axe1993

I went bracket racing the other day and I ran two time runs at 13.90. Then first round I ran a 13.90 on a 13.90 dial. Second round was a by and I ran a 14.10. Blew it off and blamed a weak burn out and third round I was on exact pace as my 14.10 pass till I lifted at the line. Why the sudden two tenths drop in one hour time. I did everything the same. Car was up to temp and everything. I was told the humidy went from 30% to 45%. Would that alone cause a two tenths drop if air temp hasn't changed?

Roarin_8

iTrader: (5)

Was your 60 foot the same? What was your MPH? Give a little bit more details on the run, what was your 1/8th mile time and mph? What track were you racing at?

axe1993

2 out of 3 of my 13.9 runs the 60ft were 2.101 the 3rd was 2.14. Both 14.10 runs it was 2.14 at the 60ft. I lost a lot by the 330 ft. Can't remember the ets at the 1/8 but it was off by .15 from what my 13.9 runs were. 101 MPH with 13s and 98-99 with 14sec runs. Same as my 14 sec runs the night before during test and tune. Never hit 13 Friday night but Saturday it wad three 13.90 runs in a row about 1.5 HR in between runs. I was at Mokan dragway in asbury mo. I don't have slips with me at the moment to give exact details. Both 14sec runs everything was with in 0.5 MPH and .01 of a sec. from each other all the way down. The consistency was there still just .20 slower.

zracer323

iTrader: (12)

A 15% change in humidity should not affect your run that much. Most likely your pcm sensed a condition that caused it to pull timing. Did you have less time in between the last 2 runs? Heat soak (especially on you IAT sensor) is a likely culprit. Also, as your engine temp rises, knock becomes more likely to happen.

MonmouthCtyLS7

iTrader: (6)

Use to kill my LT1 but w/ my exp. with LS's it'll hurt your trap speed more then your ETs

axe1993

Thanks. Is their something I can do to prevent this from happening again? Maybe change my iat sensor? My car was the most consistent car at the track that day and I was killing the tree. I literally was the man to beat till the 3rd round when it all went to heck.

wicked383lt1

Don't come to So.Fla you'll be really disappointed!

zracer323

iTrader: (12)

Do you have a way to log temps? If so, keep an eye on them at the track and make sure you cool the car the same in between rounds.

axe1993

Just an update. I went against today and left hood up in between runs to keep under Hood temp down. It work that and kept car in shade. Car ran fine with no issues. Except speeding up and breaking out. 13.86 on a 13.88 dial. I'm pleased with the way the day went compared to last week. Thanks for all your inputs.

z28241

iTrader: (13)

I always tell new guys to keep that hood up between rounds and if theres a wind , face the car to it, and if u have someone that tune ur car , things will help such as having ur fans commanded to turn on at earlier temps..fyi, u might want to play w/tire pressure to get ur 60' down..and do ur free mods as well.

axe1993

I run MT et streets at 19psi at the moment. Has anyone use these on a bone stock car? What pressure works for you?

BlackScreaminMachine

iTrader: (17)

Fuel Injected cars do not "drop off" as bad as carburated cars. From exp. But you can be effected by weather and internal temps. More to the point you need to start logging data for reference and know when you need to change your dial in. Having a Meter tends to be key as you can really get to dialing in your number.

When I used to run these types of races at my home track, you could est by just the time of day and temps and the car was auto so there was consistancy. But that wont work everywhere.

S8ER95Z

iTrader: (3)

You have to look at more than just humidity. FWIW

My car bone stock... ran it in the summer when I first got it.. then again in the late fall.

3200DA - 13.4 @ 104mph 2.1 60ft
0DA - 13.1 @ 108mph 2.1 60ft

BlackScreaminMachine

iTrader: (17)

DA = Density Altitude takes all that into consideration.