performance slow down as day goes on

[falcongeorge]

In my mind that would depend on if I am winning or not. If my car slowed down a tenth later in the day and I still was able to win, I would be fine with dealing with it. If I was losing races because of it, well then I would be doing some tuning.

As long as everyone else is happy to stand still for you and watch you win every weekend...Good way to go home early.

[cgarb]

That was pretty much my point falcongeorge, everyone wants to win. I'm sure nobodys car in prostock in the finals is set up the same as it was 1st round.

[falcongeorge]

Ah, I see, you were just being more subtle that I was... When I was doing the small tire thing, it was like this. Probably 3/4 of the field was happy to just come out on race day and race. As far as the rest, we pretty much knew who each other was, all we had to do was look around for the other guys that were out there making laps on Friday and Saturday with "no time" written on the window.

[stokerboats]

Weather station weather station weather station. Log each and every pass along with data you have. Keep an eye on track temperature and log that data as well. Eventually you will have enough data to reference and dial accordingly, assuming you are bracket racing.

[stokerboats]

Trying to tune between rounds can get stressful, especially when the rounds come more frequently.

[brechlrl]

Joe I am just a nostalgia, exhibition, and grudge racer. Occasionally offer myself up as a first round duck in brackets.. I can almost guarantee that the first pass off the trailer is the fastest of the day.. Does not seem to matter if it is a well prepped track or a landing strip. I quit chasing it and live with it.

[racinnut15xm]

The tire dope is wearing off as the day goes on

[F-BIRD'88]

Take 100 pounds out of the car after the first run. Repeat as required.

[rfoll]

I almost always get faster, but we race evenings from 6 PM on. Not uncommon to run 2 tenths faster. Traction can deteriorate faster than the air temp falls.

[roadrunner]

Have you thought about checking rear tire pressures after a few runs? Do you cool your fuel?

[greywolf]

Joe, in my opinion losing 1000 feet of altitude density is going to slow down any car, all other things being the same. The overall tune up will dictate how much this is.
Being a bracket racer myself I find my car tends to slow down a bit as the density gets worse if the tune up it is a tad on the rich side. What I have done is leaned the carb down 1 - 2 jet sizes and it tends to be more consistant (lose less et), as the day progresses. But this tune up typically would be a little bit slower on the first pass of the day.

Another thing I believe that can sometimes affect ET throughout the day is heat sink in the engine.

[stokerboats]

Have you thought about checking rear tire pressures after a few runs? Do you cool your fuel?

Just before every run.

[Aukai]

One other variable I would like to mention, tire heat/overheat. I haven't been on the track for awhile, but have been keeping up. One of the guy's that campaigns for points has a routine that heats the tires on the first burnout, but only does a short burnout for the rest of the day if the temps are up. Evening, into the night the burnouts are a bit longer. Just a thought.

[roadrunner]

Have you thought about checking rear tire pressures after a few runs? Do you cool your fuel?

Just before every run.

Then as far as I can work out, it's a tuning issue, warmer , thinner air will slow almost everyone else down too! What happens to the burn speed of the air/fuel mix when the induction air goes up in temp?.....maybe some different carb boosters (coarser droplets) will help!, or mabe less ignition advance...just thinking out aloud!

[vortecpro]

As the DA rises, and the Baro declines, along with hotter intake temps, performance suffers, all you can really do is change the water and cool the intake, and monitor the oil temp. And keep in mind a 4000 DA with a 28.5 Baro is nothing, a 23.9 baro with 10,000 DA is my reality......for now.