How many hosses??

[Captain_John]

...which is one reason FOR the CS Prop. My other reason is airspeed control, both in formation and in the pattern.

Speed management, CG and economy. This is offset by the added cost of the airscrew, of course.

A worthwhile investment, I think. Not everyone does, though!

You like the E-Mag? Cool! I am thinking dual P-Mags. Why didn't you get a P-Mag, Penguin?

CJ

[penguin]

I was one of the first emag customers (only 1 flying when I ordered) - it seemed like a good product, but I didn't want to spend any more money than I had to in finding out. I've now got around 40 hrs on the emag and am very happy - I'll be adding a pmag in place of the remaining magneto in 2 or 3 months (as disposable income allows). At the time emag were advising that the "standard" configuration would be one emag & one pmag. So I thought I would start with the emag - now many people seem to be opting for 2 pmags. I don't think 2 pmags buys very much (I wouldn't fly for very long with a dead alternator) and an emag saves $250.

I agree with all of your reasons for using a CS prop - if I had an additional $7K I would buy one tomorrow. I think a CS prop makes the airplane so much more fun.

Pete

[mahlon_r]

CJ,
The stock engine at 8.7:1 with P mag should fit your requirements. The P mags should deliver a little bit more power even though most EI's don't significantly change the timing schedule or map at full power unless you are at an elevated field. I have yet to run an engine with P mag or Emag. We have several scheduled, but so far no product to run them with. If you have any intention of using Emag or Pmag, my advice would be to order them way in advance of your engine and way in advance of when you will think you will need the engine. In my view they have been very SLOOOOOOOOOOOOOOW in filling orders.
As Pete said the exhaust can play very big part in the actual power output of an engine. Any system that helps get the exhaust out with a scavenge or augmentation system will yield big power results.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at you own risk

[Captain_John]

Thanks Mahlon!

cj

[GRANT ED]

Out of interest Mahlon, what exhaust system do you recommend? This is one area I have not looked into.

[mahlon_r]

Personally, I would most likely use the Vetterman system Van's sells. I wouldn't be so concerned with power as others are. If you are a power fanatic and want all that there can be, definitely turn to a scavenge type system. It will normally cost more and often take up more room. We have worked with Kevin Murray at Sky Dynamics and have had good product with good results on some of our higher performance engine applications. Good stuff.
http://www.skydynamics.com/homepage.html
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at you own risk."

[penguin]

E mag is only two guys working in a small shop doing all of the R&D and making the production ignitions - I think they have been somewhat overwhelmed by the demand for their product!

Seems that the Sky Dynamics maxi-sump is a good alternative to the M1B sump or the Superior plastic sump?

Pete

[gmcjetpilot]

Why more compression ratio?
Is that going to make that much difference?

Take a 180 hp engine, and assume 205 mph cruise. Add high comp pistons, say 190 HP the new cruise in round numbers

205 mph x (190/180)^.33 = 208.7 mph

Yes climb would also be a little better, but you are only getting 3 mph. There are ways to gain speed with out adding HP. Reduce cooling drag, as with a cowl & pressure plenum is worth 7-10 mph for example. The nice part is this speed does not burn more fuel like more HP does.

What is the down side?
Read articles from Lycoming on HC pistons, they will warn of reduced detonation margins. Something to think about. HC pistons do have the potential to reduce reliability. Here is an article regarding HC pistons and Turbo charging:

http://www.lycoming.textron.com/main...kWhatThey.html

Also, many are aware the Hartzell found that prop fatigue increased with higher compression pistons and electronic ignition. Some of the effects to consider as Lycoming is concerned:

http://www.lycoming.textron.com/main...eModifier.html

I rebuilt my O-360A1A with stock 8.5:1 comp pistons, after talking to Tracy Saylor who has one of the fastest RV-6s around, as demonstrated by his race results. Of all the mods he made, going to HC pistons was one of his later mods. He found they made little difference in his top speed.

If you really want to make more HP you have to modify everything to take full advantage. New HC pistons, needs a different cam grind to match the exhaust system, requiring induction changes and so on. Bottom line these are airplane engines and reliability is of premium importance. The more HP you draw the higher the pressures , temps and stress, the lower the life and reliability. Does your flying consist of racing at Reno 90% of the time, or flying yourself and your wife to airshows and the kids house, occasional aerobatics, formation flying and x-c?

Simple drag reduction and engine changes like exhaust and ignition changes can improve engine efficency and add a little performance with less down side. Internal changes should be thought out carefully. Also there can be insurance implications. Some companies will frown at modified engines and they do ask. Denial of coverage or higher premiums may result. I am not against a small increase in Comp ratio but it is not for everyone and don't expect it to make a huge difference in a RV that already fly?s very well.

Cheers George

PS
4 into 1 exhaust is a good start at making improved engine power. It has been difficult if not impossible to use these on "A" models with the center nose wheel, but Exhaust Technologies now has one. I have a custom 4 into 1 "tuned" exhaust for my RV-7, and they are very good quality. They also now have off the shelf RV exhaust systems and even offer a muffler combined with a heat muff. They use some techniques from their certified side of their shop, like porcupine studs, that makes the heat muffs very efficient for their size.

http://www.aircraftexhaust.net/exhaust_photo_album.html
http://www.aircraftexhaust.net/Custo...8_Exhaust.html
http://www.aircraftexhaust.net/Vans_...1_Exhaust.html
http://www.aircraftexhaust.net/index.html

Cross over is not the best system and produces uneven power pulses due to the different pipe lengths. (Ref cafe foundation exhausts research). 4 into 1 "tuned" exhaust is best, followed by 4 separate pipes and than cross-over. The worst are Y-pipes, 2 into 1, joining cylinder 1 & 3, and 2 & 4.