March 2015

Friday, March 13, 2015

DynoTech : Axys 800HO troubleshooting....

Homing in on a few issues--primarily lack of HP on some engines. My cousin-in-law Bill Rogers had that first 85 mph Axys that his excellent dealer traded even-up for their 100+ mph demo sled. The dealer had used the demo sled as a donor--swapping every component possible from one to another--including a new wiring harness and still Bill's original sled runs 85 mph.

This week the dealer removed the exhaust valve operating cable from the motor and tie wrapped the valves open. Now it struggles to get going, but runs 100 mph+ on top end. So that one dyno test line in the graph (Todd's 1200 miler) on this website showing HP flatlining at about 120 HP is probably what was happening with Bill Rogers' machine all the time! Putting 120 HP worth of airflow to a set of clutches calibrated for 155 HP will surely result in underrevving, low MPH operation.

Another clue I picked up talking to some very smart dealer technicians is that some of the slow Axys' pick up speed as throttle opening is reduced! Perhaps if the ECU thinks valves are wide open and are delivering 85 lb/hr fuel flow, and the valves are partly closed the A/F ratio might be 11/1 instead of the optimal 13/1. Then, if exhaust valves are partially open, and throttle is closed slightly, fuel flow might drop some % causing A/F ratio to lean out and make more HP. Testing at part throttle shows identical peak RPM HP at 90% and 100% throttle!

Does that suggest that Todd's low HP Axys is due to exhaust valves not being fully open, or is it poor ring seal from lack of breakin? And does that explain why it took 75 full throttle dyno tests to bring Heath's Axys up 10 HP?

Some of the smart tech people who communicate with DTR suggest their may be an electrical system design issue that causes exhaust valves to fail to fully open initially (like Bill Rogers'), or to gradually close after extended operation at WOT. Could this explain the revs dropping after extended operation at WOT? 

There's more to figure out, more to learn. But as always, this is just a machine.