QuestionQUESTION: I drive a 98 nissan maxima, is it possible at all to modify the ecu so that the injectors are injecting less gasoline, either by reducing the frequency or the pulse width? i have been told that i could use 2 o2 sensor simulators with variable output in lieu of the 2 o2 sensors before the cat converter, the idea is to send a signal to the ecu that indicates that the o2 concentration in the exhaust is low so the efis receive less fuel. thanks a million, hope you do not mind the unusual question.ben
ANSWER: Ben,
Yes, you have the ability to reduce the fuel by reducing the pulse width via a computer program. But, on Nissan Technosquare is the only one that I know that does it. The oxygen sensor simulators are a better option. Also, the fuel pressure regulator could be used to lean things out. But, you risk melting the pistons if you get around 17:1 air fuel ratio. If you are trying to increase mileage the better bet is a free flowing exhaust and a free flowing air intake setup with something like a K&N airfilter. Other things that can be done to increase mileage are things like under drive pulleys. Reduced rotating mass like lighter wheels (do not exceed 18 inch rims as the rotating mass is moved futher out on the moment arm. High air pressure in the tires like 40 PSI when the tire indicates such. Remove the tiedowns to reduce weight and make sure you are not hauling around excess things in the trunk. Leaning out the mixture is not recommended since you can melt engine parts. The 17:1 air fuel mixture ratio is on the edge and currently you are around 14:1 to 15:1 running at a steady state at operating temperature. So, you are close anyway. Another thing you can do is bump the timing until the car pings and then back it off a degree to keep from knocking the rod bearings out of the rods.
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QUESTION: thank you for your great response. my goal is to install a gasoline vaporizer that will vaporize gasoline by mixing it with air and injecting it into the intake manifold, if you go to www.fuelvaporcar.com you will see that this has been done successfully while operating with a airfuel ratio of 20.The idea is that by running the engine on vapor gasoline we are doing what the otto cycle is designed to do, consequently a lot of fuel is saved while pollutants are greatly reduced. the vaporizer will run in conjunction with the injectors, so my goal is to use as much vaporized gasoline as i can and as little liquid gasoline as possible. should i still be concerned about melting the pistons, can you elaborate on why the pistons might melt? can you also suggest an outfit that makes o2 sensor simulators. Thanks a million. ben
ANSWER: Ben,
I would say good luick to you and if it were me I would have a back up engine. A vapor system has been tried before and is problematic in regards to how the engine responds. This is a major undertaking getting the computer to accept outside fuel not regulated by the system. Interesting to be sure. Oh, the pistons tend to melt at the top ring lands when the fuel mixture leans out too much. But, remember that you are introducing extra fuel with the vapor setup so you might not be attaining a true 20 to 1 mixture.
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QUESTION: thanks for your prompt response. why would the pistons melt? just curious. ben
AnswerBen,
When the air fuel mixture gets really lean the temperature goes above the melting point of aluminum. The upper compression ring area gets really hot and under normal driving can withstand the temperature. But, as temperatures go up the thinnest part of the piston, just above the upper ring land, melts away. Then, there is a driect path to the crankcase. I have seen it where someone was using laughing gas, nitrous oxide, and the piston and cylinder wall actually melted together.
