well as the title says.... i have put about 25k miles on my car since a rebuild and the other day i went WOT getting onto the freeway and i heard a noise i have never heard before. hard to describe. the closest thing i can think of is rod knock. since that is an impossible noise to hear, i want some input. i immediately got off of it and drove easy the whole way home. it was still driving normal and boosting normal. i didn't drive it for about a week, took it out again, drove it for awhile, got on it and the same noise was experienced. that brings me to about now when i drove it today and couldn't get the noise to happen at about 3 WOT pulls in first second and into third. i had a passenger watch the knock on the PFC and highest it got was 52. i was wondering if that is normal for knock reading and if you have any idea what that noise was.
thanks for reading this long post and for any input you give.
Charlie

PS MODS: 16lbs boost, streetport, FMIC, supporting cooling mods, ect

 

well it's hard to say if that's normal since knock numbers will vary car to car. Best thing is to do more WOT runs and see what your tends to average for those, then you know if 50ish is your car's baseline and then a 90 or something is what you need to worry about. The manual I think says over 60 you need to start to check the tuning, tighten the knock sensor to spec, etc. but it's been so long since I've seen my old PFC manual that I can't be sure. Hopefully someone who still has the manual or better memory can chime in on that.

Tim

 

Also have the passenger watch the knock readings on a WOT run and see what they are typically for the whole run. If the 52 happens in the same general spot everytime it could be a few cells that need a little more fuel or timing pulled out.

When I was first tuning my car for higher boost my knock was in the low 20's at 20 psi, but around 12 psi on the ramp up I had some cells that were tuned more aggressively, and my knock hit around 43 or so. So make sure the tune is okay throughout the run. I wouldn't say 52 is bad knock but it's more then I would like to see on mine especially if the whole run is say 25 and then one spot hits 52.

Is it at all possible your car was sitting in traffic or in a parking lot, or any situation where the intake temp sensor would have heat soaked, and then you got on it before the AI temps reached a normal temp, and this then created a lean situation?

 

it is possible but i dont remember. i really dont think so. I am not THAT concerned at low 50s, i am more concerned about the noise i heard. it honestly sounded like a piston with an under spec sized skirt slapping the wall. this is my 7th rotary, 3rd of which is boosted and i have never heard a noise like that. i do plan on a single turbo and meth injection in the near future and at that time i will probably tear it down and rebuild it.

 

Hmm, was it definitely coming from the engine? That noise described doesn't sound like knock, usually knock resembles the sound of a can of marbles, and it can be hard to hear in the rotary.

 

engine bay area for sure. knock, not exactly but closest thing to describe. it was a little deeper. but i have no idea because i can not duplicate the noise now so idk....

 

you guys havepfc manual over there?! cant get it here only in japanese!

 

im new to this, is the number of knocks actual knock counts? if so i didnt know the rotary can handle that much

 

i think the knock reading on the pfc is useless.

 

I think I set a new world record... 179! This isn't under boost though. I know I need to add a bit of fuel. I just haven't done anything yet becuase I hate using the commander to "tune" with. New laptop's on the way for some trouble free datalogging....

 

Matty,
Not totally useless since if you know your car averages 50ish on WOT and decel (read engine noise) but then have a 150, I'd be worried about the 150. Granted unless your logging then you won't know what cells to looks for but it gives to something to be aware of..the conditions (hot cold weather, was it 3/4 throttle, WOT, decel etc)

Tim