I am going to be starting a 7 project as soon as the dust settles and have an opportunity to purchase an 200hp angle valve engine for a good price. My original plan was to go with the 180 but am considering using the 200. The one 7 that I have flown had the 200 in it and seemed to fly well. Any thoughts regarding CG or weight or flyability?
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Paralell valve vs Angle valve
- Thread starter skybolt31
- Start date
Kyle Boatright
Well Known Member
The AV is heavier, more powerful, and more efficient.
If the deal is good, I'd take the 200 HP AV and put a composite prop on the airplane to mitigate the forward CG.
If the deal is good, I'd take the 200 HP AV and put a composite prop on the airplane to mitigate the forward CG.
I have a parallel valve. With a constant speed prop, I still have an aft CG problem. When these airplanes were designed, everyone had a vacuum system and heavy radios, all forward of the CG. Now, we don’t have vacuum systems and, depending on what you install, a lot of the heavier electronics go in the back. If I were building, I’d probably prefer an angle valve and expect to be OK with a constant speed prop to boot!
This would be for a 7, not the 7A
I have flown both a lot.. the angle valve climbs much better, but one real benefit is the CHTs stay cool, you can climb at 90-110 and not overheat.
I have as well, climb rate could be variations in different a/c and conditions. I never noticed this. Can't speak to CHT. I can tell you those in the acro community obsessed with power/weight ratio and handling feel favor parallel valve 360s. Matters less in an RV though.
dmattmul
Well Known Member
Seems an increase of 11 to 17% hp increase and a 2% increase in weight could be an advantage. I agree CG needs to be considered but like others have said a composite prop and a pad mounted alternator would help and improve smoothness and safety. I really like my AV engine.
AV engines don't make the stated HP. PV engines are usually making more HP than stated. A PV engine can be messaged into making 190-195hp very easily with injection, ram air, good exhaust, plenum intake and ported valves. AV engines weigh more, cost more and the cylinders are not as robust as the PV cylinders. You can work with items in the tail to reduce weight if you are aft CG.
If you go to overhaul a AV engine you will be also paying more and parts are harder to find due the shear amount of PV engines out there. They are also more complex and have more parts to fail (like the bushings on the counterweight). An RV-7 or RV-8 will fly nicer with the less weight on the nose.
If you go to overhaul a AV engine you will be also paying more and parts are harder to find due the shear amount of PV engines out there. They are also more complex and have more parts to fail (like the bushings on the counterweight). An RV-7 or RV-8 will fly nicer with the less weight on the nose.
The reality is nothing like that though, and really zero increase in added power after accounting for the weight. See post above. I've flown a bunch of of PV and AV 360s on the same airframe and the AV just makes for an airplane that's heavier in pitch with no added performance.
PilotjohnS
Well Known Member
I would not use a pad mounted alternator as a primary.
I tried this on my RV9A and quicklyntook it off and went with a standard B&C belt drive alternator.
I found several issues with a pad mounted primary:
1) it doesnt charge at idle RPM. So after start, the battery is still being drained, unless I taxi at a high rpm and drag the brakes.
2) After landing, during the taxi back to hangar, invariably the radios, lights, and sometimes transponder is still on, so the battery is being drained on the taxi back. The next morning start is then with a battery that is not fully charged.
3) The capacity of the belt drive is so much better at low RPM, so I can cruise around and never worry about low rpm on final ( I have a fixed pitch prop)
scsmith
Well Known Member
In absorbing people's opinions here, bear in mind a few points.
1) RV-8s tend to be nose heavy. Putting battery and some avionics in the back, and a composite C/S prop are a necessity. With those done, an angle-valve equipped -8 can get the c.g. in about the same place as a parallel valve equipped one with a metal C/S prop. Flying an RV-8 that is nose heavy really is noticeably less 'nice'.
2) RV-7s tend to be tail heavy. Putting an angle-valve engine on would be a good way to expand your useful cross country baggage-carrying capability, and handling will be fine, since the c.g. will still be in a very good location. Flying an RV-7 with an angle-valve engine is not going to be quite as responsive, but it is plenty responsive enough to be really nice, and will be more broadly mission-capable. More baggage without hitting aft c.g. limit, better high-altitude ops for mountains, high desert.
3) Although it is true that angle-valve 360s really only make max 195 hp, that is still more than a parallel valve 360 will do with stock compression ratio, even if ported/polished, etc. Yes, a PV engine can get souped up to 195 or more hp with increased compression ratio, but there are other ramifications to that choice. This partially negates the perceived benefit of more readily available, lower-cost parts. I would be comfortable running a CR 8.7:1 angle-valve on UL94 fuel, but NOT a CR 10:1 parallel valve engine.
