Is there any wisdom / experience out there around how a higher altitude will affect a racing engine, and what changes will likely improve performance from factory settings. Specifically looking at a Nelson LS Q40 deck and head clearances when operating at 3300' above sea level. I have searched the forums and cannot find any guidance.

wkevinm

Your air density at 1000 M (3300ft) is about 90% of S.L. on a standard day. Not really considered high altitude, but when I've raced at even higher courses a .002 - .003 shim came out from under the head. It's not too critical with sport fuels.

you could also run a bigger prop(more pitch) since your DA(density Altitude) will be a wee bit higher than,,, I would suggest to locate a Density Altitude calculator on the web,,, plug the required numbers in,,, choose a prop,,, take notes of the days practice with the calculated DA, props used and go from there. The data you collect will show all


BV

DHG, where are you? You fly up there in that thin air...

I put in quite a few flights on 428, 422, and FAI at about 7500 feet in Mexico City about ten years ago. All three classes ended up with essentially the same setup at used at normal elevations. Yes, the engines made less horsepower, but the props had less air to bite into so it evened out, with RPMs in the same ballpark as at home. Lowering the head seemed to do very little if anything Bob (HighPlains) said, it's not too critical with sport fules The only real difference was takeoff distances were increased, as were turning radius and landing speeds.

More recently, I flew a couple Q40's (Nelson LS) at 4300' field elevation a couple years ago, with density altitude around 5000'. They ran just like they did at Florida, Phoenix, and LA with no changes.

What Gary said.


Kurt in Denver where we fly nelsons in 428. Same setups but down on hp. We all stopped tinkering with them several years. Duane might be doing something in his dungeon, but he's hard to communicate with with all the painting he does in there. He really should open some windows once in a while!