Turbo Subie Passes 250 Hours on the Hobbs - Page 3

GregClawson · #21 02-01-2009, 10:47 PM

Ross-
Great to hear of a successful Subie-IVO combination. Were they able to deliver a prop that could be bolted directly to the PSRU hub? Or, did you need to manufacture/purchase any bushings, spacers, etc? Did you go with 3-blade? Ground adjust or inflight adjust? I welcome all details.
Thanks,
Greg

rv6ejguy · #22 02-14-2009, 06:02 PM

Quote:

Originally Posted by GregClawson

Ross-
Great to hear of a successful Subie-IVO combination. Were they able to deliver a prop that could be bolted directly to the PSRU hub? Or, did you need to manufacture/purchase any bushings, spacers, etc? Did you go with 3-blade? Ground adjust or inflight adjust? I welcome all details.
Thanks,
Greg

Sorry I missed your post from a while back.

IVO supplied the prop and adapter to SAE 2. The gearbox manufacturer machined the drive lugs to suit the IVO adapter. I did have an issue with incompatible radii on the prop flange and adapter which took a little lathe work to rectify: http://www.sdsefi.com/air18.html

I have a 76 inch Magnum 3 blade with the high pitched blades, in-flight adjustable.

Interesting to look back what I wrote 10 years ago now- I was hoping for 3000 fpm solo and 200 knots... I was young and foolish back then. I ended up with 2000 and 180.

TSwezey · #23 02-14-2009, 07:23 PM

Quote:

Originally Posted by rv6ejguy

Interesting to look back what I wrote 10 years ago now- I was hoping for 3000 fpm solo and 200 knots... I was young and foolish back then. I ended up with 2000 and 180.

It never hurts to dream!

rv6srb · #24 03-10-2009, 07:37 PM

HI Ross, I started with a NSI 2.5 installation. I was buring 100LL and made it to 75hrs before removing the highly modified engine. It had burnt exhaust valves. I replaced it with a STI SOHC engine, all stock. I ran a turbo for the first ten hours and after that I took the turbo off. Running 100LL with an additive this time, I got to 80hrs before burning the exhaust valves. I rebuilt the heads and this time I got 75hrs before burning the exhaust valves. Max EGT's 1425 or less. I have just rebuilt the engine. New SS valves, new pistons etc. It's running better than ever and I am running 94 car gas this time. I don't know what is burning the valves, I give it lots of gas and the timing is max at 31degree's under high power. A friend is running a NSI engine on a Glass Star. He had problems at 250hrs with burnt valves. Once that was fixed, all he does is fly.........over 1000hrs at this point. He burns car gas. His timing and fuel tables are close to mine. So??? I am going to burn car gas this time around. Time will tell:-))
Steve rv-6 2.5 sti 9.5 to 1 compression 27"/4400rpm/1950rpm prop 1600' 162kts

rv6ejguy · #25 03-10-2009, 11:01 PM

Hmmm. Very interesting. I've clicked over 300 hours now and the valves are not burnt yet but it does not seem entirely happy on 100LL either. I'm burning 80/20 91 unleaded/ 100LL now and checking the vapor pressure with a gauge from Peterson. The winter gas up here is apparently kinda scary so I need that Avgas in there.

One other guy in Oz had a reported 3800 hours on an EJ22 in a gyro trainer, always run on unleaded. There seems to be a common thread here.

Out of curiosity, how wide were the exhaust seats ground?

I'm really impressed with the speed you are getting from yours.

Randy · #26 03-10-2009, 11:34 PM

Ross, Steve and or anybody. What would be the mechanism at play here when we see 100LL as the commmon thread for burnt valves? How would the 100LL contribute to that type of problem?

I can understand the lead getting the rings gummed up or stuck. Does the lead get the valve guides stuck enough to prevent proper valve closing?

Buildup on the valve faces?

I am more than a little curious as you can imagine

Randy C

rv6ejguy · #27 03-11-2009, 07:33 AM

I never see any evidence of lead buildup in the guides or stems. In the old days of leaded auto fuel, burnt exhaust valves were somewhat common on certain engines. This seemed to be due to lead buildup between exhaust seat and valve face.

Rotary10-RV · #28 03-11-2009, 11:11 AM

Quote:

Originally Posted by rv6ejguy

I never see any evidence of lead buildup in the guides or stems. In the old days of leaded auto fuel, burnt exhaust valves were somewhat common on certain engines. This seemed to be due to lead buildup between exhaust seat and valve face.

Ross,
I have seen several examples of burned exhaust valves caused by leading of the valve stems in the guides. These were not subies, rather motorcycles, and VW's used in migets, and both in racing applications. Not being a subie expert I'd ask you are they using sinstered iron or typical bronze guides in the late-model Subarus?
Bill Jepson

rv6ejguy · #29 03-11-2009, 11:25 AM

All the Subes I've worked on have cast iron guides. Not sure the guide material would make any difference in this respect. I've never seen a stuck valve on on a Sube either. Would be interesting to borescope a Sube with a few hundred hours of 100LL operation to see if lead deposits are building up on the stems.

rv6srb · #30 03-11-2009, 08:49 PM

I am not sure of the valve grind. I will have to check. Each time I take the heads off I find a layer of something on the piston and heads?? I don't know what it is, but I would think it would be clean after only 75hrs. I was guessing that maybe some lead gets under the valve seat and starts the whole problem. Don't know.

Steve