4) The bigger benefit from the angle-valve design is not the max Hp, it is the better breathing so that WOT operations at cruise RPM and cruise altitude DOES yield significant horsepower improvement compared to the parallel valve engine. The performance difference at high density altitude is VERY noticeable. A horizontal cold-air induction/sump on a parallel valve engine would get some of this same benefit, but it is an expensive add-on that offsets some of the cost differential between the AV and PV.
5) The angle-valve engines extract a lot of their heat thru piston oil squirters, so the cylinders run nice and cool (and last a looooooong time) but the oil gets really hot unless you put significant effort into designing a good oil cooling system. Plan ahead to install a large cooler on the firewall, supply it with lots of air with minimal pressure loss (lots of threads here on VAF about doing that).
1) RV-8s tend to be nose heavy. Putting battery and some avionics in the back, and a composite C/S prop are a necessity. With those done, an angle-valve equipped -8 can get the c.g. in about the same place as a parallel valve equipped one with a metal C/S prop. Flying an RV-8 that is nose heavy really is noticeably less 'nice'.
2) RV-7s tend to be tail heavy. Putting an angle-valve engine on would be a good way to expand your useful cross country baggage-carrying capability, and handling will be fine, since the c.g. will still be in a very good location. Flying an RV-7 with an angle-valve engine is not going to be quite as responsive, but it is plenty responsive enough to be really nice, and will be more broadly mission-capable. More baggage without hitting aft c.g. limit, better high-altitude ops for mountains, high desert.
3) Although it is true that angle-valve 360s really only make max 195 hp, that is still more than a parallel valve 360 will do with stock compression ratio, even if ported/polished, etc. Yes, a PV engine can get souped up to 195 or more hp with increased compression ratio, but there are other ramifications to that choice. This partially negates the perceived benefit of more readily available, lower-cost parts. I would be comfortable running a CR 8.7:1 angle-valve on UL94 fuel, but NOT a CR 10:1 parallel valve engine.
4) The bigger benefit from the angle-valve design is not the max Hp, it is the better breathing so that WOT operations at cruise RPM and cruise altitude DOES yield significant horsepower improvement compared to the parallel valve engine. The performance difference at high density altitude is VERY noticeable. A horizontal cold-air induction/sump on a parallel valve engine would get some of this same benefit, but it is an expensive add-on that offsets some of the cost differential between the AV and PV.
5) The angle-valve engines extract a lot of their heat thru piston oil squirters, so the cylinders run nice and cool (and last a looooooong time) but the oil gets really hot unless you put significant effort into designing a good oil cooling system. Plan ahead to install a large cooler on the firewall, supply it with lots of air with minimal pressure loss (lots of threads here on VAF about doing that).
As long as you don’t exceed MTOGW. But then again many builders do not set their MTOGW to what Van’s designed the airplane to.
[email protected]
Well Known Member
As all stated above.
But I look at this a bit different
I have a Nissan 2017 370Z hot rod. I started out with 215 HP and we worked on it a bit and am now getting about 285 HP.
does it go faster? not really. does it burn more rubber? NO. is it more fun? EH! Not really.
But in a car you feel the horse power, gravity and thrust. Spinning around in a circle and corners and all. In a plane not really.
I have an I0-360 8.5-1 PV with SDS EM5F fuel and ignition in my RV-6A and would never spend the money on an AV.
These RV's climb and fly real well. But doesn't burn rubber. Ha Ha
OH ya, and by the way. I burn Costco Premium on all my local flights. Have a tank in the back of my van.
My luck varies FIXIT
which alternator were you using. i just installed a pad mounted monkworks 30amp pad mount. it is making 14.6 V taxiing at low speed. it is small and light.
I saw the YouTube video where Danny King shows off Beautiful Doll, and said he wouldn’t do the angle valve engine again if he had to do it over.. how about other RV-8 owners out there with the AV? (Dan H, I’m talking to you). My buddy has an AV engine in his -8, with aluminum Hartzell prop and Vans steel gear legs. Very nose heavy. Not as “fun” to fly as a light weight engine plane. I didn’t feel the same on a -7 with the AV engine.. it didn’t seem as nose heavy on the -7.I would love to fly a 390 equipped -7 to try it out! I like the additional power and cooler CHTs here on the west coast.. East coast guys may not need or want the extra power, heck a 320 RV is a blast to fly around the lower a altitudes of east coast sea level airports!
climberrn
Well Known Member
These are all valid points, but here is my experience:
I've flown my 7A about 700 hours with a Lycon modified IO-360 PV engine without a counterweighted crank, 10:1, Cold air sump & intake, and a WW constant speed prop. Lycon estimated north of 210HP. From day 1 I've had aft CG issues, limiting baggage. Needed a flywheel weight to help CG. Harmonic issues (Prop and P Mags sent in a couple of times for OH. The engine was balanced to .02 IPS from the start. Difficulty with CHT's in climb, and high oil temps from the piston squirters, requiring oil cooler upgrade and mount moved. In my opinion, this was a high stressed engine and climb outs were not as easy as I would have liked. Would still be flying it if not for a major issue with the case that took the engine out of service.
