I am wondering if a reverse turbo set up would be the way to go..... a bypass that keeps the mild turbo out during low rpms but closes at high rpms. This way you can have a torquey high compression motor that goes crazy with the mild boost of extra air when you get on the gas pedal. Keep the nice low end torque but lots of power when you need it.

 

A weird former roommate of mine did close to the same thing by using a boost controller on a Volvo wagon turbo.  The gist was that the boost controller manipulated the waste gate to bleed off pressure as desired, his was fancy enough to make a program similar to a fuel curve.  Mechanical controllers usually have 2 boost levels controlled with a switch, but you could easily turn it down for smog testing

 

Getting a turbo swap smog approved is another story though

Hey Jason, you have any experience with the CA emissions testing? I'm hoping a wideband o2 sensor will help me tune for the emissions testing.

Edited March 12, 20159 yr by rcb280z

One easy small step up in usable power is the exhaust system, apparently.  Shouldn't affect emissions negatively.  If you have a catalytic converter, there might be better flowing newer options out there than the stock unit.  Slightly bigger pipes, new cat, better muffler.

Exhaust isn't new but I have an exhaust header, 2.5" exhaust, a CA approved catalytic converter, and I forget what muffler I have. This stuff is only at the most 5 years old. Have you ever noticed when you are looking for an aftermarket performance cat that it always says either its not sold in CA or only 49 state legal, meaning the same (not sold in CA). I get CA wants clean air but.....I could go on forever on this topic but wont.

maybe get a cat from a calif scrapped S2000

Robert, this may help with emissions

Adjust AFM spring for the higher rpm a/f

Once it is set, adjust the bypass screw in the afm to set the a/f ratio at idle.

Thanks Philip. The 16.0 range is where CA likes the A/F ratio to be. With that said I'm trying to adjust the AFM right now without the wideband and am doing something wrong. I can tell I'm "richer" (not too much) at idle but lean at WOT. I get some "ping" at WOT. I can't seem to find a happy medium yet. Not sure why its so difficult. 

So you are saying the spring is more for WOT? What about the wiper? I think that is where I made my mistake...messing with it. I have been trying to get it right by adjusting all three. Spring, bypass screw, and wiper.

 

Oh, the cat has to have certain info stamped into it. The emissions station will verify this before passing the vehicle. No stamps, no pass.

The spring tension adjusts how much fuel is added as the rpms (air flow) goes up. If the spring is too tight, the wiper will not go far enough and the engine will run leaner. If the spring has less tension, the wiper will go too far and too much fuel will be added.

There is no need to turn the wiper unless it goes too far CW and overshoots the end of the carbon trace when the engine is off.

Set the air bypass to it's middle position when adjusting the spring. The bypass changes can only be read with a gas analyser or A/F meter so don't bother with them until you have an A/F meter.

Hey Jason, you have any experience with the CA emissions testing? I'm hoping a wideband o2 sensor will help me tune for the emissions testing.

 

I do.  I'm not a professional mechanic but I did perform a motor swap on a fox chassis Mustang that required seeing the BAR "smog referee" for a very in depth review.  Ill tell you that more important that your actual output, the smog people are going to test your car to its exact specifications as detailed by the emissions sticker that at least once existed on your car.  The timing and idle speed have to match exactly and every vacuum line must be perfect or you fail the visual inspection before they even probe the actual output, and Im not positive but they might fail you for not having the sticker too.

 

Ok will do. Time to order one.

Oh, the cat has to have certain info stamped into it. The emissions station will verify this before passing the vehicle. No stamps, no pass.

Back in the day you would buy a replacement CAT based on the type and weight of the vehicle so there were like 10 generic options that you could walk into an exhaust shop and have installed.  Now you have to have a CAT with either a direct replacement or CARB executive order (official waiver) declaring that exact CAT is approved for that exact car.  On newer vehicles this is a royal PITA but for cars this old many of the universal CAT's are on the executive order list. http://www.magnaflow.com/02catalytic_converters/02product/shopdisplayproducts.asp?portal=CALIFORNIA&year=1975&make=Nissan&model=280Z&engine=2.8L&splityear=PRE

Here is a quick reference for your AFM position at 4000rpm with the car not moving (thus not a lot of air flowing into the motor as it has no load).

If you hold the motor at 4000rpm the afm wiper should be close to this location: