When my car was stock I got false knock when I went WOT. After bolt ons and headers it was worse. At this point the timing was stock, my fuel injectors were cleaned and flow matched, and my laptop showed no lean condition. If I went WOT @30mph, I would see 20 degrees of knock retard, and it would slowly go down to 0 at around 45-50. If I went WOT at 50, I would see 20 degrees of knock retard that would again slowly go down to nothing. After my H/C/I swap it was even worse.

I got my new chip after the H/C/I, and replaced my KS. I was seeing 6 degrees of retard now at WOT. I figured this was accurate. Well I got the bin file from my chip and it's set to not have more than 6 degrees of KR at WOT. The chip has my timing at 31 degrees at WOT (minus the 6 it's pulling I take it?). I was told AFR's like around 34 degrees of timing.

So for the heck of it (just a test), I set my WOT timing to 34 degrees, and zeroed out my knock retard only at WOT. All I have to say is WOW. Night and day, like I added 50 hp to my car. To the point I was breaking the tires loose at 30 mph, and kicking the rear end out on the shift into second which it NEVER did before. And the car shifts 1000 rpm too early due to the stock shift points!

I was told by some locals that the KS is not an accurate tool when you're heavily modded, and to check my spark plugs to look for detonation. I'm just curious to what you guys think of this? Sorry for the long story.

 

Yes, look for pepper flecks on the porcelain center cone. That is a sign of detonation. May need to put a new set of plugs in first. Be sure to R&R them with the heads cold and they are the 3/4" reach plug (such as Autolite 3922 or 3924).

As for the knock system, if it is false knock there are a bunch of items that can cause it. Any sudden change in drive train noise will trigger it. Such as an auto down shifting. Then any high level of noise can trigger it. Bad bearing in an accessory will also trigger it.

Exhaust rattles, every so slight, are a prime false knock generator.

Can also be caused by the knock sensor being too tight. Torque is 11 to 14 ft/lbs. If still running the '7165 ECM can also swap ESC modules (knock filter) for others. Being separate this is an advantage. Can try the latest truck filter, labeled HKR. Or even an early CCC based filter from a 3rd gen.

Some folks just do away with the knock retard and call it a day.

RBob.

 

I just set up my puter to max on sound. So now when I shift manual I hear the KC at every shift. My tranny is clunky to say the least. Someone posted the 4.3L sensor is less sensitive. All of my KC's I believe are mechanical. I seldom see them over 3200 rpms. I recall pulling SA there once or twice before.

I just studied my most recent log this am. It appears the K occurs just B4 I shift? Maybe that is SA related. I pulled another 1 deg where the KC occurred.

 

Thanks for the reply. I really appreciate it. It was always when my tranmission downshifted. I can't count how many times I was under the car looking for things that may cause it. Such as a header hitting the frame...etc

I'm really interested to see what this thing can do at the track.

 

My '92 does the same. Doesn't matter if the throttle gets punched or rolled into. When the trans downshifts there are knock counts with the resultant spark retard.

Since I've kept the knock system I reduced the attack rate and increased the decay rate. This way the retard is less and it goes away faster.

Another trick to reduce the sensitivity of the knock detection is to put the knock sensor on a 45* elbow. In plumbers talk use a "street elbow." Threads into the block, then the sensor threads into it. Also try to get an early f-body CCC knock filter.

RBob.

 

Cool. Thanks for the suggestions!

 

Rbob, would you mind taking a look at this datalog of mine? I wonder if this is also a case of false knock. I'm working with a stock tune on the EBL Flash, and I've made no spark advance changes or other performance adjustments to the tune, so I'm hoping most of these knocks are not real.
Aside from new plugs, wires, an air fliter, high performance dist. cap, msd coil and 6a amplifier, my car is stock - an iroc '89 305 tpi with about 155,000 miles on it.

If it is false knocks I'm getting, I'll be heading to the hardware store to find a street elbow. About your suggestion of a CCC knock filter, can the EBL do this?

By the way, I tried the EBL_F_PT bin but the car was pretty week at low rpms. Using the EBL_F_1003 it seems to have a healthy amount of power at all revs. Thanks for all the help!

 

Looks like there is some consistent knock in the 50 - 75 KPa, 3200 RPM and 60 - 70 KPa, 3600 RPM ranges. Odds are it is true knock.

There is also knock at the throttle blips. This could be real or false, as the blips are heavy. And it may be knocking a little or the driveline slack could be causing false knock.

Yes, the CCC filter will work with the EBL. It is located behind the relays next to the brake booster.

RBob.