PFC - Knock Reading

[ECR033]

I had my PFC tuned recently and the car's been running well, so I've been pretty happy (see here) ....till I noticed something today which got me a little worried. I've been running 9psi since the tune (using Greddy Profec B Spec II), although the car was tuned on 12psi. Just for something different, I ran 12psi when I took the car out at lunch and I gave the car a quick squirt at full throttle in 4th gear (from around 3500rpm) and the knock reading went through the roof to 133. Obviously I backed off very quickly when the engine light came on, although I've done the same thing before at 9psi and the knock reading went to just over 40 so I was a bit shocked when I saw 133 on the hand controller...especially considering that the max knock reading generally stays between 10 - 30 under normal driving conditions.

I just gave the tuner a quick call and he said that my EBC may have overboosted (apparantly Profec B's have a tendancy to do that when you just floor it from low rpm in 4th or 5th) causing the knock reading to go through the roof momentarily. Apparantly there's not too much that can be done about it on the Profec B, although you have additional parametres to deal with this sort of thing with an AVC-R.

Does this sound right? Should I be worried?

I'm not too worried as I wouldn't normally drive like this and the car's been running fine otherwise (I also trust the tuner and went to him on good word of mouth), but I just wanted to post this up to see what other people think...hopefully to ease my mind a little.

Any thoughts would be great - thanks

[Cubes]

Simple.. Do it again and see if the ebc does indeed spike.

Could also be bad fuel, failing fuel pump etc..

Safest way is to pay for a power run.

[GroundRun]

This happened to me as well with my 34. But mine was in 3rd gear. But i've also noticed that this only happens with a slight incline or decline(only happened once with decline) in the road. I havent had time to send the car in for another tune yet so have just decided to stay away from that danger zone.

[Robo's]

If its tuned for 12psi then it should be ok but 133 knock is a little high. The only thing i could think of if he tuned it too 9psi and now the pfc load is in the next level where he didnt tune it, but you say he did. Mine at 15psi was hitting load 15 on the power fc, but now on 18psi, it hits load 16 if you follow the trace. Trace it under 12psi, then have a look at the ignition and fuel maps and see if there is a difference between that load and the load point above it.

[ECR033]

Thanks for the advice Robo - the car was definately tuned on 12psi and the knock reading usually doesn't go any higher than 40-50 even when I give the car a bit of stick (usually stays under 20 when driving normally).

When you say "follow the trace", are you talking about the graphs on the PFC hand controller or am I missing something (which is probably more likely ).

[GunMetalR33]

MASON:

When you go into monitor mode you can select how many things you want to display on the screen at once. You can select trace mode from there, basically it will tell you where you are on the map under driving conditions.

NOTE: you can also set it to save where it has been so you dont have to look at it while driving. Just do a power run, pull off the roads and look at all the balck squares on the map.