Why is FAST data log rpm jagged by 2-300 rpm at WOT?

[S351 R]

Took new setup to track yesterday (427W NA) and data logs show the RPM line to be vary jagged by as much as 300 RPMs between frames as it climbs at WOT in 3rd & 4th. 4th was smooth enough while on the dyno.

Is this simply the result of drivetrain, suspension, and tires 'squirming' under torque? Or is there something taking place in the computer/ignition/engine that is not well? Maybe a clutch that likely just about maxed out?

The runs themselves sounded smooth enough but you could feel that squirm most of the run even with radial road race tires.

Any insight is appreciated.

 

[pacecarta]

how many frames per second are you recording at and how many fields?


if you want better resolution try to limit how many data fields you record to around 14 and increase the frame rate on the recording

 

[S351 R]

Running 11 fields at 15 frames per second. I could go higher resolution or RPM HR, but there is still the issue of the up-down-up zigs associated with the RPM that has me concerned.

Since this log is much rougher under a full drag run vice dyno, my guess is that it is more mechanical, but wanted to see who else may have experienced this and if I need to consider this as an idicator of maxed/slightly slipping clutch or not worry about it.

 

[XXQUICK6XX]

I'm thinking combination Clutch/tire as you mentioned or even a little bit in the suspension since i feel you pry picked up on more hp. . Since on the dyno as you stated it seemed fine and when you applied it to real world it ain't happy.

 

[S351 R]

yeah that's what Im figuring unless someone else has experienced this and it was ignition/computer signal related. I knew that the clutch was a gamble - hate this may be sign that its not gonna make it... This is on Nitto NT-01s with 478rwhp/488rwtq. Guess slicks arent going to improve chances for it.
Thx