very aggressively. When guys refer to hot start problems they're usually stuck in the old Bendix era, but it's a good idea to turn the fuel selector to off when parking a high wing plane to prevent leakdown, a practice that API recommends even with their zero leakdown servo. Low wingers don't share the gravity feed problem. At any rate if you use electronic ignition hot starting is a breeze. When I hot start I prime like a cold start and it fires right up every time.

The bigger issue will be changing to a forward facing induction and what that'll do to your cowling, exhaust, etc. And while you're at it, you should look into cold air induction. There's a cha-ching factor but your performance will improve.

And FWIW, my EGTs are within 5* of each other throughout the throttle and mixture ranges. No nozzle balancing required, but that is available if needed.


FM200A.jpg
 
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Ted DuPuis said:
Bill, the HP difference has nothing to do with the O vs. IO - it has everything to do with the angle valve heads.
Click to expand...

So the angle valve allows bigger valves, a little better breathing?
 
Bill Jennings said:
So the angle valve allows bigger valves, a little better breathing?
Click to expand...

I can't remember if the valves themselves are bigger on the angle valve or not. They probably are. But they have much more flow, more than anything that's due to a better port design. They also have more cooling fins to handle the extra heat that comes from the extra power.
 
And hemi combustion chambers, if memory serves. Even with 10-1 compression my IO-390 has cool CHTs but warmer than normal oil temps. And that's exactly what I expected.
 
Salty said:
There's a lot of benefits to IO, but when I reviewed all the SB's and AD's for my 360 overhaul, there are probably 100 more for the IO than the O. Take that for what it's worth.
Click to expand...
It's a reflection of the increased complexity. More places for the manufacturer or aftermarket parts maker or rebuilder to mess up. More stuff to wear out or age out.
 
Stewartb said:
There are some really good fuel injection systems available for exp Lycomings...
Click to expand...

LOL! It took me a second to figure out what was wrong with that picture... No ring gear!
 
I've had an O-360 and an IO-540. Any power/fuel consumption comparison would be meaningless since they're totally different animals.

I will say overall the O-360 was easier to start, it liked a lot of primer and it tended to be a little rough initially, it also was difficult to get going in temps below 35F or so without preheat. Hot or cold though it would start.

The IO-540 will start up smoothly IF I absolutely dial in how long I run the pump and have the throttle set just so and it's not hot. Get all that just so and it almost starts up like a modern EFI car... get it wrong and you have to crank and crank. Hot starts are also iffy, the best strategy seems to be to go ahead and flood it then start it like it's flooded. I have never been unable to start it though.

Not sure what the advantage of IO really is other than being able to do LOP, we're still controlling mixture manually. Curious if anyone knows the reasoning behind why engine/aircraft manufacturers use it. Could it be as simple as marketing? It wouldn't make or break a purchase for me either way, I can live with either option.
 
OneCharlieTango said:
That, too. But amazing speed with range is better than stupendous speed without range if you're going somewhere.
Click to expand...
Sometimes there's just nothing better than a full afterburner dash. :cool:

Nauga,
gated
 
I can burn Mogas with my O-470, but cannot do so in an IO-470. That's the only reason to likely keep me with an O instead of an IO next overhaul.
 
cowman said:
I've had an O-360 and an IO-540. Any power/fuel consumption comparison would be meaningless since they're totally different animals.

I will say overall the O-360 was easier to start, it liked a lot of primer and it tended to be a little rough initially, it also was difficult to get going in temps below 35F or so without preheat. Hot or cold though it would start.

The IO-540 will start up smoothly IF I absolutely dial in how long I run the pump and have the throttle set just so and it's not hot. Get all that just so and it almost starts up like a modern EFI car... get it wrong and you have to crank and crank. Hot starts are also iffy, the best strategy seems to be to go ahead and flood it then start it like it's flooded. I have never been unable to start it though.

Not sure what the advantage of IO really is other than being able to do LOP, we're still controlling mixture manually. Curious if anyone knows the reasoning behind why engine/aircraft manufacturers use it. Could it be as simple as marketing? It wouldn't make or break a purchase for me either way, I can live with either option.
Click to expand...
No carb ice.

You've had your Lance longer than me but our hot start procedure has worked every time. I can send it to you.
 
Mtns2Skies said:
I can burn Mogas with my O-470, but cannot do so in an IO-470. That's the only reason to likely keep me with an O instead of an IO next overhaul.
Click to expand...
That's all about compression ratio, not fuel delivery.
 
The cylinders for the I0360 in the Mooney M20E coast twice as much as those for my M20C. They do give you 20 extra ponies though.
 
FORANE said:
+ & -...
IO VS O
Which is better and why?
We all know io eliminates carb ice.
IO also requires higher pressure fuel pumps.
I hear IO can be hard to start hot and suffer from vaporization in the lines.
Any reason one is better than the other?
Click to expand...

Whichever one can burn 87 octane mogas
 
Stewartb said:
That's all about compression ratio, not fuel delivery.
Click to expand...
I thought injectors have to be calibrated to a specific fuel weight? So you wouldn't be able to interchange 100LL & Mogas at will?
 
Mtns2Skies said:
I thought injectors have to be calibrated to a specific fuel weight?
Click to expand...
Difference in fuel density will be minimal. And, if it were significant, you would have the same issue with a carburetor. Both rely on carefully sized holes to meter the fuel. When you get into E-85, yea big difference. But for straight hydrocarbons, not so much.
 
Mtns2Skies said:
I can burn Mogas with my O-470, but cannot do so in an IO-470. That's the only reason to likely keep me with an O instead of an IO next overhaul.
Click to expand...

The way the fuel is delivered has nothing to do with that. There are a couple of IO-470s approved for use on car gas.
 
Bill Jennings said:
a little more horsepower, although that my be due to the angle valve heads as well.
O-360: 180hp
IO-360: 200hp
Click to expand...

That's not universally true... it's the angle valve engines that are more horsepower, the IO360A, C, and E engines... the IO360 B and D engines are parallel valve, and make 180 HP.

At a discussion at Oshkosh hosted by the ECi/Titan (now owned by Continental) folks, they explained that the horsepower increase from O360A to IO360A, about 20 more horsepower, was half due to the better breathing of the angle valve cylinders, and half due to the higher compression ratio of the IO360A... 8.7:1, versus the O360A 8.5:1
 
PaulMillner said:
That's not universally true... it's the angle valve engines that are more horsepower, the IO360A, C, and E engines... the IO360 B and D engines are parallel valve, and make 180 HP.
Click to expand...
And then there's the 160HP IO360-L2A
 
PaulMillner said:
That's not universally true... it's the angle valve engines that are more horsepower, the IO360A, C, and E engines... the IO360 B and D engines are parallel valve, and make 180 HP.

At a discussion at Oshkosh hosted by the ECi/Titan (now owned by Continental) folks, they explained that the horsepower increase from O360A to IO360A, about 20 more horsepower, was half due to the better breathing of the angle valve cylinders, and half due to the higher compression ratio of the IO360A... 8.7:1, versus the O360A 8.5:1
Click to expand...

How much HP do they make with the helicopter pistons, something like 9.7:1 compression IIRC?
 
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