Bought a 6A with basically the same engine, but with counterweighted crank, and Hartzell CS prop. The engine is so much smoother than I ever had with the 7. Climbs great, although not as fast as the 7. CHT's a little more difficult to manage, and it is difficult to keep the nose wheel off with an empty baggage area. But I like this setup better than the 7 right now.
The 7A is currently getting a IO-390. The dyno shows same HP as I was getting before. The extra 30 lbs (+ or -) will allow me to get rid of the 14lb flywheel ring and greatly improve the CG issues. Should be able to keep the CHT's down easier. Counterweighted crank and internally balanced rotating mass *should be smoother. The most important thing for me is this is a STOCK compression engine with a 2400 suggested TBO getting the same power as I had before. And it should fix some squawks I had before. Should be flying soon. Waiting on a new prop cable....
First, what Steve said...ditto.
Monty Barrett created the 390 to satisfy a market wanting 200+ HP without 1000 hour rebuilds. Barrett (and others) could easily pump up a parallel valve, but going to TBO if consistently run at high power levels was (and is) a wildcard. The 390 was a low stress approach; lots of cubic inches in better cooled cylinders.
Not a free lunch. With a small main 390 and a metal Hartzell, my -8 exhibits heavy stick forces in pitch when flown solo. It's not as sweet as the lightly warmed PV with Whirlwind I was flying two weeks ago...when judged by that single parameter. If I wanted an -8 to fly solo acro, I'd go PV. In all other circumstances, you can have my 390 when you pry it from my cold dead fingers
Gusting 20 knot direct crosswind this afternoon, 40 ft wide strip, Ms Patti in the back seat. Really nice to get up and flying with a short ground roll, then straight to 10.5 and arrive with 350 CHT.
Smiley Creek, Idaho, mid afternoon, ballpark 75F, density altitude roughly 10,000 ft. Full load of gear. Short soft field off the dirt, pick up some speed, then up and gone. HP is good.
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RV7 To Go
Well Known Member
A friend on our field has an AV powering an MT 3 blade composite in his 8. Wishes he hadn't done it. Runs hot oil temps all the time, even here in the great white north with the 13 row cooler. More engine than we near sea level flatlanders require.
I traded an AV IO-360 for a PV IO-360 to put in my 8 with a 300 series WW prop. I anticipate similar cruise with much better TO and landing (slowing the plane down) performance with this setup than in my Sensenich FP PV O-360 powered 7. No W&B issues with my 7 in this configuration. W&B to be determined on the 8.
Thanks everyone for the insights. It seems that the 8 is a better plane with the 180 but with the 7 there have been more people having good luck with the 200. Both of my planes so far have had the 200, so I have a lot of experience with them and like them. It is certainly true that cylinders for the 180 are much less expensive and there are options.
PilotjohnS
Well Known Member
The monk works was not available when i built my bird. I had a B&C alternator. I have no info on the Monkworks, so my comment only referred to the B&C type. The B&C pad mount is a great alternator; it just didn't fit my mission.
andoman
Well Known Member
I’ve read thru this thread. I built an early -7A with a stock AV. I offer the following:
-the AV makes more HP and it is noticeable everywhere. Those that say it’s a wash are, respectfully, incorrect.
-high oil temps are easily solved. Worry about being able to cool the oil is not a reason to choose one lycoming over another. Else we’d all have a 150 hp 320‘S. And some would still have high oil temps….
-the -7 nose can use a little weight. With an AV engine one can load up and go and never fret aft CG.
-if the primary mission requires the the feel of a light nose RV then the AV is indeed a liability.
-the OP’s initial post mentioned an available engine at a good price. In this building environment that may carry more weight than anything discussed.
-the AV makes more HP and it is noticeable everywhere. Those that say it’s a wash are, respectfully, incorrect.
-high oil temps are easily solved. Worry about being able to cool the oil is not a reason to choose one lycoming over another. Else we’d all have a 150 hp 320‘S. And some would still have high oil temps….
-the -7 nose can use a little weight. With an AV engine one can load up and go and never fret aft CG.
-if the primary mission requires the the feel of a light nose RV then the AV is indeed a liability.
-the OP’s initial post mentioned an available engine at a good price. In this building environment that may carry more weight than anything discussed.
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