Angle vs parallel engines

[Chewie65]

What makes them what they are? Whats the difference? What makes them better or worse then the other?

 

[fodrv7]

Inclined Valves, Hemispherical Combustion Chambers.

?Angled Valve? Engines have the valves Inclined relative to each other, such that they encourage smoother airflow through the combustion chamber than do Parallel Valves; where the valve arrangement necessitate the airflow reversing direction between intake and outlet.

See; http://en.wikipedia.org/wiki/Wikipedia:Featured_picture_candidates/Internal_Combustion_Engine

The higher the RPM of an engine the more it benefits from Inclined valves as there is progressively less time for the flow to reverse.
If you can be bothered trying to extract the figures from the pathetically small Performance pages of the Lyc Manual, it is all revealed and some of the info is not as expected.
The ?Angled Valve? IO-360 engine produces a nominal extra 20 BHP at 2,700 RPM than the ?Straight Valve? engine even though they are of the same capacity. This is due to the superior airflow.

However, the advantage is negated at lower RPM, and this is the interesting bit, at 2,300 RPM they have virtually the same output. As I read the Charts!

So to answer your question, unless you are going to run your engine over 2,500 RPM, I don?t see that you are gaining much accept at Take-off. (Did Mr. Lyc bring out the Angle Valve to lift obese Cherry-trees of the runway?)

If you are more interested in cruise performance then TORQUE is more important, because POWER = TORQUE x RPM.
So, if two engines are running a given Cruise RPM, say 2,400, then the one with the Highest TORQUE will produce the most POWER.

For this reason Aero Sport Power use a camshaft optimised for Cruise Torque rather than Max Power.

The other consideration is that for the extra power, the ?Angled Valve? is about 30lb heavier.

 

[dan]

The ?Angled Valve? IO-360 engine produces a nominal extra 20 BHP at 2,700 RPM than the ?Straight Valve? engine even though they are of the same capacity. This is due to the superior airflow.

Not only that, but angle valve 360s also typically make use of COLD AIR (and horizontal) induction sumps. That's where a good chunk of the extra HP comes from.

I know two parallel valve vertical induction guys (RV-4 and RV-6) who badly want to convert their engines to cold air induction. For good reason.

I'm an angle valve IO-360 fan myself, but if I was going to run a parallel valve engine, I'd do my best to equip it with horiztonal cold air induction.

 

[Chewie65]

Thanks guys,
I hear these terms batted around. Now I know what people are talking about.

From what I read, angled engines are physically a wee bit bigger (hense the weight diff.) and a little harder to fit under the cowls on RVs. Is this true? If so does it affect cooling at all?

 

[dan]

Angle valve cylinders are known for running COOL. They have more cooling fin area, and I don't know a single RV with an angle valve engine that has ever seen high CHTs.

OIL TEMPERATURE, on the other hand...

Stock Lycoming IO-360-A* engines (and IO-390-X) have oil squirts on the piston skirts, which is one reason they tend to have more demanding oil cooling needs than the parallel valve variants.

So here's my take on it:
Parallel valve engines (without piston skirt squirts):
- higher CHTs
- lower oil temp

Angle valve engines:
- lower CHTs
- higher oil temp (or, more demanding of oil cooling)

And here's my further take...we change our oil every 50 hours (or whatever). How often do we change our cylinders? I'd rather dump heat into the oil than dump it into the cylinders!

My IO-360-A1B6 has NEVER seen a CHT higher than 374F. Normal cruise sees between 290F and 310F running LOP, and between 300F and 320F running ROP. Oil temp on the other hand...it runs 178-185F in LOP cruise, and 195-210F in ROP cruise, but it can easily reach 225F+ in abusive conditions.

 

[Russ McCutcheon]

To add to what Dan has said, I have one of the angle valve A1As squeezed into an RV-4, my oil runs about 197 to 200 in summer and 185 in winter, have seen it at 220 on a climb to 10k? with a temp. inversion in the summer. My cylinders never exceeds 300. Equipped with a non counter weighted crank, Sky Dynamics magnesium sump and MTV-15 prop it ways about the same as the parallel valve O-360 with a Hartzle. The only reason not to do this on a new build is money, if you have lots of that then go for it. On the other hand an O-320 and wood prop is much lighter and that has its advantages also, I?d rather have more power.

