exhaust throttle ring - again

I tached my un-throttled TD049 (with a non-SPI cylinder having 2 boosters, that i guess I bought from Bernie) and measured close to 21k. Because my TD051, having a throttle ring on it, but with original SPI cylinder also tachs around 21k, it sort of started to smell that the throttle ring may choke the TD051 even if the throttle openings properly align with the exhaust ports and are fully open.

I removed the throttle ring and widened the openings (making sure the surgery was done symmetrically on both openings and on both ends of each opening) using a small cylindrical file.

When I tached again the TD051 with the thottle thus modified, I ran @ 22,1k (5x4 bblack prop from bernie). My Toucan R/C flies at some 5-10km/h faster as the GPS shows.

Just in case some of you are interested, it was worth the exercise..

Make sure the widening is not excessive i.e. the openings of the throttle ring remain not wider than the circumference of the cylinder between the , 2 adjacent exhasut ports otherwise you will not be open to fully close the throttle and your low idle speed is gone...