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Too much Horsepower

C

Chalmous

I'm New Here
Hello Everyone
I am brand new here and need help. I want to buy a 2014 RV7a. The one I am looking at has an IO390 exp engine that has been modified to produce 240hp.
Vans website says that the max is 200. Is this engine going to cause problems on this airframe. Might there be structural issues? The engine has been polished and ported, I think, and Lycon installed higher compression Pistons to bring up the horsepower. Will the engine not last as long as a result of these changes?
Will my fuel burn at cruise be significantly higher than if it had an IO360. Would you shy away from this airplane because of that engine?
 
Hi Chalmous, welcome to VAF! The official "greeter" will be along shortly to make your welcome, ..... well,....... official! :)

Sending you a PM (Private Message).
 
Welcome to VAF!

Chalmous, welcome aboard the good ship VAF:D

Extra HP is good-----------if used correctly. Great for climb performance and high DA stuff.

The big issue I would be concerned with is exceeding the design speed red line, that is what can really make the factory folks cringe.

Yours is not the first RV to have HP levels above factory recommendations.
 
Chalmous I think it would be an excellent idea to sell that motor to me and get one that's more suitable for your aircraft.
 
Here's a better deal.

salto said:
Chalmous I think it would be an excellent idea to sell that motor to me and get one that's more suitable for your aircraft.
Click to expand...

I have just the engine for you and will consider an even trade. I hate to see you make the mistake of having too much horsepower. In inexperienced hands too much horsepower can be deadly! Mine has over 2000 hours on it so you can skip the break-in and uncertainty of an unproven engine. It's a win-win!
 
240HP ? IO390?

I would want certified and corrected HP data from a known dyno before I believed that.
 
I'm with David on this one. A claim of 240HP is easy to make, but hard to verify. I don't personally see a big problem with the IO-390. High compression Pistons can increase horsepower, certainly, but how high is the compression, and what type of cylinders? I worked on an -8A with an IO-360 angle valve with 10.5:1 Pistons, which normally would decrease the TBO. However, when it was built, they used turbo cylinders that were made to handle higher power (being turbocharged). After about 800 hours the cylinders looked great. The valves practically looked new and e compressions were well into the 70's. So, how high is the compression and what cylinders were used? The normal IO-390 is 210HP, right? You could certainly get that to 220-225 with compression, but I don't know about 240.

There was an RV-10 with a parallel valve engine that claimed 325HP. I also find that extremely hard to believe. It made for a great N-number, though.
 
I'd want to see the dyno sheet as well eg 240HP at 3000rpm is interesting but not prop relevant. Also you have to ask about cooling - that's a lot of HP heat to get rid of. You can't fly much if you cant keep CHTs in check.
 
I have an angle valve 360 and 10:1 in my -8. While it is fast, I'm in no danger of exceeding VNE when flown normally. Have to watch the descents of course but that's true of any engine. Climbs like a banshee and with my plenum I'm running too cool actually (lean of peak, wide open...CHT's in the 270's, rich of peak around 300) Our resident glass guru Horton has a 390 in his -8 with no issues either.

Bottom line, that engine wouldn't scare me if the airframe and cooling looks as it should.
 
Chalmous said:
Would you shy away from this airplane because of that engine?
Click to expand...

To your questions...

To make a fair judgement about the extra HP, you'll need to determine how it was produced.

Just putting 240 on the meter is not very difficult. A dead stock 390 makes 409 lbs-ft of torque at 2700; (409 x 2700) / 5252 = 210. Assume a compression bump, some port work, a cam to push the torque peak up the RPM scale just a bit, and an extra 1/2" of manifold pressure due to being run on a prop dyno rather than a water brake. Peak torque might be pushed to 420, a very moderate increase. To log 240 HP, just turn it to 3000 RPM. Is an extra 11 lbs-ft of torque going to hurt the airframe? Not likely.

Of course, it's a different deal if the shop folks managed to get 467 lbs-ft at 2700, with air density corrected to Standard Day conditions. Or it could be a combination somewhere in between. Point is, bragging HP doesn't tell you what you need to know. Get a raw data dyno printout.

