Need some feedback

[greychevy]

I went to the track Friday night to do some data logging and get everything dialed in before we start having the good weather. I was running consistent 13.8s and 1.9 60s with the DA being around 1500. My previous best back in April, with 1350 DA, was 13.3 and high 1.7 60s. I wasn't expecting a new PB in the 1/4 but was expecting at LEAST the same 60'. On the 13.3 pass I had stock shocks, 265 street tires on 4x4 17s, and was shifting at 5700rpm. Since then, I installed rancho 9000XLs on all corners, 28" DRs, am shifting at 6100rpms, and rear 2" drop springs. Take a look at the slips and let me know what you guys think....the left is my pass back in April and the right is the best from last night.

 

[greychevy]

The datalogs looked good other then the a/f being a little rich at the top of 3rd. I'm thinking the problem is in my 60' as I picked up the same or better MPH between the 1/8th and 1/4th as my 13.3 slip. Here's the A/F video:

Log B

 

[Hemi450hp]

Ethan, the low end power is definitely hurting on your passes Friday night. You were .2 slower in the 60', but you also lost almost 4mph in the 1/8th. The positive side of this is that you picked up almost 21mph between the 1/8th and 1/4 as apposed to only 19mph on your previous 13.3 pass. This means the truck was pulling harder on the big end of the track than it was last time out. DA can have a huge factor even if it was only 150-200' different than the last time, so give it another shot in some cooler air.

Also, did you notice any additional lag in the shifts? Could it be shifting slower than last time causing you to lose some time on the 1/2 and 2/3 shift?

 

[greychevy]

Yeah, I'm gonna keep at it, just wanted to get some other opinions on what the problem is. I didn't notice any lag in the shifts.

 

[meadows]

air temp?? cool down?? weight?? many factors

 

[truckin151]

DA, air temp, how well the dr's were warmed up, track prep, fuel in the tank, weight..... it all plays a role in it.

 

[greychevy]

Anybody else?

 

[blk00rt]

do you load up the torque converter or launch at idle? did hemifever turn off torque management? Chrysler usually pulls timing out if you load up the converter to keep the weak trans safe.

 

[greychevy]

I launch at idle....no loading the converter for me.

 

[Jerseymike]

Hmmm. So you did a bunch of stuff to help traction and ended up with slower times. That is a head scratcher. Assuming that you did everything the same as before (1/4 tank gas, launch technique, etc) the only other change was to your shift points. Since you are running the stock cam, shifting at 6100 rpms might be to high. I could see that helping with a stock torque converter to help with shift recovery but since you have a 3000 stall maybe the higher shifts are taking you out of the powerband on the top end then if you are only dropping back to 4500 after the shift you may be losing a little on the bottom end. From what i have read the stock cam peaks at 5600 and really drops off at 6000. You could try some runs back at 5700 and see what happens.

 

[greychevy]

Yeah but I'm picking up even more MPH between the 1/8 and 1/4....which is where I think you would see a fall off if the higher shift points were the problem.

 

[Jerseymike]

Yeah you did pick up some mph but lost another .15 secs from 1/8 to 1/4. Also, the drop in tire size def changed your gearing from 4.56 to something over 5 which is gonna make your stall lower and effect to 60ft. Its weird though I would have though the truck should be quicker. Maybe it is just the change in DA from the spring to now.

 

[greychevy]

Yeah, it's confusing. Just gonna have to do a lot of passes and adjust ****.

 

[TylerB]

Might be like mentioned on NA and you're actually bogging off the line because you're hooking too hard and wasting energy in the truck squatting instead using power to move forward. My best 60s were when the tires chirped slightly.