Couple of questions here..Last weekend I think I may have been a tad lean..Carb is an 1150 Dominator that is square jetted at 90. I know that you should jet for mph,not et. I don't think I can get out today but it is supposed to be 85*. So the D/A will be pretty much like summer. Next weekend should be much cooler with temps back into the 50s...Is there any way to guess this? There won't be anytime to test in cool air. Also haven't checked the timing yet,but I think Jim had it set at 36* Any ideas appreciated...I need a tenth by next weekend!! Thanks,guys!!

Just throw 2 in the front and 2 in the back for next weekend and let it alone this weekend?

Just depends on what "tad" lean is...

Just a gut feeling...I think it would be safe to go up to 91s or 92s... We only get two time trials next weekend...If it slows from the last outing,then we can put the 90s back in.

Ted what makes you think you are lean?
What did the carb come with from builder/manuf.?
This weekend could be deceiving, the temp is up... But the Barom. is VERY high 30.32"

A weather station is needed to keep track of DA/ ETs.

The only way you can get a .1 sec ET on tuning is if you were WAAAAAAAY off to start with.
More info and good luck, Don

Thanks,Don! I haven't a clue as to what the carb had in it...I don't have a weather station but here is the best mph run from last weekend with the 90s in it
Temperature...62.6
Humidity......16%
Barometer.....30.27
Corrected Alt.1129'
MPH...........103.95
Perhaps I should just leave it alone?

Why not run it as is and then jet up on your next run and see what you pick up, or are you restricted on runs.
Mick

is it consistant?
or do like mike (deaks) said if it goes faster dial off that run.
if it slows, put the old jets back and dial off that run.
it does look like it will be cooler next week. if the baro. stays high it could be GOOD air.

if your current tune is right the DA won't change enough to need a jet change. IMHO
Don

Thanks,Mick and Don! The car never varied more than .077 from morning till afternoon.

As a round figure I use 20*... if the temp drops 20*
I do a single jet change but this is dependent if you
were on with the tune up

Thanks,Mike! I think I will leave it alone and just check the timing!

I think you will run better both in the hot & cool sq jetted @ 92 .

I would use a weather station. Track the DA, temp, jet, etc.

I have a "summer" tune and a "fall" tune...but usually leave it alone,,and dial the car to the weather...this way i know if something is going on with the car,,,if it falls off or picks up,,etc.

Took a few seasons to "figure" it all out...but now i know what the car "should" do.

Even won some $$ at Norwalk with my weather station...going rounds with Jack Moore

Doug

This is the weather station i used to have,,,then upgraded to a TAG,,,lol

Go get em Ted ! Ron

Doc...I can always count on you for a laugh!! That thar hillbilly weather station is cool...If I ever get one,I want a Kestrel..

This is the weather station i used to have,,,then upgraded to a TAG,,,lol

---

I use to have one just like that but I got rid of it..
mine was broke... it never changed at all IN THE
TRAILER so thats when I got the TAG unit

Jim...What calculator are you using? I have seen that the tracks elevation is 850'-889'..

850-900 ft elevation sounds about right.

There are a few, but this one has track's listed for elevation and "estimated" conditions for any day. After using their estimate, you can change the numbers to actual track and hit calculate again. The big thing is putting in the correct barometer, some calculators want "aviation" barometer and they correct to track elevation. Others want actual track barometer (most), or you can put in zero track elevation and actual track barometer.

Drag Times calculator

Also:
http://wahiduddin.net/calc/calc_da_rh.htm

And the tons of them at Wallace Raceing:
http://www.wallaceracing.com/adi.php

I used the Drag Times one,Jim...That is how I got my numbers from the last time out..

Yes, Drag Times uses the reported barometer (which is corrected to sealevel). They have the track's elevation and their calcuation changes the reported barometer to actual barometer based on elevation (like I did).

And their numbers are useful if you have no track measurements. But since they are not temp and humidity from the track, they can be off the actual due to local conditions:
-the airport cools/heats faster/slower than the track
-the track's pavement (acres) might cause locally higher temps
-the track's location might have different humidity (nearby river, lake, etc.
IMO, the baro correction is pretty good (if the track elevation is correct) since that doesn't change much over 10-20 miles. But clouds can shade the track (or airport) and with the pavement have 5-10 degree different temps (worst case)

I may go back thru my logbook and put some figures in from warm weather...That may be interesting!!

Here is an example Maryland International Raceway, 10/8/2011, 11:30 am:

Actual track measurements: 69ºF, 43%RH, 30.45"Hg, calc 184 ft DA (80 ft track elevation).

Drag Times: 66ºF, 56%RH, 30.54"Hg, their calc 33 ft DA (87 ft track elevation)

-------------------------------------------------------
9pm
Track Measure: 54ºF, 97%RH, 30.39"Hg, calc -690 ft DA
Drag Times: 52ºF, 82%RH, 30.49"Hg, -881 ft DA

The other thing to note was that the actual performance didn't change as much as the DA might indicate. A 900 ft change in DA might indicate an ET change of 0.09 seconds (gas, normally aspirated), but nobody saw that much. That is my feeling about the equations not reflecting the actual humidity effects.
FWIW, my car went 5.778 at 11:30am and 5.794 at 9pm. (not bad)
All runs (in order) 5.778, 5.790, 5.788, 5.790, 5.792, 5.794 (lost -0.001 red)
Gas cars change more due to temp, alcohol due to humidity.