Well, here's another thread about my emissions... Some of you know the trouble i've been going through with my last two threads about this, but since then I found a blockoff plate that was installed for the check valve and split air selenoid valve that was probably making it worse. Anyways, i took that off and plugged 2 vac nipples that would (i was told) cause air to be pumped into the cat constantly rather than just at cruise. Along with that I also got an S-AFC and in lo-throttle for the test i was running -16 at 1000rpm, -20 at 2000 to 4000 rpm. Last test I failed both idle tests and passed both cruise. But the test i took today I was passing the CO% at idle but not the HC

Last test idle
HC - 1346 CO% - 5.4

This test idle
HC - 399 CO% - 0.15

Limit for idle
HC - 220 CO% - 1.2


So I did make an incredible improvement on the idle. I even made a good improvement on the cruise with 0.02 CO% this time and 69 HC where limit is 1.1% and 160 HC. So what's left to try? Ive tried to fix everything and I'm startin to get stuck. Ive heard that some people say to change the spark plugs every oil change and its been about 1.5 oil changes since I changed mine, but I dont think this could account for all of it, right? What exactly are Hydrocarbons (HC) and where do they come from/what creates or blocks them? One last note, I am running premix now, but from the threads I read about premix and emissions people didnt think it was that big of a deal, is that whats wrong? Thanks for any help or input you all can give me.

 

i dont know what else to tell you about what to fix or what raises or lowers your hc. i know that alot of people around here fall back on denatured alcohol if they cant get theyre car to pass emissions. and once they run the alcohol through it passes no problem

 

yah ive been told that but im not sure i wanna run alcohol through my engine, i mean, it cant be the best thing for it... thats why im trying to do it with things working correctly

 

what about your headers? if that was taken care of sorry I didn't see your past thread about emissions...

 

could that really effect emissions that much? plus i dont have the stock exhaust manifold and my cat doesnt sit in the stock place because of the header, so the exhaust manifold/downpipe wouldnt match up

 

what ratio pre mix are you running

 

1 ounce per 1 gallon

 

have you tried adjusting the idle a/f mixture with the variable resistor on the passenger side of the engine bay by the shock tower?

 

yep, i turned it to as far lean as it would turn

 

the t2 fuel pump might have bumped up the fuel pressure, making you run leaner. Have you ever had the car on a wideband with the safc?

When I had the walbro on my otherwise stock fuel system and tried to pass emissions, my Hydrocarbons were tripple the limit, something like 800. When I put my stock fuel pump back on I passed easily.

 

hmmm really... i was wondering about that, but when i asked before i was told that the TII fuel pump wouldnt make it that much worse i guess i can try that too, i just hate changing the fuel pump, oh well

 

where is the fuel pump anyway?

 

cat and alcohol

 

under the hatch carpet/mat

 

forum lag..

 

HCs are HydroCarbons (basically your gas/fuel).
okay, i'm going to do some visual thinking and see what all i can put together:
Last test idle
HC - 1346 CO% - 5.4 <<well that's horrible

This test idle
HC - 399 CO% - 0.15 <<nice improvement

Limit for idle
HC - 220 CO% - 1.2

HC is your fuel + Oxygen (and other gasses; you dont even mention NOx, another result of combustion, nor CO2).
do you by any chance have your CO2 or NOx numbers?

honestly, to me (a non-professional), it appears you're merely still running rich. yes, there are ways to pass emissions, but sometimes youre cheating yourself. this, of course, isnt always true, but here i would think it is. your system seems to be functioning properly, how else would you have such a great (low) CO%? you need to get rid of those HCs (which is extra fuel). i think you're still running rich at idle. if i'm wrong, i hope someone could explain why.

 

no CO2 or NOx. I have a CO+CO2 % is that what you mean? I also have an O2% but neither of those seem to matter for passing the test, because they say N/A for results

 

weird. in DFW, my test gave the results i believe. its been about a year and a half since i tested it.
NOx is a result of temperature, and HCs affect temp (run richer = lower temps, leaner = hotter) so there's a correlation. CO2 also is a clue to how well your cat is working. and O2 shows how rich/lean you are as well compared with stoich (if i remember right).

 

This doesn't help much for this thread, but I'm just gonna post this neato pic for future use.

 

haha, everything i've been saying in the form of a picture! that is pretty cool, where's it from? i'm sure there's more info where that came from.

 

I've done it (methyl hydrate in my case,) as have many others. It won't hurt your motor. If you put a high ratio of it in, your 7 will idle like **** and be underpowered for the drive in to the test, but that's it.


Your premix ratio could be knocked down a bit. Try 140:1 (13oz / full tank) at your next fill up, which is what I run. Every bit helps, right?

 

Since I'm so close to passing, would running lower premix in combination with alcohol and a full tank help me get to passing? Like putting in the alcohol with everything else?

 

Its from my autotech book, theres about 60 pages in it devoted to how emissions work and emissions troubleshooting and repair.

 

why not try leaning out your idle with the safc?

 

i'm not sure how premix hurts. i dont know the composition of 2-stroke (if its an HC or not). and alcohol wont hurt your engine. dont know what you meant by that. it takes more alcohol to make the same amount of power and i believe to meet the same stoich number (i need a graph of all these facts). but alcohol runs cooler and can make more power in the end (like nitro- which makes ~twice the power as gasoline but requires 4 times the amount to do so). so i would think this slight bit of alcohol would run cooler (less NOx) and leaner (less HCs). thats just my guess.
problem with alcohol is that it has a tendancy to attract moisture which eats through parts of your fuel system. as far as engines, i think its quite a pleasant chemical. i did very little research and found how difficult it is to run alcohol (as the main fuel) and left the idea at that.