[lhawkins]

Would like to hear from you engine guru's out there on your thoughts about buying investment cast cylinders apposed to the regular cast. It's about $225 extra for the investment cast is it worth the extra coin.

 

[hevansrv7a]

It depends

When I bought my Superior XP-IO-360 I asked them and, in effect, they talked me out of them. If you are going to do high-stress stuff to the engine, then yes else, not worth it. If I am not correctly explaining it, call them and ask. I have found them very helpful.

 

[RV6_flyer]

I am running the first Generation Investment Cast cylinders on a Narrow Deck 320. They are S/N: 8, 9, 10, and 11. They have been flying 9 years and 1,953 hobbs hours and about 1,890 tach hours.

At the time I thought they were worth the extra $1,000 for four extra over the Lycoming cylinders. Sometime in the next two years, I will be removing the cylinders for rebuild. At that time I will know if they were worth the extra money.

From a technical standpoint, the investment cast is a stronger way to fabricate the heads. Superior has a longer warranty on them.

Many shops say the sand cast heads are good for one run to TBO but the investment heads are good for two.Sometime in the next year or two, I will find out if the extra money up front was cheaper in the long run. NO cracks, they get rebuilt. If there is a crack, I buy NEW cylinders.

 

[gmcjetpilot]

info

Here is a good thread I found with a simple search of the forum:

http://www.vansairforce.com/community/showthread.php?t=10433&highlight=superior

There is a lot of good info there and opinions you will want to read the whole thing. Any time you have a casting where you use the AS CAST surface it precision. I forgot all my engineering manufacturing stuff but at this level of casting it is very high quality. Now there is different alloys? Read the thread.

I think if you are asking is it better? They look pretty. There is a lot more to a cylinder than the casting finish. I remember when they came out, there was some talk about the advantage or disadvantage of smooth or rougher cast surface. Those have gone away, but there are difference other than the casting, bust as far as the casting my answer is does not matter, they are all class A-1 precision castings with tight QC and accountability. Now there is art in making them and not all casting houses are the same but not aware that any of the players have an edge in casting technology that has been around forever. I do know the superior jugs weigh more for those pretty outside surface finishes

As far as crack susceptibility that Gary has mentioned, I have not heard that. That is totally new to me. I would do more research. Call ECI, Mattituck and Superior and ask them. Prove it. Not that Gary's sources are wrong, but I would have to see the data. I had taken a pair of Lyc jugs thru two rebuilds and sold them with 4,500 hours service and still going strong. There is no doubt thermal cycles and fatigue gets to any cylinder. At some point they all have to be retired. To say that Superior jugs have longer life potential sounds like any rumor or urban legend. Like all urban legends there may be a shred of truth mixed with wishful thinking and bogosity. It's true that a rough surface is considered to have potential of being a stress concentration or riser. However if the stress is very low it does not matter, the stress is low. The fins are not under a lot of stress. Clearly smooth and de-burred it better, but ECI and Lyc jugs have a specified surface finish. The real stress is in the combustion and valve areas, which are under very high temps and pressures. All those surfaces are machined smooth and de-burred.

I heard that ECI uses a better metal alloys, which can take higher temps than the Superior! Others say the rough surface fins are better for heat treansfer. More rumors and legends may be? Again I am not from missouri but "show me", on both count. When you do charge more for something you have to justify it.


Your other choice is either the Lyc and ECI cylinder. I would look at cost, warranty and the company support. I have nothing bad to say about any of them, ECI has always done right by me. Read the thread above for more info. All the cylinders are OEM or STC'ed as copies of OEM. So their designs are the same except for what the FAA felt was a minor variation. Those minor variations my be a turn on to you. For me its a balance of cost, quality and support. Castings can only be so good. Aesthetics is not a major influence on my engine part buying decisions. Gary mentioned the long warranty, which is good. I also have heard ECI honor cylinders outside warentty. I am so confused, what to do?

 

[bumblebee]

Here is a good thread I found with a simple search of the forum:

http://www.vansairforce.com/community/showthread.php?t=10433&highlight=superior

There is a lot of good info there and opinions you will want to read the whole thing. Any time you have a casting where you use the AS CAST surface it precision.....

Insofar as the thread mentioned above says absolutely nothing about investment casting, allow me to provide some meaningful information.

Investment casting has several benefits vs sand casting, all of which add to the cost of the final product.

Investment casting is virtually finished as it comes out of the mold, whereas a sand-cast component requires machining to achieve final dimensions.

Investment casting is MUCH more expensive than sand casting even when machining is taken into account. It takes a high volume to justify investment casting, and even then only when high precision is required.

COST
1) molds are made of ceramic vs sand
2) "bucks" (original master for molds) are same as finished product
3) finished surfaces rarely need to be machined

Investment casting is normally too expensive for low-volume production. Aircraft cylinders certainly qualify as "low volume".

QUALITY
IC produces fewer flaws due to highly controlled temperatures and metal flow during the casting process. IC molds can be heated to same temp as molten metal prior to pouring.

Cold sand causes molten metal to cool unevenly, creating microscopic defects and stress within the hardened metal.

PRECISION
IC allows higher tolerances and less machining than sand casting due to precision molds.

TBO
As for longevity, investment casting "should" provide a more uniform casting
and therefore a higher margin against cracking. HOWEVER, both casting methods are equally at risk for alloy-related problems (bad mix, poor engineering, etc.)

You can still crack an investment-cast cylinder via shock-cooling and running very lean.

BOTTOM LINE
Invstment casting will NOT make up for bad design, bad alloys, bad manufacturing or bad pilots.

Is IC worth the added cost? For low-time recreational use, probably not. For fleet operators, it's a coin-toss b/c there is a wide tradeoff between upfront and ongoing costs along with much greater wear&tear.

Buy standard-cast cylinders and use the saved money for gas. Keep those CHT's down and don't be afraid to run a little rich. Even at $4/gal, gas is cheaper than cylinders.

 

[lhawkins]

Bumblebee's reply

Now that is the kind of information I was looking for. No BS just the facts. I appreciate that. Makes it all more clear. I think I will go with standard cast.

Thanks

Larry

 

[Superior-Sales]

To invest or not!

Hi Larry, the standard cast will be an excellent choice. In the number of years that Superior has had both types available for Lycomings there has been virtuallty no cracking in either as the heads were beefed up to protect against that. The tensile strength is indeed a great deal higher in the investment cast heads, almost double in fact, but in the real world both have held up equally well. One comment, all heads have to be machined, the original castings are just that and require a great deal of machining before they can be fitted with guides, etc. The surface is indeed smoother, but not ready for installation. Hope this makes you feel better as well!

Knick Curtis

 

[bumblebee]

One comment, all heads have to be machined, the original castings are just that and require a great deal of machining before they can be fitted with guides, etc. The surface is indeed smoother, but not ready for installation.

True. I should've been clearer on that. The "working" surfaces are machined in either case. The difference with investment casting is that tolerances are much tighter, thus requiring less machining than sand cast components. "Outside" or "finish" surfaces are much smoother with investment casting.