So before I begin explaining how it is done I would just like to say, do this as a last resort. There have been no reported problems with this method and it also seems to work in piston cars too, but its requires you to run denatured alcohol which is obviously not gasoline, so its probably not the best thing to run in your engine
Always first make sure that all of your emissions equipment are on the car and working, and try it with that.
Ill first give the condition of my car so you guys have a reference as to what kind of car passed.
My car: RX-7 FC3S 1986 S4
Mods: On engine and emissions related equipment.
Small air filter for Airpump
some after market spark wires
And an engine rebuild with less then 10K miles on it. Total mileage is 174K
Royal purple 20W-50 motor oil and filter
Other then that its all mostly stock
(look at my pics for reference)
Problems: Ridiculously high HC and slightly high CO
-It was running with around 300+ PPM of HC (Hexane) passing is 141PPM at 15 MPH and 116PPM at 25MPH
-And was very close to not passing on CO (carbon monoxide)
-Pipe connecting the airpump to CAT was broken so I fixed that.
THE SMOG TEST CHEAT!
What you will need:
-One gallon of Denatured Alcohol. DO NOT get a methyl/methanol based one it will eat away at your seals and or gaskets, get a ethyl/ethanol based one, I bought a gallon at Home depot in the paint section for about 14bucks.
-A gas container filled with gas (this is not required but its comes in handy after the test)
STEP ONE : Drive around for about 30mins or more to fully warm up your engine and expel all of the bad start up gases from your system. Run your gas tank down as low as you can safely do without getting stranded and get to the SMOG station.
STEP TWO: Once there DO NOT turn off your engine. I had a little more then two gallons of regular in the tank so ended up a 25-33% content of alcohol. Its been tried at many varying percentages, any where in between 25% to 100% I was aiming for 50% but I still passed. Its has been observed that the engine stumbles sometimes but mine seemed to have no change at all. I also poured in the alcohol with the engine running. You may want to drive it around the block to get it mixed up inside the tank.
STEP THREE : Pray that it passes.
STEP FOUR : When done with the test use that extra tank of gas to fill her up a bit and get to the nearest gas station ASAP and fill the tank full.
HC 139 PPM at 15 MPH- Passing is 141PPM (kinda close but compared to 300+ is a big improvement and I only used about 25% alcohol)
HC 65PPM at 25MPH - Passing is 116PPM (great numbers here)
CO 0.11PPM at 15MPH - Passing is .86PPM (this is really nice, its actually lower then the ave passing numbers at 0.13PPM for other cars)
CO 0.07PPM at 25MPH - Passing is .66PPM (Thats right! 0.07 way below the allowed limit! and ave of .11PPM)
Well this is all based on what I have read on various forums and also EXACTLY what I have done.
Big thanks to Funkjaw for letting me put my RX on the sniffer a couple times!!! You are a great man!