C

costa

Member
Hi.
I leave in Europe and I'm thinking build a RV.

I'm not sure what model I must choose. 7A or 9A?.

I'm not sure if I can use mogas 95 into the O360 or O320??? because the low wing. For the engine no problem I guess, the question is the plane that use a pump to pump the fuel to the engine!! Vapor lock?

what are the advantages or drawbacks of the RV7A compared with the 9A?

Thanks
 
Which RV

Hi,

By the way, welcome to the VAF forum!

The 7A is much sportier with the shorter wingspan. Very quick roll rate. It is capable of aerobatics. It typically uses the o-320 or o-360 engines. It still makes an efficient cross-country cruiser, but probably not quite as economical as a 9A.

The 9A has a higher aspect-ratio wing, which will allow it to fly on a smaller engine if you want the best cruise economy. o-235 and o-290 are popular engines.
With an o-320 engine, the 9a is still a very fast, efficient airplane (maybe still more efficient than a 7A at high altitude). It is not designed for any aerobatics.

I think you will be very happy with either one. It depends on where you put your priority - sportiness, or cruise efficiency.
 
Last edited:
You can certainly

95 octane mogas with the standard 8.5:1 compression ratio in either engine. And based on the prices I have seen for 100LL there I would want to make sure I could!

Peonsally i wouldn't do it without a modified fuel system however..There are many posts on how to build such a system if indeed your local country regulations permit you to do so.

Frank
 
frankh said:
95 octane mogas with the standard 8.5:1 compression ratio in either engine. And based on the prices I have seen for 100LL there I would want to make sure I could!

Peonsally i wouldn't do it without a modified fuel system however..There are many posts on how to build such a system if indeed your local country regulations permit you to do so.

Frank
Click to expand...

Maybe Portugal doesn't require ethanol as an addative so the modifications wouldn't have to be as extensive?????
 
efficiency?

scsmith said:
The 7A is much sportier with the shorter wingspan. Very quick roll rate. It is capable of aerobatics. It typically uses the o-320 or o-360 engines. It still makes an efficient cross-country cruiser, but probably not quite as economical as a 9A.

The 9A has a higher aspect-ratio wing, which will allow it to fly on a smaller engine if you want the best cruise economy. o-235 and o-290 are popular engines.
With an o-320 engine, the 9a is still a very fast, efficient airplane (maybe still more efficient than a 7A at high altitude). It is not designed for any aerobatics.

I think you will be very happy with either one. It depends on where you put your priority - sportiness, or cruise efficiency.
Click to expand...

In regards to efficiency........

It sometimes seems that it has a lot to do with the pilot, and perhaps not the plane... ??? :eek:

I fly my 6A quite regularly with a pilot who owns a 9A. I have an 0360, his has an 0320. Both have carbs & C/S props. The 9A pilot tends to fly his plane at the most economical cruise he can get, without going LOP. Yet twice, when he's flown my plane, and someone else has flown his (same place, same altitude)...........he beat his own plane --- fuel efficiency wise; by using less fuel in mine when both were refueled.

On the other hand, when I fly mine, and he fly's his, he always get's better milage than I do. But I tend to usually fly higher and faster to the destination.
The point is, he's getting some good efficiency out of my 6A, although it's 50 lbs. heavier. He can monitor all four cylinders, and I just have CHT & EGT on cylinder #3. These flights were at the 6500' levels.

L.Adamson --- RV6A
 
Depends

mannanj said:
Maybe Portugal doesn't require ethanol as an addative so the modifications wouldn't have to be as extensive?????
Click to expand...

Sucking fuel uphill with a hot (mechanical) pump is a hydraulically flawed solution. Given enough motivation it will boil, its just that 100LL has a sufficiently high vapour pressure to prevent this in most situations. I think there are plenty of instances of mogas boiling in low wing airplanes, with or without ethanol.

I'm afraid the engineer in me wants to do it the right way and avoid the mechanical fuel pump (hence the issue) altogether, at least when using mogas.

There are some reid vapour pressure numbers for mogas vs avgas kicking around somewhere, but I know the VP for mogas is somewhat higher.

Certainly a standard system with FI and the boost pump running all the time should not be an issue..as long as the boost pump is running at least.

Frank
 
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