Weird misfiring on cold start up + a weird AFC/MAF issue.. (RB) - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

OKR_240SX · 11-09-2008, 11:57 PM

Figured I'd combine those issues into one thread.

Got an RB20. Important mods included GT32, Knockoff Intake Mani (iffy about), Apexi SAFCII ( which I hate ), Tomei Poncams, Deatchwerks 440CC injectors, Megan FPR, and a Z32 MAF. And being monitored by Zeitronix wideband.

Issue 1:
I set the AFC to 2 in 4 out for the maf. but as soon as i applied load to the engine it cuts out and surged like crazy, afr's all over the place and i cant make it to 3000 rpms. I reset the AFC to 1 in 1 out.. the car runs great. Here's my Zeitronix log when tuning in that setting

I've tried a different MAF, ECU, and grounds.

I dont have a EBC or anything right now. So that chart is on only 3 psi tops, due to my exhaust mani and wastegate (I presume). Under boost the afr readings are from 11.5 to 12.5ish, at idle 14.5 to 15.

Issue 2:
From some reason at cold start ups, it hesitant and misfires if I try to drive it, quite bad. I dont have a graph for whats going on with my afr when that happens right now. But I dont think thats it. But if a start the car and let it idle for like 10 minutes, its fine.

I searched and couldn't come up with anything. Possibly wrong wording. If so my bad. But any help is great.

OKR_240SX · 11-24-2008, 10:56 PM

anyone???? still having the problem

steve shadows · 11-24-2008, 11:48 PM

Why do you have an AFC if you hate it?

Have you thought about an L-jetro PFC or a tuned ecu even?

-Either way.

What are stock RB20 injectors? A GT32 turbo would require at least 550 cc imo.

Also your Z maf should not be running so smooth with 1in and 1out settings, is that not the same as stock? Or could it be the RB20 voltage for the RB20 MAF are very similar in range to the Z32 so it runs close to stock when warmed up and in the primary maps, but shitty when in the colder.lower load regions of the startup/warm up side of the map.

Just some things to think about .

Also make sure you have the right plugs (heat ranges and gap).

hayai_240 · 11-24-2008, 11:53 PM

Try setting your SAFC to 4 in and 4 out. I have a rb20 maf on my sr20det and i have it set to 4 in and 6 out.

OKR_240SX · 11-27-2008, 10:58 PM

Quote:

Originally Posted by steve shadows

Why do you have an AFC if you hate it?

Have you thought about an L-jetro PFC or a tuned ecu even?

-Either way.

What are stock RB20 injectors? A GT32 turbo would require at least 550 cc imo.

Also your Z maf should not be running so smooth with 1in and 1out settings, is that not the same as stock? Or could it be the RB20 voltage for the RB20 MAF are very similar in range to the Z32 so it runs close to stock when warmed up and in the primary maps, but shitty when in the colder.lower load regions of the startup/warm up side of the map.

Just some things to think about .

Also make sure you have the right plugs (heat ranges and gap).

I'm saving for Nistune and larger injectors right now. When I started this project tuned ecu's were hard to find (most were Mines for small stuff) and couldn't get the PFC due to cost and if I could I would of just went AEM. Stock size is 270. I'm running 440's and the FPR is set at the right psi, so I'm getting enough fuel for how much boost i'm running. The Voltage to the maf is correct and wired right (I've checked 3 separate times) IDK what the stock setting is for the RB20 maf. I'm keep thinking bout that tho, maybe I still missed something. Just threw a fresh set of NGK "BCPR7ES-11" in, that was the first thing I checked.

- hayai -
I'll try setting it to 4-4 tomorrow (if i can remember before work)

thanks for the input

11-09-2008, 11:57 PM	#1
OKR_240SX Zilvia Member Join Date: Feb 2005 Location: Oklahoma Age: 32 Posts: 189 Trader Rating: (0) Feedback Score: 0 reviews	Weird misfiring on cold start up + a weird AFC/MAF issue.. (RB) Figured I'd combine those issues into one thread. Got an RB20. Important mods included GT32, Knockoff Intake Mani (iffy about), Apexi SAFCII ( which I hate ), Tomei Poncams, Deatchwerks 440CC injectors, Megan FPR, and a Z32 MAF. And being monitored by Zeitronix wideband. Issue 1: I set the AFC to 2 in 4 out for the maf. but as soon as i applied load to the engine it cuts out and surged like crazy, afr's all over the place and i cant make it to 3000 rpms. I reset the AFC to 1 in 1 out.. the car runs great. Here's my Zeitronix log when tuning in that setting I've tried a different MAF, ECU, and grounds. I dont have a EBC or anything right now. So that chart is on only 3 psi tops, due to my exhaust mani and wastegate (I presume). Under boost the afr readings are from 11.5 to 12.5ish, at idle 14.5 to 15. Issue 2: From some reason at cold start ups, it hesitant and misfires if I try to drive it, quite bad. I dont have a graph for whats going on with my afr when that happens right now. But I dont think thats it. But if a start the car and let it idle for like 10 minutes, its fine. I searched and couldn't come up with anything. Possibly wrong wording. If so my bad. But any help is great.

11-24-2008, 11:48 PM	#3
steve shadows Post Whore! Join Date: Aug 2003 Location: LA and OC Posts: 8,202 Trader Rating: (5) Feedback Score: 5 reviews	Why do you have an AFC if you hate it? Have you thought about an L-jetro PFC or a tuned ecu even? -Either way. What are stock RB20 injectors? A GT32 turbo would require at least 550 cc imo. Also your Z maf should not be running so smooth with 1in and 1out settings, is that not the same as stock? Or could it be the RB20 voltage for the RB20 MAF are very similar in range to the Z32 so it runs close to stock when warmed up and in the primary maps, but shitty when in the colder.lower load regions of the startup/warm up side of the map. Just some things to think about . Also make sure you have the right plugs (heat ranges and gap). __________________ Like Me on FaceBook !

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11-24-2008, 10:56 PM	#2
OKR_240SX Zilvia Member Join Date: Feb 2005 Location: Oklahoma Age: 32 Posts: 189 Trader Rating: (0) Feedback Score: 0 reviews	anyone???? still having the problem

11-24-2008, 11:53 PM	#4
hayai_240 Leaky Injector Join Date: Jul 2006 Location: Seattle Posts: 142 Trader Rating: (2) Feedback Score: 2 reviews	Try setting your SAFC to 4 in and 4 out. I have a rb20 maf on my sr20det and i have it set to 4 in and 6 out.