For the sake of discussion, assume it makes 240HP at 2700. The $$$ question then becomes a matter of cooling it if run continuously at that power in the RV-7 cowl, CHT and oil.

Yes, if run at high power and hot it won't last as long as one run gently and cool.

Cruise fuel burn can be whatever you want, within reason, as the mixture knob is really a "speed and range selector". It will never make 240 at efficient cruise altitudes, as you're limited by MP.

I can't speak for a -7, but my -8 will exceed published VNE in level flight with a dead stock 390. Note that a few 7's have lost vertical tails at some unapproved speed. With a big boy motor you're really talking about an increase in climb performance, not a practical speed increase.

Note that nothing here is a deal breaker. A 240HP RV-7 could be a lot of fun, but it may not be entirely what you think.
 
Weight difference between a 200HP angle valve IO-360 vs a IO-390 is negligible. Plenty of angle valve powered -7As flying that don't bend the nose gear.
 
Chalmous in regard to you selling me that motor, I like Ron would be happy to throw in some extra.
I recently bought a beautiful female pup, it's loving, attentive, seems to train easily however it turns out my wife is allergic to it so I need to find her a new home.
She's 57 years old, cooks and cleans like them best of em
 
322 HP from an IO 540 parallel valve?

I have an IO 540 flow balanced and 10:1. The shop that made an identical engine for a friend said it Dynoed at 322 HP. My engine is exactly the same but only burns 25 gallons an hour at full throttle/full rich at take off from sea level. (should be a lot more fuel burn at the claimed HP). With all those wild Dyno claims I believe that my engine is making about 280 HP.

It's plenty and I'm happy with it.

Some one once said "HORSE POWER IS GOOD, LOTS OF HORSE POWER IS BETTER AND TOO MUCH HORSE POWER IS JUST ABOUT RIGHT"
 
Steve Barnes said:
I have an IO 540 flow balanced and 10:1. The shop that made an identical engine for a friend said it Dynoed at 322 HP. My engine is exactly the same but only burns 25 gallons an hour at full throttle/full rich at take off from sea level. (should be a lot more fuel burn at the claimed HP). With all those wild Dyno claims I believe that my engine is making about 280 HP.

It's plenty and I'm happy with it.

Some one once said "HORSE POWER IS GOOD, LOTS OF HORSE POWER IS BETTER AND TOO MUCH HORSE POWER IS JUST ABOUT RIGHT"
Click to expand...

That would be 0.47 lbs. per hour, per horse power which is possible with a 10:1 engine like yours but it would have to be very efficient.
 
How much is too much...

Chalmous said:
Hello Everyone
I am brand new here and need help. I want to buy a 2014 RV7a. The one I am looking at has an IO390 exp engine that has been modified to produce 240hp.
Vans website says that the max is 200. Is this engine going to cause problems on this airframe. Might there be structural issues? The engine has been polished and ported, I think, and Lycon installed higher compression Pistons to bring up the horsepower. Will the engine not last as long as a result of these changes?
Will my fuel burn at cruise be significantly higher than if it had an IO360. Would you shy away from this airplane because of that engine?
Click to expand...

Chalmous,
The Harmon Rocket 2 is a classic example of a Van's design with "too much horsepower" or to be more exact, twice the design HP. John Harmon took the basic RV4, made a few slight changes to the design and voila' new performance specs, well beyond Van's original design. Realize that for every action there is an equal and opposite reaction. Fuel efficiency, engine life and airframe stresses notwithstanding.

My HR2 had (like you) a Lycon built engine. It was a flowed and ported ND IO-540 C4B5 10:1 compression B&B'd with Kenny's "Magic" performed. It Dyno'd at Lycon (theirs is certified) at 320HP at 3000 RPM. I believe it.
Hence, my Rocket performed very well....an old F16 quote from my past goes like this:

You can always throttle back, but why?
:)
V/R
Smokey
 
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You may want to ask an insurance agent what the difference in premium is for going above Van's recommendation.
 
Oh, boy, this could be a can of werms.

