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.fodrv7 said: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.
Dan, Dan, Dan,dan said: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.
William, William, William,w1curtis said: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.
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.gmcjetpilot said:..
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!)
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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.gmcjetpilot said: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.
Russ,Russ McCutcheon said: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.
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.w1curtis said:No, they produce the additional 20HP at the same 2,700 RPM.
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.w1curtis said: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.
Russ McCutcheon said: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.
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 said: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.
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.w1curtis said: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.
penguin said: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
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.rgbewley said: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 said: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.