I'm struggling with a problem of spark retard after the knock sensor detecting knock (ex: 22,714 knock counts in 1 min @ 2000RPM) No knock other than 2000RPM range.

What actually causes knock? What causes false knock and how do you determine real and false?

Could a bad opti cause knock?

Thanks in advance

 

Knock is the audible result of two different, but related, phenomina:
Pre-ignition and detonation.

False knock can be from several sources; loose bearings, loose pistons, loose valvetrain, broken crankshafts, etc.

I won't go so far as to say the Opti distributor can't cause pre-ignition, but I'd really doubt it.


Larry
code5coupe

not easily impressed....

 

Interesting. Thanks

 

Jehovah's witnesses.

 

if you are using datamaster, I thought it rolls over at every 250 cts.
is it lean @ 2k? I would throw more fuel at it in that range and or back off the timing in that area or slightly before (ie . 1800rpm)

 

Bear in mind one of the tests of the knock sensor is to tap, lightly, on the block or head with a hammer while watching the timing. If the timing retards, the knock sensor is working. Therefore, it stands to reason that there can be any number of things that can cause false knock, both internally and externally. It could be caused by a loose component of the exhaust system; the infamous engine mount bolt hitting on the (Hooker) headers. Some roller rocker arms, timing sets, etc. can set off the sensor. There is no end to the possible causes. The best way to determine if you have false knock, is to eliminate the real thing. If you still get counts after you have eliminated the possibility of pre-ignition or detonation, you can be confident you have false knock. Caution! Just because you have false knock doesn't mean that you don't have the real thing, too.

RACE ON!!!

 

I just checked my datalog and didnt see any major leaning. The LTerm seemed a little rich and the STerm seemed a little lean. I dont really know much about this stuff.

If anyone wants to see, I posted my Datamaster log HERE. Skip to record #4000 where you see all the spark retard


Here is the link to download Datamaster to view the log

 

Thanks for the info. I think I have noisy RR arms. It ran great for over a year with them before though. Not sure what happened

 

IMO, in general the tune needs to be worked over. Is this a stock tune to begin with?
This is what I see, first the bl's in the low 100's in many areas, and the 1300-2400, range needs works. 1300 -1400' around 40 kpa is rich and is not comping fast enough, hence you see a rich number (bl)as you accelerated to around 1700-1800 +(S.K.starts here ) at 80 -90+kpa. (like wise this was happening above 18k -24k @70-85ish kpa). In those KPAvsRPM areas, the int (short term) is into the upper 140-150's, considering the BL here, the int, is removing quite a bit to try to get 128, even with advance being reduced isn't helping. This tells me it needs more fuel in that area (if I remember you had approx. 24* timing there, not that much IMO). Depending on whats in the tune, it may also need some tweak in the Accel Enrich tables. To get a better understanding, it would be best to get the 13k-14k @40 areas under control first, so that corrections in the higher kpa/rpm ranges would be more accurate. At 3100 @100 kpa it is advanced about 1* to much (or add fuel AFR), even though you are seeing it at about 3400 on the s.knock.
You have a check sum error from loading the tune? I don't think it is entirely responsible for the K.C.(weird overall number). It is also picking up counts in a couple of other places in the normal driving range (1200- 1400 lower kpa )fuel in certain places and leaning it out in others should get it under control. It 's only backing the timing down aprrox. 2* max. which is not that terrible IMO(you really want 0), but everytime it retards timing performance is reduced (bl changes etc.) but it should not be wrecking the motor. Good thing gm had the forsight to use a knock sensor. Hope this helps, are you doing the tune or ??

*edit, Forgot to mention...If I can suggest, when datalogging to work the tune better it would be easier to "see" the areas if you try to hold it at certain ranges which allows seeing the trend/stabalizing (as to then add or take away fuel) to build the tables (goal is being at 128 or close). Seeing the upper kpa is good but I prefer to work it gradually. I started with everything below 1600rpm light accelerater to stay in the 40-50 kpa. range (idle to 1500). This allows building this area first and you can then see some trends. Once a solid table is built there do the same above 1600, and keep gradually adding to the higher kpa (lower vac) ranges. You will still be working the lower table @20-40 kpa., that only from decell from a upper rpm becomes more obvious. Some tweaks of timing to get the "in between areas" that can't always be comped from fuel may then be needed. Then with some safe settings in AFR vs rpm, adjust and tweak timing and fuel for PE (wot). w/AFR meter. sorry for the long post

 

Wow, thanks for the indepth info and taking the time to look at my data log It's going to take me a little bit to figure out what all of that means Thanks again, much appreciated

 

you're welcome and hope it helps you get it done. If I can help further feel free to PM or email me.