I read somewhere that you can mix a gallon of denaturated ethanol (from home depot) in with 5 gallons of regular gas, and greatly improve your chances of passing a smog check. Has anyone heard of someone trying that?

 

https://ls1tech.com/forums/showthrea...55#post4384455

 

My only guess of how this could be true is that when alcohol burns it releases less volumetric gasses which they are checking for than octance+gasoline so it appears the engine is burning cleaner while it is still outputting the same amount of gasses.

In summary, the ratios of gasses in the exhaust are different.

I am guessing this would result in severly degraded power. I don't think it would mess up the fuel lines though.

 

it would result in a leaner mix which would decrease hydrocabons but I think would increase NO?

if it did help any, best to get it checked immediately because as soon as the LTRIMS learn to add more fuel to maintain stoich.. they'll peg at 25% and then set a lean code

 

Are you saying that the computer doesn't understand how to fuel the engine with alcohol so it will get the mix wrong?

 

more like the computer is too smart... when you add alcohol (at least ethanol... I may be 100% off w/the use of denatured alcohol) it makes the mixture less efficient ...

The PCM would normally add say 10 units of fuel.... but if you dilute it, the O2s will detect a lean condition (now you need say 14 units of fuel), cause the fuel trims to up the fuel, if the mixture is too diluted (or rather too inefficient) it will max the fuel trims and set a code


I'm basing my assumption on ethanol based diluting where ethanol is 70-80 % (depending on where you check) as efficient as 100% gasoline (efficiency = power output per unit of measurement)

so when a large quanity of alcohol (assuming similar to ethanol) is introduced to a gasoline mix.... it will cause the mixture to go lean while the PCM determines what the new fuel trims should be.... but if the alcohol makes the gasoline inefficient enough, it could max the trims at 25% and cause a lean code....

This is all theory on my part though.... I don't know how similar denatured alcohol is to ethanol .. and the hydrocarbon part is again a theory ... if alcohol leans the car... then it'd decrease hydrocarbons... but in leaning will increase NO output... (lean = > NO, rich = > HC right?)



remember that ... air intake is a constant... the vehicle can't change the amount of air that's entering into it for combustion.... it can only change the amount of fuel.... decrease the efficiency of the fuel, and not all the air is used for combustion... if not all the air is used then it's a lean condition...

Fuel adjustments react to the O2s.... it can't guess (Reactive (notice a change and fix) vs Proactive (guess a change and fix) vs realactive (WB02 based, fix as fast as the O2 sensor and electronics can respond)

(unless it's a flex vehicle in which case there is a seperate sensor that determines the amount of ethanol in the fuel source and then determines the appropriate values for that mixture to apply to all other fuel related tables)

 

I think this is a solution for an older carbbed car, I remember something about adding a couple bottles of heet to help your car pass smog.

 

First hand experience, it works at least for Carbbed cars, I remember doing it with early EFI systems but not sure... Drive through the emissions test, fail, go into the parking lot, *whistle while you pour*, then drive back in...

 

do you have cats? If the answer is no then I doubt it! Don't they do visual inspections of the car too? IE if you remove the pcv and AIR then they will probably notice that!

I live in Florida so to be honest I really wouldn't know

 

Doesn't Ethanol carry a bit of oxygen with it so that it about evens out as far as the O2 sensor is concerned?

 

well... the issue is the O2 sensors measure stoich ... the issue people have run into when using (or trying to use) alcohol based fuels such as E85 is that stoich for E85 is something like 9.5:1 whereas gasoline is 14.7:1

So in order to keep the mixture stoich with ethanol for example, you need to inject 150% more fuel... the PCM can only swing +/-25% w/the long term fuel trims, so it will eventually give up trying to fix in this example....

However, adding only a small amount of alcohol to the fuel should lean it out enough to reduce the hydrocarbons and still be within the range the PCM can correct for... Not saying that it will definetly work as I've never tried or seen results on a sniffer doing this in an EFI car... but the key will be to not add too much alcohol to the fuel mixture...


(also do to the extra oxygen in ethanol, the O2 sensor will detect an even leaner condition and want to add even more fuel so it won't balance out... abundance of oxygen = not enough fuel to use it all up)

 

If the PCM adds more fuel, will I see a net HC loss?

 

I believe that hydrocarbons are a result of a rich condition... too much fuel... NO is from lean condition (though I may be off on NO)

So when adding the alcohol, the initial effect would be the car would go lean, thus increasing NO and decrease HC ... however as additional fuel is added by the PCM via the LTRIMS not sure if it'd put you back to where you were... or if because of the cleaner burning alcohol if it's lower total HC output...

Hopefully someone can setp in to confirm or deny what I've said... I don't have any first hand experience so this is just thinking out loud basically

 

True story...I have a Ford Ranger 4x4 with the 4.0L V6 in it and I had some problems with the engine...I lost compression in one of the cylinders. Well it turns out that after I noticed the problem I only had about 2 weeks before I was required to get echecked or I couldn't renew my registration. In that two weeks I was superbusy with school and didn't have time to pull the head and figure things out so I just went and had it tested. Turns out my hydrocarbons (unburnt fuel) was through the roof at 10x the legal limit. Whoops!

Me, not wanting to waste money on a Ford at the time, researched different solutions.

What I ended up doing was practically running the tank dry and pouring 2 gallons of denatured alchohol in the tank. Just enough to get to the echeck station and then to the nearest gas station. She fired right up, got me to echeck and got me to the gas station. Needless to say, I passed with flying colors. something lik 1/5 of the legal limit! I was super lucky because the engine started running pretty rough and the check engine light came on as I was pulling out of echeck. If it had lit up 2 minutes earlier when they were testing it would have been an automatic failure.