Check out these dials that go on the HSN

http://rchardware.com/

On the R/C Harware website they have a link to a tuning and tracking sheet. You cant track and monitor your exact settings and and see if you have a performance gain with different dial settings, plugs, fuel, etc.

http://rchardware.com/ntunesetupsheet.html

These dials really help you track the performance of your engine and make precise adjustments. The difference between the "Sport" and "Race" dials are:

"SPORT" After a base tune is dialed, loosen the set screw and
Rotate the Dial until the HSN Reference Point aligns with "3"

Snug the set screw.

When making tuning adjustments, the tuning direction is easy to remember. The higher the number = more fuel (rich) and the lower the number = less fuel (lean). This "starting point" is only an average from engine to engine. Ideally the tuning distance to
"0" is for leaning out the engine to produce maximum power. Turning the HSN all the way to "0" is set to be the upper limit for engine performance and temperature.

Use the tuning dial to record and track HSN settings.

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"RACE" After a racing or base tune is dialed, loosen the set screw and Rotate the Dial until the HSN Reference Point aligns with "0"

Snug the set screw.

As running conditions change, controlling engine temps and performance with exact needle adjustments are more manageable. Use the +/- signs for decisive adjustments for a rich or lean fuel mixture.

Use the tuning dial to record and track needle settings.

they're pretty funky.

In my opinion, they really help especially if you race. It is easier to track and monitor your settings for optimal performance and with the tuning dials, it is easier for your pit person to make adjustments during a race.

I emailed Mark at R/C Hardware about engines not on the list. He said it was hard to keep up with all the new engines coming out these days. Their is only a couple hobby shops in his area and most of their engines are what comes on the rtr stuff. He usually buys the HSN housing for a particular engine on-line but sometimes it's hard to get or not available. He told me he's always looking for new engine info and even to help confirm current engines on the list. This is his way to stay on top of things in case the manufacturer makes changes to the HSN during production. He said send him an email anytime and would be happy cut you a sweet deal on some new engine info. Also if you would like to purchase multiple dials for your rigs or group of friends, drop him line with what you got. He will give a discount.

He seems to be really honest guy to deal with. I've purchased from him 2 times in the last 2 years. They took about 3 days to come from Arkansas to California. He said the dials are uniquely made for each engine or group of engines with similar HSH dimensions. They are very precision made and the engraved tuning scale is superior to any laser etching. The tuning scale is resistant to scratches and scrapes and very detailed making them very easy to read.

A few pics of the tuning dials on my Go Tech 5 port