Superior XP-400 Service Bulletin

[Gusmax]

Kudos to Superior for the incredible way they are handling this issue! Any guess as to how many engines are being bought back?

Phil

[rv6ejguy]

Originally Posted by RV8JD

Interesting article from a Sun 'n Fun podcast with Superior’s VP of Sales and Marketing, Scott Hayes:

http://flash.avweb.com/avwebflash/ne...-232603-1.html

Interesting but I don't buy the detonation angle since there were failures even with only 20 degrees of advance. IO-390 Lycs aren't breaking cranks even with EIs installed.

Many IEs only advance timing at lower MAP where cylinder pressure is lower anyway.

I'd like to see data on what ignition systems the broken 400s were running. Any mags in that group of engines?

[Full Throttle]

The biggest difference is the bore and stroke...

Bore Stroke

Lyc. 390 5.139 X 4.375

Superior 400 5.250 X 4.625

Not the same crankshaft at all...

[gmcjetpilot]

Originally Posted by RV8JD

Interesting article from a Sun 'n Fun podcast with Superior’s VP of Sales and Marketing, Scott Hayes:

http://flash.avweb.com/avwebflash/ne...-232603-1.html

Interesting detonation causes crank failure. I always thought detonation would destroy the piston first. I have first hand experience. What is the compression ratio? I see they had 8.5:1 standard; 7.2:1 low, and 9:1 (8.9:1) available. 9:1 is too much. You will not have detonation issues at 7.2:1, and will have good margins with 8.5:1. That is why I have a stock O-360-A1A (8.5:1).

Lycoming played around with high CR for years, one example O-235. They had the standard version, 115HP (typical in C-152, Tomahawk, Grumman Yankee). They did make for a time a 125HP high compression engine for a time, but discontinued it, due to detonation. Years later the Grumman Yankee folks came up with STC to put the Lycoming high compression pistons back in. I test flew flight hours off for one of the STC's. I had detonation destroy one of the pistons. I had to make a quick landing at a grass strip with partial power, plane shaking like crazy. There was no indication of issue as the plane was fully instrumented. It just went. The O-235 came in 100HP, 115HP (L2C) or 118HP typically. 6.75:1, 8.1:1 and 8.5:1 were typical compression ratios. The higher compression was 9.7:1, and made 125HP (F2A). Anything over 8.5:1 is too much in a Lyc 4 banger (in my opinion).

That is why I have a stock O-360-A1A (8.5:1). That is a sweet spot. Anything more reduces your detonation margins. I know it can be done with the right fuel, timing, mixture... however reliability is far more important to me than a few HP.

Final report on XP-400 accident with (N838RV) from a crank failure. The report says 215HP. I assume CR was 8.9:1. The report says:
crankshaft had fractured forward of the No. 2 connecting rod journal. Further testing of the crankshaft revealed that the fracture was the result of fatigue cracking. There were no chemical variations or foreign material present in the metallurgical testing. The crankshaft only had 20 hours total time in service, suggesting that initiation of the cracking and the subsequent failure of the crankshaft was almost immediate.

http://www.vansairforce.com/communit...d.php?t=166173

[theduff]

Originally Posted by Full Throttle

The biggest difference is the bore and stroke...

Bore Stroke

Lyc. 390 5.139 X 4.375

Superior 400 5.250 X 4.625

Not the same crankshaft at all...

Typo: The 390 has a bore of 5.319 ( 5-5/16” )
I’ve been waiting for someone to manufacture a set of parallel valve heads with this bore. I know of one set that was prototyped and showed promising results. No substitute for cubic inches !

[Toddsanderson]

SO, Superior is buying the XP-400 back, but what are they offering that is equivalent in performance? I am looking at a newly built RV that had not flown yet. The owner is sending back the 400 and Superior is supposedly sending back a different engine. The owner is not sure what he is going to receive.

Anyone else doing an exchange?

[walter]

I'm not doing an exchange with Superior, instead I had them ship my XP-400 to Barrett to rebuild it into an IO-390.

I removed the (never flown) engine and hauled it to Superior, about 30 minutes away. Scott gave me a tour of the facility. It's a pretty impressive shop and Scott was very friendly. Superior shipped the engine to BPE and they will tear it down and send the cylinders, crank, etc back to Superior for destruction. What's left (case, sump,...) will give life to an IO-390. The baffles, cables, hoses and wiring *should* reconnect to the new engine without major hassles.

I'm about 1 to 2 weeks from tear down at BPE. Unfortunately, the next batch of cylinders from Lycoming won't arrive until July. I'm probably not in that batch but a subsequent one. It's going to be a long wait... In the meantime I'm still waiting on 'the' check from Superior. They are waiting for the tear down to confirm serial numbers. I dropped off my engine on 3/18.

[Toddsanderson]

Interesting. I guess I need to talk to the owner of the plane I am looking at. It is a RV-14 and should have the IO-390 in it. If the "exchange is any less than 210 HP I would not want it. In fact, I'm not sure I would want the Superior engine at all.

[dmattmul]

Any idea the wait time to get a Superior 400 to Lycoming 390 rebuild is ?

[Full Throttle]

Now that the smoke has settled on the XP-400 buy-back program, does anyone have any parts left over. I am looking for a set of xp-400 cylinders. Maybe someone has some that didn't get returned. Any news would be appreciated.