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Author Topic: Cut out and Crazy Exh pcv oil blowby  (Read 3568 times)

Offline nismo_200sx

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Cut out and Crazy Exh pcv oil blowby
« on: 08:58:14 PM / 06-May-13 »
my ca18det used to shoot out 3-4 qts of oil on one 20-30 second drift run so I replaced the pcv valve now it doesn't do it unless I hotlap the car and hotlap I mean like a continuous 3-5 minute hard drift track session and even then it is only 1/2 qt to a full 1 qt. My engine has 1000miles on the rebuild compression is 160psi up here at 4800 ft of altitude. no leakdown test yet but since it's fresh I would expect 5%. How do I fix this so I don't have to buy new oil every single drift event?

Also I have an s13 redtop sr20det t25 turbo on my ca18det and I can only run 9psi because if I go above 9psi it hits boost cut. I have a walbro 255lph pump and factory ca18det maf do I need to upgrade to a z32 maf? My question is if so should I send the ecu out to get a retune or hookup the z32 maf and trust the blitz chip that is on the ecu board? I cracked open the ecu case and it's a genuine blitz chip on it. That's how I got it when I bought the swap. any ideas? I need more power for drifting now that I have my driving figured out.

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1987 Nissan 200sx

Offline IggyEGuana

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Re: Cut out and Crazy Exh pcv oil blowby
« Reply #1 on: 11:28:36 PM / 06-May-13 »
crankcase ventilation is a disputed topic but what I've decided works for me is routing the crank gases to a ventilated catch can. i dont use the pcv system. The ca18det is kinda odd that it has two valve covers so theres more to consider about the way the air flows. but routing the air from the air/oil separator box (on the side of the block down by the oil filter) to a vented catch can will get rid of most of the oil loss problem. Route all the valve cover lines so they tee together and go to the same catch can. There wont be much flow out of them anymore after routing the block vent away from the valve covers but you still want the top end vented. you can cap the pcv valve or even better remove it and install a plug in its place. The fwd dohc CA has a cool head vent in the middle of the valve covers right behind the timing belt. You could use that to the vent the head instead of the valve cover ports and just cap those or even shave the valve cover ports and baffle boxes off. that would be pretty cool. haved seen a ca18det without the baffle boxes before. The catch can wont collect much oil after rerouting the block vent away from the pcv valve. It'll mostly collect just the blow-by gas content like nasty contaminants and unburned fuel. Stuff you dont want back in the engine oil.

The boost cut issue is more complicated. I had it on my dohc CA too and it pissed me off all the time. my setup was full retard tho with the wrong harness and wrong ecu. Boost cut happens when the ecu PRECEIVES the "load" on the engine to be beyond a preset safe limit. Load is calculated by maf signal, throttle position, and engine speed. as well as the coolant temp and who knows what else the dumbass ecu looks at. I would definetly run the MAF that the ecu wants to see, stock or chipped, whatever its modded for. Be sure the ignition timing is set to 10 or 15 degrees btdc. follow the FSM precedure for setting timing. Good luck after that.
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oh and check out this thread about crank venting
« Last Edit: 11:29:11 PM / 06-May-13 by IggyEGuana »

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