Van, has done a good job of staying within the limits of accepted aircraft standards. You can quote part 23 to name one. This reserved approach has given way to a line of good simple and dependable aircraft. I respect that and hope to keep taking advantage of the good fortune to have a part of this product. It is your choice, and your comfort zone. I would have to say your concerns are valid and would urge you to keep digging and do your homework at length on this subject. This is one of those debates that is best held around the picnic table over hot dogs and beer. Just a thought, Yours, R.E.A. III #80888
 
?? More HP

I agree with above,
Horse power, my addiction, my quotes are, "No replacement for cubic displacement" "more is better, way to much is just right"
It's been awhile for a chime in.
Thomas
 
Air below you, runway behind you and horsepower you don't have...

There's really no such thing as too much power. But there is too weight/fuel burn, other issues. Aircraft are all trade-offs, this one will climb great, go fast, burn more fuel and weigh more. Tada!

-Bruce
 
Hi Chalmous,

First off, wish I could play the guitar like you...I have one but don't know how to hold it. :)

Except in time of war, where more HP always is better, it is no good here. The RV-7 does not need anything more than 200 and more is a waste of money.

I remember when this airplane first flew and was reported, I thought what for?

Well, to each their own. It sure will take off and climb like a rocket but to use that much power in cruise will put it near or over TAS red line. That is not good.

I wonder how much the airplane weighs?
 
https://youtu.be/fzMvZW09n18
fzMvZW09n18


Posts 10 & 23 say it quite accurately for me.

Notice in the video how well 150Hp with a simple fixed pitch wood prop gets the job done in a 7.

Sexy women , too much HP and excess speed can all get you killed in a heartbeat, and they WILL all cost lots of money even if you are careful,:D but what a way to go....
 
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CG benefit

It hasn't been mentioned but you will have a better CG range with the 390 and the additional weight up front. My first 7 was with a parallel valve 360. If I had lots of baggage on board and let the fuel get too low I could definitely feel the sensitivity.

On my new 7 I was going to put a 360 angle valve on but a 390 became available. I had Barrett Precision Engines do their thing and I ultimately ended up with an engine that dyno'd at around 212. Alan estimated it would go up as it broke in.

Being in AZ with high DA's and significant mountains to deal with, I wanted the extra HP for climbs. I don't plan on going any faster. My thinking is you have more engine doing less work. Shouldn't see any significant differences in cruise fuel burn.

As Dan mentioned, it would be not worthy to know how the cooling is set up. I'm using the RV10 oil cooler and plenum with 4" scat tubing. This has been successful in several other 390 equipped 7's.

Finally, make sure you get a solid pre buy from an experienced RV builder and preferably one that is an A&P also.

Good luck. Sounds like it could be a great plane.
 
Just a clarification to the OP that mentioned a 7A. Darwin is correct about W and B for a 7 but the 7A is opposite. 7As are easily nose heavy with a CS prop. It goes along with what Walt posted earlier.
 
Think about Vne!

Vne is calculated for MSL! So if you fly higher, TAS is the correct speed to look for the Vne. If you have a EFIS it is easy, most of then show the TAS numbers.

Otherwise, a rule of thumb: Your Vne is decreasing by 2tk per 1'000ft altitude.

Example: If 200 KTAS is your Vne, then it is at 10'000ft (200-(10*2))
= 180 KIAS

With so much power you have to be careful on the throttle high up.

BR, Dominik
 
Chalmous said:
Hello Everyone
Would you shy away from this airplane because of that engine?
Click to expand...

No. I have a friend with a 390 on a -7 and he loves it. I have flown in it and it is a great performer.

Don't tell your insurance agent about the horse power claim - it is likely wrong anyway and irrelevant. Just operate the airplane according to VAN's speed and g limitations and you will be fine.
 
@ Jesse

No Jesse, I really meant 180 KIAS

TAS is TAS, the plane is limited to TAS. If you have no TAS display you can calculate it or have to use this rule of thumb:

Vne is decreasing by 2kt per 1'000ft altitude, if you look at your ASI which shows KIAS

In switzerland we had to place a sticker by the ASI with exactly this information.
 
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