IO390 EXO 119 Cowl Mods

[DanH]

Originally Posted by Cwood2000

Yes, the exhaust and cowl flap were my areas of concern along with the prop governor. That is going to be a lot of cutting. I’ll call Van’s today and inquire as to what they have, if anything. I can use anti splat’s cowl flap, because of the 8 more narrow fuselage, not sure how the exhaust will workout.

I've been flying a forward governor IO-390 eleven years now. Mine has much revised cooling air intakes, one of which incorporates a molded rubber seal for the governor. Plan B might be the cutout in the upper cowl's intake ramp, like the 14's, although it cold be done more artfully.

I think the issue with bolting a 119 on the -8 will revolve around exhaust system fit, notably clearance for the cyl 1 and 2 headpipes. The tailpipe end appears to be well inboard, and the composites work for the cowl outlets is straightforward.

Note a lot of the 119/RV-14's speed improvement is based in drag reduction, not the HP increase, so drag work is important if this project is to be worthwhile. I'd lop off the entire stock "coal shovel" outlet, replacing it with a flat panel flush with the belly skin. The resulting fixed exit at the belly recess slot would be roughly 13 x 2-5/8, IIRC. Given good baffling, the aircraft would probably cool fine with the combined area of the three exits (two at the pipes and one at the slot), and there would be some reduction of frontal area.

Splat's cowl flap hinges at the front, and is thus pretty draggy. A center-hinged door is less draggy when open and easier to actuate. If a variable area exit is desired, I'd put it in the new flat area just forward of the slot exit.

[Cwood2000]

Originally Posted by DanH

Are you planning to use the exhaust intended for the 119 version of the 14, and install a variable area exit?

Dan, not sure what a variable exit means, but it looks like the 8 cowl I have will work with some mods. I’ll probable want to add a cowl flap as well.

[DanH]

Originally Posted by Cwood2000

Dan, not sure what a variable exit means, but it looks like the 8 cowl I have will work with some mods. I’ll probable want to add a cowl flap as well.

Here variable area is a functional description. Implementation may take the form of a conventional cowl flap hinged at the leading edge, or some other manifestation.

For any given addition of exit area, the best design is arguably the one which results in the lowest external drag when open.

[pipern9175d]

Hello guys,
I didn’t want to get ahead of myself and post anything until I Had flown 332RT after the installation. Flew Her 05/18/22. I have some pics I will post and a full recap. For now I will post the cowl stuff I had to do. I needed no modifications to the lower cowl, I did have to cut and make a ‘pocket” that was bonded to the ramp just above the prop governor. I used the -14 air intake with extensive mods. Flew the intake up to Don @ Airflow, he flow tested it and gave me his approval the 4 into 1 was very aggravating and took 2 tries to get the fit right. Second time was the charm though. Scott

[Cwood2000]

Thanks for the feed back, sure looks nice. I'd be interested is seeing your temps and air speeds.

[Cwood2000]

Originally Posted by DanH

I've been flying a forward governor IO-390 eleven years now. Mine has much revised cooling air intakes, one of which incorporates a molded rubber seal for the governor. Plan B might be the cutout in the upper cowl's intake ramp, like the 14's, although it cold be done more artfully.

I think the issue with bolting a 119 on the -8 will revolve around exhaust system fit, notably clearance for the cyl 1 and 2 headpipes. The tailpipe end appears to be well inboard, and the composites work for the cowl outlets is straightforward.

Note a lot of the 119/RV-14's speed improvement is based in drag reduction, not the HP increase, so drag work is important if this project is to be worthwhile. I'd lop off the entire stock "coal shovel" outlet, replacing it with a flat panel flush with the belly skin. The resulting fixed exit at the belly recess slot would be roughly 13 x 2-5/8, IIRC. Given good baffling, the aircraft would probably cool fine with the combined area of the three exits (two at the pipes and one at the slot), and there would be some reduction of frontal area.

Splat's cowl flap hinges at the front, and is thus pretty draggy. A center-hinged door is less draggy when open and easier to actuate. If a variable area exit is desired, I'd put it in the new flat area just forward of the slot exit.

Thanks for the pictures, as always, excellent workmanship.