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Z20E emission control hacks.


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Hi guys, me and my friend Hybridchemistry we intend to run an old busted 1981 200sx (s110) in the 24 hours of lemon. (http://www.24hoursoflemons.com/). If you've missed my "hello" thread, I am new here and I shall post all about this fantastically stupid project in the project thread very soon. So far we've been rebuilding the engine and are looking for ways to cheaply increase power a bit.


Since the 24 hours of lemons rules are very strict on prep budget ($500 max for car + prep) and since we spent already $250 for the car and about as much for gaskets + rings + misc stuff to rebuild the engine, we're looking at um... not much left. :D So when I say "cheap ways of improving performance" I should really say $0.00.


As you all probably know the s110 has the Z20E (lame), NAPZ (LAME!), engine *WITH* injection (SUPER LAME!). To me the thing is a testament to overly engineered, overly complicated, early 80's injected non-sense. But maybe someone in here can prove me wrong? Now if I had more money than sense I would probably buy some mikunis side draft carburetors, rip out the ECU + injectors, add the Z18ET turbo and exhaust, etc... but that would never fly with the lemons judges at the BS inspection and they would slap me 1,000 laps. (and that would be generous of them).


SO! Since this car is NOT intended to be street legal, my idea for now is to take out as much as possible of the emission control system + increase air flow. Now the following is going to give some peoples a heart attack. Keep in mind that I know next to nothing concerning emission control so this is NOT what I actually plan to do. This thread is mainly aimed at getting constructive comments from knowledgeable peoples who know way more than I do and tell me whether those mods are realistic or not. The schematics are taken from the shop manual for the specific year and model for the car and the Haynes manual.


Crankcase Emission Control System.


This mod seems like a no brainer. I am not too sure about the idle screw. It is not present in the 1980 model for some reason...




This also looks like a no brainer.


Fuel evaporation system


WHY can't the fuel system be simpler? Fuel in, fuel out, done? no?


Vacuum control valve


This is really meant to minimize back firing... do I care?


Vacuum switching valve

WTF is this for??? Both the Haynes and the shop manual are very terse about this little guy. delete?


Catalytic converter + muffler

Delete, replace with straight pipe + glasspack. yes?



Edited by KraZ
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The crankcase emission controle has no effect on running or performance. You can run or not but it's time wasted for something more constructive like the exhaust system.


ERG... all you have to do is disconnect the vacuum supply and it won't work. Again easy and quick to disable, no need to waste time removing.


Fuel evap system.... has no effect on running. No gains from removal.


Vacuum switching valve ... just disconnect and plug hose.



There is an idle adjusting screw. It's over beside the MAS on the driver's side.

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Sadly, taking those things off will have less cumulative effect than removing the rear seat cushion. The NAPS-Z isn't a race engine, but it did have one thing going for it over the L-series... no parasitic emissions components (the L-series had the belt-driven air pump).


None of those changes will increase air flow except removing the cat. The ONLY way to increase intake air flow in a Z20E is to replace the intake manifold and throttle assembly with something less clunky and restrictive. In fact removing the crankcase valve-cover breather will probably just make it want to eat gaskets- I'd at least leave the top breather open with a filter. But at worst it could mess with the proper airflow settings and confuse the ECU, which is quite primitive.


The injection system is actually very simple- it's just a batch-fire Bosch L-Jetronic EFI system. Problem is it's tuned for having all that stuff there, and it's not programmable. You can most likely get away with plugging off the EGR system (which I believe that's what the vacuum switching valve is for), and the evaporative system for the tank (you'd HAVE to eliminate it if using a fuel cell anyway).

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Thanks for the input guys. This will definitely help. When I mean "delete" I really mean "not put back on". The engine along with all the emission control contraptions are currently sitting outside the car in pieces. So the less I have to put back together the better. :D Also I don't feel like replacing the zillion crusty vacuum hoses... No one has chimed in on the Vacuum *control* valve yet. It's the little thingy on the intake manifold... what do you guys think?



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The thermal vacuum valve (TVV) does two things.


1/ once the motor warms up it opens and allows a vacuum signal to the EGR. Cold engine = no EGR.


2/ once the motor warms up it closes an air bleed to the vacuum advance line to allow full vacuum advance. Colt engine = retarded ignition.


Disconnect the three hoses and plug them. You now have NO EGR and proper vacuum advance at all times.



The VCV (Vacuum Control Valve) is another control that retards vacuum advance under certain conditions of high carburetor venturi vacuum. Disconnect hoses and plug to disable this system.



Most of this stuff is benign and doesn't seriously affect performance. I think EGR does limit some power making as it's job it to dilute the air fuel (without affecting the 14:1 ratio) by mixing inert (burnt) exhaust to lower cylinder temperatures. True it would reduce ping, but more or less in the same manner as letting up on the gas peddle. Not really an option. If you want power, expect to make lots of heat in the combustion chamber. Deal with it be reducing the timing slightly, cooler plugs or better gas. The NAPS dual plug design runs much less initial advance than the L series because of the shorter burn time with two spark plugs. KraZ I assume your Z20E has dual plugs???

Edited by datzenmike
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