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Old 22-08-16, 14:56   #1
Skweek's Avatar
Join Date: 22-08-16
Location: QLD, Hervey Bay
Car: '86 Red VL SL Turbo
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VL Turbo Backfiring when changing gears.

Hi Guys,

Been doing alot of looking around but can't seem to find an answer. hopefully someone can help.

My VL is backfiring at high RPM when i change gears. now i suspect its just popping from overfueling in the exhaust as i am not running a CAT at the moment. But i just want to run it past you guys first.

Car runs 98 only from BP. Has a big 800x600 Intercooler on the front. 3 inch piping. timing is set at 16 degrees. to avoid pinging. running 80psi fuel pressure using NA injectors and a Chipped stage 3 NA computer. Highflowed Turbo, 3 inch pacemaker front pipe to a hollowed CAT, 2 1/2 Cat back redback exhaust. brand new Sparkies and Leads. New Dist Cap and rotor button. triple checked for vac leaks and and leads in right spot. AFM is set at 1.3v between pins 3 and 4, and 3.5v between pins 1 and 3. idles at 750 ish. Runs between 7 - 8 psi boost. using a aftermarket fuel pressure reg. have an inline tee before with a pressure gauge to show pressure.

Car runs drives amazing no spluttering pinging or lean out issues. (i have a AFR gauge on the dash which sits in rich or just before rich all the time. under full boost comes too halfway). no issues with idles except when cold it hates starting. but once going and warmed up runs like a dream. the rish running thats shown from the AFR gauge is whats making me think its just popping from excess fuel in the exhaust especially since there is no guts in the CAT to burn it off.

Am i right in making this assumption and maybe dial back the fuel pressure a little??
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Old 22-08-16, 16:28   #2
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Join Date: 01-03-06
Location: VIC, Tongala
Car: VE SS Sportwagon, VL Berlina Turbo, VL 5.0 Berlina, Slocus work hack
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Yes - its over fueling
WTB: OEM 17" Holden internationals
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