KevinT707

So after reading numerous threads on passing emissions using denatured alcohol, methanol, E85 etc. I would like to try it out because I've failed emissions 3x already and tag has been expired. I already purchased denatured alcohol and intend on trying it out on the CRX. As it sits with the proper street tune it fails 3/3; when I turned the fuel pressure down (via B&M min. 42 psi min.) it passed 2/3 but would still fail HC (which means it's too 'rich'); It's a little over double the allowed amount on HC. So my question is should I try running the alcohol without modifying the fuel pressure at all 1st? and ALL 32oz. mixed w/ 1/4 tank gas?

I don't know the chemical reaction that happens when using denatured alcohol (make engine run lean/rich?) so that's why I want to be safe. Also running on a high-flow cat, never used O2 and has always passed every year (except this) by turning FPR down all the way.

Suggestions, insights, comments please, thanks!

fourthgenhatchB17

You need to include engine modification/management details. Did I read that right, you are not using an O2 sensor?

KevinT707

That's right, have never used an O2 sensor. When I had it tuned they turned that option off but like I was saying it use to pass by just turning the FPR down.

Engine is a LS/VTEC with forged internals (B16 head), and running a Magnaflow high-flow cat.

fourthgenhatchB17

I dont see why they would "turn off" the O2. For now though, hook up a wide band and see what your afr's are at idle/cruise or wherever the rpm/load is when they smog test it. Your cat could also be no good depending on the tune and how long it was ran for. Lots of possibilities here..

KevinT707

I guess they just disabled the O2 when they tuned it & after I converted from OBD0 to OBD1. I don't have access to a wide band. So you think my cat isn't as well as it use to be, is the only choice to replace it then? Also, with the fuel pressure turned all the way down & it still doubling the allowed HC it is IMPOSSIBLE to drive. Confuses me that it puts out this much 'unburnt fuel' yet it's not even enough to get the car moving.

Scott_Tucker

High HC does not mean that it is rich, it is usually caused by a misfire. If your CO is high that indicates it is running rich.

fourthgenhatchB17

Exactly.

KevinT707

Hydrocarbons are a precursor to ground-level ozone, a serious air pollutant in cities across the United States. A key component of smog, ground-level ozone is formed by reactions involving hydrocarbons and nitrogen oxides in the presence of sunlight. Hydrocarbon emissions result from incomplete fuel combustion and from fuel evaporation.

Taken from EPA.gov, and that's also what I read from the brochure given to me at the emissions place too.

Scott_Tucker

I'm not exactly sure what you're getting at. 'Incomplete fuel combustion' means misfires, not 'running rich'.

KevinT707

Eh, well anyway denatured alcohol didn't affect my emissions at all. I'm going to purchase another high-flow cat since I've been using mine for about 5 years now and I've been told that they lose their effectiveness.

Scott_Tucker

Why don't you post the emission readings and we can help you better?

KevinT707

Georgia - This is with fuel pressure turned down all the way too and Passed 2/3.

25/25 Test:
HC- 528 (Reading), 227 (Allowed)
CO% - 0.24 (Reading), 1.47 (Allowed)
NOx - 1439 (Reading), 1678 (Allowed)
RPM - 2200 (Reading), 3000 (Allowed)
CO+CO2% - 13.2 (Reading), 6.0 (Allowed) min.

50/15 Test:
HC- 543 (Reading), 234 (Allowed)
CO% - 0.21 (Reading), 1.32 (Allowed)
NOx - 1517 (Reading), 1839 (Allowed)
RPM - 1988 (Reading), 3000 (Allowed)
CO+CO2% - 13.0 (Reading), 6.0 (Allowed) min.

Scott_Tucker

You said that you had the fuel pressure turned down for these tests and that the car runs like crap. Does it run like crap when you turn the fuel pressure up? Does it ever run perfect?

I am assuming by your NOx readings that you either don't have EGR on this car or that it is disabled?

Your HC is high which most likely means that the car is misfiring. This could be due to a mechanical problem like low compression or a secondary ignition system problem like it has a bad (or fouled) plug or an open wire, or from being lean. Being way too rich could also cause HC to be high but in your case since the NOx is high I would suspect that it is lean. An excessively rich mixture will draw heat out of the mixture and lower the temperature enough that NOx can't be formed.

So I suspect that the mixture is too lean and causing a misfire, there is a mechanical problem, or a secondary ignition (plugs, cap, rotor, wires) probelm. The car either needs to be tuned again or you need to make sure that the engine is sound.

KevinT707

This is WITH the fuel pressure turned down all the way, which causes the car to run like complete crap. It does and is running perfect as it did when I first had it tuned several years ago when the fuel pressure is where it's suppose to be at (fails all 3 in this option though). I'm still running the stock EGR on setup; never messed with it. I maintain my car pretty well and when I notice even the slightest change whether it's a hiccup or lag I always try to figure it out so yes all of my ignition gear is up to date & fully functional.

With an old high-flow cat cause it to spit these #s out? Because it use to pass with this method 3-4 years consecutively after I 1st installed the current cat.

Scott_Tucker

Why did you make it lean to pass? You may be able to get away with a new cat but it's a crap shoot. If your fuel mixture was correct you would have a better chance of passing. Since you are not running an O2 sensor your cat is going to die pretty quickly. Cats need the rich/lean switching that the feedback system provides.

KevinT707

Ah I see, what O2 sensor would you recommend me getting that doesn't cost too much and is it as easy as wiring it in & then turning it on through the ECU (Crome)? I've always had to make it lean to pass or else it never will pass on the street tune.

thedrick101

i could not pass emissions on my car either. I have a 92 civic with a b18c1 in it. The guy i bought it from put a nos kit in it but it was never used. Could i not be passing cause they did something wrong when they hooked up the nos kit? The hydrocarbons were almost double the first time and the last time they were 3x as much. What could be my problem?

Scott_Tucker

You need to post all the readings from the printout or no one can help you

B20Monster

Holy crap. Here in cali, our HC cutpoints are below 100ppm. A new cat should help you pass the emissions, but it's only going to work as a temporary band aid fix. I'd say put on a new cat, get it tested, and when you are done, put the old one back on for the time being. Get the car retuned, with oxygen sensor working. Aftermarket converters don't put up with aggressive driving too much either, thats why its HUNDREDS of dollars less than oem.