Slower ET when the weather is cool

[Indiana]

Tonight the air temp was cool, the humidity was low. My ET was 1/2 a second slower. The engine was at temp. Do you think my carb may be too lean?

[Indiana]

I expected the truck to run faster in the cool weather. It actually ran slower. I had a guy adjust the mixture and it ran great.

[smoothdime]

were you not hooking with the cooler temp? smooth

[Indiana]

I was hooking fine. From what I understand, cooler air is more dense than hot air. So the air/fuel mixture is different. It went from high RH (60-65 RH) and higher temp (85-90F) to about 40 RH and 65F. My wife is recording my launches to see how well I take off and watch traction.

[grimpuppy]

Did your 60\' times change any? If 60\' is slower and your trap speed stayed the same then it would be a tracion issue. If your 60\' stayed about the same and your trap speed dropped then it would be a horsepower issue (lean maybe). Compare all the information you have have with all your previous runs to find out excatly where you lost the 1/2 second. Remember that a tenth slower in 60\' can make a big differeance in your E.T. unless you have logged many of runs on the truck you probably wouldn\'t notice a slight loss in tracion like a tenth on 60\'. Crunch the numbers and let us know what you come up with.

[Indiana]

That is what we did. We compared the numbers from last night to the runs a few days before. I did not make any changes to the truck at all befiore last night. The only change was the weather. Well, I am sure the track was different in a way. I even had the same fuel in the fuel cell.

[Scotty_S-15]

Indy, like Grimpuppy said, in order for us to offer any thoughts, please tell us the 60 ft. times and MPH before and after (weather-wise).

............. Earlier you mentioned that someone adjusted your mixture.... was that idle mixture, or jet changes?

......... BTW, my truck can vary 4 tenths and 3 MPH between a hot, steamy August night, and a cool, crisp (low humidity) October evening.

[Indiana]

Sorry, I don\'t have the numbers wth me. I left the papers in my camper at the track. He adjusted the idle mixture. He has a dyno in his shop and we are going to check it out on Tuesday. I will post the times as soon as I get them. I was frustrated when I first posted.