Alternate approach to using race gas to validate knock

[righton]

Setup: LS2, cam 227/230, Fast 90, ported 243 heads, headers

I have been experiencing burst knock in the low to mid 4k rpm range. I have lowered the timing to near stock at those rpm ranges but I still have Burst Knock. There is no normal Knock Retard occurring and the Burst Knock is 1 degree or less.

It has been suggested to use race gas to determine if knock is real. Since I am using stock O2 sensors along with a wideband I am concerned that leaded gas may ruin the stock O2s. So, I intend to lower my timing to lower than stock incrementally to see if I can eliminate the burst knock.

Has anyone used this method to determine of Burst Knock is real?


btw, I have altered my Burst Knock Retard vs. Cylair Delta table

[KShef]

unleaded race gas
________
Mb100

[righton]

Sure, you could use unleaded. However, I would like to use a different approach besides switching fuels for different tunes or timing changes.

I would prefer to run a few diferent timing changes without changing fuel each time.

[LSX378]

Burst knock retard is not real knock. It is purely a predictive function based on air flow deltas to try and prevent any real knock from occuring as a result of rapid throttle movements. Though with a cam and resulting intake pulsations it may create enough airflow ripple to cause the PCM to think it is seeing rapid throttle variations.

Not a fan of this for regular street use but if you zero it out it should stop.

[midgetracr]

Run your fuel tank low and add a gallon of toluene. This will raise the octane without adding lead. Toluene has a motor octane rating of 104 and is commonly used as a paint thinner. It is readily available at your friendly Home Depot, Menards or Lowe's. It is also relatively cheap.

[S2H]

as a temporary check you can change the values in the burst knock table so that it would take some extreme circumstances to trigger it, then you will see if its real knock or burst knock..

in which case you can adjust your burst knock tables so that they are less agressive and dont cause burst knock in normal circumstances