some people say they are useless because the work under 4000 k rpm.

is it useless, it wouldnt work on higher rpm?

i dont think rotaries detonate under 4k unless some1 tuned it with a gameboy.

 

the stock one probably isn't all that great (at least how the stock one is setup with the ecu etc...) however if you get a knock box like msd that is made to do only that then it is great and will detect even the slightest signs of knock especially when you turn the sensetivity to max.

 

But, as ive heard before, rotaries are rather violent combustion engines. So couldnt normal engine "noise" be mistaken for knock if you were to set your sensitivity level up max? All i know is its better to have more fuel than too little with these problems.. my car runs very rich and ive never had a problem with a 3" exhaust, no cats, and no FCD.

What i THOUGHT was knock turned out to by my crappy tranny making "knocking" noises under full load

 

Has nothing to do with RPM's.. the knock sensor does not care if it is @ 1500rpms or 8000 rpms...knock sensors are a piezoelectric sensor, IE, they create their own voltage through a process of what engineers call vibratory acceleration, basically vibration will cause the sensor to create a certain voltage. At a certain vibration and voltage the ecu will think it is seeing an engine knock and automotically retard the timing to save the engine...that is why a knock sensor is usually just a 1 wire sensor, that sends a voltage...hope that helps...

Dave.

 

thats the sensor on the middle iron ??

 

problem with detonation in rotaries is usually octane of fuels vs internal combustion temps vs boost level. too much boost, too low of octane and too high of combustion temps cause detonation, when detonation occurs it instantly comes on and as well the damage is instant, a knock box won't be able to help prevent the damage already done. a knock box can only help if you have some fool messing with ignition timing curves and getting a bit too serious with them.

 

great explanation!!!

 

Are knock sensors a Most when tuning our turbo II's with EMS?

I know ems's like haltech dont even use a knock sensor.

I plan on getting ZEMS. Does anyone know anything about it using the stock knock sensor for dataloging?

 

talk to jrat about what he does with his msd unit and stock knock sensor. You do not need a knock sensor to tune with however if you are pushing the limmits of the tune and a conservative tune is no where in your vocabulary then yes a knock sensor is prety important to have.

 

The stock knock sensor is ignored after 4kRPM's.
It's documented somewhere.
Mazda R&D realized that the 13B is just too noisy to reliably having a knock sensor active at higher RPM's.
The stock knock sensor system is primarily to prevent detonation and damage from BAD GAS.
You can detonate the engine hard under 4kRPM, and the stock knock sensor (system) cannot prevent it.
BTW, that's all from an SAE ( http://www.sae.org ) published paper...


-Ted

 

is the mds knock worth it

 

It's only a monitor.
It doesn't do any kind of ignition processing (unlike the J&S products).

I've asked about the MSD monitor but only got very limited responses.
I might order one soon myself.
I already have a J&S, so it would be kinda neat to compare them.


-Ted

 

j&s has display as well? does it work fine at high rpm?

 

My MSD box with the stock sensor has served me very well.

 

cool thanks for chiming in! Just for the sake of everyone elses conserns, do you ever get knock alerts because the rotary "burns more violently" than a piston motor?

 

Nope, seems to work very well. One time the engine suffered some problems and got some fairly audible knock, and it lit up that knock alert.

 

nice! looking forward to using it in conjunction with my ai system.

 

ok, guys that use j&S safe guard, what is the reason if knock sensor cant read after 4k.??

 

J&S uses it's OWN knock sensor; it does not use the stock knock sensor.
You need to fine-tune the J&S with an adjustable **** to try and ignore the excessive engine noise at higher RPM's.


-Ted

 

ok, does it sence very mild detonation ? if so it would be a good engine saving tool.

 

When i drive my 90 GTU hard, it usually has a loud "knocking" sound in third gear from about 5.5k until around 7k rpm. Is that the knocking that the sensor is supposed to be sensing? It has done that since I bought the car. It has increasingly gotten better every mod I put on the car. I know that right now my ecu reads that I need to replace my OMP and O2 sensor. Could it be that I need a rebuild at 104k miles? Sorry, I'm trying to steal the thread.

 

You can adjust the J&S to detect "very mild detonation", yes.
It will not save the engine if you encounter sudden, violent detonation.


-Ted

 

the big problem with a knock sensor is other noises in the drive train, most knock sensors are vary sensitive to any kind of "knock". if u have some funny knocking noises from your tranny its gonna sence it, if your clutch is falling apart and makes weird noises its gonna sence it.

 

I personally think, if you're worried about such things, you're better off watching your EGTs and AFRs.

 

where is the knock sensor located.