TraviZ

iTrader: (2)

I'm only get knock retard in fourth gear wot pulls starting around 3500rpm. I never get more than 2.5 degrees pulled out. I was running 16 degrees at that rpm. I reduced it to 14 degrees and its still showing about 2.5 kr. Do I keep reducing timing until it goes away? This is a baby cammed 5.7 stock exhaust stock 243 heads with vortech blower that makes 10 psi at 6400rpm
Thanks

HCI2000SS

iTrader: (2)

I had the same issue. Are you positive its not a false knock?

TraviZ

iTrader: (2)

No I'm not. That's what I'm trying to discern. I don't feel like filling up with 100 octane yet to rule that out. I will if there is no other choice.
I do l live in California where I only have access to 91 pump gas

joecar

If you keep seeing the same amount of KR even after pulling timing, then possibly you may have to replace both knock sensors and their subharness.

76 has a few locations that sell unleaded 100 at the pump (typically for offroad toys).

TraviZ

iTrader: (2)

The knock sensors are about 4k miles old. The harness is good. I replaced them with gm pieces when I put in the new motor.
I ran another datalog. I did a wot pull in fourth at 3k rpm. At 3200rpm, knock retard jumped to 3(max retard under PE) and tapered to 2.2 when I let of the throttle at 3600 rpm

Is this considered burst knock by chance? Timing was 19, dropped to 16 with the knock retard. Is this too much timing under boost for this Low rpm? I don't recall how much boost I make at that rpm. Around 5-6 I imagine

joecar

Can you hear it knocking...?

Are you sure that you're not going lean...?

Are you sure that oil is not getting ingested (sucked in thru PCV plumbing)...?

There's a rule of thumb for decreasing timing for each psi of boost...

TraviZ

iTrader: (2)

I don't hear it but with a blower, it's not too quiet. I understand the rule of thumb for boost and timing but I bought this car already boosted so I don't know what the original timing values were.. I'm confident in my afr. I have a wideband and my gauge displays 11.3-11.1
Also I have a catch can and all the necessary rerouting to avoid any oil being sucked in.

TraviZ

iTrader: (2)

Update: I removed yet another 2 degrees where I first saw knock. From an original 21 to 17. The rest of the spark table was reduced the same each time too. After 3800rpm my timing was at 10.
Now I have no knock!
So now I'm clean, I'm slowly reintroducing timing one degree at a time until the knock comes back and in only going to reduce timing in that cell area, until I'm good to redline in fourth thanks everyone for your help