Possible tuning related backfire...please help
04-30-2009, 05:27 PM
#1
Possible tuning related backfire...please help Have a backfire & can't tune it out. Checked valvetrain for a collapsed lifter or dropped valve, no missfire code, tried reducing base spark, high octane spark, low octane spark, tried VE table changes, tried different plugs & wires, tried DFCO changes.
I don't know how to correctly reduce injector pulse/output...etc.. Don't know how to correctly make spark dwell time changes.
Winter mods included reducing the length of my exhaust of which eliminated 2 90 degree bends & rear resonators, only bullet mufflers remain. Distance from LT 1-5/8" header collector to exhaust exit is approx. 4 ft per side; 2-1/2" true duals.
98 Software, 30# Accels, 59 psi pressure, AFR 205 heads .560 lift cam. MAF table is calibrated for 85mm intake. Plugs gapped to .044" NGK TR5's. Car was fine prior to Winter storage & exhaust length mods.
I understand that backfires are unburnt fuel in the exhaust. Am thinking that an injector application (pulse timing related) change will help. Also, maybe a spark time related mod..
Comments please
I don't know how to correctly reduce injector pulse/output...etc.. Don't know how to correctly make spark dwell time changes.
Winter mods included reducing the length of my exhaust of which eliminated 2 90 degree bends & rear resonators, only bullet mufflers remain. Distance from LT 1-5/8" header collector to exhaust exit is approx. 4 ft per side; 2-1/2" true duals.
98 Software, 30# Accels, 59 psi pressure, AFR 205 heads .560 lift cam. MAF table is calibrated for 85mm intake. Plugs gapped to .044" NGK TR5's. Car was fine prior to Winter storage & exhaust length mods.
I understand that backfires are unburnt fuel in the exhaust. Am thinking that an injector application (pulse timing related) change will help. Also, maybe a spark time related mod..
Comments please
05-01-2009, 08:02 AM
#2
You can get backfires from the car being too lean on off-throttle as well.
Have you tried adding fuel rather then cutting fuel to fix the situation?
I usually attack these problems on the VE table.
The exhaust changes are most likely the culprit. I hear this on the bikes I tune fairly often. "All I did was change the pipes..."
Have you tried adding fuel rather then cutting fuel to fix the situation?
I usually attack these problems on the VE table.
The exhaust changes are most likely the culprit. I hear this on the bikes I tune fairly often. "All I did was change the pipes..."
