I am also getting high knock readings, like 180 peak. The car seems to be running fine.. So, let me get this straight, the main reason for high knock is the timing being advanced? or is it fuel, or what? I'd like to install a J&S knock sensor, but will this take care of my problem? Will the J&S retard the timing from the PFC?? Also, is the stock knock sensor picking up external noise levels, such as louder noise from exhaust being opened up, ie. downpipe, midpipe?? Will the knock readings generally be higher w/ hi or low intake temps?? If anyone can help answer these questions, I'm sure it would help out many w/ this problem. Thanks a lot!!

 

If your getting readings that high your sensor is probably just loose. I'd try to tighten that first. Maybe pull it out and clean it good then reinstall it. What the knock reading is SUPPOSED to read is knock that could cause detonation but it doesnt really work that great. The J&S might be a good solution but I think Chuck said he wasnt sure if they were really worth the money or not. If your J&S is having to retart timing then you need to tune the car better but it might be a decent safegaurd if it works right. I think the main prob with the J&S is that it only works for the leading rotor.

Yes the sensor might be picking up external noise that affects it.

Yes having extreme air temps either way without any tuning can cause detonation (or knock).

Basically I'd start by making sure the sensor is secure and clean then start going from there.

Have you made any tuning changes prior to this? What map are you running? What mods do you have?

Later,
STEPHEN

 

retard the timing. check if a/f ratios are cool, if not then bring them to what you want. use higher octane gas.

 

Maybe you got some bad gas. After verifying that everything is good, drain the gas, and start with a fresh tank.


Two problems with a J&S:
You will need to run over 12degrees of timing split, 15 would be better.
And, the PFC can show normal knock levels but the J&S will still retard
even when it has the sensitivity set lower than normal.


Both of these have happend to me. The first case will by itself cause pinging when it did not exist to begin with or could not be heard.

 

I also have high readings.
With my car in neutral, if i rev it up past 3K rpms the bar graph looks like its pegged & the peak # is in the 140-150 range.
I was concerned so I retorqued the sensor, no help.
Bought a new knock sensor, from MR. MAZDA, cause the tar/wax **** was melting out.
Also no help.
IM using the base mod map & other than the readings, the car runs great.
The general consensis is to retard the ignition in all the cells above 3K rpms & see if it helps??
If I understand correctly, that wont hurt the motor any, just take away some of the available H.P.

 

Are you still running the base map??? What mods do you have and how much boost are you running? What grade fuel do you run???

Later,
STEPHEN

 

get the highest octane you can get, retard the timing 1 degree just to see what the numbers goes to then.

Tim Benton

 

Regarding J&S, PFC knock disagreement, I've attributed (maybe incorrectly) a lot of it to the fact that the retard monitor is not the same as the PFC knock indicator. J&S has spent some degree of effort to write software which distinguishes other noise from knock. The J&S mike is picking up a lot of stuff which I assume the software decides is not knock and doesn't retard. The PFC on the other hand, just displays noise level. I've also wondered if the fact that the mikes are on different housings makes a difference.

Alan

 

My mods are as listed, I am running Houston 1 maps w/ a couple more bits of fuel added. The other map that is close would be Tim Bentons. Anyhow, the sensor is tight and the problem has worsened since the addition of the midpipe/Air pump removal.. I am running about a 96 octane and run about a tank full in two weeks time, so the bad fuel is out of the question. I replace the fuel filter every 10k so that's out. The air temps here in Seattle have been around 40f-50f outside, so intake temps are relatively low. My coolant temps are about 170f on the freeway and 185/190f in the city. If I attempt to retard the timing, I should retard it in equal amounts to leading and trailing? and what type of numbers are we talking, 1 or 2 digits until it lessons the knock to safer readings? I know not to go advancing the timing, time bomb.. I talked to Mazda, they said there was an update on the stock knock sensor,,hummm..wonder why? I am running a bit leaner than stoich, but not much,, add more fuel?? Like I said priviously, the car runs great, just this damn bar w/ a reading of 180. I can sit idle and blib the throttle and get that reading, up to 2K rpm the readings are cool. Man this is irritating! Thanks for the info guys. I'll try retarding the timing first..

 

is the high number as you blip the throttle or when you let off? Same thing goes for when you are accelerating, what does it display as you are accelerating? Some people have stated that the high number comes when they let off the throttle, why I don't know.

Tim Benton

 

Ummm, the PFC does not have a TRUE knock reading.
It's reading the voltage from the knock sensor, yes, but it's not the
same thing. Ask Eric at Apex.

-Les

 

if you are running basically stock do u need a J & S, or will u encounter knocking problems?

 

Well,, let's see.. While at cruise (freeway speed), I hit the peak hold and it maxed at 150 +/- 10. When at idle, when the throttle is blipped, it will hit 180 on accell, I think.... I have noticed the knock lessons to 3/4 (148?) of max when I am @ WOT for a couple of secs, probably due to the timing retarding itself. I'll let you guys know how it goes. I'm bound to get to the bottom of this.

 

I've had similar readings, thought not quite as bad, on my FD for months now. It seems to be worse when blipping the throttle while going downhill. I am stock except for an M2 DP, Apex'i N1 Dual, and of course the PFC v2. Since my engine seems to run as well as it did the first day I bought the car I just ended up eventually ignoring the knock readings.

 

After getting similarly high knock readings (<100), I tried retorquing my sensor, but apparently I broke the sensor, because now it doesn't read at all. I've just ignored it since then however, without any adverse effects. Keep in mind that all the sensor is measuring is essentially just engine bay noise, it would need some sort of signal processing to distinguish a knock from any other noises, and AFAIK the PFC does not provide this. I believe it even says in the PFC manual that high knock readings do not necessarily mean your motor is detonating.

 

will only take HP away if the setting was too retarded to begin with or just perfect. If you are getting the high knock readings from being to advanced, retarding ignition will give you more power.

 

I always thought you will make more HP with more advance, up until you blow your motor. So if his PFC IS to advanced and not just picking up engine noise, then he'd lose some HP by backing out timing.

Now I'm not sure

Tim Benton

 

if backing out timming means retarding, then no. he would gain horsepower. but I think that is what you tried to say. the pinnacle setting or apex if you will of power IS the point of proper timing, retarding from that point decreases power, advancing from that point looses power and detonation. basically if you ignite the gases too soon(too advanced) it will force the rotor the other way, and bamn no more engine. however, if it is just slightly too advanced then you won't get detonation, but still lack of power, as some of it is trying to rotate the rotor the other way. if it is retarded too much you are not getting as a complete a combustion as possible. in general terms you can tune for timing with a dyno, the point that gives most power is perfect.

oh, I shoudl say we are assuiming that knock is engine knock and not some other noise. for some have stated that just geting more HP out of the motor raises the knock reading. this means that if the gain in HP say was from timming adjustments, we can conclude that in fact Knock is not higher, but lower.