ok guys, we all know the basic layout for getting the car to run reasonably consistent. try to roll into the beams the same amout each time, stall the same rpm each time, keep the car as straight as possible going down track, and master hitting the shifts at the blink of the shift light.
thats the basic format, however the weather changing from day to night, sudden cloud cover, or even after a 15 minute rain shower all effect the engine. the numbers will move when the air does. a lot for some, not so much for others. thought it would make for an interesting thread, if we all posted any tricks or changes that we use to try to hold the car to tight numbers. I'll start with a few that are common knowledge, and then some that maybe are not.
1.) RUN ALCOHOL. carb is great, and fuel injection is better. if you don't mind the maintenance that goes with it, it will flat out repeat. the burn rate of alcohol is not affected by the weather nearly as bad as gasoline. while a 200 foot drop in density altitude may speed up a gas motor by .01, it often will take a 400 to 500 foot drop in the DA, to speed up an alcohol engine by .01. you will burn twice as much fuel while using alcohol, as you would if running gas in the same engine. however, the alcohol is around 3 dollars a gallon vs 7 to 12 dollars for race gas, depending on which type.
2.) RUN CARB ON THE LEAN SIDE. I use an EGT monitor to keep an eye on the exhaust temp, of the leanest burning cylinder. I try to stay around 1375 degrees in the day time, and no more than 1420 degrees at night when the temps drop. hot air is thin, and as the air cools, it gets heavier. this means the carb will take in more air at cooler air temps. if the carb is just a little rich during the day, then of course we know the engine is getting more gas than air. you may run close numbers like that through out the day, but look out when the temp drops!!! that engine that wanted more air to go with that little too much fuel, is going to get it, and speed up she will. often by 2 to 3 numbers between rounds. it makes the car harder to dial, and breaking out more likely. my theory is run it lean, and it starts the day out wanting a little more fuel. when the temp drops, and the heavier air is forcing more volume to the carb, it won't move very much at all. the reason being is that it already wanting a little more gas to start with, and the better air will not meet axtra fuel waiting for it, through the carb. much easier to keep the numbers tight. it works. the car won't be as fast as it could be, but it won't lose much, and will reward you with tighter numbers.
3.) RUN A SMALLER CARB OR A RESTRICTOR PLATE. same game as running lean on the jetting. just choking the air flow down a little, and trying to keep an air/fuel ratio, that won't be as affected by the weather.
thats just a few of mine. some may disagree, but they work on my car, and I have a ton of runs in my log book that back it up. Lets hear some from you guys. this could be an interesting thread with lots of tips, tricks, theories, and deep thinking, LOL!
thats the basic format, however the weather changing from day to night, sudden cloud cover, or even after a 15 minute rain shower all effect the engine. the numbers will move when the air does. a lot for some, not so much for others. thought it would make for an interesting thread, if we all posted any tricks or changes that we use to try to hold the car to tight numbers. I'll start with a few that are common knowledge, and then some that maybe are not.
1.) RUN ALCOHOL. carb is great, and fuel injection is better. if you don't mind the maintenance that goes with it, it will flat out repeat. the burn rate of alcohol is not affected by the weather nearly as bad as gasoline. while a 200 foot drop in density altitude may speed up a gas motor by .01, it often will take a 400 to 500 foot drop in the DA, to speed up an alcohol engine by .01. you will burn twice as much fuel while using alcohol, as you would if running gas in the same engine. however, the alcohol is around 3 dollars a gallon vs 7 to 12 dollars for race gas, depending on which type.
2.) RUN CARB ON THE LEAN SIDE. I use an EGT monitor to keep an eye on the exhaust temp, of the leanest burning cylinder. I try to stay around 1375 degrees in the day time, and no more than 1420 degrees at night when the temps drop. hot air is thin, and as the air cools, it gets heavier. this means the carb will take in more air at cooler air temps. if the carb is just a little rich during the day, then of course we know the engine is getting more gas than air. you may run close numbers like that through out the day, but look out when the temp drops!!! that engine that wanted more air to go with that little too much fuel, is going to get it, and speed up she will. often by 2 to 3 numbers between rounds. it makes the car harder to dial, and breaking out more likely. my theory is run it lean, and it starts the day out wanting a little more fuel. when the temp drops, and the heavier air is forcing more volume to the carb, it won't move very much at all. the reason being is that it already wanting a little more gas to start with, and the better air will not meet axtra fuel waiting for it, through the carb. much easier to keep the numbers tight. it works. the car won't be as fast as it could be, but it won't lose much, and will reward you with tighter numbers.
3.) RUN A SMALLER CARB OR A RESTRICTOR PLATE. same game as running lean on the jetting. just choking the air flow down a little, and trying to keep an air/fuel ratio, that won't be as affected by the weather.
thats just a few of mine. some may disagree, but they work on my car, and I have a ton of runs in my log book that back it up. Lets hear some from you guys. this could be an interesting thread with lots of tips, tricks, theories, and deep thinking, LOL!
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