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Extra HP vs cost?

bret

bret

Well Known Member
So, it looks like Ill be in the market for a power plant next spring and wanted to get a start on my homework. looking for feedback with those that bought Titan, Lycon, ECI ect... was the cost for say....215+HP worth the extra cost. My field ele is 4722 and I will need to climb-cross the Sierras often. Also, any performance data on the 390s? Thanks.
 
Only you can answer if it is worth it. I would guess those that put the 390's in will absolutely say it was worth it. We tend to justify our own decision.

PM Christo. He has a 390 in his 7. One thing I can tell you is he does his own flight planning. Doesn't want to wait up on us lowly 180HP guys. ;)
He also burns less fuel.

I can add, all RV's, regardless of power plant, are more than capable at those field elevations.
 
I put an IO360 in my 9A for the same reasons. I know I don't *NEED* it, but I want it, for the rate of climb. I will be taking it into and through the Rockies frequently and I just wanted the extra displacement at altitude.
 
you can never have to much HP.

seriously, the only one that can answer that is you. you need to decide what your mission is an how much you what to pay for it.

if you want speed, remember, you need cubic HP to get an increase in speed. you can get much more speed by cleaning up the airframe than by going to a bigger motor. case in point, the super corsair, big big motor never got the speed they hoped for.

if you want climb rate the key question is how much added climb will you get for the added weight. what is the difference in climb between a heavy big engine airframe vs a light weight lower HP airframe. sorry, i don't have that data and to get real data will take some careful measuring, not just "I know a guy with xxx and he gets this climb rate".

I went with 180HP O-360 and constant speed in my RV-4 I love it but is it worth the extra thousands of dollars? im still not sure.

If I were considering a 360 i would consider the 390 instead, however, If I were considering a 320 I would not even look at the 390. way to big of a difference in price for performance, IMO.

my thinking now is leaning to what van envisioned, light, simple and fun.

bob burns
RV-4 N82RB
 
I was thinking 390 but wish I could fund a 409.....now then......how much for that high compression, ported, EFII 360? goal is to get close to 230 HP and under 30K....ya, no?
 
I have an IO-375 (dyno-ed at 200hp) and fly out of an airport at an elevation of 5700' at the base of the Rockies--which I also fly over. No doubt, I wish I had a bigger engine. When a hot summer day brings the DA to 9000' on takeoff roll...200hp isnt enough IMHO.
 
bret said:
I was thinking 390 but wish I could fund a 409.....now then......how much for that high compression, ported, EFII 360? goal is to get close to 230 HP and under 30K....ya, no?
Click to expand...
I understand you are looking at the 360 for the HP but I have to add this since it is what I have. You might want to look at the performance numbers for the ECI IO-340. Rated HP is 180 for the 9.0:1 pistons. The weight is about half way between a 320 and a 360 (the ECI spec sheet states 245lbs). That HP to weight ratio is what convinced me to go with this engine. Not sure if you have thought about it or if you would even consider it an option but it is a very good engine for which I have nothing but praise.

My .02.

Live Long and Prosper!
 
other side of the coin

I have an O-375 making about +-200hp with a Hartzel, and I worry about my speeds.

I am a new RV-7 owner and not a Vans expert (or expert pilot) but my concern is over-speeding the airframe. If you are already cruising above 5000' when you T/O, your true airspeed should be pretty high with that kind fo power. Unless of course you cruise at a lower power setting I guess.
 
RVbySDI said:
I understand you are looking at the 360 for the HP but I have to add this since it is what I have. You might want to look at the performance numbers for the ECI IO-340. Rated HP is 180 for the 9.0:1 pistons. The weight is about half way between a 320 and a 360 (the ECI spec sheet states 245lbs). That HP to weight ratio is what convinced me to go with this engine. Not sure if you have thought about it or if you would even consider it an option but it is a very good engine for which I have nothing but praise.

My .02.

Live Long and Prosper!
Click to expand...

Less weight, and better cooling space under the hood I would imagine!
 
Bret -

One thing to remember is that in order to USE all that extra horsepower, you have to COOL it - the more power generation you pack under the hood, the more waste heat you have to get rid of. We generally have to back off on a climb (in our area) becasue of temprature issues before we actually run out of performance.

Now you can do many things to increase cooling - they all take attention to detail and some experimentation. Some have done this quite well, thers - not so much. So its a trade-off if that is worth it to you. But expect that the more power you are generating, the more "off stock you'll have to go.

You can also get better climb by reducing weight - another option, depending n your mission.
 
Thanks Paul, good point, so I have the SJ cawl in the living room, (along with the rest of the plane) will the SJ plenum or homemade help with this heat issue, and while we are talking heat, is the firewall mounted oil cooler the way to go? Or no?
 
