Angle vs parallel engines

[Chewie65]

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

[fodrv7]

?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/Wikiped...bustion_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]

Originally Posted by fodrv7

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]

Originally Posted by dan

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]

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]

Originally Posted by w1curtis

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.