What is the norm? Set it up fat at the beginning of the day and dial down as the air comes in? Change pills every 300 feet?

The little bit of data I have on our bracket beater it seems pretty predictable either way, but I was kind of expecting to set it and forget it... doesn’t seem to work that way

Never change during the day unless you are tuning. Find where it runs fastest, maybe go a little fatter, and leave it. I had one pill for summer and one for spring and fall.

Even on a 2000 ft swing in adjusted from day to night?

If it slows up at night you just dial for it?

Or you set it up so fat that it will never slow up?

quote:

Originally posted by Bucky:
Never change during the day unless you are tuning. Find where it runs fastest, maybe go a little fatter, and leave it. I had one pill for summer and one for spring and fall.

I agree with Bucky, I do not change my main unless there is a substantial DA change. (1500 feet?) You still need to track weather and how it effects your ET. From my experience if you change jets all the time you end up chasing your tail. I run 8 - O2 sensors and with all that info if you make a change every time then it gets crazy and hard to keep track.

Don’t overthink it. Set it up where it’s fastest, maybe a touch fatter (which won’t slow it down), and go like Bucky said. I also usually only change pills in spring and fall. The tuning window on alky is huge.

I still don’t get the comments that say set it up a touch fatter than perfect. To accommodate for 2000 ft swing is more than a touch fatter, else it will slow down. Maybe you guys don’t see that much of a swing in DA from day to night?

I use the jetting option in the computech hand held weather station...you just plug in the adr of a good run and then the computer gives you a pill map to follow with the current weather.its foolproof

I only change for cpl 1000 foot or more swing and then its only .005 jet change. No most of the time thats not same day or even same track.Problem is with size pumps run on injection a .005 jet difference which is what most are setup for is too big flow wise.

Example .When we ran TA/FC and TA/D we had 18 to 21 gpm pumps and rule of thumb was .001 per 100' and even then it took 300 plus swing before making a change and that was small percentage of fuel.

Now with a 7 gpm 80-A the same change is lot higher percentage of pumps flow. So you can not go by that old rule of thumb and you need lot bigger swing.

All combo's have little different attitude as to what will effect them. IMO if I was expecting a 2000' swing on regular bases I would run which ever pill ran best in middle of your DA numbers and keep close eye on when change occurred in relation to humidity and temp swing tracking individually .Engine temp will have more effect than DA also.Have seen .1 with 20 degree on two combo's.

No such thing as too much data,but there is such thing as too many changes. Data is just a tool.Like a gun if used wrong you can shoot yourself in the foot.

quote:

Originally posted by 183N:
Don’t overthink it. Set it up where it’s fastest, maybe a touch fatter (which won’t slow it down), and go like Bucky said. I also usually only change pills in spring and fall. The tuning window on alky is huge.

Exactly this. A 2000' DA swing will move the ET but by much less than it would on gas, although you will notice that humidity change will play a bigger part in ET swings than the other things that factor into DA). If its moving around on you a lot, your tune up may be further off than you think. Tune for the fastest ET and appropriate temp gain during a run (I think about a 10 degree increase during a 1/4 mile pass) and consistency should follow...

^^^^^^ All of what BD and others posted. Once you determine fastest (for me highest MPH) I try both ways, 1-2 lean and 1-2 richer pill sizes. Right now I’m 1 lean.

What also makes the most consistency for me (sbc) is leaving the starting line at as close to 170* water temp as possible. I adjust the barrel valve to maintain this water temp at idle with the fan off after the burnout. I also want the oil temp to be a minimum of 140* in the staging lanes.

quote:

Originally posted by BJs Wild Ride:
Even on a 2000 ft swing in adjusted from day to night?

If it slows up at night you just dial for it?

Or you set it up so fat that it will never slow up?

