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Power gains?

Lufthans

Well Known Member
Hi guys,

On my RV-3B, I am converting my 150 hp (with 7.0:1 compression ratio) narrow-deck O-320 to EFI and electronic ignition.

I'll have a new fixed pitch prop, most likely a Catto on there. Craig will want to know my power figures in order to make me a suitable prop. Which poses the interesting question:

How much (if any) power will I be likely to gain?

Substituting the carb with a properly dimensioned throttle body.
Keeping the hot intake manifold (with intake tubes running through the hot oil sump)
Running the engine low down (it's all class A above my head here) and most likely ROP.
Keeping the 7.0:1 pistons
Running on Mogas

What power figures can I expect?

Thanks

Hans
 
Hardly any.

The injection should help make a much smoother LOP machine.

Do not expect a power gain of much if any, and keep the timing in the 23-24 degree range for ROP ops and 28 for LOP ops if your system is programmable.
 
Mid-50s O-320

LuftHans: I bought an 0-320 (no suffix) off a 1955 Apache for my RV4. An old A&P at STS told me that replacing the 7.0 pistons with 8.5 was a common, but not certified, mod on old narrow deck 320 Cubs. One reason was 10 more hp, another was 80 was becoming scarce. I ran it for 5 years as a 150, and then rebuilt is with 8.5 pistons; same case studs; same thin base cylinders (no B hold downs) that I chromed; same internal splined nuts. The original rods were tiny, so I changed to newer 0-360 rods and heavy wall pins.

I have about 1350 hours on it all over US, and no problem. I am (still) using the original Pacesetter 200 68x66, and the 160 turns it quite a bite faster. My plane cruises flat out at 2850, so my guess is there is something around 170hp at the prop. You mentioned auto fuel: for many years, I ran the left tank on 100LL for operating near the airport, and 92 premium auto in the right tank at cruise. I averaged 5-6 tanks of auto for every tank of 100LL, and the plugs were gorgeous tan with no lead build up. I quit auto when US went to ethanol....Anyway, just my story, and something to think about. A -3 with an 0-320 should be quite the performer whether 150 or 160! John
 
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