200hr TBO MT prop on ECI IO-340X
 

I am helping a friend build an RV-3. We are convering the engine from an O-320E2D to a IO-340 with a ECI stroker kit. We would like to use a MT prop. and after talking with them today they said that this would reduce the prop. TBO to 200 hours. this is because there props have never been strain tested on that engine. OH My Goodness! this changes everything. Is ther anyone out there flying an IO-340X and if so what prop are you using? Buyer beware!

IO-340
 

This is pure CYA on the part of MT. IIRC the "Twin Navion" of the 60's &70's used a Lycoming O-340. That engine had a constant speed prop. You might research the Type Certificate Data Sheet for that aircraft and find the prop they used. It would be a good place to start after you check ECI for their reccomendation of the right prop to use.

Which prop??
 

That is the only reason why I didn't go with the Stroker kit when I overhauled my O320 several months ago. My crank failed inspection so I was at a crossroads and needed to purchase a new one. The Stoker kit is essentially the same price as a new OEM Lycoming crank. I still think it?s an attractive option. Both MT and Hartzell told me they don't make a product that is ?suitable.? You might give Whirlwind and Aero Composites a call to see what they say. I never called them. I also could not find anyone to do testing to see if a prop is compatible with the O340. I think only the manufactures have the equipment and expertise to do such testing. I realize my blah blah blah isn?t helping you sort this out. I did do a lot of checking into it with phone calls around the country.

I used to own a Navion (although not a twin). IIRC there were two separate manufacturers of the conversion, Riley and ?Camair. The only two I ever spent any time around had Continental O-470s and props off of a Baron. One of the conversions was underpowered but I can't remember which

To get the bigger vertical stab/rudder necessary for the twin on one of the conversions, they took a surplus horizontal stab/elevator and mounted it vertically.

Harmonics testing for the 340
 

I know that ECI was conducting harmonics tests a few months ago with Hartzel and maybe other prop mfrs. I'll bet the ECI guys can shed some light on this issue. I have heard that they were very impressed with the smoothness of the 340 engine. Good luck.

MT Propeller TBO
 

The advantage of having a certified propeller is the FAA control (in Germany it is EASA) of the TBO requirements. (In this case, TBO determination is not a "lawyer" thing.)

I have a 200 hour TBO propeller on my RV-3 because it is only the second MTV-7 type Propeller installed on my type engine.

When three of these specific propellers on this type engine have been overhauled at flight time TBO within the 6 year TBO, then the flight time TBO will be increased for all of this type propeller on this type of engine.

Actually, this applies to all of the constant speed MT Propellers.

So, the flight time TBO is a moving number. To a maximum of 2500 hours.

On MT Propellers "production" website, www.mt-propeller.com in the "Service Docs" page in Service Bulletin # 1 is a list of flight time TBO which are updated regularly. http://mt-propeller.com/pdf/sbs/sb1af.pdf

My interpertation of flight time TBO is as follows:
200 hour TBO - New propeller design and/or New engine type combination.
1000 hour TBO - Modified propeller design on know engine design.
1800 hour TBO - vibration analysis successfully completedfor specific propeller design and engine combination.
2000 hour TBO and above - Three propellers overhauled at flight hour TBO prior to 6 year TBO without abnormal internal wear or damage. Usually applies to propellers used in aircraft at flight schools.

I hope this helps.
Jim Ayers

Be careful assuming
 

That is a good idea but the props on those old twins where probably steel hub Hartzell's, feathering. Probably will not help much with info, but it's a nice approach.

The "old" O-340 was a little different? I know it had lower compression version for third world use and low octane gas. I use to think it was a "de-stroked" O-360, but I am not sure of that?

The new ECI IOX-340 "stroker" is a 320 stroked for 20cc more displacement with higher compression. This would affect the prop somewhat. I am guessing it would be worse than a stock 320 but not worse than a 360 with electronic ignition, but you need to test each variation of course to be sure, even if it's CYA.

What does that mean? It means they are two different engines. I'm not implying one is worse or better for a prop than the other. Bottom line it has to be tested. With out testing, MT probably would put a 200 hr TBO on the "old" O-340-A1A.

(what I found)
Lyc O-340-A1A, bore x stroke, 5.125 x 4.125, 8:50:1 cr, octane 100/100LL, 170 HP
Lyc O-340-B2A, 7.15:1 cr, octane 80, 160 HP
(Note: just for ref. stock 360 has a bore x stroke of 5.125 x 4.375)

ECI IOX-340, bore x stroke 5.125 x 4.125" (0.25" over stock), 9.00:1 cr, 185hp (?)