SMOG: Low compression built motor
02-05-2009, 04:34 PM
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SMOG: Low compression built motor
So, all you California folks with their 6 year free ride expiring soon, how are you going to smog your built motors with low comp pistons? Instead of paying the "applicable" fee to "fix" this problem, I have a thought... why not just smog the car in stock trim with the built motor? Yeah, sounds idiotic, but I think the low compression (along with some band-aid fixes) may help during smog, especially when one does not have the time nor the resources to swap in a stock long block just for smog. Here's what I researched so far.
Facts:
1. Low compression pistons have a tendency to decrease the combusting efficiency within the chamber, hence leaving high amount of HC in the exhaust pulse. Note I said "tendency" because that's not always the case as chamber design also plays a role here.
2. Lower octane fuel have lower activation energies, meaning the fuel will need lesser amount of energy to initialize the chemical reaction of combustion.
3. Lower octane fuel have a higher chance of exploding (aka detonation) compared to higher octane fuels. In a respectably high compression ratio motor, the engine must retard the timing by restricting the amount of air introduced into the combustion chamber in order to reduce the amount of detonation the lower fuel produces.
Speculation:
1. Fuel spiked by xylene, acetone or ethanol alcohol produces a "cleaner" burn, according to enthusiasts of different forums. This will help reduce HC emissions for smog but in turn increase other emissions.
So, hypothetically speaking, a retarded lower compression motor fueled by 87 octane spiked by an additive would probably wouldn't have a higher HC emissions than a stock motor, assuming everything works as planned. The downside is that the motor could misfire, basically a failure to ignite, due to lack of compression.
Anyone gone for the tail sniffer yet with a built block? I am very interested and curious to see your results.
Facts:
1. Low compression pistons have a tendency to decrease the combusting efficiency within the chamber, hence leaving high amount of HC in the exhaust pulse. Note I said "tendency" because that's not always the case as chamber design also plays a role here.
2. Lower octane fuel have lower activation energies, meaning the fuel will need lesser amount of energy to initialize the chemical reaction of combustion.
3. Lower octane fuel have a higher chance of exploding (aka detonation) compared to higher octane fuels. In a respectably high compression ratio motor, the engine must retard the timing by restricting the amount of air introduced into the combustion chamber in order to reduce the amount of detonation the lower fuel produces.
Speculation:
1. Fuel spiked by xylene, acetone or ethanol alcohol produces a "cleaner" burn, according to enthusiasts of different forums. This will help reduce HC emissions for smog but in turn increase other emissions.
So, hypothetically speaking, a retarded lower compression motor fueled by 87 octane spiked by an additive would probably wouldn't have a higher HC emissions than a stock motor, assuming everything works as planned. The downside is that the motor could misfire, basically a failure to ignite, due to lack of compression.
Anyone gone for the tail sniffer yet with a built block? I am very interested and curious to see your results.
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