Knock Sensor On Power Fc

[boostED82]

Hey guys,

Has anyone experienced this;

I have a tuned RB25DET with all the usual bolt-on support to sustain a high-flowed R33 turbo with steel wheels at 18psi. After several tunes and re-tunes on the dyno using a Power FC with Z32 AFM, the knock meter on the FC Commander intermittently spikes to 40 - 60 knocks, and on a few occassions 110 when driving spiritedly on the road - however on the dyno the AF ratio and state of tune is next to perfect. My understanding is that anything above 40 knocks is somewhat audible pinging so you should use this threshold as a measure to know when the mixtures are too lean. However, having said this the knocks do not follow a pattern as the knock meter shows knocking at start up, on the odd downchange through the gears, and intermittently when fully giving it shit on full boost and hi rpm. Octane Boost doesn't seem to have a constant effect in curing the knocks so I'm beginning to beleive that my knock sensors are playing up and on the way out.

Can anyone with an R33 or any other Skyline relate to this?

[dan_the_man]

moved to general area

[Robo's]

I have familiar results with my tuned R33 with a HKS 2535 running decent boost. I always get 40 knock on start up.

As far as fixing your problem, its not your A/F ratios that is causing the knock, its the timing. You are probably running too much timing. The only way to trace it, is to use the MAP Trace and finding what RPM you are knocking at. However, i have refused to do this as i cannot hear any ping on my car and the old rule of thumb is to advance it until it knocks and the retard it a little. I've been running like this for over a year now, but ive always got one ear open and one eye on the knock.

Also i have just found that the new Shell Extreme Fuel (100) is reducing my knock, i like it.

[Sydneykid]

Knock sensors are simple microphones, so they pick up stuff that may not be pre-ignition. Things that have made my knock sensors record stuff that isn't knock;

Starter motor

When cold, forged piston knock

Loose knock sensor bolt

Twin plate clutch rattle

Too much tappet clearance

Loose engine mount bolt to block

Loose exhaust pipe

Alternator bearing

AirCon compressor tensionor bearing worn

cheers

[Robo's]

Where is the knock sensor located?

[boostED82]

Aha found my post (it got moved)...

Robo's - you've given me some assurance that my car isn't just gonna fall apart on me. I use it a sa daily driver with the occassional weekend flogging etc. (as you do). I too haven't heard any audible pinging when it claims to have knocked. And also, it's not constant knocking, more so a spike to 40 or 60 for a split second as recorded on the graph mode. As with the startup, apprently it doesn't matter - although still odd. Oh, and in Perth we don't have Optimax, only Ultimae 98 from BP. I'm always running Ultiomate and Octane Boost just to be safe but the knocking is still intermittent wihtou any apparent pattern.

Sydneykid - good to know these extra things. Sometime I think having a knock meter is more trouble than its worth. Especially when you've forked out for a couple of re-tunes on the dyno only to find out that everything is running perfect.

Cheers fellas - good info!