Dave B

Last night I was inspecting the engine mounts on my car because I got bad wheel hop on one of my launches at the track the prior night. While I was looking at my mounts, I glanced at my knock sensor and remembered I had adjusted it's position a few weeks back. I thought to myself, "I remember loosening it, but not torqueing it down". Sure enough when I grabbed the harness, the sensor moved!!! Crap!!! No wonder I could hear some knock when I'd punch the gas from 3000rpms. It took two solid turns to torque the sensor down.

I ran at the track on Wednesday in honest to God 100+ degree heat (14.61@94.5mph). Either the loose sensor could have slowed me down or it could have put me dangerously close to severe knock. I noticed I could only gain 19mph in the final 1/8th where as I usually get 20-21mph. I orginally attributed the lack of topend to the heat and my 17s which I never raced on at the track. Now I'm wondering if the car was experiencing knock because the car pretty much uses 3rd for the final 1/8 and stays in the upper rpms longer which = more prone to extended knock. Oh well.

BTW, I'm happy to report my engine mounts are still completely intact. 7 years old, 98K miles, and 130 1/4 mile passes and they're still happy.


Dave

Jeff92se

iTrader: (82)

Maybe you should try relocating it like the other gentleman did. Might make it less sensitive and not pull your timing back as much. SCC did a write up where their Sentra's KS was WAY over sensitive and made the dyno graph choppy as hell.

kushane

How would a loose knock sensor cause knock?

Dave B

It's purpose is to pick up knock. If it's loose, it might not be able to do it's job (regulate knock) therefore the motor is able to knock badly until the sensor finally picks up the sound. Once the sound is heard, then it does it's job. A loose sensor may also generate false knock when the knock sensor vibrates. False knock is worse because it will run the engine less efficently.


Dave

Blu

iTrader: (63)

well since its fixed go back too the track and see what it runs. Then there will be no excuses on how fast or slow you run

kushane

Agreed! But assuming your KS was was not picking up any knock - then wouldn't your ECU be on it's optimum mapping. Then under ideal conditions, unless you were using a lower grade gas or the environment was really really unfavourable - you should not be knocking in the first place. Does the JWT ECU optimize it's mapping any differently that the stock ECU's?

I agree on what you said about KS picking up false knock (vibration), but then the ECU would switch to the safe table.

My understanding by looking at SteVTEC's data logging was that the ECU would advance timing only upto some predetermined point and under normal conditions - you should NOT be knocking at that point.

Please correct me if I am wrong on this one - I would like to learn more on how this works. Heck - on my first car, I would adjust the timing by flashing the timing light at the pulley and rotating the distributor. The scary part is that this wsa not too long ago and I am only still only 24. Not trying to sound too old school - but this entire ECU deal is new stuff for me..

Dave B

I should, it's 15 degrees cooler out today than it was when I ran. It's only 90 right now


Dave

mzmtg

iTrader: (11)

The KS issues on newer Nissans (Sentras) do not apply to older cars. Nissan changed the signal processing in the ECU for the new cars. This has made them oversensitive. The newer ECUs are much more agressive at retarding timing than the older cars. This is why the Sentras get such erratic performance on bad gas.

MaxSpeedSE

iTrader: (3)

did you ever get to try the difrence between the intakes?

Blu

iTrader: (63)

well thats good news for you if you had planned on visiting the track again today

Dave B

Unfortunately no. I ran with the stock resonator and my hacked airbox setup. Check my "The JWT ECU really does work, even in the heat" post.


Dave