 

[w1curtis]

Not only that, but angle valve 360s also typically make use of COLD AIR (and horizontal) induction sumps. That's where a good chunk of the extra HP comes from.

I know two parallel valve vertical induction guys (RV-4 and RV-6) who badly want to convert their engines to cold air induction. For good reason.

I'm an angle valve IO-360 fan myself, but if I was going to run a parallel valve engine, I'd do my best to equip it with horizontal cold air induction.

Dan, Dan, Dan,

Tell me where you are finding this information? I've seen you mention this before and nothing I've seen corroborates this--at least on stock angle valve engines.

A stock angle valve engine from Lycoming also runs the induction air through the oil sump picking us some residual heat. This is regardless of sump position, horizontal or vertical. The additional horsepower an angle valve engine makes over a parallel valve engine is from better engine breathing and better volumetric efficiency. Now the aftermarket "Cold Air" Induction from Barrett and others, do add *some* additional performance, but nowhere near what is achieved by the valve arrangement and porting of the angle valve engines.

Barrett makes a "Cold Air" Induction system for the PARALLEL valve IO-540. I have an angle valve IO-360 in my Cardinal with the horizontal induction and the intake pipes run through the oil sump, just like the the parallel valve engine-no *Cold Air* induction there and it still produces 20 more HP than the equivalent parallel valve IO-360.

I'm always willing to learn, so please show me how in a stock angle valve IO-360 engine, a "good chunk" of the 20 additional HP comes from "use of COLD AIR (and horizontal) induction sumps."

Here is a picture of an IO-540 with a *Cold Air* Induction system. Note how intake pipes are outside of oil pan. This is a key ingredient of a *Cold Air* induction system.

 

[gmcjetpilot]

5 star thread

Great info guys. The average empty weight of RV's with angle valve, when compared to apples and apples to parellel valve RV's weights about 49 lbs more. It could be larger oil coolers or the fuel injection v. carb? Some of the angle valves extra weight is from the counterweight crankshaft v. the typycal non-counterweighted crank on 180HP 360's. There are are non-counterweight crank 200HP angle valve engines.

If no one mentioned it, angle valve engines are more $expensive$ to buy & overhaul than a parallel valve by a good margin, but it's 20 HP more at higher RPM. (Thanks Pete, interesting post!)

With the better flowing heads, it seems to me from what Dan has said, lean of peak ops (LOP) may be easier or more efficient. Dan can tell you about that. He does amazing econ ops w/ his 200HP angle valve. However if you're a normal pilot and operate and lean casually, you'll likey burn more block to block fuel.

 

[asav8tor]

<And here's my further take...we change our oil every 50 hours (or whatever). How often do we change our cylinders? I'd rather dump heat into the oil than dump it into the cylinders!>

You need to factor in the co$t of the cylinders....

Angle Head... http://factorycylinders.com/lycoming/05k21120.htm

Parallel Head... http://factorycylinders.com/lycoming/05k21104.htm

As pointed out before if you are running at reduced power sfc difference is small. Cooling advantage at RV speeds is small.

However if MONEY is no object.... and I did not care about how much fuel I burned, and I was going to fly WOT, I would get the angled head 200 HP.

Since I do need to consider MONEY... the choice is clear... parallel.

 

[dan]

A stock angle valve engine from Lycoming also runs the induction air through the oil sump picking us some residual heat. This is regardless of sump position, horizontal or vertical.

William, William, William,

Have you looked at the IO-360-A1* series? Stock, the induction air is NOT run THROUGH the oil sump. The intake plenum is beneath the oil sump, and the intake tubes do not run through any of the oil-bathed areas. If you need a photo just holler.

 

[w1curtis]

..
If no one mentioned it, angle valve engines are more $expensive$ to buy & overhaul than a parallel valve by a good margin, but it's 20 HP more at higher RPM. (Thanks Pete, interesting post!)
..

Yes, they are more expensive and heavier. No, they produce the additional 20HP at the same 2,700 RPM. Oh, one more difference and I think the biggest factor in the additional power-- the typical stock parallel valve IO-360 has an 8.5:1 compression ratio, the angle valve is 8.7:1. So the two key things that provide the increased horsepower in the angle valve engines are the increased volumetric efficiency (better breathing) and an increased compression ratio.

