Rotary Engine Audio Knock Detection

Hi Everyone,

First time posting, I've tried to search for this (I'm not too great at searching the forum for terms with more than 1 word, any tips here would also be appreciated! 😂)

Getting ready to tune my first rotary, as Andre says in the course, if you're hearing knock on a rotary its probably already too late,

And I do plan on sticking to conservative timing, and monitoring egt's for if it's too too retarded,

That being said I still think using knock detection is a good backstop as you never know might get super lucky and save the engine,

For those who have heard it, does knock in a rotary have the same 'popcorn' 'pinging' sound that piston engines do?

Plenty of examples of piston knock audio files on the interwebs but funnily enough no one seems willing to ping the brains out of their rotary engine for the sake of a YouTube video!

Thanks in advance!

Jake

Hi Jake,

as you’ve alluded to I think audio knock detection is a bit too little too late in Wankel engines. Like in piston engines with gear driven valve train and motorcycles, audio knock detection is difficult to get useful data from properly since the noise generated from straight cut gears are pretty similar to early onset knock.

pressure transducers are a better option for Wankel engines but the frequency of firing events means the signal processing is challenging and expensive so rather cost prohibitive.

Hi Scott,

Thank you for the reply,

That would make sense as to why my ECU knock detection is going off even at idle with 4° of timing,

I was hoping that I could listen to the engine confirm there is no knock and apply some filters so my knock sensor could still play a factor in an emergency,

However sounds like that may be very difficult/ nearly impossible without prohibitively expensive equipment to verify?

And therefore I should simply disable knock protection on the ECU?

All of this on the understanding that I am setting an extremely safe timing table and would only consider advancing if I see abnormal spikes in egt (I am individually monitoring egt on each manifold outlet)