Detonation and Backfiring Low RPM Help
10-31-2018, 12:03 AM
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Detonation and Backfiring Low RPM Help Hi Guys and Girls,
I am having an issue with detonation at low RPM medium to High Load. Specially at 2400rpm and 0.60 to 0.68 Cylinder Air Mass (20-22* timing). I would post a log but my knock sensors are useless and nothing looks out of the ordinary. My fueling is between .90 - .83 lambda depending on load. No matter how much timing I pull the knock doesn't go away and is definitely audible. From about 2300 to 2600 rpm the engine also backfires out the rear accompanied by the knock. As I said going by my wideband which I have verified against another shows good safe fueling. So far I have changed from NGK tr6 to NGK BR7EF with no change. Tried new leads and coil packs as well. I put a bore scope though the plug holes to see if there is any carbon buildup and the pistons look almost new. No oil, no carbon, no oil consumption issues, catch can doing its job.
Engine Mods
Ls1 383 Stroker all forged bottom end
AFR 230cc V2 heads at 11.75:1 static comp
Custom Cam 248/258 112lsa
FAST 102 manifold and throttle body
E85 Fuel! Test content before use every other tank
HP Tuners Custom OS Speed Density Open Loop tune
Any Ideas? Thanks a lot!
I am having an issue with detonation at low RPM medium to High Load. Specially at 2400rpm and 0.60 to 0.68 Cylinder Air Mass (20-22* timing). I would post a log but my knock sensors are useless and nothing looks out of the ordinary. My fueling is between .90 - .83 lambda depending on load. No matter how much timing I pull the knock doesn't go away and is definitely audible. From about 2300 to 2600 rpm the engine also backfires out the rear accompanied by the knock. As I said going by my wideband which I have verified against another shows good safe fueling. So far I have changed from NGK tr6 to NGK BR7EF with no change. Tried new leads and coil packs as well. I put a bore scope though the plug holes to see if there is any carbon buildup and the pistons look almost new. No oil, no carbon, no oil consumption issues, catch can doing its job.
Engine Mods
Ls1 383 Stroker all forged bottom end
AFR 230cc V2 heads at 11.75:1 static comp
Custom Cam 248/258 112lsa
FAST 102 manifold and throttle body
E85 Fuel! Test content before use every other tank
HP Tuners Custom OS Speed Density Open Loop tune
Any Ideas? Thanks a lot!
11-10-2018, 05:26 PM
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11-10-2018, 05:30 PM
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If you believe I'm not hearing detonation what do you think the noise could be? To me it sounds exactly like detonation. Marbles in a can rattling in the same cells every time. Happens as I drive through 2200-2400rpm, .60-.68 grams in the spark tables.
11-11-2018, 03:36 PM
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What balancer? I've seen balancer cause it before
11-11-2018, 11:55 PM
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11-12-2018, 12:03 PM
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It was kind of what you are describing. Knock I couldn't get rid of even with really good fuel and no timing. Mine was a stock balancer going out. Replaced with ATI and all better. I have never used powerbond, but I actually expected you to say it was a stock balancer.
11-12-2018, 03:13 PM
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It was kind of what you are describing. Knock I couldn't get rid of even with really good fuel and no timing. Mine was a stock balancer going out. Replaced with ATI and all better. I have never used powerbond, but I actually expected you to say it was a stock balancer.