my car:

90 DX HB
stock motor
MPFI conversion
91 SI ECU
I/H/E
gutted cat

so i failed emissions today, no surprise. anyways, all the results point to running too rich, so im planning on buying a B&M FPR system and an air/fuel gauge. my question is, whats the stock pressure so i can get a baseline, and also, whats the lowest PSI i can go without running too lean and damaging my motor. here in tucson we have to pass the idle AND loaded tests, so i need to be able to run a very lean mixture, but not so lean that the motor is jepardized(sp). oh and i just replaced my plugs, cap, rotor, wires, O2 snesor, fuel filter less than a month ago.

 

umm did you just feel like wasting your money? trying to smog with a guttet cat? umm tyr putting a new cat on and you will pass.
if you want to know the stock fuel presure you have to get a fuel presure gauge and measure it before you put on the B&M FPR.

 

right.....heres a piece of advise, know what youre talking about before you open your mouth. i know plenty of people with b18c swaps in their EFs and EGs that have gutted cats and pass with no problems, so its obviously possible.

 

To get a car to pass with a gutted cat is extremely difficult. If you are in California, be aware that the state has lowered cut points to the bone. The car has to be tuned perfectly !!! Without a four gas analyzer to check emissions, you will be going back time and again and failing.

 

in tucson they only test hydrocarbons and carbon monoxide.

 

disconnect one injector,itll lower the HC and CO.

 

i just went through emissions again with number 2 injector unplugged and i still failed, it helped CO but HC got worse. im probably just going to have to put a cat back in for testing.

 

WHAT????!!! If you unplug a an injector the car will misfire and get much worse! If your worried about HC and they don't test for NOX, just advance the timing until it starts pinging, usually 3-4 degrees advanced more than spec. BE careful though, the car will be running lean and you don't want to drive it fast or like ths very long because it can cause detonation. What are the numbers and the limits?


[Modified by sp, 10:57 PM 11/27/2002]

 

not true,i use an emissions dyno and when you do a test on it like that it does knock the HC and CO down,i just tried it on a 87 maxima and the before and after was a good 20% lower but thats when its spinning the rollers,i didnt try it as a idle test yet.

 

How will emissions get worse if you unplug an injector? You will be pumping more oxygen into the exhaust stream, but no fuel (HC) and no partially combusted fuel (CO). It will help. If you pulled a spark plug wire it would be a different story. But I don't endorse this approach (disconnected injector).

 

but on some cars it wont work,the ecu ends up making the other injectors dump more fuel in when it see its running too lean.Kinda like a safety thing so the exhaust doesnt get redhot and burn up the cat.

 

Yeah, I thought that any car that had an o2 sensor would get worse due to the overcompensation. At least that's been the case on the 4 cyls and V6s i've seen.

 

That may be true. I will have to test the unplugged injector theory next time I run an IM test.

 

Anyways to answer your question, fuel pressure should be 40-47 PSI, stick with 40.

 

oh,and another thing,if the car is running really bad and the HC is way too high and you unplug an injector,its possible itll get it too around normal emissions level and not an overly lean condition where the o2 sensor would go full lean and dump more fuel in....just a thought.

 

damn now thats an idea!