...

The 390 is great... engine and oil cooling have been a non factor with unrestricted climbs, cruise, race, aerobatics, any sort of play ;)

There are many claims of HP, speed, efficiency, etc... YMMV. I have 1200+ hours with quite a bit of testing and in flight comparison to give a big thumbs up to this combination.
 
bret said:
So, it looks like Ill be in the market for a power plant next spring and wanted to get a start on my homework. looking for feedback with those that bought Titan, Lycon, ECI ect... was the cost for say....215+HP worth the extra cost. My field ele is 4722 and I will need to climb-cross the Sierras often. Also, any performance data on the 390s? Thanks.
Click to expand...

My RV7A Construction Manual says that the RV7A is approved for Lycoming engines up to 200 HP. This is what Vans says:

"Engines with more horsepower can easily drive the airplane past redline in level flight. Just because you CAN install a big engine doesn't mean it is a smart thing to do".

I'd be inclined to heed the advice of Richard VanG. The man might know a thing or two about the aircraft he designed. ;)
 
I had a conversation with a respected engine shop about IO-390s a couple weeks ago.
Despite having built a ton of them they said there is better stuff (same/more Hp, cheaper to build and maintain, lighter etc) out there and while they would be happy to build one for me they suggested other engines.
 
Yes and thanks. I am not looking for level flight speed, only climb performance as Ron has stated in his post about DA. There is a throttle and or blue knob for speed control at cruse alt.
 
Horsepower

Adding horsepower is the most expensive and least efficient way to gain performance. Particularly when your potential for speed increase is limited because you will run into VNE. Building light and clean will get you there in the same amount of time for less money and lower operating costs. Nice challenge too.
 
Vne is a long way out there...

Vne in a -7 is quite a way out there and not so easily reached in level flight... even using TAS... wish I could get closer. At the very best I get 192 knots but that is burning stupid amounts of fuel... 16+ gph... normal high cruise is at 170-175 at around 8.5.

As far as climb:

(from an earlier post)

My home airport, KAWO, is just above sea level (128 feet at the 34 threshold) and today the density altitude -640.

I rolled on to the runway without any special issue and smoothly applied power.

Airborne within 10 seconds.
Build speed just off the runway to 110 mph at 14 seconds with an immediate pull to maintain 110 mph.
Rate of climb is above 3,000 fpm at 20 seconds and peaks at 3,500 at 27 seconds while holding 110 mph.
Still climbing at 3,000 fpm passing through 1,500 AGL holding 110 mph right at the end of the runway...

WOW ;)

Okay, I admit, I am gloating a bit... but WOW... I love my plane!

The whole climb is maintained at just under 30 degrees holding 110 mph and averaging around 3,200 fpm.

screenshot20130220at856.jpg


screenshot20130220at616.jpg
 
The IO -390 Lyc uses a roller cam. Cam lobe and lifter wear is gone and because there is less friction, there is less heat generated that the oil needs to deal with. Most of the 390's are 215 -220 HP out of the box. Just do what Dan Horton has done for cowling and cooling.

I have long thought the ultimate retirement machine for myself would be a sport wing Rocket with a 150 HP 320 and fixed pitch prop.
Light and simple as I can make it with lots of leg and shoulder room. There is a lot to be said for light and simple.
 
F1R said:
The IO -390 Lyc uses a roller cam. Cam lobe and lifter wear is gone and because there is less friction, there is less heat generated that the oil needs to deal with. Most of the 390's are 215 -220 HP out of the box. Just do what Dan Horton has done for cowling and cooling.

I have long thought the ultimate retirement machine for myself would be a sport wing Rocket with a 150 HP 320 and fixed pitch prop.
Light and simple as I can make it with lots of leg and shoulder room. There is a lot to be said for light and simple.
Click to expand...

I like like it light and simple for retirement....if there is a need for speed and performance up to 40,000' I go SWA. :)
 
bret said:
Yes and thanks. I am not looking for level flight speed, only climb performance as Ron has stated in his post about DA. There is a throttle and or blue knob for speed control at cruse alt.
Click to expand...

You have it right Bret.

My climb performance is generally like Stephen's. I love it...but the knobs come back for economy cruise just like everybody else.

LOP, 178 KTAS on 7.8, similar to the smaller displacements.

 
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F1R said:
I have long thought the ultimate retirement machine for myself would be a sport wing Rocket with a 150 HP 320 and fixed pitch prop.
Light and simple as I can make it with lots of leg and shoulder room. There is a lot to be said for light and simple.
Click to expand...

As I recall, Larry Vetterman pulled the 540 from his rocket, installed a four banger and loves it.
 
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