bad mileage
- Thread starter S13<3
- Start date
any ideas, maybe a bad sensor, right now no codes 
homeskillet305
Driver
try cleaning the maf and changing to O2 sensor, also check the timing on the dizzy. you might want to switch to 87 theres no reason for you to use 93.
another thing thats important is your tire pressure under inflated tires decrease gas mileage
another thing thats important is your tire pressure under inflated tires decrease gas mileage
homeskillet305
Driver
maybe cant say for sure, they do wear out though. this is a good way to test it, you could get the exact voltages from the fsm. http://wiki.answers.com/Q/How_do_you_test_an_oxygen_sensor_with_a_volt_meter
your timing seems like i'd be optimal for maximizing hp but not for fuel mileage, i would change it back to stock. on a miata stock timing is at 10* advanced. at low rpms the motor is soo advanced that its working against its self because its building too much pressure while still on the compression stroke. thats the way i see it any ways. for max hp at high rpms thats desirable to give it more time to burn.
yes a bad o2 will drop mileage noticeably especially on the highway.
yes a bad o2 will drop mileage noticeably especially on the highway.
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ive thought about this, its possible because the filter is bigger it drops the fuel pressure tricking the ecu into dumping more fuel to maintain the proper pressure idk
i dont think 2 degrees advanced will drop mileage that drastic, ima do the o2 sensor test with the volt meter tommorow
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oh ok well if its only 2 degrees then w/e. you should at least lower your octane to see if theres any effect. and about the bigger fuel filter, if anything it would drop pressure before the filter and increase the pressure after; in essence equalizing the pressure on either side. the ecu cannot detect fuel pressure, it is maintained mechanically by your fuel pressure regulator and vacuum.
homeskillet305
Driver
another thing do you have a thermostat? might want to check your coolant temp gauge too.
in my physics class we learned about electrical circuits. electricity flows exactly like a fluid and so a resistor is exactly like a restriction. the filter is a restriction, the bigger the filter the less the restriction like trying to blow through a skinny straw compared to a bigger straw. the greater the restriction/resistor the greater the difference in pressure/volts across the restriction. so the larger the filter the more it will be like it wasnt there and the less the pressure difference. you are right about the bigger it is the more the the pressure required but that applies just to the line between the filter and fuel pump. like i said the pressure drops before the filter but increases after, and after the filter is your fuel rail.
yes a cold engine will run less fuel efficiently.
yes a cold engine will run less fuel efficiently.
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highway is light load my friend. load is measured by the percent throttle. 100% throttle is 100% load. on the highway you are like what 20% throttle, that is low load. if you make the worst mileage on the highway i really wanna say its your 02 sensor. get that checked out and reset your ecu.
after a preset time at constant throttle your ecu will think its in cruise and try to be most fuel efficient by reading off of your 02 to determine a/f ratio and it runs lean.
after a preset time at constant throttle your ecu will think its in cruise and try to be most fuel efficient by reading off of your 02 to determine a/f ratio and it runs lean.
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