Pat Gonsoulin at Lancair put me on to Mike Snow at Snowline. Mike's number is 514 617 1107. He confirmed that the configuration I need is the type Ex-5. It's a crossover system with the two forward cylinders plumbed together and the two aft plumbed together into two tailpipes. They fabricated one for me for $700 several weeks ago and I received it last week. Nice craftsmanship.

 

I just tried to fit it to the engine without success. None of the four pipes fitted. I was as clear as I could be about the the engine type. It's a new Lycoming Thunderbolt  IO360-M1A/B with injector mounted on the front of the sump casting.

 

So presumably there are several variants of sump for forward facing injectors as has been suggested. I just returned it to Mike with photos showing what's wrong, and I'm sure Mike will work with me to resolve this.

 

I understood that crossover exhausts performed best in terms of power with diagonally opposite cylinders plumbed together which isn't what Mike does. I gather that plumbing the two clinders each side of the engine isn't great, and that four separate pipes is another alternative, though it's probably not easy to find space for them. I'm interested in the views and experience of other readers on exhaust configurations, and I'd also appreciate any advice that helps get an exhaust mated to my engine.

 

Chris Skelt

LNC2 N99XP 8x%?