Let’s have a good track weather (bar, temp, humidity, corrected altitude) discussion

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At my local track, it seems people have a couple of different carb "tunes". As in, a set of bleeds and jets for good weather and the typical summer weather. The summer tunes are used mostly through out the season. With that being said, I don't see anyone changing jets or timing throughout a given race. People just adjust the dial up or down accordingly. From what I've read about basic tuning for weather(heat) is more timing and less fuel. Less timing more fuel for cooler air. I think I have that right..... It's frickin hot here today and brain is mush. I shouldn't be trying to have intelligent conversation.....

P.S. People I speak of are running gas.
 
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408 swinger said:
At my local track, it seems people have a couple of different carb "tunes". As in, a set of bleeds and jets for good weather and the typical summer weather. The summer tunes are used mostly through out the season. With that being said, I don't see anyone changing jets or timing throughout a given race. People just adjust the dial up or down accordingly. From what I've read about basic tuning for weather(heat) is more timing and less fuel. Less timing more fuel for cooler air. I think I have that right..... It's frickin hot here today and brain is mush. I shouldn't be trying to have intelligent conversation.....

P.S. People I speak of are running gas.
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What if instead of changing the dial we were talking stock, super stock, or even pro stock.
 
167 water grains today and 4260 foot density altitude at US131, my home track today. 78 dew point
don’t think I have ever seen the water in the air so high before.
Will be even worse tomorrow
 
pittsburghracer said:
What if instead of changing the dial we were talking stock, super stock, or even pro stock.
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Well, they have a different brain trust to keep track of conditions, lol. I would think different types of gas have an effect. Let alone methanol. Methanol definitely seems to be more consistent in varying conditions. But, gas can be consistent with the correct tune as well. Also more than carb tune, timing plays a role as well. I'm assuming you don't really change much on your car in varying conditions? With the stock and super stock, the big dogs have cooler machines to cool engines down between rounds. I would think that would be standard on all the pro stock stuff. Getting rid of the heat soak helps, i reckon.
 
408 swinger said:
Well, they have a different brain trust to keep track of conditions, lol. I would think different types of gas have an effect. Let alone methanol. Methanol definitely seems to be more consistent in varying conditions. But, gas can be consistent with the correct tune as well. Also more than carb tune, timing plays a role as well. I'm assuming you don't really change much on your car in varying conditions?
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I haven’t changed the tune on my duster for three years. I took a carb out of the box from APD and leaned it out 4 jet sizes and put it on. I set my timing for first fire up in 2021 and haven’t had a timing light on it since. My break in pass it ran a 6.06 or 6.07
 
Found this on yellow bullet.. shows how bad the water grains were today… 150+ at times

For crew chiefs, the amount of water in the air isn't expressed simply as a percentage. To them, relative humidity is determined by the number of grains of water per pound of air, or, as crew chiefs say, simply "grains."

"Anything below 50 grains is considered dry," Walsh says. "Anything above that is wet, and anything above 100 is really bad. The worst I've ever seen was in Memphis a few years ago, when that race was in August: 130 grains. The cars don't want to run at all when there's that much water in the air. At the first two races of the year, Pomona and Phoenix, the grains varied from 20 to 50. When we get to Gainesville, it should be somewhere around 80."

For Brian Corradi, crew chief for Toyota-supported Antron Brown, driver of the Matco Tools Top Fueler, the amount of water in the air at a place like Gainesville is taken into account by some small tweaks to the baseline setup.

"Normally, we add a little timing for Gainesville, just a degree or two,” he says. “We also take a little fuel [nitro percentage] away from it and lower the static compression.
 
pittsburghracer said:
I figured guys could see what it took to make bad air.
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yea. I have a hard time figuring out how you get a dew point almost to 80.
crazy, that’s friggin humid..lol.. super humid

i have also learned, just going by density altitude alone can get you in trouble dialing a car, but lots of guys seem to only look at that number alone.
 
pittsburghracer said:
I haven’t changed the tune on my duster for three years. I took a carb out of the box from APD and leaned it out 4 jet sizes and put it on. I set my timing for first fire up in 2021 and haven’t had a timing light on it since. My break in pass it ran a 6.06 or 6.07
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I had edited and added to the post you replied to. I spoke of the categories you mentioned. We're you eluding to the coolers they use?
 
