What am I missing

[6.4 Stroker]

Hey guys, last night I went to a local 1/8th mile track and needless to say I'm pretty disappointed.
Last year with stock fuel and Industrial Injection drop-ins I was able to run a 7.9 with a weak 1.8 60ft.
Tonight, the best I was able to put up was a lousy 8.1 at 86 MPH.
Is there anything I'm missing?
Gate it opening at 65 psi on my H&S.
Boost is roughly 48psi, and truck his holding 26k rail the whole way down the track.
The density altitude was around 8,400 with the humidity 87%, but I would still think I should be in the 7.5s or7.6s with a decent 60ft.
Thoughts?

 

[6.4f350]

What was DA when you ran a 7.9? What MPH was it at?

DA of 8,400 ft and 87% humidity are about the absolute worst conditions to make a pass in. I wouldn't even consider any times made in those conditions unless that's how it is every time you race.

 

[6.4 Stroker]

What was DA when you ran a 7.9? What MPH was it at?

DA of 8,400 ft and 87% humidity are about the absolute worst conditions to make a pass in. I wouldn't even consider any times made in those conditions unless that's how it is every time you race.

I don't have the slip for the 7.9 but it was 84mph.
DA that night was probably 2800 at the same track.
I never would have guessed it would have that much affect on power.

 

[tbsimmons]

2800-8400'. I bet you lost 20% range of your power. More so if you were in a NA car.

 

[6.4 Stroker]

That's kinda relieving to hear.
Maybe I'll give it another try with better conditions.
Thoughts on tightening up the gate a little bit, or leave it be?

 

[6.4f350]

You picked up 2 MPH on the new run so you were making more power even in those conditions. More seat time will get you better results on the ET side of things.

 

[si3328]

Don't know a ton about drag racing rigs but in our dragster DA and humidity is the first two things we look at when we are dialing the car. You picked up mph so it might have spun just a little at the line. Did you change the gear ratio? Larger or smaller tires?

 

[6.4 Stroker]

Same gearing, same tires. Only difference was the 60% overs and dual fuelers.
It was tough to tell how hard to launch since they couldn't print 60ft times.
I'll just keep practicing along with better air. Hopefully I'll get a better end result next time.

 

[si3328]

If we knew 60 foot time that would help eliminate any kind of spin or sputter off the line. With high MPH I am leaning towards something happening at the launch. Were the rpm's the same when you launched the truck? Seems that it should have made a much better pass than it did.

Keep me posted buddy.

 

[6.4 Stroker]

If we knew 60 foot time that would help eliminate any kind of spin or sputter off the line. With high MPH I am leaning towards something happening at the launch. Were the rpm's the same when you launched the truck? Seems that it should have made a much better pass than it did.

Keep me posted buddy.

Will do man. I do think a poor launch had something to do with it.

 

[6.4 Stroker]

I still feel it's lacking power a little.
With stock fuel I was able to get to 70 psi of backpressure no problem. Now even with the 60 overs it's kinda a chore to reach that with the gate fully closed.
I took a vid of gauges doing a boosted launch doing 0-85.
Tell me what you think.
Gauges read as following Boost, Rail psi, Backpressure, coolant.
Go easy on me, I don't know how to embed lol
6.4 boosted launch gauges: https://youtu.be/0zmVkLf3EYA

 

[Fenner408]

Your not going to make 7.6 with that setup unless you shave some serious weight.


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[6.4 Stroker]

I agree that I'm asking an awful lot of this setup, but I wasn't far from that with stock fuel and a decent 60ft...
I'll eventually get bigger lungs, just wanted to see what this would do. I think it has a bit more in it.

 

[6.4 Stroker]

I found bad seal leaking pretty bad between the low pressure turbo and the VGT crossover pipe. Hopefully that will help out a bit!

 

[6.4 Stroker]

Update.
Went to the track again tonight, only with much better conditions. Got the weight down to 7750 with me in it.
Still only managed 8.2 at 86.
Eighth mile of course.
Full rail pressure, boost touching 50s, and backpressure around 68.

Wondering if I'm blowing through my conveter?
Any ideas?
I'm about ready to strike a match on this thing!

 

[6.4 Stroker]

Truck definitely feels stronger at half throttle, than WOT.
Figured I would have gained SOMETHING from diching 500lbs.

 

[Fenner408]

What's your rail pressure

 

[6.4 Stroker]

25k the whole way down the track.

 

[6.4f350]

Need to log the truck and see the whole picture. Trying to diagnose based off of two different runs on two different days is a crapshoot.

MPH will tell you if you're making the right power. ET is up to you as the driver.

 

[djr4x4]

Kindof thinking its the off the line launch. Tires breaking loose badly? How about suspension? I know they are heavy trucks but still suspension does play a role in this..