SR Failing Emissions: Computer Spike

[vansrswap]

I swapped in a sr20det into my 1990 240sx. I have a greddy profec 2 boost controller, and a walbro high flow fuel pump installed. I temporarily reinstalled the stock boost solenoid for emissions testing. The only thing missing is the AIV. Everything else is stock on the engine. I put 94 octane in the tank I heard it's needed to run on the proper fuel map.

I'm trying to pass the local emissions called aircare (vancouver bc) and it's failing on everything but Nox (fails HC, cO, idle tests). I have done all the tune up items, cat, plugs, airfilter, oil change, o2 sensor. It's running very rich and the dyno run it shows a spike every 25 seconds of readings off the chart. Does this mean the computer is toast or perhaps does the aftermarket fuel pump upset the factory FPR? Any other sensors that might be causing this emissions spike?

[IanS]

The factory fuel pressure regulators are notorious for running too high of pressure when paired with a high volume pump. Get a Nismo direct fit regulator, and set it properly. The only other thing that would help would be reinstalling the AIV. Without the AIV your catalytic converter will not preheat properly, and it may not be storing enough oxygen.

I would start with the regulator, then make sure your cat is good and hot before going in for the test.

[vansrswap]

I came across something else I didn't mention, the engine came with a HKS bov (older style with a big cone and dome shape in the middle) which is vented and not recirculated. I've heard with the sr20det I need to run a recirculated BOV or else the MAF cannot figure out where the air is going. Is there a way to change my current BOV to a recirculated style? Would this be causing some problems?

My other option is putting the factor bypass valve? back on, is this taking a step backwards?

[IanS]

I came across something else I didn't mention, the engine came with a HKS bov (older style with a big cone and dome shape in the middle) which is vented and not recirculated. I've heard with the sr20det I need to run a recirculated BOV or else the MAF cannot figure out where the air is going. Is there a way to change my current BOV to a recirculated style? Would this be causing some problems?

My other option is putting the factor bypass valve? back on, is this taking a step backwards?

Yes, recirculation will be necessary to pass emissions. You could get a recirc fitting for the HKS, which is what I would do. Or you could reinstall the factory bypass for the test, then take it off afterwards. Thats still not the only problem though, I would definitely still get a new FPR.

[vansrswap]

Thanks!!! I found a thread on how to tune an aftermarket FPR but what PSI am I looking for?

[IanS]

Thanks!!! I found a thread on how to tune an aftermarket FPR but what PSI am I looking for?

I dont remember off the top of my head, IIRC it is 36 with the vacuum line unplugged, and 43 with it plugged in, or may be its the other way around, I cant remember. You could search more, or if you want to know for sure, check the FSM.

[Spegt]

NOx has nothing to fuel with high fuel pressure. On that note its 43psi with the vacuum disconnected. Your high NOx is due to a lack of EGR. You can combat this buy reducing timing. Knock timing back to 8 degrees and lean it out a bit(because the reduced timing will richen the mix). Hope that helps

[IanS]

NOx has nothing to fuel with high fuel pressure. On that note its 43psi with the vacuum disconnected. Your high NOx is due to a lack of EGR. You can combat this buy reducing timing. Knock timing back to 8 degrees and lean it out a bit(because the reduced timing will richen the mix). Hope that helps

He said NOx is the only thing it is passing, thats why I focused on fuel issues.

[Spegt]

Sorry i miss-read. in that case you have a very small margin to advance timing. High CO is directly related to complete combustion, because HC is actually increase with an extreme lean mixture. I would check timing, and fuel pressure. Set all specs to factory. Then pull back timing to 10 deg. And open spark gap to .030.

[vansrswap]

Checked the fuel pressure today, with the vaccum on I was getting a reading of 40-42psi. Is this too high if it should be 36 with the vaccum line? How does one adjust the timing on these engines?

[vansrswap]

Alright I did everything as posted above, with the recirculating BOV and checking timing, and fuel pressure. Still failing aircare with the exact same results. How can I test the computer? Could this be caused by something wrong with the ECU?