408 swinger said:
Well, they have a different brain trust to keep track of conditions, lol. I would think different types of gas have an effect. Let alone methanol. Methanol definitely seems to be more consistent in varying conditions. But, gas can be consistent with the correct tune as well. Also more than carb tune, timing plays a role as well. I'm assuming you don't really change much on your car in varying conditions? With the stock and super stock, the big dogs have cooler machines to cool engines down between rounds. I would think that would be standard on all the pro stock stuff. Getting rid of the heat soak helps, i reckon.
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Dont they dyno engines at a cooler temperature too. I won’t mention names but some head porters HATE alcohol and guarantee they can produce more horsepower and quicker ET’s with gas than they can alcohol. And now we have oxygenated fuel. That opens another can of worms.
 
pittsburghracer said:
Thanks guys that are engaged in this discussion. We can all learn something from discussions like this.
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God knows I need to learn a little something! When I finally get a car together, I have vowed to myself to not be lazy and start keeping track of the very info I see you have written on your time slips.
 
I run at Orlando Speedworld and it is always wet. Humidity changes really effect my ET. The other variable that is hard to track is wind direction. My Dart is not what I consider to be the best body for aerodynamics; it's like a brick at speed. One other factor in my case is I am at the mercy of the 93 octane pump gas that comes out of the pump on a given day.
IMO the closer you are to the optimum tune (baseline) the tighter the ET spread will be as conditions vary.
I have a warm and cool air jetting package depending on the time of year. Since I run an Eddy DP airgap all four jets are a different size due to the shallow and deep port variations. I spent a lot of time deep porting and experimenting with stagger jetting to get all 8 holes to be as close as I can get them. An EGT probe on each cylinder would be the ideal way to tune but that's not in my budget.
I run a Demon 750DP on my stock stroke 340 and have found the .024, .025, .026 emulsion stack on the 3 hole metering blocks keeps my AFR curve flat and steady. A MAB in the .030 to .033 range allows me to keep the AFR at WOT in the 12.4 target. Each .001 difference changes the AFR .2
I use the Air Density on line to check the forecasted weather Drag Times DA calculator for corrected times to check my baseline on a given day.
Orlando Speed World - Orlando, Florida - Engine Tuning Weather
DA Calculator - Density Altitude Calculator - DragTimes.com
 
Personally I try to monitor all of the weather conditions that my PerformAIRE Eclipse provides, but mainly I watch the correction factor. Since I am not that smartest, even a dummy like me is able to understang that the higher the correction factor, the slower the car SHOULD go, and vice versa. When John and I were at Quaker a few weeks ago, the correction factor was 1.111 I think at its worst (I can't exactly remember but Id have to check). That was about the worst weather I have raced with, in years. The altitude was over 4000', temp was 85 degrees, barometric pressure was 28.50" ish, water grains over 100 the entire weekend. Sunday when the weather got better, everyone was going faster. I saw guys going .09-.10 faster, some going .05-.07 faster, and some only .02-.03 faster. Everyone's car is different. Gotta spend time with the car and figure out what its effected by the most.
 
71Demon528 said:
Personally I try to monitor all of the weather conditions that my PerformAIRE Eclipse provides, but mainly I watch the correction factor. Since I am not that smartest, even a dummy like me is able to understang that the higher the correction factor, the slower the car SHOULD go, and vice versa. When John and I were at Quaker a few weeks ago, the correction factor was 1.111 I think at its worst (I can't exactly remember but Id have to check). That was about the worst weather I have raced with, in years. The altitude was over 4000', temp was 85 degrees, barometric pressure was 28.50" ish, water grains over 100 the entire weekend. Sunday when the weather got better, everyone was going faster. I saw guys going .09-.10 faster, some going .05-.07 faster, and some only .02-.03 faster. Everyone's car is different. Gotta spend time with the car and figure out what its effected by the most.
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That Saturday was crazy. It was real Hard dialing a 6.15
 
I know, I couldn’t believe yours went that slow. Tim was clear back to a 5.95 which was also hard to swallow.
 
I can go from basically sea level, and go to another track i race at where the DA can be 7000 ft or more, and i always jet down 3 or 4 sizes front and rear, so the car runs it best. I believe getting your jetting right is crucial.
 
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