[DevDad]

Now that my workshop is almost totally set up, it is time to make a final decision regarding which model I am going to build. I'm wondering about some actual cost differences for FWF kits for O-320's vs. IO-360's (180 HP). Right now, I'm pretty torn between the -9A and the -7(A), but I am trying to determine a realistic difference in total costs for equally equipped airplanes (save for the different engines).

I realize I can just call around, but the reality is, I haven't yet learned enough to determine what needs to be purchased to complete an engine installation. I appreciate you guys' help!

Mike

 

[AltonD]

If you go with the IO, add in the $600 fuel pump kit. This is not part of the FWF kit.

 

[scard]

I think you'll find that the actual cost difference between the two options you are looking at are quite small. I would recommend that you not use this as a driving factor for what you want to build.

 

[lostpilot28]

I agree with Scott regarding the difference in model pricing. The 9 and the 7 are virtually the same. But engine prices do differ a bit and so do their fuel consumption. You can get a 0-320 or smaller for a -9 for thousands less than a 0-360.

 

[Martin Sutter]

The cost difference between an O-320 and an O-360 is only $300.- (taken from the Aerosport Power web site). Weight difference is about 8lbs. If you add fuel injection to the 360 then why not to the 320? Both the RV9 and the RV7 can be powered by the same O-320 if you so choose. As far as the fuel consumption goes, flow at the same speed and comparing carbureted 320 to a carbureted 360 the fuel burn will be the same as the specific fuel consumption PER HORSEPOWER is the same. The comparison for the fuel injected versions the same also. Since it takes a given number of HP to move an airplane thru the air at a given speed, the fuel consumption will be the same regardless if the HP is produced by an O-320 or anO-360.

Martin Sutter
building and flying RV's since 1988

 

[DevDad]

Thanks for the responses so far. I was trying to find out, because identical options (save for the engine change) lists a -7A as $8-10K more than the -9A, as per Van's cost estimator.

So, say I build a -7. What should I expect to spend on a new IO-360, with mid-level ignition, etc.? Ball park?

Mike

 

[Jim P]

Engine Cost

http://www.xp-360.com/ is a good site to get you an estimate. There's an on-line tool to build and estimate a Superior engine.

http://aerosportpower.com also has price listings for their engines and overhauls.

For estimating purposes at your stage in the project, these are going to be close enough to give you a good idea.

Jim

 

[Ola]

What about the difference between used 320s and 360s? I'm under the assumption there is a higher demand for 360s in the 2nd hand market.

 

[N916K]

I haven't yet learned enough to determine what needs to be purchased to complete an engine installation.

Then go with a carb and mags with a CS prop. 320 for the 9, 360 for the 7. You can't really go wrong with that engine setup and you can always add EI and such later on. Unless you have specific engine needs then keep it simple. It will get you in the air sooner and you will have no problem meeting Van's numbers.

Cam

 

[whifof100ll]

O320 and O360

But engine prices do differ a bit and so do their fuel consumption. You can get a 0-320 or smaller for a -9 for thousands less than a 0-360.

I think you have to be careful with this statement as there are alot of common misperceptions out there. It is only true if you are comparing a new 360 with a used 320. If you are comparing new with new, which is what I think the poster was asking. the price between an comparably equipped parallel valve O360 and an O320 engines is negligible. You pay only a few hundred dollars for the additional displacement. Also note that if you go with a new Lycoming clone from Mattituck or Superior, the cost for fuel injection is also negligible, about $300.

As far as fuel savings, An O360 will burn more than an O320, but it pushes the plane faster as well. If you throttle back to the same speed, you will burn about the same amount.

Here is another misnomer. I've had many tell me to buy an O320 because it is lighter. Ive recently investigated this carefully and an O360 is only 7 pounds heavier than an O320. Precision airhawk fuel injection adds 3 pounds to either the 320 or 360 if you go that route.

Another thought, If you throttle an injected O360 back to the same speed as an O320, it will burn less fuel than the O320. Of course you can also get an injected O320 as well.

You are barking up the wrong tree if you are building a 9 to save money.

I think both are great planes, but given the choice, the RV-7 is a no brainer for me. You can put a parallel valve 180HP engine in it (the 200HP is really pricey and much heavier), and maintain acro capability. It is just too much fun to pass up!!! You will also have a faster airplane as you can push the throttle in all the way without passing Vne.

Remember. speed is your friend!!!

Regards,

 

[N941WR]

Mike,

As a guy who went with a -9 and installed an oddball engine, take it from me, build the airplane you want to build, not the plane others want you to build.

I realized that most of our flights would be local so speed wasn't an issue. I would have really liked to do the acro thing but I have a 2G back, thus I didn't see a need for the -7.

Between the back and some thoughts on how I would use the plane, I elected to go with a -9. Once that selection was made I started building. About 1/2 way through the wings I stared looking for an engine to rebuild. I kept an open mind on engine size. Even looked at Egg engines but ruled them out early as I didn't want the weight penalty.

After stumbling upon the 0 SMOH O-290 I'm now flying behind for $3,500, I couldn't be happier. 300 mile trips that take less than 2 hours and 14 gallons, isn't that bad.

What I'm saying is figure out your mission and then you will know what the right plane and engine combination will be.