IAT and AFR - my theory
11-09-2005, 09:26 AM
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IAT and AFR - my theory Maybe we're looking in the wrong place saying the IAT is the culprit for leaner results in warmer temps?? I have a theory that may be worth looking into. How many of you have been out logging and stopped to get gas in the middle of your log? Did your fuel trims take a dive as you're pulling away from the gas station and slowly begin to recover about 30-45 minutes later? Well, why wouldn't the temp of the gas in our tanks affect AFR? They store it in tanks quite a few feet under ground where I'm sure it's nice and cold. I'm not the best when it comes to chemistry, but I know cooler things generally tend to have a greater density to them whether they be gases or liquids. So if our cars open the injectors for a given period of time regardless of fuel temps, could we be letting a greater amount of fuel into the cylinders if the gas is colder? This could explain why we run leaner on warmer days and richer on cooler days....just a thought.
11-09-2005, 10:08 AM
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i thought this was affected more by the air. I see where your coming from too and it does make sense..maybe a mixture of colder air mixing with the colder fuel during combustion? i may be over or under thinking, but wouldnt that also mean that the denser the 2 are, the less of both you would need to get the same effect as if they were warm??
11-09-2005, 10:31 AM
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More likely the situation is that the cooler fuel cools the air as it is sprayed into it.
Definetely will cause that phenomenon somewhat, we used to run the fuel lines through an ice bucket on drag cars in the 70's and 80's. It would be interesting to measure the fuel temperature and then measure the AFR variance as a function of fuel temp.
Interesting thought guys, that's using your head !
Definetely will cause that phenomenon somewhat, we used to run the fuel lines through an ice bucket on drag cars in the 70's and 80's. It would be interesting to measure the fuel temperature and then measure the AFR variance as a function of fuel temp.
Interesting thought guys, that's using your head !
11-09-2005, 01:27 PM
#4
Originally Posted by SSpdDmon
How many of you have been out logging and stopped to get gas in the middle of your log? Did your fuel trims take a dive as you're pulling away from the gas station and slowly begin to recover about 30-45 minutes later?
Active purge, after a fill up, would result in condensed fuel added into the intake.This is unmetered fuel so it will change your trims. FWIW.
11-09-2005, 03:05 PM
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its your purge. With the addition of my fast 90/90 i got rid of the solenoid. After a fill up and depressurizing the gas tank the AFR runs at 10:1 for a few miles until the excess air is sucked back outta the gast tank. The car barely wants to stat after a fill up becaause of the rich AFR. If ym purge was still on the car it wouldnt be that bad but i will still see some richness as it controls how much vacumm the gas tank is seeing