News from the engine shop

It's been a long time since I wanted to write this update and the Christmas holidays is perfect for it : )

The main symptom my engine had was typical: corroded lifters and cam lobes. Two lifters were definitely not airworthy:

The source of the metal found in the filter was mainly from the lifters. When reading this article about lifter destruction stages, it is pretty evident that these were in stage #3 and had to be replaced.

Since the cam was not in good shape neither, it also had to be changed. Took the opportunity to switch to a high performance cam (different lobe shapes that modify the lift and duration to optimize valve timing and increases combustion efficiency)

This engine only has 500h since new. The cylinders were inspected at the shop and were found in good condition so it was worth taking this opportunity to proceed with porting/polishing of their induction and exhaust tracts as well as carry out a flow balancing on them. This allows a higher volume, to flow with greater efficiency to and from the combustion chamber, hence producing more power.

While the cylinders were getting ported, the crankcase and oil sump got completely cleaned and painted:

The reassembly was also initiated:

Once the cylinders were back, they went for honing, but this revealed an unpleasant surprise: the inside of the cylinder walls were also affected by corrosion:

The solution for this was to oversize the cylinders by 0.010". This howevers means new, oversized pistons and rings. Here's a shot with the cylinders painted and the new pistons followed by pictures of the final assembly:

Once the final assembly was done, the engine got installed on a test bench with a dyno. They ran it for a few hours and checked twice the oil filter for metal. Thank God nothing was found this time! Testing on site is is nice because the break-in of the engine is actually done at the shop. Dyno results were also interesting: with the high performance cam and ported cylinders, the engine produces about 10% more power at 2700 rpm.

The engine is still in the shop of Aerorecip in Winnipeg; it will be shipped right after the new year! Been working on a new firewall in the meantime which is going to be the topic of my next post.

Happy holidays to all of you my readers! I hope 2018 will be full of happiness and interesting projects for you!

Removal of exhaust wrap

The other day I was driving to the hangar just like I routinely did for the last two years, but when I arrived, I realized I was almost at the end of my to do list (!)

I am waiting for a few small replacement parts that are not critical for first flight. I am also waiting for the availability of the local maintenance shop here in CSE4 to inspect my airplane. Strictly speaking, I could legally take-off, but having a second pair of eyes going through my work is not a luxury imho, especially since I have been closely into it for a long time.

While in waiting mode, I made a little research on the benefits of having fibreglass wrap around the exhaust. The wrap I have was installed when I bought the airplane, but it was getting very dirty and hairy.

I found this thread on the Vans Air Force forum which pointed to the Vetterman Exhaust website. Here is an extract of the website in question:

Can I wrap my exhaust with automotive type of wrap material and obtain more power? 

Any material on the exhaust will shorten it's life and failure will occur. We are using air cooled engines and one the best heat sinks on the engine is the exhaust system. The mass air flow comes in and is forced down and around the cooling fins and then is directed over the exhaust system and then exited out the bottom. If the exhaust is covered it cannot aid in the cooling process. Our tests show that any type of wrap on the exhaust makes both the cylinder head and exhaust temperature run higher. The stainless steel used (type 321) will degrade if the surface temperature is over 1250 degrees F. We also did not find a power increase of any kind by wrapping the exhaust.

More weight. Less cooling, no additional performance. Hmmm.

I also checked pictures of the Red Bull Air Race airplanes and confirmed that they don't use such exhaust wrap. I guess if it was creating any major power increase, these guys would use it!

The other reason a previous owner could have needed to use such wrap is perhaps to limit heat radiation in the bottom cowl. I never had any oil temp issues in this airplane...

I finally decided to remove the wrap, but keep a close eye at my oil temp during the first few hours of operation. 

It was a mess. At some point I had to put a mask to avoid breathing all the fiberglass dust flying around. Some guys say that exhaust wrap also traps moisture. What I found underneath tends to confirm this:

It was only surface corrosion that could easily get wiped off, but still... Here's what the whole thing looked like once removed from the airplane:

I was expecting to save about 1/2 lb, but with all the steel clamps, it was weighing close to 1.5 lb!

Finally I cleaned the exhaust using water with mild soap. This was enough to remove most of the old wrap traces. Looked nice and clean at the end.

What could I do next? Perhaps getting some dual time on a nice red S2C would be a good idea!