Myths and Choice of IO-360 Lycomings

[fodrv7]

Dave,
I did not see the Cracked Cylinder discussion as the pissing competition. That was a reference to earlier post about Angled Valve Jealousy.
No, on the contrary and in hindsight, the ?Look after your CHTs? is good educational information.
Besides, I have been guilty of hijacking threads and, I will quietly admit, inadvertently winding up George too. He is a good sport, but sometimes his enthusiasm for aviation gets the better of him. Do love his inputs.

No! The thread went well.
I was just a little surprised however, considering how many kits are out there under construction and how many builders must still be deliberating over an engine choice, that the discussion did not develop into, ?Who can tell me more.?

Thanks All,
Pete.

[David Johnson]

Originally Posted by fodrv7

It begs the question as to why Lycoming made the Angle Valve engine. Was it to provide obese Spam Cans with another 20BHP for Take-off. If so, it has no applicability to RVs.

Look forward to some input on the matter from the Engineers amongst us.

Pete.

Thanks for your additional comments, Pete. I appreciate them. To address your original question, I don't know what engineering information you're looking for as you appear to have the data you need on the performance curves of the engine. Perhaps perspective is what you're after. My guess is that Lycoming had a market need for precisely what you've suggested. An additional 20 HP at takeoff with 4 burrito-eating adults, or 2 adults plus lots of luggage improves high D/A performance, a distinct plus in some areas.

As for its applicability to RVs, here in the Rocky Mountains, I've departed Leadville (9927' MSL) in the summer with density altitudes of 13,500' MSL (84 deg. F OAT) and headed west toward Hagerman Pass, at 11,925'. Even with only 2250 lb. total weight with the 182, and 230 HP, it was a long, slow climb. RVs are far better performers obviously, but if the winds are blowing, that extra 20 HP could come in real handy if you need it to escape a downdraft. For some of us who live near the tall rocks, the extra take-off and climb power will be used frequently, so I wouldn't go quite as far as saying that it has no applicability to RVs. I guess it just depends on where you live and your mission profile.

Cheers,
Dave

[N395V]

It begs the question as to why Lycoming made the Angle Valve engine.

Back to the original post.

I originally wanted an RV8 but being one of those wide body burrito munchers mentioned above I was worried about performance off the deck as well as climb performance.

Flew 8s with 180hp and 200hp and the difference in takeoff and climb with full fuel, me and a passenger was noticably better in the 200 hp.

On the website noted below a Cherokee 140 owner (over the span of 2 web pages) does an elegant job of comparing climb performance in his Cherokee with an old muffler having a displaced baffle and a newer more efficient muffler.

He calculates for a 7hp gain he derived a 114fpm climb improvement. If things are proportional that means the extra 20 hp would give an improvement of 300 fpm off the deck.

7 HP increase gives >100fpm climb improvement

[fodrv7]

Now here are some good reasons for every HP you can get. Hard to find any dirt with an airport over 3000' in Australia.
Leadville (9927' MSL)?
You have to go to New Guinea for that sort of challenge. Home of the 800' TORA. 20% slope, 7000' Elev. Grass Airstrip. In a Gully. MORA FL145. Afternoon CB.

And I am sure if you are a burrito muncher, you will need all the Burros you can get.

Pete.

[praterdj]

I would love the additional horsepower and performance that it brings but I?m a big guy at 6?-5? 250 Pounds so my decision is easy. I?m going with a IO-360. I?m building an 8 so unfortunately I can?t afford the additional 30 or 40 pounds up front.

I?m going to try to compensate by keeping my plane as light as possible. I?ll use a lightweight starter, alternator, avionics, etc.

I did find Milt?s calculations about HP versus climb very informative. Is there any information in regards to weight versus climb? I know there would be many factors that would make it difficult, if not impossible, to provide dead on performance results. (engine performance from one run to the next, density altitude changes, ets.) but it would be very interesting to know what types of increase/decrease in vertical climb speed are seen with weight variations.

I read an article in one of the aviation magazines where a guy went through his plane to reduce as much weight as possible. Even to the point of shortening all of his wiring and eliminating unnecessary wiring loops to reduce the weight. He mentioned that overall he saved several pounds but I don?t think he mentioned what performance gains was achieved.

I think I?ll start a thread specifically to address this issue.

Regards,

Donald
RV-8 Empennage
N-2845 DP Reserved.

[fodrv7]

Donald,
This will not be absolutely accurate as the change in ROC with change in AUW will not be linear.
But it will give you an idea of what to expect.

From Vans Website Performance, an RV-8 with 200hp has a Rate of Climb of:
2700fpm @ 1800lb
1900fpm @ 1400lb
So, for a difference of 400lb the ROC differs by 800fpm
Therefore for each 100lb increase in AUW, the ROC will decrease by 200fpm.(800/400=).

Or for every 1lb weight you save in the airframe the ROC will increase by 2fpm.

Pete.

[tloof]

I personally think the O-360-A1F6D (from out of a Cessna 177 Cardinal) that I have in my RV6 is the best overall O-360 to use in an RV. It is a parallel valve 180 hp version with the counterweighted crank (same as the 200 hp angle valve has) but is obviously 30 lbs lighter. With 9:1 pistons (O320-H pistons) in it and ported heads along with electronic ignition & an Ellison TBI injector it makes between 200-205 hp or so. It is also a dual mag version that I have installed a more powerful single Bendix 1200 series mag with impulse coupling in place of the original dual mag unit, and also installed the Lightspeed ring gear trip electronic ignition system on. This engine allows an oil filter & prop governor to be installed without ANY holes being cut in the firewall of the RV6, so it is an excellent combination in the RV6!!!!!!

Just my 2 cents!!

[penguin]

Originally Posted by tloof

I personally think the O-360-A1F6D (from out of a Cessna 177 Cardinal) that I have in my RV6 is the best overall O-360 to use in an RV. It is a parallel valve 180 hp version with the counterweighted crank (same as the 200 hp angle valve has) but is obviously 30 lbs lighter.

I think the weight reduction from an angle valve motor is not obvious - the counterweighted crank is responsible for a fair amount of the additional weight. But, it may be a reasonable trade for smoothness if you are really producing 200+hp.

BTW why use an Ellison rather than FI?

Pete

[osxuser]

Another point of interest about the two engines is that, at the same power output, the angle valve will burn less gas (according to the pilot get aways, installed in a Husky up to .8GPH). That might be worth it...

[David Johnson]

Originally Posted by osxuser

Another point of interest about the two engines is that, at the same power output, the angle valve will burn less gas (according to the pilot get aways, installed in a Husky up to .8GPH). That might be worth it...

That claim from PG raises a few questions in my mind. I'd be very surprised if there is a 10% improvement in BSFC between the two engines. The angle valve may have better fuel distribution and run smoother, leaner in cruise, but the power output would be slightly less in that case.

Dave