See here for more details:
http://www.lycoming.textron.com/engines/series/pdfs/360ci Engine Insert.pdf
THis brochure also has a pretty good picture of an angle valve IO-360 with an horizontal induction with the intake pipes going through the oil sump.

 

[dan]

With the better flowing heads, it seems to me from what Dan has said, lean of peak ops (LOP) may be easier or more efficient. Dan can tell you about that. He does amazing econ ops w/ his 200HP angle valve. However if you're a normal pilot and operate and lean casually, you'll likey burn more block to block fuel.

To add a little perspective to this... On the trip to OSH and back, my buddy with an RV-4 with a parallel valve O-360 converted to IO w/AFP injection was burning ~0.4 gph less than I was, consistently on every leg. That's not from floscan readings...that's from actual quantity of fuel added at each stop. He burned just over a gallon LESS than I did on each of the ~3 hour legs.

I was able to beat him on two legs by climbing LOP, but I normally climb ROP.

Apples to oranges...his very slick RV-4 compared to my pudgy RV-7. Drag-wise he has me beat hands down.

 

[Russ McCutcheon]

I have reported this before and I will again, apples to apples sort of, RV-4 O-320 wood prop verses RV-4 IO-360 angle valve and MTV-15 prop, down low at the same speed we are neck and neck on fuel burn, up high I go off and leave him at 20 to 25mph faster, get there sooner and burn less fuel for the same leg, 1 to 2.5 gallons less on a 2.5 hour leg, and its pumped by the time he gets there. The only argument against this engine is weight and money, fuel burn is equal or better with this engine and that?s comparing to an O-320 and I?m not doing anything special. My cold air induction is Sky Dynamics same as the sump, don?t know anything about what is available stock.

 

[fodrv7]

Beating the Air to Death.

I have reported this before and I will again, apples to apples sort of, RV-4 O-320 wood prop verses ....... MTV-15 prop, down low at the same speed we are neck and neck on fuel burn, up high I go off and leave him at 20 to 25mph faster.

Russ,
I suspect that a lot of the difference you found is more due to the CS Prop.
The fixed pitch at high TAS at high altitude would be wishing for more pitch and beating the Air to death.

The attraction of the CS prop is exactly that. You can set the RPM and independently set what ever MP you desire.

Though my next RV (When Vans brings out the QB version) will be an RV4 with fixed prop ASI, ALT, wrist watch and an oil Pressure gauge. And a WAC.
Pete.

 

[mark manda]

when i bought my IO-360 180 hp the main reason was i was told by a guy at LYCON that,

"they just seem to handle and perform better with the lighter engine. Guys have put in both, we've done both and the RV with parallel valve engine just feels better..... etc."

that's why I did what i did. listened to experts and I could have gone either way.

the 180hp I have was $38K when it was all said and done.

shoulda listened to George.

 

[gmcjetpilot]

Me speak-ee english kind of

No, they produce the additional 20HP at the same 2,700 RPM.

ha ha me R-tard with English, doha! You are right of course, they are both rated at 2,700 rpm. Thanks for the clarification cheers.

I was referring to Pete's interesting post that angle and parallel valves 360's, at the same but lower RPM/MAP, make the same HP. In other words, the angle valve head helps most at higher RPM, verses at lower RPM, is what I meant. (per down under petes post, makes sense)

Also, good point on 8.7:1 compression ratio (verses 8.5:1), but interesting thing is if you put pistons with a 0.2 cr bump, on a parallel valve engine, it would only be a HP or so. Those angle heads are truly better flowing.

 

[Kevin Horton]

Oh, one more difference and I think the biggest factor in the additional power-- the typical stock parallel valve IO-360 has an 8.5:1 compression ratio, the angle valve is 8.7:1. So the two key things that provide the increased horsepower in the angle valve engines are the increased volumetric efficiency (better breathing) and an increased compression ratio.

The small increase in the compression ratio plays a relatively small role in the HP difference. If all other factors remained the same, and you increased the CR on a 180 hp O-360 from 8.5:1 to 8.7:1, the HP would increase by about 0.7%, or about 1.2 hp. See this earlier posting for details on that calculation.

