Possible False Knock
05-13-2009, 08:30 AM
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Possible False Knock First, some information about my engine/car.
2004 GTO LS1, in a 93 RX-7
Texas Speed stage 2.5 CNC ported 5.3l heads. Milled to 59cc chambers. Stock head gaskets. Valve reliefs cut 0.080". Slightly over 11:1 compression ratio.
LS6 intake manifold, ported stock throttle body
Dual 3.5" intake pipes, running open loop speed density.
1 7/8" long tube headers with 3" collectors, to a 3" x pipe, and 3" true dual all the way out back.
60 lb injectors
Texas Speed (PRC) pushrods, dual springs, and Ti retainers. New LS7 lifters, stock rockers.
Stock bottom end, LS2 chain, LS6 shimmed and ported pump.
ARP rod bolts
I have been getting knock pretty much at the same RPM, no matter what I do with the tune. I have tried many AFR/timing combinations.
I did some testing today. I tried three different timing maps, and did two 3rd gear pulls with each map. The timing maps were identical except they differed at 6000+ and high load. One map was my nomal map, with 25.5 degrees of timing right before it knocks, one was a lower timing set at 22 degrees, and one was a higher timing set at 28 degrees.
I did six pulls total, and looked at the rpm where it knocked, and here is what I found:
RPM----Timing---KR----AFR
6664----22------5.0---12.47
6693----22------5.0---12.49
6655----25.5----1.0---12.50
6667----25.5----4.0---12.48
6699----28------2.9---12.45
6720----28------5.0---12.48
If it were real knock, I would have expected to see some difference between the 22 degrees pulls, and the 28 degrees pulls, but nothing. That leads me to believe that its not actual knock, but some other noise the sensors are picking up on. Do you think it would still be worthwhile to try a few gallons of race gas and see what happens? Can you help point me to where I can desensitize the knock sensors at that rpm range? When you desensitize the sensors, do you get worired about covering up, or not picking up on real knock?
2004 GTO LS1, in a 93 RX-7
Texas Speed stage 2.5 CNC ported 5.3l heads. Milled to 59cc chambers. Stock head gaskets. Valve reliefs cut 0.080". Slightly over 11:1 compression ratio.
LS6 intake manifold, ported stock throttle body
Dual 3.5" intake pipes, running open loop speed density.
1 7/8" long tube headers with 3" collectors, to a 3" x pipe, and 3" true dual all the way out back.
60 lb injectors
Texas Speed (PRC) pushrods, dual springs, and Ti retainers. New LS7 lifters, stock rockers.
Stock bottom end, LS2 chain, LS6 shimmed and ported pump.
ARP rod bolts
I have been getting knock pretty much at the same RPM, no matter what I do with the tune. I have tried many AFR/timing combinations.
I did some testing today. I tried three different timing maps, and did two 3rd gear pulls with each map. The timing maps were identical except they differed at 6000+ and high load. One map was my nomal map, with 25.5 degrees of timing right before it knocks, one was a lower timing set at 22 degrees, and one was a higher timing set at 28 degrees.
I did six pulls total, and looked at the rpm where it knocked, and here is what I found:
RPM----Timing---KR----AFR
6664----22------5.0---12.47
6693----22------5.0---12.49
6655----25.5----1.0---12.50
6667----25.5----4.0---12.48
6699----28------2.9---12.45
6720----28------5.0---12.48
If it were real knock, I would have expected to see some difference between the 22 degrees pulls, and the 28 degrees pulls, but nothing. That leads me to believe that its not actual knock, but some other noise the sensors are picking up on. Do you think it would still be worthwhile to try a few gallons of race gas and see what happens? Can you help point me to where I can desensitize the knock sensors at that rpm range? When you desensitize the sensors, do you get worired about covering up, or not picking up on real knock?
