VX270 Plug Checking

[eluminous]

Hi Al,

I was curious to hear your perspective on checking a plugs condition after shutting the engine down at high idle following TH from heavy collective/cyclic flying at 1950HS (Idle Up 3)? We're talking 5-10 seconds of idling.

A number of flyers talk about cutting engines only during high collective climb-outs with the engine under load, but personally I think this is a little overkill. Useful information can still be extracted from plugs after a very brief idle. Realistically, the change in plug condition is going to be very minimal between these two scenarios.

Could you give your thoughts, and explain why?

Cheers
Steve

[Doug Darby]

I agree with your assessment totally..... Flying 3 gassers with multiple engine and pipe configurations I check the plugs almost every flight when I am adjusting for optimum conditions. I try to work it hard for about 45 seconds before landing and shutting the engine down with the throttle trim. As an example, today I put 4 hard flights on the Whiplash 29.5 at different head speeds and each time was able to see subtle differences in the plug color that fit the changes I had made to carbeuration and head speed....

[eluminous]

Thanks Doug for your feedback. What oil are you using and at what ratio?

[Doug Darby]

Pennzoil Fully Synthetic Marine oil at 32:1 For the past 2 years...

[Azalin]

Doug can you post a good plug photo just for example?

[eluminous]

Hi Azalin,

Here's a couple of plug shots Doug posted on another topic I started on VX270tt needle tuning.

https://www.helifreak.com/showpost.p...11&postcount=3

Cheers

[Azalin]

Thanks Eluminous. So the color of the plug in a well tuned motor will be brown?

[eluminous]

No worries Azalin,

Most flyers call it a sort of honey, to golden brown.

I did remove the plug from my engine just after a mishap the other day. The engine was run-in nicely and the plug was starting to show that tan colour. So yes, I guess your on the right track.

Al did say the other day that plug colour can vary a bit depending on type of oil, and fuel you are using. He also recommended cross referencing engine temps with plug colour to find out where a particular engines sweet tuning spot is. Get it running a little on the rich side (so it's four stroking a little) and slowly start leaning the needles a little each flight while checking the temps regularly. Just pick a spot on the head and make sure you check in the same spot every time so it's consistent.

You'll know you've gone too lean when the temps start to change/jump dramatically and when you may hear the engine getting a little "tinny". If in doubt, just er on the rich side a little until you get a feel more for what the engine does and how it sounds under normal flight conditions and under load. What can be a little difficult is that once the engine is properly run-in, it will bog more either side of the optimal carb setting. But It is often difficult to tell if this is lean or rich. So always start from the rich side then "work in" so you can be certain it's not the lean side. Good load tests I find are: Full pitch climb outs, Hurricanes and Tic-Tocs. There are lots of other posts describing different techniques.
If you haven't already, Tom Welsh created two video's (part 1 and 2) of his tuning approach here:
https://www.helifreak.com/showthread.php?t=530528
https://www.helifreak.com/showthread.php?t=530782

There is also some useful info in here: https://www.helifreak.com/showthread.php?t=529820

I'm sure your not a beginner and that you already have a good amount of experience under your belt, so I won't try to preach to much too you.

Not sure if this will help at all? Good luck.

Cheers

[Azalin]

Hey, thanks.