 

[David-aviator]

I have reported this before and I will again, apples to apples sort of, RV-4 O-320 wood prop verses RV-4 IO-360 angle valve and MTV-15 prop, down low at the same speed we are neck and neck on fuel burn, up high I go off and leave him at 20 to 25mph faster, get there sooner and burn less fuel for the same leg, 1 to 2.5 gallons less on a 2.5 hour leg, and its pumped by the time he gets there. The only argument against this engine is weight and money, fuel burn is equal or better with this engine and that?s comparing to an O-320 and I?m not doing anything special. My cold air induction is Sky Dynamics same as the sump, don?t know anything about what is available stock.

The only argument against this engine is weight and money,

It is.

Using Van's catelogue as a base cost line for an experimental engine, the difference between parallel valve 180HP/FP and angle valve 200HP/CS is about $15710.

You pay for the satisfaction of going faster and burning less fuel. Or you can have the satisfaction of keeping the 15 grand in your pocket and not go quite so fast on less fuel.

The neat thing about RV's is there is something here for everyone....the airplane flies great, even with a Subaru.

 

[w1curtis]

The small increase in the compression ratio plays a relatively small role in the HP difference. If all other factors remained the same, and you increased the CR on a 180 hp O-360 from 8.5:1 to 8.7:1, the HP would increase by about 0.7%, or about 1.2 hp. See this earlier posting for details on that calculation.

Agree, for the parallel valve O-360. But looking at it the other way, how much HP would you lose if you reduced the compression of the angle valve IO-360 with the better breathing to 8.5:1. I don't know but it would be an interesting test.

 

[Kevin Horton]

Agree, for the parallel valve O-360. But looking at it the other way, how much HP would you lose if you reduced the compression of the angle valve IO-360 with the better breathing to 8.5:1. I don't know but it would be an interesting test.

The standard theory says you would lose about 1.3 hp, if everything else was equal. A change from 8.5:1 to 8.7:1 is really not very much - it is only a 2.4% change in CR. Look at the O-320s. The 150 hp version has a CR of 7.0:1. The 160 hp ones have 8.5:1. That 21% change in CR is worth 10 hp.

 

[penguin]

One other thing to consider is that stock Angle valve engines don't always make 200hp (see Skydynamics Homepage, click on Maxi-sump and scroll to the bottom). Urban legend has it that parallel valve engines often make 183 to 185hp (no evidence to back up that statement). So the advantage of an angle valve motor could be only 10hp.

Also consider the beating a non counter-weighted parallel valve crank gives a constant speed prop - many prop manufacturers recommend a counterweighted crank. But, that crank is heavier and more expensive to buy and overhaul.

Its all a compromise!

Pete

 

[steveKs.]

You pay for the satisfaction of going faster and burning less fuel. Or you can have the satisfaction of keeping the 15 grand in your pocket and not go quite so fast on less fuel.

This reminds me of a sign that was on the wall of a race car driver that also owned a speed shop.." Speed costs money, how fast do you want to go?"

 

[rgbewley]

One other thing to consider is that stock Angle valve engines don't always make 200hp Urban legend has it that parallel valve engines often make 183 to 185hp (no evidence to back up that statement). So the advantage of an angle valve motor could be only 10hp.

Also consider the beating a non counter-weighted parallel valve crank gives a constant speed prop - many prop manufacturers recommend a counterweighted crank. But, that crank is heavier and more expensive to buy and overhaul.

Pete

Absolutely true Pete, in all the years of dyno testing, we have consistently seen that the angle head only generally makes about 196 horses (even with higher compression and bigger valves.) The p/h 360 however in stock configuration makes a true 180 horse. The ct'wt crank is heavier, but a lot smoother than that p/h engine rattling your baffling/cowl to death! The majority of the weight difference in the engine is in the cylinders. Cases, gears, etc., etc. are all the same.

But, (don't shoot me Dan) if you're considering the a/h 360 because you want hp, I still think the 390 wins hands down. I might be a little biased!

 

[dan]

But, (don't shoot me Dan) if you're considering the a/h 360 because you want hp, I still think the 390 wins hands down. I might be a little biased!

