Superior XP-400 Service Bulletin

[Jim Ellis]

For those who may not have already seen it, Superior Air Parts published a new Service Bulletin, XPB02, on January 14, 2019 that changes the advance timing from 25 degrees BTDC to 20 degrees BTDC.

It also calls for removal, disassembly and inspection of any engine that has flown with the 25 degree timing advance setting.

The XP-382 that I have is not included in the Service Bulletin.

You can read the Service Bulletin by clicking here.

[Walt]

Wow, that's going to be painful for both customers and Superior.

But good for them for jumping in and taking care of it, if it was me, I'd push for a new crank.

Dramatic evidence of what can happen with a "minor" timing change on a high performance engine.

[Jpm757]

No doubt a result of the 2016 fatal RV-8A accident due to a fractured crankshaft in an XP-400. Although compliance not required, good judgement would necessitate the required teardown.

[rv6ejguy]

Timing recommendation is now in line with Lycoming IO-390s.

I'd be very surprised if this crank failure was due solely to too much timing though. Short of long duration detonation, a few more degrees of timing shouldn't put much more load on the crank. They should have a massive safety factor in there. We triple the power output of Lycomings and Continentals at Reno (yes 300% over the stock rating) and they don't break cranks.

I hope Superior ran at least one at full rated power for the full TBO period to prove the design is robust. Anybody know how these were tested and validated?

[N54SG]

Well...

I am almost to 600 hours on my XP-400, serial #2. My data plate says 28 degrees at 3,400. Obviously I have never done 3400, but I did run the engine from when I got it (32 hours) for a fair amount of time at 28 degrees. I ended up backing it off to 25, and later to 23, which is where I have been running it for the bulk of its life. 20 degrees does slow it down a noticeable amount, but also lowers all the temps, which shouldn't be a surprise.

So the real question I have (and have had since I bought it) is why is this engine so freaking good? My talks with different Superior guys over the years never yields much information, although I haven't tried to contact them in a long time. My engine is pre-bankruptcy, back in the Thielert days, and supposedly was assembled in Germany. You can say what you want about how that whole deal went down, bankruptcy, etc.. but the guys knew something because I have the fastest 4 cylinder in my class at Reno for a seriously long time. It, is, awesome. How/why it runs so well is a bit of a mystery. It just runs too well to tear open and find out. Maybe, now I will find out, if I'm supported under this service bulletin. Or...

My engine goes back, and what is returned is a 'stock' XP-400, which would be a real shame. I'll have to think about this one. I'm not sure if I should call them or not. Hmmmm

[F1Boss]

Originally Posted by N54SG

Well...

My engine goes back, and what is returned is a 'stock' XP-400, which would be a real shame. I'll have to think about this one. I'm not sure if I should call them or not. Hmmmm

Life or death, Tom! You gotta get rid of that engine!

[N54SG]

Originally Posted by F1Boss

Life or death, Tom! You gotta get rid of that engine!

I had a feeling a few people would have that opinion. lol

[N941WR]

Originally Posted by N54SG

Well...
.... How/why it runs so well is a bit of a mystery. It just runs too well to tear open and find out....

As they say in (auto) racing, an engine runs its best just before it blows up.

Good luck!

[RV10inOz]

Originally Posted by rv6ejguy

Timing recommendation is now in line with Lycoming IO-390s.

I'd be very surprised if this crank failure was due solely to too much timing though. Short of long duration detonation, a few more degrees of timing shouldn't put much more load on the crank. They should have a massive safety factor in there. We triple the power output of Lycomings and Continentals at Reno (yes 300% over the stock rating) and they don't break cranks.

I hope Superior ran at least one at full rated power for the full TBO period to prove the design is robust. Anybody know how these were tested and validated?

5 degrees has a big effect on peak pressures and the crankshaft torsional loads. Do you measure torsional loads on cranks on your dyno Ross? I would hate to be a crankshaft

[rv6ejguy]

Originally Posted by RV10inOz

5 degrees has a big effect on peak pressures and the crankshaft torsional loads.

Not compared to tripling the BMEP. THAT is a big effect.