There's tons of info out there, and I'm not too familiar with Sentras, but would their "knock sensor mod" be a possibility for us.

Basically the knock sensor on their car is sensitive enough to retard timing when it doesn't always need it. Extra mods seem to compound the problem, and dynos have even shown gains from relocating the knock sensor.

Here's some reading:
Some new Knock Sensor info...
Q: Can you elaborate a little as to what the knock sensor does and how to desensitize it? Is the dummy sensor an aftermarket item or just the original one moved and grounded?
Relocating the Knock Sensor

Finally,
Several people talked about buying the KS from the dealer for ~$14 or so. I know ours are wayyyyyy more than that, so what's the deal with that :P
-hype

 

I guess I'm the only one who cares
-hype

 

The knock sensor is essentially an accelerometer that creates a voltage when it experiences shock waves. so the normal output of a knock sensor will be a sinusoidal output with a steady amplitude. When the engine knocks, it will output a sharp spike that exceeds the noraml amplitude (or a preset voltage level). I would think that one way to desensitize the knock sensor is to put some shock (not electric shock) insulating material such as some cardboard or gasket material. Be careful though, if you put too much in there and desensitize it too much, you may end up destroying your engine because it may not be detecting knocks that it should be.

Then again, this approach could be moot because the knock sensor is secures straight through with a bolt will should still transmit quite a bit of the shock. There's only one way to find out though, and that's to try it.

 

Yeah I understand what the knock sensor is and what it does. I believe it's a piezoelectric sensor (microphone) rather than an accelerometer though. Thus any increase in noise which could be interpreted as a knock would cause the engine timing to be retarded.

The idea is that if you know your engine is in good running shape, at the track (or on the dyno) you could disable the knock sensor to get the extra power back (stop the timing retardation). Then under normal conditions you would let the knock sensor do its job to prevent engine damage.
-hype

 

Many if not most accelerometers are piezoelectric.

 

You could disconnect the knock sensor and connect a ~460 kohm resistor to the wiring harness so that the ECU thinks there is a working KS in the loop. This is a good way to determine if your KS has crapped out: if it has, then substituting the resistor will result in an immdediate regaining of low end power that was lost due to timing retard. Use at the track at your own risk.

 

This sounds like an interesting mod. Wouldn't it be great to see a good HP increase with a cheap mod like this? Maybe the VQ is even more powerful down low. =) Maybe the low end that we lose from the intakes are from the knock sensor. Anyone want to try?

 

It will only make a difference if your knock sensor is being triggered by extraneous noise and vibration. I don't think there's much evidence of that in Maximas. We have pretty smooth running engines.

 

I would think the new QR series of engines would be pretty smooth running engines too. Though 4 cylinder engines do tend to have more vibration. I guess I'm just being optimistic. I'd love to get some free horsepower. =)

 

So, an out of spec, ultra sensitive knock sensor can ruin performance, yet not send a code, eh?

The best way to determine a sensor problem is to hook up a OBD II reader with a display and graph screen to the computer and drive the car around. You can see real-time if everything is in spec. Too bad they don't loan them out at part stores.