I don't disagree. It's just that I haven't seen an RV with a 390 achieve the same speed-for-economy that my a/h 360 has achieved. I know more SLOW RV-7[A]s with 390s than I do FAST ones. Why is that?! It's gotta be the airframes, right? It's gotta be all that extra cooling drag of louvers and bigger oil coolers, etc., right? Well, it has me wondering...as I contemplate engines for my RV-8, I have yet to be sold on the 390. HP for $, the 390 is pretty much the winner in my book. But HP is not the only factor when it comes to speed. If you have to "give up" speed in order to keep it cool, then it's on the "back side of the curve" imho.

 

[gmcjetpilot]

The diff O-360-A1A & IO-360-A1A, by lycoming

"Because of the similarity in designation, it would be easy to believe that the O-360-AlA and the IO-360-A1A are the same engine except that the first engine has a carburetor and the second a fuel injection system. Here are some features of each engine for comparison. The O-360-A1A has a bottom-mounted updraft carburetor, parallel valves, 8.5:1 compression ratio and produces 180 HP. The IO-360-AlA features a horizontal front-mounted fuel injector, angle valves, 8.7:1 compression ratio, and is rated at 200 HP. The IO-360-A1A incorporates additional design items which are not included in the O-360: piston cooling nozzles, stronger crankshaft, tongue and groove connecting rods with stretch bolts, tuned intake system and rotator type intake valves. There are actually few similarities except for the 360-cubic inch displacement." Key Reprints - "The Same Engine Myth"

 

[rgbewley]

It's just that I haven't seen an RV with a 390 achieve the same speed-for-economy that my a/h 360 has achieved. I know more SLOW RV-7[A]s with 390s than I do FAST ones. Why is that?! It's gotta be the airframes, right? It's gotta be all that extra cooling drag of louvers and bigger oil coolers, etc., right? Well, it has me wondering...as I contemplate engines for my RV-8, I have yet to be sold on the 390. HP for $, the 390 is pretty much the winner in my book. But HP is not the only factor when it comes to speed. If you have to "give up" speed in order to keep it cool, then it's on the "back side of the curve" imho.

Interesting points. I've seen your comments on this before and never really thougth through them extensively. From an engine builder's perspective, I'm interested in knowing more. How many 7s are we talking about here that you've seen/flown with that have the 390? Assuming you flew Ross Schlotthauer's -7. The new owner of that airplane reports great performance with no engine issues at annual a few months ago.

Cooling issues can be caused by a number of factors, including magneto timing. An engine timed at 25-26 degrees is going to get the cht up pretty quickly. Electronic ignition advancing the timing at low RPM (say on ground run up) will also create heat more quickly than you want. Lots of variables to consider.

Every other model airplane that we've put the 390 in, including the-8, Giles 202, Christen Eagle, Extra 200 and Extra 230 report exceptional performance/handling improvements with no more that .5 gph additional fuel consumption during normal operation.

We all know that the 390 is 9 lbs heavier than the a/h 360, but does anyone have any weight comparisons on the airplane as a whole (bigger cooler, etc., etc.)? Additional drag created by cooling mods is out of my scope of knowledge - but I'd love for someone to enlighten me about it.

 

[RV8RIVETER]

Not always more $$

Angle valves are not always more expensive. I was open to either and the best deal that presented itself was an counterweighted angle valve. Am about ready to assemble the engine and the total cost will be $13-14k. A bit concerned about the extra weight, but easily fixed by going with a Whirlwind 200RV prop.

Of course for those of you fortunate enough to able to by new, then it will always be more $$.

 

[ron voss]

Angle valve O-320?

Gotta ask-anyone running an angle valve O-320 like I am? Mine started life as an O-320-E2D, overhauled with 160 HP pistons and new ECI angle valve cylinders from a GO-480. Just got it flying July 15th and after 11.5 hours so far all is well. Running an E-mag & P-mag with a 3 blade Catto prop. After talking with Craig, we propped it planning on 170 HP out of this engine and so far it seems right on. Although I don't have wheel pants or gear leg fairings on yet, it turned up 2640 rpm at 9300' DA and 182 mph TAS. I know these cylinders are heavier, but the empty weight for my -6 was only 1015 with everything except gear leg and intersection fairings.
Ron Voss
N642R Finally Flying!