Read the weather and dial for it. Like said, the window is large. Frankly, air temperature has never affected my times much on injected alky. I watch more closely the dew point....moisture

quote:

Originally posted by Bucky:

quote:

Originally posted by BJs Wild Ride:
Even on a 2000 ft swing in adjusted from day to night?

If it slows up at night you just dial for it?

Or you set it up so fat that it will never slow up?

Read the weather and dial for it. Like said, the window is large. Frankly, air temperature has never affected my times much on injected alky. I watch more closely the dew point....moisture

You said you change pills from spring to summer. What is the DA change from “spring” to “summer” and what is the max DA change you see in a day?

3700 ft - 5.15

2700 ft - 5.13

1700 ft - 5.15

1700 ft with .003 richer main - 5.12

For me, spring to summer is negative a couple hundred at best to 4000+ and 125 water grains on the worst day.

Race day max swing is probably close to 2000 but that’s not average. Probably more like 800-1000 normally.

I’d try running your .003 richer pill all the time. I bet it doesn’t slow up much if at all at 3700 and it’ll be more predictable. Also keep an eye on the water grains or dew point with alcohol.

Makes sense I guess. If it goes .17 off the trailer with the night time pill then its still only moving .05 over 2000 ft. I’ve almost always tried to run my stuff so the dial in never changed during the race (change throttle stop settings, change blower pullies, hold .05, whatever). The ol lady probably isn’t going to keep 5 in her purse so guess I’ll have to carry the shoe polish for her.

quote:

Originally posted by 183N:
I’d try running your .003 richer pill all the time. I bet it doesn’t slow up much if at all at 3700 and it’ll be more predictable. Also keep an eye on the water grains or dew point with alcohol.

Good advice here. I never ever mess with the tune. I dyno it, and when I leave I fatten it up 4 numbers from best power and leave it.

No need to be changing pills during a race day. Find the tune the engine likes and leave it alone.

quote:

Originally posted by BJs Wild Ride:

quote:

Originally posted by Bucky:

quote:

Originally posted by BJs Wild Ride:
Even on a 2000 ft swing in adjusted from day to night?

If it slows up at night you just dial for it?

Or you set it up so fat that it will never slow up?

Read the weather and dial for it. Like said, the window is large. Frankly, air temperature has never affected my times much on injected alky. I watch more closely the dew point....moisture

You said you change pills from spring to summer. What is the DA change from “spring” to “summer” and what is the max DA change you see in a day?

3700 ft - 5.15

2700 ft - 5.13

1700 ft - 5.15

1700 ft with .003 richer main - 5.12

I never track DA. I look at temp, dew point and BP. BP seldom changes much unless there is a weather event pending. If that is the case I pay attention because that can throw me a number. I look at what it runs off the trailer and the weather then. Then I adjust during eliminations using the dial board depending on what I see the weather doing.

I tested once in the summer to find the fastest pill, and richened up by whatever increment I had 1 size.
I tested once in the fall and found the fastest pill, and richened that by one as well. Generally, this is not something that needs or warrants fussing over. Once you have your tune, you have it.

The other thing you need to address when you change your pill is your barrel valve setting....sometimes. If you have your summer tune all set, and like your barrel valve setting, take note of your idle rpm when warmed up. Change the pill. Now adjust your bv for the same idle rpm. done

Oh, the reason I avoided DA, was that alky is more sensitive to water in the air than actual air temperature. That DA can change due to temperature, and your car ends up running the same. And if the temps get lower toward night, but you start approaching the dew point, you will probably get a run that gets slower, not faster like that DA would have told you.
I have known a few people who used DA and tried to get their program to work with that data, and they didn't do well with alky

This is good to know info guys, thanks! I'll take notes for when I make the change soon!

I bet I never changed the main pill the last 3 years I ran Rons Injection and it would print tickets in both spring and summer. Like others have said watch the water grains and dew point when dialing your car but mine would not normally vary more than .020 all day, hell most are holding more than that.
Now my blown TD deal is a whole different animal when it comes to tuning..