performance slow down as day goes on

[bigjoe1]

We run a pretty fast small tire drag car--- It always makes the fastest run of the day on the first pass... It then runs slower each run after that as the day goes on.. I look at other cars that run similar times, and some slow down just as we do, but a few do not slow down at all ( or VERY LITTLE ) The big tire cars seem to not be affected as much as the small tire cars. We also run at a track where the corrected altitude is a little higher than moct== It starts out at 3000-3300 feet , but in the middle of the day , it is usually in the 4000 to 4300 feet range. Should I try to tune for this slow down, or just put up with it ?


JOE SHEERMAN RACING

[406shark]

I bracket race, so I just change my dial as needed. I go to the track to race, not tune. If I was class racing where I needed every little bit out of it... it would be a different story.





Jeff

[bigjoe1]

I understand completely--- We match race and grudge race only---NO DIAL IN !



JOE SHERMAN RACING

[Walter R. Malik]

I guess my decision on that matter would depend upon where exactly on what part of the strip does the car become deficient.

Correct what I can control and just live with the rest.
For the Super Stock guys with intake charge restrictions, they can usually add a degree of timing for every 1,000 feet of "density altitude".

[falcongeorge]

I would try to tune for it. I used to race heads-up small tire, I had the opposite scenario, finals were usually close to dark, and we were at sea level, so more air later in the day, but the track would get slicker as the day wore on, so I would try to soften the bottom of the power curve and get more fuel into it to take advantage of the air. Its hard to quantify, but I kept logs, and the car seemed to respond to the tune of a few hundreths relative to if I changed nothing.
I remember one time beating a guy in the finals by a substantial margin at 9 pm, he had out-qualified us by an equally substantial margin that morning. Afterwards, he came up and shook our hands, and said "where in the hell did THAT come from?" The car owner pointed at me and said "George always keeps a tenth in his back pocket". Guy gave us a funny look and walked away.

[cgarb]

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.

[JoePorting]

Maybe try a better set of valve springs.

[Strange Magic]

3000-3300 feet , but in the middle of the day , it is usually in the 4000 to 4300 feet range.

A swing of 1000 feet of da in a day is quite a bit in da, although I guess I can see that type of swing in the west or mid west where there typically is lower humidity.

Post the 60fts and time of day. This will tell quite a bit about whats going on. Automatic or stick?

[BrazilianZ28Camaro]

We run a pretty fast small tire drag car--- It always makes the fastest run of the day on the first pass... It then runs slower each run after that as the day goes on.. I look at other cars that run similar times, and some slow down just as we do, but a few do not slow down at all ( or VERY LITTLE ) The big tire cars seem to not be affected as much as the small tire cars. We also run at a track where the corrected altitude is a little higher than moct== It starts out at 3000-3300 feet , but in the middle of the day , it is usually in the 4000 to 4300 feet range. Should I try to tune for this slow down, or just put up with it ?


JOE SHEERMAN RACING

Joe, look where the car is losing ET, if the car sixty foot is the same or near the same through the day, but car lose top end MPH I'd try a little more ign timing with higher DA. If the oposite happens, worse track conditions may be the culprit, as you have noted that bigger tire cars lose less ET.

[bigjoe1]

While it is true, many guys slow down as the day goes on, but some guys are only tho or three hundredths slower, instead of seven to nine hundredths off.. NOT valve springs


JOE SHERMAN RACING

[Strange Magic]

You first have to determine where the issue is, and by posting the 60fts and time of day will determine somewhat of what's going on. Sounds like this is not a big tire car. Forget what anyone else is doing.

[bigjoe1]

The 60 foot times do get worse too--- 127 is pretty good for us, then it slows to 130-132 if it is rear bad


JOE SHERMAN RACING

[kirkwoodken]

Joe,
You don't use a data logger?

[289nate]

Are the cars that stay more consistent running alcohol?

[fdicrasto]

Losing a 1000 ft of air plus .04-.05 60 ft. is going to hurt you and be tough to just tune out of. Could the 60 ft. be partially an issue with track maintenance during the day,in other words, not enough effort to keep the starting line in good shape? Seen that a lot over the years. If your mph is real close, sounds like the track condition more than anything else. Phil D.