Black Smoke - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Cheng · 04-18-2003, 10:50 PM

Lately the whether has been fairly good around here, so I took my car out on the free for a joy ride. I notice that when i shift from 3rd - 4th at about 6500rpm. I big cloud a black smoke puffs out from the back firing. Does anyone know how can prevent this from happening again or is it the norm for all SR with 3" exhaust and stright pipe? Running at 10 PSI

AKADriver · 04-18-2003, 11:18 PM

If your BOV vents to the atmosphere, then backfires when shifting under high load (like 3-4) are a normal consequence. If you set up your BOV properly (recirculating) then that won't happen.

It's aided by the lack of a catalyst, which would filter out some of the fuel you're dumping out the exhaust on each shift.

Cheng · 04-18-2003, 11:25 PM

I have a Blitz BOV, it shoots off to the atmosphere. I don't get how would you be able to recirucate the air? Where would the release air go to?

AKADriver · 04-18-2003, 11:30 PM

Back into the intake stream, after the MAF and before the turbocharger. A lot of aftermarket BOVs come set up with a horn, for sound purposes, that won't let you attach a pipe... there might be a kit to allow you to replace the horn with a connector for a hose.

Cheng · 04-18-2003, 11:37 PM

I don't believe the Blitz BOV allows you to be able to do that. It comes with a small blitz sus fliter but that won't do any good.

04-18-2003, 10:50 PM	#1
Cheng Leaky Injector Join Date: Mar 2002 Location: MN Age: 40 Posts: 103 Trader Rating: (0) Feedback Score: 0 reviews	Black Smoke Lately the whether has been fairly good around here, so I took my car out on the free for a joy ride. I notice that when i shift from 3rd - 4th at about 6500rpm. I big cloud a black smoke puffs out from the back firing. Does anyone know how can prevent this from happening again or is it the norm for all SR with 3" exhaust and stright pipe? Running at 10 PSI __________________ 90' 240sx fastback Mods: Sr20DET: (BLITZ: FM/IC, BOV, DOWNPIPE, INTAKE) (5zigen Fireball 3" Exhaust) (Bee R testpipe) (Walbro Fuel Pump)

04-18-2003, 11:25 PM	#3
Cheng Leaky Injector Join Date: Mar 2002 Location: MN Age: 40 Posts: 103 Trader Rating: (0) Feedback Score: 0 reviews	I have a Blitz BOV, it shoots off to the atmosphere. I don't get how would you be able to recirucate the air? Where would the release air go to? __________________ 90' 240sx fastback Mods: Sr20DET: (BLITZ: FM/IC, BOV, DOWNPIPE, INTAKE) (5zigen Fireball 3" Exhaust) (Bee R testpipe) (Walbro Fuel Pump)

04-18-2003, 11:37 PM	#5
Cheng Leaky Injector Join Date: Mar 2002 Location: MN Age: 40 Posts: 103 Trader Rating: (0) Feedback Score: 0 reviews	I don't believe the Blitz BOV allows you to be able to do that. It comes with a small blitz sus fliter but that won't do any good. __________________ 90' 240sx fastback Mods: Sr20DET: (BLITZ: FM/IC, BOV, DOWNPIPE, INTAKE) (5zigen Fireball 3" Exhaust) (Bee R testpipe) (Walbro Fuel Pump)

04-18-2003, 11:18 PM	#2
AKADriver Post Whore! Join Date: May 2002 Location: Springfield, VA Age: 43 Posts: 3,517 Trader Rating: (1) Feedback Score: 1 reviews	If your BOV vents to the atmosphere, then backfires when shifting under high load (like 3-4) are a normal consequence. If you set up your BOV properly (recirculating) then that won't happen. It's aided by the lack of a catalyst, which would filter out some of the fuel you're dumping out the exhaust on each shift.

04-18-2003, 11:30 PM	#4
AKADriver Post Whore! Join Date: May 2002 Location: Springfield, VA Age: 43 Posts: 3,517 Trader Rating: (1) Feedback Score: 1 reviews	Back into the intake stream, after the MAF and before the turbocharger. A lot of aftermarket BOVs come set up with a horn, for sound purposes, that won't let you attach a pipe... there might be a kit to allow you to replace the horn with a connector for a hose.