somebody help me detect knock

Bruce Plecan nacelp at bright.net
Tue Nov 21 13:19:22 GMT 2000



>Reading the plugs won't help much if the crank's buried in the road.

That's why you start with low timing and rich, and then work your way up to
making HP.
Using electronics as a crutch will rarely be a winning combo.
How do the really fast guys do it, without a lnock sensor,  you know the
car's like John Force runs?.   Not picking on JF, same holds true for
NASCAR, and alot of other NHRA classes.  They have a known baseline tune
that works and tailor that to local conditions.
Getting a baseline is the *hassle*.

>The thing that killed it was the ACT function adding timing when the NOS
was on.  I pulled extra >timing in my nos program only to have the EEC add
more than I had pulled when the intake went >cold.

You find these problems when you start slow and work up to things
Are you running NOS and a blower?.
Or that program in conjucntion with just the blower for timing control?

> I was hoping I could easilly use a sensor to kill the spark.  How do these
sensors work?

Piezioelectic.
Its a piece of quartz, and when you shake it hard enough it generates a
voltage.

 > Do they use something to convert the sensor's output into something
meaningful?

J+S supposedly has one that works well,

>  I just didn't think it would be a big pain to set one up, MSD sells a
knock alert for just over 100 >bucks.

Big difference from turning a light on to retarding timing (in small
increments) unless you just want to nail 20d of retard and hope that will
save ya.
Bruce


From: Bruce Plecan
Your out of luck.
If your making that HP, and not reading plugs your way over your head IMO.
the oems and MSD use acoustic devices, they are not absolutely fool proof.
They just listen for a noise that sounds about like knock.
Only good system that makes sense to me is the Saab Ion stuff, and that is a
saab only so far.
Lacking anything else though look at the 89 Third Gen Camaros/Firebirds for
one of there K/S and ESC contol module.  Then use the output from that as a
trigger for a light (thru addition drivers)
Bruce

I want to throw together a knock sensor for my mustang.  I have no
experience with them at all.  Anybody know how I should go about this?  What
sensor, where to mount it, how to hook it up etc.  I was thinking about
rigging it up to kill the power to the MSD box.
Next spring I'll be well past the point where knock not only blows the
gasket or pistons, but could split the block.  I'm moving to a T-Trim with
new heads and custom cam.  Add the EEC tuner to the mix and I'm a keystroke
away from accidentally killing the fresh motor.
Even a suggestion as to which sensor I should use and possibly a data sheet
for it would be helpful.
Thanks for any help.

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