jeff spahn

Greg at Precision told me my knock sensor was not functioning (taped up and out of the way is how he put it). What is this downside to this. I only run 92 Octane, drive like an old lady (cept when I mashed it and throttle stuck open).
Am I missing out on power. My car kind of feels doggy.

Thanks,

David L. Lutz

Look at post #6 in this thread.

https://rennlist.com/forums/928-foru...questions.html

AO

A non-functioning knock sensor will retard the ignition 6* ALL THE TIME! This is a huge loss of power. It will be slow off the line (I mean really slow) and will not rev as it should.

I'm curious about 2 things.

1. How did he determine it was bad?
2. Why would it be taped up out of the way... there nothign for it to get in the way of.

BC

A working car is a good thing. You keep on saying you drive like an old lady. I hope you are joking.

mark kibort

im wondering if the knock sensor in my car is now working, as i was a little down on power when the Holbert car had this stroker engine. now that it is in the new chassis, the car seems way faster. I wont know until I dyno it, but the only changes were that the new chassis had different coils. possibly, the knock sensor, in the re-install, got it working. I bet the timing change of it not working, might be worth 10hp or so. I dont know. I would be curious to know.

AO

My bet is way more than 10HP. More like 25-30 RWHP on a stock motor.

Vilhuer

Non working hall sensor in all stock S4 lowers hp from 320 DIN to 285 and tq 430 to 400 Nm at crank according of one dyno test we did while back. Ignition is retarded 9 degrees IIRR.

Vilhuer

Why wonder when its easy to test with correct tool like Theo's laptop setup.

AO

ST also works, but I have both.

Vilhuer

Retard is 6 degrees in high load situations when either hall or one of knock sensors is not working.

Vilhuer

I have two on hand, one of each, ST and ST2.

mark kibort

I bet that is going on with my motor, because it feels so much faster now. I would like to just replace the one that didnt get replaced during the rebuild. (my order was on back order and I only replaced one of the two that both looked bad visually) So, has anyone replaced the rear one with the engine in the car and the intake installed? Ive heard small hands can do it, but heck, just getting the MAF hose clamp loosen or tightened is a chore. I wonder how hard it is to get that "rubber U" out of there to get some room to get to that knocksensor bolt.

Vilhuer

Its doable.

dr bob

Yes, I've replaced the rear with the intake in place. It takes small hands and some patience. MAF boot to the throttle is displaced some, and the fittings to the oil vent hoses get twisted around a bit, but it can be done. The original cable routing is not easily used for the new sensor with all the fuel rail plumbing in place on the right side of the engine (pass side on US cars...) . I temporarily ran the new cable around some stuff that was in the way, and will restore the original routing when the intake is off.

Another sensor-related possible cause of low power is the hall sensor at the rear of the right-side can drive sprocket. The diagnostic tool showed it bad, but function was restored by correcting the cable routing of the FOE harness that wraps around the sensor bracket. Turns out the easy way is the wrong way on that routing, and there's enough interference with the Hall sensor that the EZK will finally give up.

Run the plug-in diagnostics and see what's really right and wrong on this stuff.

Tails

I have gained access to the aft and knock sensor without removal of the inlet manifold. + 1 to Dr Bob's post. WYAIT it is a good time to chean up the earth points.

The front knock sensor is also accessable without removal of the inlet manifold, by removal of thermostat housing and the oil filler tubing.

To try and prevent the knock sensors picking up stray noises I have installed split plastic covering over the knock sensor wiring.

Tails 1990 928S4 Auto