PFC & Knock Sensor Readings
 

Hi,

I recently bought a 3rd Gen. Management is a Power FC and it has "supposedly" been mapped for the modifications on the car.
When cruising on part throttle, at 2700 rpm (on stock tach - so probably not too accurate), the cat heat light warning comes on. One person I have spoken to reckons that it is knocking badly. Having hooked up his commander, knock levels were registering fairly high (anything between 50 and 120) but even at part throttle cruising off boost.

Now I ant for life of me believe that it is knock..in fact, Im convinved the mic is picking up some other noise.

Basically, I need to know on the PFC, which wire is for the knock sensor so that I can remove it (I would do this electronically if I had a commander/dataloggit - but I dont).

If I remove the knock sensor wire, will it throw the cat heat light on permanantly till I re-connect it?

The other alternative I was looking at was to remove the sensor from where it is located and wrapping it up in rags so it cannot pick up noise. Does anyone know what size wrench it is as I live miles from a tool shop!

I only want to remove it so that I can test the car at the same part throttle conditions and see if it is still throwing the light..

And if I find that the light isnt being caused by knock, what else could it be?

Thanks

Jitesh

Why would you remove the knock sensor?? Knowing the read out is important IMO, even though the PFC will not pull timing you should still be aware. I would do a search and find out the normal range for knock sensor readings before you go and remove yours.

Yeah knock readings are particular to each car. I have read that Knock sensors can become loose and throw off some wild readings. If I were you I would go easy on the car and not boost it. If your knock readings are accurate, and they are high, you could blow you motor. Get the car tuned or at least hook up a wideband and verify that your AFR's are safe throughout the boost range.

During cruise, off boost, I see normal knock readings up to 40, usually around 33. My car is tuned for 11.2-4 AFR at WOT 10.5 AFR past 14 psi. Based on my datalogit readings my knock levels at WOT under boost (15 psi) stay below 20, usually in the teens. However, when I am driving around and doing freeway blasts going through the gears 3rd through 5th, I often see high knock readings between 40-69, sometimes 80. I am only guessing here, but I believe that the higher readings are caused by drive train noise, shifting, the blow off valve releasing pressure etc. Although, It still freaks me out when I see high numbers

Do a search on how to check your Knock sensor. Make sure it's working properly and then get to know what is normal for you car.

You can disable the knock sensor warning with a commander. Since you didn't quote any #'s I assume you don't have one.

Either way. The PFC doesn't retard spark, like the stock ECU. I t just displays the value.

No harm done other than the light.

I peg my sensor at cruise speed between 3-4K rpms (no load).

Interestingly enough, under boost from 2K on up the #'s stay low.

OK, as I understand it, there are 2 reasons for knock. First is AFRs running too lean, the second is over-advanced ignition timing.

What I want to know is, are there reasons why low-ish compression (say 6.4bar, 6.5, 6.5 @ 283rpm (note the higher rpm) on the front rotor) would cause knock. What I want to basically know is, If the engine has been built somewhat to a budget, is it going to affect the knock. Ive thought long and hard about it, and I cannot see how it might do that.

Or if I give my car to be re-mapped, will this solve the problem once and for all?
Once its mapped on AFRs and EGTs, I should be able to set a higher threshold for the light to come on right?

Basically, what Im asking is, If i get the AFrss and EGTs checked out and the car mapped correctly, can I safely assume that I wont blow my engine due to knock!!

Thanks